The research was born of necessity. Temminck’s pangolin (Smutsia temminckii) is classified as Vulnerable by the International Union for Conservation of Nature, and its populations have declined drastically across its range due to poaching for illegal wildlife and traditional medicine trades, habitat loss, electric fences, and overexploitation. Individuals rescued from traffickers often arrive at rehabilitation facilities in poor condition and require extended care before they can be released. Yet the species is notoriously stress-prone, and ethical, logistical, and conservation constraints make it impossible to capture, hold, or conduct experimental manipulations on pangolins purely for research purposes. Traditional physiological validation, which involves administering a compound such as adrenocorticotropic hormone to artificially activate the stress axis, was therefore off the table.

To understand why this matters, it helps to look at how stress hormones work. The physiological stress response involves two main systems: the sympathetic nervous system, which triggers the familiar ‘fight or flight’ release of catecholamines, and the hypothalamic–pituitary–adrenal (HPA) axis, which drives the secretion of glucocorticoid steroid hormones. An acute rise in glucocorticoids is adaptive, mobilising energy, enhancing cardiovascular activity, and shifting behaviour to restore homeostasis. But chronic elevation carries serious costs, including immune and reproductive suppression and a general decline in fitness. Researchers therefore track glucocorticoid concentrations as a proxy for the stress an individual experiences and its likely consequences for survival and reproduction.

Blood sampling, the traditional route for hormone monitoring, is particularly problematic for pangolins. Capturing and restraining an animal to draw blood activates the very stress response researchers want to measure, with blood glucocorticoids rising significantly within three to five minutes of capture. Repeated collections are impractical for small-bodied species with limited blood volumes, and serum or plasma hormone levels fluctuate with pulsatile secretion patterns, circadian rhythms, and feeding state. For threatened species, invasive endocrine monitoring has fallen out of favour across much of the research community.

Non-invasive monitoring sidesteps these problems. Once steroid hormones are secreted into the bloodstream by the HPA axis, the liver metabolises them and excretes them in bile and faeces. Because metabolites pool in the gut, faecal glucocorticoid metabolite (fGCM) concentrations provide a smoother, longer-term signal spanning several hours, rather than a snapshot distorted by episodic hormone pulses. Collecting faeces requires no direct human–animal interaction, eliminates stress-related feedback from handling, and allows repeated longitudinal sampling from small-bodied species. But there is a catch: hormone metabolism and excretion are sex- and species-specific, so any EIA must be validated in each species before its results can be trusted.

The team, led by Juan Scheun of the BioPulse Research Group at Tshwane University of Technology, together with colleagues from the South African National Biodiversity Institute, Tshwane University of Technology, and the Mammal Research Institute at the University of Pretoria, turned to biological validation. They opportunistically collected 28 faecal samples from five Temminck’s pangolins—three females and two males—confiscated from the illegal wildlife trade and admitted to the Johannesburg Wildlife Veterinary Hospital during 2020 and 2021. Samples were gathered before and after known stressors such as confiscation, veterinary handling, and transport, with samples collected during periods of no handling serving as baselines. For security reasons, the animals were housed at an undisclosed off-site location, and the hospital’s welfare policies meant no strict sampling regime could be imposed; staff simply collected fresh faeces whenever animals defecated, sometimes days apart.

In the laboratory, frozen samples were lyophilised, pulverised, and sieved, then extracted with 80% ethanol and analysed at the Endocrine Research Laboratory of the University of Pretoria using five different EIAs: a cortisol assay, a corticosterone assay, two 11-oxoaetiocholanolone assays (designated 72a and 72T), and a 5α-pregnane-3ß,11ß,21-triol-20-one assay (37e). Serial dilutions produced displacement curves parallel to the standard curves in all assays, confirming analytical validity. The researchers then applied a stringent criterion: an assay was considered reliable only if it detected peak fGCM increases exceeding 150% above baseline, a tougher threshold than the 100% often used in comparable studies, to reduce the risk of false positives.

