The investigators extracted volatile organic compounds from plant material with HS-SPME and then analyzed them by GC–MS. The analysis detected 94 compounds across several chemical groups: fatty acid derivatives, alcohols, hydrocarbons, monoterpenes, sesquiterpenes, phenylpropanoids and isoprenoids. The number of volatiles recorded in the investigated plants varied by genus, with 24 detected in Lamium , 56 in Salvia , 59 in Stachys and 43 in Betonica .

Leaves consistently yielded rich volatile-compound profiles and were identified as suitable material for comparative analyses across the taxa. Principal component analysis and hierarchical cluster analysis showed strong agreement in classifying the samples. The taxa clustered according to their taxonomic relationships, indicating that the chemical profiles carried a signal associated with classification.

Hierarchical cluster analysis also found greater phytochemical similarity between Salvia and the Stachys / Betonica group than between Salvia and Lamium . Plants within a genus showed similarity irrespective of geographic origin, although the study covered a selected set of taxa from two European regions rather than a comprehensive sampling of the family. The authors also identified genus-specific markers of chemical diversification and compounds with high discriminatory value, features they said could help distinguish taxa at the species or subspecies level.

Chemical variation also appeared within each of the four genera. The researchers identified three distinct chemotypes in every studied genus, showing that plants grouped under the same genus did not all share one volatile-compound profile. The results show that HS-SPME–GC–MS combined with multivariate statistics can organize Lamiaceae samples into taxonomic groups and reveal chemical diversification within genera.

Because the evidence comes from 14 selected taxa, the findings do not establish how the method will perform across the wider family or whether it can resolve every taxonomic boundary on its own. Overall, the study presents plant volatiles as a complementary layer of evidence for plant classification. Its most directly supported result is not that scent can replace botanical description, but that solvent-free VOC profiles, when combined with statistical analysis, tracked the taxonomic placement of the sampled plants and exposed multiple chemical forms within each genus.

For the investigated Central and Southern European Lamiaceae, leaves provided information-rich profiles that allowed researchers to connect volatile chemistry with classification at species or subspecies level.

Subject of Research: Chemotaxonomic discrimination of selected Lamiaceae using volatile organic compound profiles

Article Title: HS-SPME/GC-MS as a chemotaxonomic tool: a study on selected Lamiaceae species

Article References: Afzal, T., Łyczko, J., & Proćków, J. (2026). HS-SPME/GC-MS as a chemotaxonomic tool: a study on selected Lamiaceae species. BMC Plant Biology. https://doi.org/10.1186/s12870-026-09898-5

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09898-5

Keywords: Lamiaceae, chemotaxonomy, volatile organic compounds, HS-SPME, GC–MS, plant classification, chemotypes, multivariate analysis, mint family, GC-MS, chemotaxonomic, tool

The story began in April 2019, when a field team working in Zayu County, at the western end of the Hengduan range in Nyingchi City, encountered a sage that looked superficially like the known species Salvia cyclostegia but carried larger leaves and a dense coating of grayish-white felted hairs on its young stems and the undersides of leaves and bracts. Even more striking was the plant’s early inflorescence: a bud-like structure wrapped in layers of broad, ovate bracts that gave it the appearance of a small peach. Follow-up surveys in 2020 and 2021 confirmed the plant was consistent in form, and herbarium specimens were prepared for the Shanghai Chenshan Herbarium.

The second species surfaced four years later and several hundred kilometers away. In August 2023, botanists exploring Songpan County in Sichuan Province’s Aba Tibetan and Qiang Autonomous Prefecture found a sage growing on shaded limestone cliffs near the forest edge. Its flowers resembled those of Salvia smithii, but the plant lacked the distinctive lemon scent of that species and bore an unmistakable corolla — slender and curved upward like an archer’s bow, its lower lip freckled with purple-brown spots. The bow-shaped flower inspired the species epithet toxantha, and the plant carries the Chinese vernacular name gong hua shu wei cao, or bow-flower sage.

Distinguishing closely related sage species demands attention to fine anatomical detail, and the team measured an extensive suite of characters in the field and on cultivated seedlings. Salvia zayuensis stands apart from S. cyclostegia in several respects: its stem leaves reach 18.2 to 24.0 centimeters in length, far larger than those of its relative; its young flowering stalks and leaf undersides carry densely hoary, appressed hairs; and its inflorescences mature into branched panicles up to 40 centimeters long. Its two-toned corolla is also diagnostic, with a purplish-brown upper lip set against a predominantly yellow lower lip, and its anther connectives are shorter in arc length — 0.60 to 0.67 centimeters compared with a mean of 0.79 centimeters in S. cyclostegia. The two species even flower at different times, with the new species blooming from August to September while its congener flowers in spring.

Salvia toxantha shows a parallel pattern of subtle but consistent divergence from S. smithii. Beyond the absence of lemon scent, it produces longer pedicels and calyxes, a corolla of 4.1 to 4.8 centimeters that is more slender and distinctly bow-shaped, and a corolla tube lined internally with purple-brown longitudinal stripes. The arc length of its anther connective averages 0.78 centimeters, roughly 0.4 centimeters shorter than that of S. smithii. The plant is a modest perennial, reaching no more than about 60 centimeters in height, with broadly ovate to heart-shaped leaves whose petioles often flush reddish-purple. Such quantitative differences, replicated across specimens, provide the morphological evidence required for a formal species description under the rules of botanical nomenclature.

Morphology alone, however, is no longer sufficient to anchor a new species in the sage family tree. To establish where the two plants belong, the researchers turned to chloroplast genomes — the DNA housed in the plastids of plant cells, which is inherited intact through seed lineages and is therefore a powerful tool for tracing evolutionary relationships. Whole genome sequencing was performed on an Illumina HiSeq platform for the new species and their close relatives, and the chloroplast genomes were assembled with the software tool GetOrganelle and deposited in the National Genomics Data Center. These were combined with published chloroplast sequences retrieved from the NCBI database, building a dataset of 44 accessions representing 26 species drawn from across the genus.

The team reconstructed the evolutionary tree using maximum likelihood analysis in IQ-TREE, a method that searches for the phylogeny best explaining the observed DNA sequence patterns, with 1,000 bootstrap replicates to gauge confidence. Every repeated sample received support above 97 percent, indicating a highly reliable tree. Both new species emerged as independently monophyletic clades with maximum support of 100 percent. Salvia zayuensis was recovered as the closest relative of S. cyclostegia, with 99 percent support, while S. toxantha and S. smithii were sister to one another, that pair in turn grouping robustly with S. roborowskii and S. tricuspis. Critically, both newcomers fall within the subclade Eurysphace of the subgenus Glutinaria, a group centered on East Asia and containing nearly 100 species.

The phylogenetic results also flagged an open question. The branch uniting S. toxantha with S. smithii carried only modest bootstrap support — around 70 percent — and their sister group was placed within another branch of subgenus Glutinaria, the subclade Annua. The authors suggest this ambiguity may stem from incomplete lineage sorting, the stochastic process by which ancestral genetic variation is distributed unevenly among descendant species, or from the existence of still-undescribed close relatives of S. toxantha. Resolving the matter will require expanded taxon sampling and more comprehensive molecular datasets, a reminder that even in a well-studied genus, the tree of life remains a work in progress.

The two species also differ sharply in how they face the future. Salvia zayuensis is known from eight populations in Zayu County, totaling approximately 6,000 individuals, growing in semi-open woodlands, forest edges and roadside habitats between 1,920 and 2,640 meters in altitude. Given the species’ robust growth, the high humidity of its habitat and minimal human disturbance in the region, and the likelihood that further populations await discovery, it has been tentatively assessed as Least Concern under the IUCN Red List criteria. Salvia toxantha, by contrast, is known from a single site at Hongyanwo in Songpan County, where an estimated 300 to 500 mature individuals cling to shaded limestone cliffs and moist valley cliffs at around 2,800 meters. Until surveys are complete, it is classified as Data Deficient — a designation that underscores how vulnerable a narrow endemic can be to any disturbance of its tiny range.

Beyond their taxonomic novelty, the discoveries carry a broader message about the Hengduan Mountains. The range hosts 44 species and 12 varieties of Salvia, accounting for 52.8 percent of China’s total, making it the undisputed center of diversity for the genus in the country and a critical hotspot for speciation and endemism within the Eurysphace subclade. That two distinctive species — one with a peach-shaped juvenile inflorescence, the other with an archer’s-bow corolla — could remain undetected in these mountains until the second decade of the twenty-first century says much about both the region’s biological riches and the incompleteness of its botanical inventory. The authors argue that continued, comprehensive field surveys are essential to uncover the hidden floral diversity that still shelters in these valleys, and each new species described strengthens the case for protecting the habitats that sustain them.

Subject of Research: Description and phylogenetic placement of two new Salvia species from the Hengduan Mountains, China

Article Title: Salvia zayuensis and Salvia toxantha ( Lamiaceae ), two new species from the Hengduan Mountains, China

Article References: Huang, Y.-B., Lin, C.-H., Guo, Z.-N., Chen, X.-L., Shi, D.-S., Luo, Y., Wang, Q., & Liu, F.-L. (2026). Salvia zayuensis and Salvia toxantha (Lamiaceae), two new species from the Hengduan Mountains, China. PhytoKeys, 280, 181-193. https://doi.org/10.3897/phytokeys.280.208592

Image Credits: AI Generated

DOI: 10.3897/phytokeys.280.208592

Keywords: Salvia, Lamiaceae, Hengduan Mountains, new species, chloroplast genome, phylogenetics, taxonomy, biodiversity, China, conservation, Zayu County, Songpan County

The story began with the American botanist Elmer Drew Merrill, who in August 1917 collected a single individual of a beautyberry shrub in thickets along a small stream at roughly 900 meters elevation on Luofu Mountain. Merrill described the plant as a new species, Callicarpa oligantha, in 1918, noting its alliance with C. dichotoma but distinguishing it by its longer, narrower leaves, subsessile and abaxially pubescent foliage, shorter filaments, and cymes bearing very few flowers. Crucially, his description rested on a single gathering from one individual. For nearly 110 years afterward, no additional plants matching that description were ever documented, and the species drifted into taxonomic limbo, categorized as data deficient in China’s national Red List and never assessed by the IUCN.

Doubts about the species’ validity surfaced early. In his 1951 review of the Chinese species of Callicarpa, Chang considered C. oligantha closely allied to C. brevipes and suggested it might merely represent a morphological variant of that species. The problem was that no one could test the idea, because there was nothing to test: no fresh material, no living plants, no DNA. That changed when a field survey at Luofu Mountain rediscovered a population of Callicarpa closely matching Merrill’s original description, with one notable exception. Some individuals bore pubescent fruits and occasional hairs on the lower leaf surfaces, traits absent from the protologue, likely because Merrill had only ever seen a single specimen from a single plant.

Armed with newly collected material, the research team launched an integrative taxonomic reassessment combining molecular phylogenetics with statistical morphological comparisons. For the genetic work, they sampled five individuals of C. oligantha from the type locality and three individuals of C. brevipes from Guangdong, Hainan, and Vietnam, embedding them within a broad phylogenetic frame of twenty Callicarpa species, with two Australian outgroup taxa anchoring the analysis. Total genomic DNA was extracted from silica-dried leaf tissue using the CTAB method, and the team amplified and sequenced two nuclear ribosomal regions, nrITS and nrETS, together with eight chloroplast DNA markers previously shown to be effective for resolving relationships in this genus.

The analytical strategy was deliberately conservative. To reduce potential bias in phylogenetic reconstruction, the researchers applied both concatenation-based and coalescent-based methods. Maximum likelihood analyses with 5,000 ultrafast bootstrap replicates and Bayesian inference sampling five million trees were run on concatenated datasets totaling 1,087 base pairs of nuclear ribosomal DNA and 7,435 base pairs of chloroplast DNA. A multispecies coalescent approach in StarBEAST2 was used to infer species trees, accounting for incomplete lineage sorting, a process that can seriously mislead standard tree-building methods. The results were unambiguous: Callicarpa oligantha was intermingled with C. brevipes in both nuclear and plastid datasets, with strong statistical support, and the coalescent species trees recovered C. oligantha as sister to C. brevipes. In other words, the ‘extinct’ species is not an evolutionarily independent lineage but part of the variation within C. brevipes.

The morphology told the same story. The team measured six characters regarded as key for distinguishing Callicarpa species: leaf length, leaf width, petiole length, inflorescence width, inflorescence branching, and filament length, using ImageJ software on both the new collections and historical type specimens, including the isotype of C. oligantha preserved at the United States National Herbarium and the lectotype of C. brevipes at Kew. Principal component analysis of leaf morphology explained 91.4 percent of the variance in the first two axes, and flower morphology 94.6 percent, with C. oligantha and C. brevipes forming a single cluster in every analysis. T-tests found no significant differences between the two in any of the measured characters. The ranges overlap almost completely: leaf length spans 8.5 to 14.5 centimeters in C. oligantha versus 8.4 to 17.5 centimeters in C. brevipes, and the two species share the same lanceolate to narrowly lanceolate leaf blades. The distributions of the two taxa also overlap entirely across southeastern China and Vietnam.

Based on this congruent molecular and morphological evidence, the authors formally propose synonymizing C. oligantha under C. brevipes, following Article 11 of the International Code of Nomenclature for Algae, Fungi, and Plants, the Shenzhen Code. As part of the taxonomic treatment, they also designated a lectotype for C. brevipes, a Champion specimen at Kew that matches the original description, untangling a complicated nomenclatural history that stretches back to Hooker’s 1825 misidentification of a living Chinese plant as Callicarpa longifolia. The rediscovered population, once a candidate for urgent protection as a last-of-its-kind survivor, is now understood to be a population of a species assessed as least concern, with stable populations and no major threats across its range in Guangdong, Guangxi, Hainan, Hong Kong, and Vietnam.

The implications reach far beyond one shrub. The study joins a growing body of evidence showing how shaky taxonomy can distort conservation priorities. The authors point to Fagus chienii, a beech designated as a key protected species in 2016 despite being known from a single 1935 collection, only for molecular work to reveal it is conspecific with F. hayatae. They also cite Torreya grandis var. jiulongshanensis, once listed as a Category II protected plant, which phylogenetic study showed to be a natural hybrid rather than a distinct lineage. Perhaps most striking is the clover fern Marsilea azorica, managed as critically endangered under the Bern convention and the European Union’s habitats directive, until researchers demonstrated it was conspecific with an invasive species and recommended its removal from every conservation list it occupied.

For Callicarpa oligantha, the practical consequences were immediate and concrete. Local forestry authorities had been likely to include the species in the list of key protected wild plants, directing substantial conservation effort toward a name rather than a genuinely unique lineage. The new study recommends excluding C. oligantha from extinction lists, freeing those resources for species facing real threats. The authors note that the only other plant assessed as probably extinct in Guangdong, the mycoheterotroph Corsiopsis chinensis, remains a genuinely enigmatic case, known from an unusual specimen collected in 1999 and not observed in field surveys since.

The broader lesson is one that conservation biology keeps relearning: accurate species delimitation is the foundation on which every red list entry, protected area decision, and recovery plan ultimately rests. When species boundaries are drawn from single specimens or superficial resemblance, limited resources can flow toward phantom extinctions while genuinely endangered lineages go unprotected. The researchers emphasize that robust taxonomic frameworks, ideally built on integrative, multidisciplinary evidence combining DNA sequences, morphology, and fieldwork, must be established before conservation action is taken. They also call for population genomic studies with expanded sampling across the full distribution of C. brevipes to reveal patterns of intraspecific genetic diversity that single-locus phylogenies cannot capture. A century-old enigma has been closed, an extinction has been un-declared, and a small purple-fruited shrub on a mountain in South China has become an unlikely poster child for the quiet, essential science of taxonomy.

Subject of Research: Integrative taxonomic reassessment of the supposedly extinct plant Callicarpa oligantha and its synonymy with Callicarpa brevipes

Article Title: Rediscovery and reexamination of a declared 'extinct' plant in South China: The species delimitation and conservation implications of Callicarpa oligantha ( Lamiaceae )

Article References: Cai, H., Yang, Q., Xu, Y., Tu, T., & Ma, Z. (2026). Rediscovery and reexamination of a declared 'extinct' plant in South China: The species delimitation and conservation implications of Callicarpa oligantha (Lamiaceae). PhytoKeys, 278, 157-176. https://doi.org/10.3897/phytokeys.278.203604

Image Credits: AI Generated

DOI: 10.3897/phytokeys.278.203604

Keywords: Callicarpa oligantha, Callicarpa brevipes, taxonomy, species delimitation, rediscovery, extinction, conservation, phylogenetics, Guangdong, Lamiaceae, biodiversity, red list

Salvia is a species-rich and easily recognizable genus within the subtribe Salviinae, comprising approximately 1,088 species distributed almost cosmopolitanly. The genus has undergone significant species radiations in three global biodiversity hotspots: the Americas, Asia, and Europe. At the country level, Mexico harbors the highest number of species, followed by Russia, Turkey, the United States, and China. Japan, though not among the top hotspots, hosts 12 distinct Salvia species, eight of which are endemic to the archipelago. The remaining four have broader distributions, including S. japonica, also found in Korea, Taiwan, and China; S. nipponica, present in both China and Japan; and S. plebeia, widely distributed across Asia and Australia. Most recently, Hayakawa and colleagues reported the first naturalization of Salvia lyrata from a roadside on Niijima Island in the Izu Islands, a species native to the United States that is cultivated as a garden herb in Japan and has shown the potential to escape from cultivation.

Japanese Salvia has traditionally been classified into three subgenera: subg. Salvia, subg. Sclarea, and subg. Allagospadonopsis. However, based on molecular and morphological evidence, Hu and colleagues reclassified all East Asian Salvia into a newly recognized subgenus, Glutinaria, and further recognized eight sections within this subgenus. All native Japanese Salvia species were placed in subg. Glutinaria and assigned to three sections: sect. Sobiso, sect. Glutinaria, and sect. Notiosphace. The recently introduced S. lyrata was originally placed in sect. Heterosphace within subgenus Leonia, a subgeneric name later noted as invalidly published. Recent molecular phylogenetic studies instead place S. lyrata within an informally named Heterosphace clade, treated by some authors as an unranked subgenus pending formal validation.

Previous studies have demonstrated the taxonomic significance of nutlet morphology in several Salvia taxa. Nutlet characters, including size, shape, surface ornamentation, and abscission scar morphology, provide relatively conservative and independent morphological evidence that complements the floral and staminal characters traditionally used for taxonomic circumscription. Although Bentham’s traditional classification of Old World Salvia was primarily based on staminal and corolla morphology, subsequent studies have shown that nutlet morphological characters, particularly surface ornamentation, correspond closely with sectional boundaries. Among these characters, nutlet surface ornamentation has consistently been identified as one of the most informative diagnostic features for sectional delimitation. Yet the nutlet morphology of Japanese Salvia remains poorly documented despite its systematic importance. To date, only two species, S. lyrata and S. plebeia, had been investigated, both of which are also examined in the present study.

The researchers examined 84 herbarium specimens representing 19 Salvia taxa, using both light microscopy and scanning electron microscopy. Mature nutlets were detached from specimens housed at the HYO and KYO herbaria. Numerical traits were recorded from 5 to 40 nutlet samples per specimen for each taxon. For scanning electron microscope analysis, mature nutlets were selected, surface debris was removed using 70 percent ethanol, and the air-dried nutlets were mounted on aluminum stubs using double-sided adhesive tape and coated with gold. The surface sculpturing was then examined and photographed using a KEYENCE scanning electron microscope. Nutlet shapes were assessed from both dorsal and ventral perspectives, with the dorsal surface used to characterize surface sculpturing patterns and the ventral surface examined to determine the position of the abscission scar.

The results revealed remarkable diversity across all examined nutlet characters. Nutlet size ranged from 0.64 by 0.45 millimeters in S. plebeia, belonging to sect. Notiosphace, to 3.27 by 2.27 millimeters in S. koyamae, belonging to sect. Glutinaria. The length-to-width ratio varied from 1.06 in S. glabrescens var. repens to 2.54 in S. pygmaea var. pygmaea. Nutlet shapes were elliptic, narrow-elliptic, and ellipsoidal in sect. Sobiso; ovoid to obovoid and spherical in sect. Glutinaria; and ovoid in both sect. Heterosphace and sect. Notiosphace. Abscission scar morphology varied among the sections, being squarish, triangular, irregular, or orbicular in sect. Sobiso; irregular to orbicular in sect. Glutinaria; orbicular in sect. Heterosphace; and triangular in sect. Notiosphace.

Four major types of surface sculpturing were recognized across the studied sections. Type I, reticulate, features a net-like pattern formed by distinct pentagonal to hexagonal cells and characterizes sect. Sobiso. Type II, tuberculate, bears prominent knob-like irregular projections and defines sect. Heterosphace. Type III, colliculate, displays low rounded hill-like elevations and marks sect. Glutinaria. Type IV, verrucate, is covered with numerous small wart-like projections and distinguishes sect. Notiosphace. Under high-resolution scanning electron microscopy, the surface cells of sect. Sobiso taxa ranged from pentagonal to hexagonal, were rarely irregularly polygonal, and were mostly isodiametric, with distinct, slightly sinuate, raised anticlinal walls. In contrast, the nutlet surface cells of sect. Glutinaria taxa appeared irregular, with indistinct, raised anticlinal walls.

Principal component analysis based on taxon means demonstrated that nutlet size-related characters contributed most strongly to the observed variation among the studied taxa. The first two principal components together explained 83.7 percent of the total variation, with the first accounting for 63.9 percent and the second for 19.8 percent. The first principal component showed similar positive loadings for nutlet length and abscission scar width, with a weaker negative loading for the nutlet length-to-width ratio, primarily representing overall variation associated with nutlet and abscission scar size. Salvia species with the highest scores, including S. koyamae, S. glabrescens var. glabrescens, and S. nipponica, grouped toward the positive side, reflecting their relatively larger nutlet and abscission scar dimensions. The second principal component was dominated by the negative loading for the abscission scar length-to-width ratio, separating species primarily by shape rather than size.

The findings align with a broad consensus that brown coloration with darker markings is a conserved feature across Old World Salvia rather than a section-specific diagnostic character. The smallest nutlets recorded in S. plebeia correspond with measurements reported by previous researchers for the same species, suggesting that nutlet size may represent a relatively consistent character at the species level. The tuberculate ornamentation with small knob-like projections observed in S. lyrata is consistent with the original description by Marín and colleagues. These comparisons demonstrate that nutlet ornamentation is a relatively stable character with considerable taxonomic importance for species identification and infrageneric classification in Salvia.

Overall, the study provides the first comprehensive account of nutlet morphology in Japanese Salvia and establishes a robust morphological framework for evaluating both interspecific and intraspecific variation. The consistency of the four ornamentation patterns, together with other nutlet morphological characters, provides additional support for the existing sectional circumscription of Japanese Salvia and is congruent with the recently proposed infrageneric classification. In contrast, some nutlet characters, such as nutlet shape, size, and abscission scar morphology, were more informative for species identification than for supporting the current sectional classification. The diversity of nutlet morphology highlights the diagnostic value of these characters for taxonomic identification at both the species and sectional levels within Japanese Salvia, offering botanists a powerful new lens through which to view the hidden architecture of one of the world’s most species-rich plant genera.

Subject of Research: Nutlet micromorphology and its systematic significance in Japanese Salvia

Article Title: Nutlet micromorphology of Japanese Salvia ( Salviinae , Lamiaceae ) and its systematic significance

Article References: Khan, A., Takano, A., Lee, C.-K., & Ishida, H. (2026). Nutlet micromorphology of Japanese Salvia (Salviinae, Lamiaceae) and its systematic significance. PhytoKeys, 279, 85-110. https://doi.org/10.3897/phytokeys.279.199134

Image Credits: AI Generated

DOI: 10.3897/phytokeys.279.199134

Keywords: Salvia, Lamiaceae, nutlet micromorphology, scanning electron microscopy, plant taxonomy, Japan, systematic botany, Nutlet, micromorphology, Japanese, Salviinae, systematic

The research team, led by Alaka Mohanty and Sujata Mohanty, began with the foundational question of any natural product investigation: what exactly is in the oil? Using gas chromatography coupled with mass spectrometry, or GC–MS, the gold-standard technique for separating and identifying volatile compounds, they analyzed the chemical fingerprint of the leaf oil, known by the abbreviation VQLEO. The analysis revealed a complex mixture of 36 phytoconstituents. Three compounds dominated the profile: longifolene, a bulky sesquiterpene hydrocarbon, accounted for a remarkable 52.87 percent of the oil, followed by spathulenol at 9.54 percent and ar-curcumene at 5.74 percent. This dominance of longifolene is notable, because the chemical composition of essential oils can vary dramatically between species, populations, and even individual plants, and the major constituents often determine the biological behavior of the whole mixture.

Essential oils are concentrated hydrophobic liquids containing volatile aroma compounds that plants synthesize in specialized glands. They have served humanity as medicines, preservatives, and perfumes for millennia, but modern science is only now systematically cataloguing their chemistry and measuring their effects with rigorous assays. The Indian team’s work fits into a broader effort to screen the genus Vitex, which includes well-studied species such as Vitex negundo and Vitex agnus-castus, both of which have extensive ethnobotanical histories. By turning to the less famous V. quinata, the researchers hoped to find a chemical profile and activity spectrum distinct from its relatives, potentially revealing new leads for pharmacology, cosmetics, and agriculture.

The first biological test examined antioxidant capacity, the ability of a substance to neutralize reactive free radicals that damage cells and contribute to aging and disease. The researchers employed two complementary colorimetric assays, the DPPH and ABTS tests, which measure how effectively a compound scavenges synthetic radical dyes. Here the results were modest. The oil showed weak antioxidant activity in both assays, with IC50 values, the concentrations needed to neutralize half of the radicals, of 18.83 milligrams per milliliter for DPPH and 18.53 milligrams per milliliter for ABTS. These figures are high compared with potent antioxidant standards, which typically act at microgram levels, and the authors’ finding suggests that the sesquiterpene-rich composition of VQLEO does not translate into strong radical-scavenging power. This is a useful reminder that a plant oil can excel in one biological arena while remaining unremarkable in another.

The tyrosinase results tell a more interesting story. Tyrosinase is a copper-containing enzyme that catalyzes the rate-limiting steps of melanin biosynthesis, the biochemical pathway responsible for the pigmentation of skin, hair, and eyes. In dermatology and cosmetics, inhibitors of tyrosinase are prized ingredients for treating hyperpigmentation disorders such as melasma and age spots, and they also serve in food preservation, where browning caused by the enzyme degrades produce. The oil inhibited mushroom tyrosinase with an IC50 of 13.85 milligrams per milliliter. While this concentration is far above that of clinical inhibitors like kojic acid, the finding establishes V. quinata leaf oil as a genuine, if moderate, anti-tyrosinase agent, and it aligns with earlier reports of melanogenesis inhibition by essential oils from related Vitex species, including Vitex negundo, whose lignans were identified as tyrosinase inhibitors more than a decade ago.

The antibacterial screening is where the study delivers its most consequential numbers. The researchers tested the oil against four bacterial species of major clinical relevance: Escherichia coli, a Gram-negative gut bacterium and leading cause of urinary tract infections; Staphylococcus aureus, a Gram-positive pathogen notorious for antibiotic-resistant strains; Streptococcus mutans, the primary driver of dental caries; and Klebsiella pneumoniae, an encapsulated Gram-negative organism implicated in hospital-acquired pneumonia. Using broth microdilution methods aligned with the standards of the Clinical and Laboratory Standards Institute, the team determined minimum inhibitory concentrations, the lowest oil concentrations that prevent visible bacterial growth. VQLEO displayed significant antibacterial activity against all four organisms, with MIC values ranging from just 12.5 to 25 micrograms per milliliter. For an unfractionated essential oil, these values are impressively low and indicate that the oil’s constituents, individually or in synergy, potently interfere with bacterial physiology, likely by disrupting cell membranes, a mechanism common to many terpene-rich oils.

But the study’s boldest move was to go beyond killing or slowing planktonic, free-swimming bacteria and attack the biofilm lifestyle itself. Biofilms are structured communities of bacteria encased in a self-produced matrix of extracellular polymeric substances that adheres to surfaces. Within a biofilm, bacteria can be up to a thousand times more tolerant of antibiotics than their planktonic counterparts, because the matrix limits drug penetration and the slow-growing cells within it evade mechanisms that target actively dividing organisms. Biofilm-mediated infections by multidrug-resistant microbes are increasingly recognized as one of the most intractable problems in modern medicine, from catheter-associated infections to chronic wounds and dental plaque. Any natural compound that prevents biofilm formation at concentrations that do not necessarily kill the bacteria is therefore of great interest.

Testing at sub-inhibitory concentrations, doses below the level needed to stop growth outright, the researchers measured how effectively VQLEO prevented biofilms from forming, using a microtiter dish biofilm formation assay in which adherent biomass is stained and quantified. The results were striking. The oil inhibited biofilm formation most strongly against E. coli, achieving 79.41 percent inhibition, followed closely by S. aureus at 78.72 percent, S. mutans at 71.40 percent, and K. pneumoniae at 65.58 percent. In other words, at concentrations that the bacteria could survive, the oil still stripped away their ability to build their protective communities. This antibiofilm effect, observed across both Gram-positive and Gram-negative species, suggests that the oil’s constituents interfere with the early stages of surface adhesion or the production of the extracellular matrix, processes governed by quorum sensing and other regulatory networks that differ from the targets of conventional antibiotics.

The chemical composition offers clues to these activities. Longifolene, the overwhelmingly dominant constituent, is a tricyclic sesquiterpene found in numerous plant oils and has been associated with antimicrobial and anti-inflammatory properties in prior studies. Spathulenol, an oxygenated sesquiterpene, has itself been investigated for antioxidant, anti-inflammatory, and antimicrobial effects, including in work on the essential oil of Psidium guineense. Oxygenated sesquiterpenes like spathulenol tend to be more biologically active than pure hydrocarbons because their polar functional groups improve interaction with biological membranes and enzymes. The interplay between these major components and the remaining 33 minor constituents may involve synergistic effects, a phenomenon well documented in essential oil research, where whole oils sometimes outperform their isolated major compounds.

For V. quinata, a species distributed widely across temperate and tropical Asia yet largely absent from pharmacological literature, the study marks a significant step from obscurity toward evidence-based evaluation. The authors acknowledge that their work was conducted in vitro, in laboratory assays rather than in living organisms, and considerable work remains before any practical application could emerge: the active constituents must be isolated and confirmed, the mechanisms of biofilm inhibition elucidated at the molecular level, and safety and efficacy established in preclinical models. Nevertheless, the combination of potent antibacterial activity, broad antibiofilm protection, and measurable tyrosinase inhibition positions this underexplored tree as a promising subject for further phytochemical and pharmacological investigation. As antibiotic resistance continues to erode the effectiveness of conventional drugs and the cosmetics industry searches for plant-derived alternatives to synthetic skin-lightening agents, the humble leaf oil of Vitex quinata demonstrates that some of the most valuable chemical libraries are still growing quietly in the forests of Asia, waiting for the right analytical tools to read them.

Subject of Research: Chemical composition and antioxidant, anti-tyrosinase, antibacterial and antibiofilm activities of Vitex quinata leaf essential oil

Article Title: GC–MS characterization and biological activities of Vitex quinata leaf essential oil: Antioxidant, tyrosinase inhibitory and antibiofilm potential

Article References: Mohanty, A., Das, P. K., Sahoo, A., Nayak, S., Panda, P. C., & Mohanty, S. (2026). GC–MS characterization and biological activities of Vitex quinata leaf essential oil: Antioxidant, tyrosinase inhibitory and antibiofilm potential. Plant Biosystems, 160(4), Article 214. https://doi.org/10.1007/s44473-026-00214-5

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00214-5

Keywords: Vitex quinata, essential oil, GC-MS, longifolene, spathulenol, antioxidant, tyrosinase inhibition, antibacterial, biofilm inhibition, antimicrobial resistance, natural products, Lamiaceae

The research team approached peppermint not as a single commodity but as a collection of locally adapted populations, each shaped by the altitude, temperature regime, and soil chemistry of its home region. Iran spans an enormous environmental gradient, from the warm, low-lying plains of Alborz province near the capital to the cooler, elevated territories of East Azarbaijan and Zanjan in the northwest. Because essential oil biosynthesis in mint species is highly sensitive to environmental conditions, the researchers reasoned that accessions collected across this gradient would display meaningful differences in both the quantity of oil they produce and the relative proportions of its constituent monoterpenes. Their sampling strategy, drawing directly from the fields of established commercial growers, ensured that the plants assessed reflected real-world cultivation rather than greenhouse idealization.

The measurements that followed were comprehensive. The team recorded morphological traits such as plant height, branching, and biomass accumulation, examined leaf anatomy under the microscope, and determined dry shoot yield on a per-hectare basis. Essential oil was extracted and analyzed to quantify both its total content as a percentage of dry matter and its overall yield per hectare, while gas chromatographic profiling resolved the oil into its major components, most importantly menthone and menthol, the two monoterpenoids that define peppermint’s sensory and commercial identity. Alongside this phytochemical work, the researchers measured the concentration of macroelements and microelements in the plant tissue, together with selected heavy metals, providing a picture of what these plants draw out of their soils as well as what they manufacture within them.

The yield results alone tell a striking story of local variation. The highest dry shoot yield, 3410 kilograms per hectare, came from the Karaj accession, demonstrating that the lowland Alborz environment favors raw biomass production. But biomass is only half of the peppermint equation, because the value of the crop lies in the oil concentrated within its leaves and flowering tops. Here the ranking shifted decisively. The highest essential oil contents, 2.36 percent and 2.31 percent of dry material, were detected in accessions from Khosroshahr in East Azarbaijan province and from Zanjan province respectively, both northwestern, higher-altitude sources. When oil content was combined with harvested biomass to calculate essential oil yield per unit area, the Khosroshahr accession led with 68.5 kilograms per hectare, followed by Zanjan at 56.01 kilograms per hectare, confirming that these northwestern plants translate their chemical richness into genuine productivity.

The composition of the oil proved just as variable as its quantity. Menthone, the ketone precursor in the menthol biosynthetic pathway with the formula C10H18O, reached its highest proportions in the Zanjan accession at 27.23 percent and the Kermanshah accession at 24.31 percent. Menthol, the monoterpene alcohol C10H20O that delivers peppermint’s signature cooling effect through its activation of cold-sensitive receptors, peaked in the Khosroshahr accession at 47.57 percent, with the Hersin accession close behind at 46.52 percent. For buyers of peppermint oil, these numbers matter enormously, because menthol content is the primary determinant of oil quality and price. An accession that converts nearly half of its oil into menthol is a fundamentally more valuable raw material than one dominated by menthone, and the fact that this difference tracks with geographic origin suggests that environment and genotype together shape the enzymatic machinery of monoterpene metabolism.

The study’s most conceptually interesting finding concerns altitude and temperature. At lower altitudes, exemplified by Alborz, elevated temperatures appeared to increase branch production, pushing plants toward vegetative exuberance and the impressive dry yields recorded at Karaj. At higher altitudes such as Khosroshahr and Zanjan, the cooler conditions enhanced plant quality, and the researchers observed that sufficient branching in these accessions rendered them superior and more suitable for consumption. In other words, the lowland plants excel at making plant material while the highland plants excel at making the chemistry that consumers actually want. This trade-off between quantity and quality is a classic pattern in aromatic plant science, reflecting the temperature sensitivity of the terpenoid pathway, and it gives breeders and growers a clear framework: match the accession to the objective, choosing highland material when oil quality is paramount and lowland material when bulk biomass is the goal.

Beneath the yield and chemistry data sits a quieter but potentially far-reaching component of the work: the measurement of heavy metal uptake. Plants inevitably absorb elements from their soil, and aromatic and medicinal crops raise particular concerns because accumulated metals such as cadmium and lead can enter herbal products and essential oils destined for human use. At the same time, plants that tolerate and accumulate metals are of interest for phytoremediation, the use of vegetation to extract contaminants from polluted ground. Heavy metal stress is known to generate reactive oxygen species in plant tissues, including hydrogen peroxide, superoxide anion, and hydroxyl radicals, which damage cells but also trigger defensive responses that can alter secondary metabolism, including the production of monoterpenoids and other specialized metabolites. By documenting how peppermint accessions differ in their uptake of macroelements, microelements, and selected heavy metals, the study provides a baseline for both food-safety screening and the potential deployment of mint in contaminated landscapes.

The element analysis also connects to the broader physiology of oil production. Essential oil synthesis in peppermint depends on adequate supplies of nitrogen, phosphorus, potassium, and magnesium, and on trace micronutrients that serve as cofactors for the enzymes of the plastidial and cytosolic terpenoid pathways. Accessions that accumulate nutrients more efficiently may be better positioned to sustain oil gland activity through the growing season, which is one plausible contributor to the superior oil yields of the Khosroshahr and Zanjan plants. Understanding these nutrient dynamics at the accession level, rather than treating peppermint as an undifferentiated crop, opens the door to precision fertilization strategies tailored to specific plant material and specific soils, reducing input waste and improving oil consistency for processors.

For Iran, one of the historic centers of mint cultivation and a country with a rich tradition of medicinal plant use, the study is a reminder that agricultural biodiversity is an economic asset hiding in plain sight. The Khosroshahr accession, with its exceptional oil content, highest oil yield, and top menthol percentage, emerges as a standout candidate for commercial propagation and for use as a parent in breeding programs aimed at combining high menthol with robust agronomic performance. The Zanjan accession, with its high menthone and strong oil yield, offers complementary chemistry. Meanwhile, the Karaj accession’s biomass dominance illustrates the value of lowland material for applications where total plant matter, rather than oil, is the product. Preserving and characterizing such landrace diversity, the authors’ work implies, is essential insurance for an industry facing changing climates and shifting growing regions.

More broadly, the research exemplifies a trend in crop science toward treating phytochemical quality as a heritable, environment-modulated trait that can be mapped, predicted, and optimized. The peppermint plant, a sterile hybrid that has spread around the world through cuttings, carries within its populations a surprising range of chemical phenotypes, and studies like this one show that those phenotypes respond systematically to altitude and temperature. As demand for natural menthol continues to grow, and as concerns about heavy metals in herbal products intensify, the ability to select the right accession for the right site, and to understand what that plant will draw from its soil, becomes a competitive necessity. The Iranian peppermints profiled in Plant Biosystems demonstrate that the future of this ancient flavor may depend less on new chemistry than on paying closer attention to the old plants still growing in the fields where they have always been grown.

Subject of Research: Phenotypic and phytochemical diversity and heavy metal uptake in peppermint accessions

Article Title: Phenotypic and essential oil profile diversity, and heavy metal uptake potential of peppermint (Mentha × piperita) accessions

Article References: Sarkhosh, M. R., Abbaszadeh, B., Ardakani, M. R., Habibi, D., & Ilkaee, M. N. (2026). Phenotypic and essential oil profile diversity, and heavy metal uptake potential of peppermint (Mentha × piperita) accessions. Plant Biosystems, 160(4), Article 227. https://doi.org/10.1007/s44473-026-00162-0

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00162-0

Keywords: peppermint, Mentha × piperita, essential oil, menthol, menthone, heavy metals, Iran, altitude, leaf anatomy, phytoremediation, Lamiaceae, crop diversity

The study, published open access in Discover Chemistry, set out to close a conspicuous knowledge gap. While close relatives such as Isodon rubescens have been extensively characterized—yielding celebrated diterpenoids like oridonin that have attracted attention for anti-inflammatory and cytoprotective effects—I. coesta has remained comparatively obscure despite its wide distribution across Bangladesh, Nepal, India, China, Myanmar, the Philippines, Indonesia, Sri Lanka, and Thailand. The researchers harvested whole plants, excluding roots, in September 2023, air-dried them for two to four days, ground them into a fine powder, and extracted the material separately with methanol and hexane over ten to fifteen days of soaking. The polar solvent proved far more generous: the methanolic extract yielded 4.02 percent by weight, while the nonpolar hexane extract yielded only 1.10 percent, a difference that foreshadowed the chemistry to come.

Gas chromatography–mass spectrometry, performed at the Advanced Instrumentation Research Facility at Jawaharlal Nehru University in New Delhi on a Shimadzu GCMS-QP2010 Plus system with a DB-5 capillary column, identified 24 compounds in each extract. In the methanolic extract, these accounted for 81.93 percent of total composition, with the acyclic diterpene alcohol phytol dominating at 12.22 percent, followed by the steroid precursor pregnenolone acetate at 7.54 percent, squalene at 6.83 percent, and methyl linolenate at 6.51 percent. The hexane extract told a different story: squalene, a triterpene hydrocarbon famous for its antioxidant and skin-protective properties, led at 11.79 percent, with the long-chain hydrocarbon 2-methylhexacosane close behind at 9.68 percent, and hexatriacontane, propylene glycol monooleate, and palmitic acid rounding out the major peaks. Seven compounds appeared in both extracts, including phytol, squalene, neophytadiene, and vitamin E, suggesting overlapping biochemical pathways that persist regardless of solvent polarity.

The identity of the dominant molecules matters because several of them carry well-documented biological credentials. Phytol serves as a biosynthetic precursor to vitamins E and K1 and has reported antioxidant, anti-inflammatory, and anticancer activities. Pregnenolone acetate sits upstream in the biosynthesis of steroid hormones and has been studied for neuroprotective and anti-inflammatory effects, making it a molecule of interest in neuropharmacology and endocrinology. Squalene, meanwhile, is an intermediate in sterol biosynthesis and a widely used emollient in cosmetics and pharmaceuticals. The presence of gamma-sitosterol, tocopherol, and linoleic acid derivatives in the methanolic extract further enriches the profile of a plant whose chemical inventory had previously been little more than a footnote in the Isodon literature.

Quantitative colorimetric assays confirmed that polarity drives the phytochemical harvest. The methanolic extract registered a total phenolic content of 31.37 milligrams of gallic acid equivalents per gram, a total flavonoid content of 313.28 milligrams of quercetin equivalents per gram, and a total antioxidant capacity of 8.61 milligrams of ascorbic acid equivalents per gram. The hexane extract trailed on every measure, with 17.19 milligrams GAE per gram of phenolics, 117.57 milligrams QE per gram of flavonoids, and 2.07 milligrams AAE per gram of antioxidant capacity. The pattern is chemically intuitive: methanol, being polar, efficiently pulls phenols and flavonoids out of plant tissue, whereas hexane preferentially dissolves lipids, waxes, and terpenoid hydrocarbons. Flavonoids, in particular, are major contributors to plant antioxidant activity, so their concentration in the methanolic fraction is consistent with the rest of the data.

The radical-scavenging results, however, temper any temptation to crown the plant a super-antioxidant. In the DPPH assay, which tracks the reduction of a stable violet free radical by measuring absorbance at 517 nanometers, the methanolic extract posted an IC50 of 748.38 micrograms per milliliter and the hexane extract 794.13 micrograms per milliliter. Those figures indicate moderate to weak activity compared with ascorbic acid, the reference standard, which achieved an IC50 of just 74.72 micrograms per milliliter. Two-way ANOVA showed that concentration strongly influenced scavenging activity, with a highly significant effect, while the difference between the two extract types alone did not reach statistical significance, though a significant interaction between extract type and concentration revealed concentration-dependent divergence in their responses. The authors caution that direct comparison with the standard should be interpreted carefully because different concentration ranges were used for the plant extracts and the reference compound.

To probe how the major constituents might behave at the molecular level, the team turned to computational docking against two enzymes that sit at opposite ends of the oxidative-stress balance. Human peroxiredoxin-5, resolved by X-ray crystallography at 1.50 angstrom resolution, is a thioredoxin-family antioxidant enzyme that detoxifies hydrogen peroxide and peroxynitrite, defending cells against oxidative injury. NADPH oxidase, resolved at 1.80 angstroms, is the enzymatic engine of reactive oxygen species generation, and its overactivation drives inflammatory damage. Using PyRx 0.8 with AutoDock Vina, the researchers docked phytol, pregnenolone acetate, squalene, and 2-methylhexacosane into both binding pockets. Pregnenolone emerged as the clear frontrunner, binding peroxiredoxin-5 at minus 6.1 kilocalories per mole and NADPH oxidase at minus 8.4 kilocalories per mole through a mix of hydrogen bonds, pi-anion, and pi-alkyl contacts. Phytol followed with moderate affinities, while 2-methylhexacosane performed worst, managing only minus 3.0 and minus 5.7 kilocalories per mole through weak van der Waals and alkyl interactions.

The ADMET analysis added a sobering pharmacokinetic dimension. All four compounds passed the molecular-weight criterion of Lipinski’s rule of five, but squalene, phytol, and 2-methylhexacosane showed MLOGP values far above the acceptable ceiling of 4.15, signaling extreme lipophilicity that predicts poor aqueous solubility and low gastrointestinal absorption. Pregnenolone was the only compound predicted to have high GI absorption, the only one expected to cross the blood–brain barrier, and the only one that is not a P-glycoprotein substrate, making it the most drug-like molecule in the set. Toxicity predictions from ProTox 3.0 were reassuring across the board: none of the compounds showed hepatotoxicity, carcinogenicity, or AMES mutagenicity, and squalene and phytol carried LD50 values of 5,000 milligrams per kilogram, indicating generous safety margins. The authors suggest that nanoemulsions, liposomes, solid lipid nanoparticles, or phospholipid-based delivery systems could rescue the bioavailability of the lipophilic constituents.

The researchers are careful to frame the docking results as hypothesis-generating rather than proof of pharmacological activity, and they recommend in vivo validation, molecular dynamics simulations, and quantitative phytochemical confirmation by HPLC or LC–MS as the necessary next steps. Even with those caveats, the study positions Isodon coesta as a flavonoid-rich reservoir of bioactive metabolites from one of the world’s great biodiversity hotspots—the Indian Himalayan region harbors roughly half of India’s flowering plant species with nearly 30 percent endemism, and Uttarakhand alone supports more than 5,000 vascular plant species. As computational screening increasingly complements fieldwork in natural-product drug discovery, this aromatic undershrub of the Himalayan slopes may yet translate its ethnobotanical reputation into molecules worthy of the laboratory bench and, eventually, the clinic.

Subject of Research: Phytochemical profiling and computational antioxidant evaluation of Isodon coesta from the Uttarakhand Himalaya

Article Title: Comprehensive phytochemical profiling, molecular interaction studies, and ADMET analysis of hexane and methanol extracts of Isodon coesta from Uttarakhand’s Himalayan Region

Article References: Mawri, D., Pujari, R., Bahuguna, A., Rawat, D. S., Prakash, O., Kumar, R., & Dubey, S. K. (2026). Comprehensive phytochemical profiling, molecular interaction studies, and ADMET analysis of hexane and methanol extracts of Isodon coesta from Uttarakhand’s Himalayan Region. Discover Chemistry, 3(1), Article 558. https://doi.org/10.1007/s44371-026-01003-x

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01003-x

Keywords: Isodon coesta, phytochemistry, GC-MS, antioxidant, molecular docking, ADMET, Uttarakhand, Himalayan medicinal plants, phytol, pregnenolone, squalene, Lamiaceae