The results were striking. In female 1, the 72a assay recorded a 982% increase in fGCM concentrations following a stressful event, with 72T close behind at 763%, followed by the cortisol assay at 481% and 37e at 317%. Female 2 showed increases above the 150% threshold for 37e (325%), 72T (221%), and 72a (201%), and her secondary fGCM rise coincided with a move to a holding facility ahead of release. Female 3 exceeded the threshold on both 72a (339%) and 72T (251%). Among the males, only 72a detected increases above 150% in both individuals, reaching 168% in male 1 and 695% in male 2, where the cortisol assay also responded strongly at 437%. Notably, in female 2, fGCM levels rose considerably before a decline in health that led to her readmission to the rehabilitation centre, hinting that hormone monitoring might one day flag deteriorating welfare before clinical signs appear.

The standout performer was the 72a assay, the only one to exceed the 150% threshold in every study animal of both sexes, making it the recommended tool for monitoring fGCM levels in Temminck’s pangolin. The 72T assay proved a strong alternative for females, while 37e, which exceeded 100% increases in all females, can serve as a back-up when the primary assays are unavailable. The cortisol assay should be treated as equivocal pending further validation. Interestingly, the finding that cortisol metabolites dominated the faecal profile contrasts with work on the Taiwanese pangolin, where mass spectrometry revealed higher faecal corticosterone concentrations, though that study measured actual hormones rather than immunoreactive metabolites, and the authors suggest mass spectrometry could further clarify active circulating glucocorticoids in Temminck’s pangolin.

Beyond the assay validation itself, the study delivers an uncomfortable but important message: direct human interaction, even in the context of care and rehabilitation, elicits pronounced physiological stress responses in pangolins, with increases exceeding 100% across all study animals. Similar patterns have been documented in rehabilitated African penguins and koalas. The findings argue for refining rehabilitation protocols to minimise human contact and for assessing individuals physiologically before release to improve survival odds. The authors caution that the small sample size limits generalisability, that excretion time lags could not be determined for the species—gut passage times in other pangolins range from roughly 20 to 60 hours—and that individual variation in stress perception likely shapes adrenal responses. Even so, the validated 72a EIA now offers researchers, conservationists, and rehabilitation managers a way to track stress in captive settings and, crucially, in free-ranging populations, where pressures such as climate change are expected to intensify. For an animal that rolls into an armour-plated ball when threatened, the ability to read its stress from a dropping may prove one of the most powerful conservation tools yet devised.

Subject of Research: Biological validation of non-invasive faecal glucocorticoid metabolite enzyme immunoassays for measuring physiological stress in rehabilitated Temminck's pangolins

Article Title: Biological validation of enzyme immunoassays for measuring physiological stress in rehabilitated Temminck’s pangolins

Article References: Scheun, J., Labuschagne, K., Jansen, R., Ganswindt, A., & Long, C. (2026). Biological validation of enzyme immunoassays for measuring physiological stress in rehabilitated Temminck’s pangolins. Discover Conservation, 3(1), Article 20. https://doi.org/10.1007/s44353-026-00090-2

Image Credits: AI Generated

DOI: 10.1007/s44353-026-00090-2

Keywords: Temminck's pangolin, faecal glucocorticoid metabolites, enzyme immunoassay, stress physiology, wildlife rehabilitation, non-invasive hormone monitoring, conservation, HPA axis, animal welfare, illegal wildlife trade, biological validation, South Africa

The research, led by Ibrahim Selvikaya and Abdurrahim Yilmaz at Bolu Abant Izzet Baysal University in Türkiye, together with colleagues at Atatürk University, Kocaeli University, Igdir University, and Recep Tayyip Erdogan University, set out to test whether foliar nano-micronutrition could fortify basil (Ocimum basilicum L.) against water deficit. The team chose a greenhouse factorial design that crossed two irrigation regimes—full watering at 100 percent field capacity and severe deficit at 50 percent field capacity—with four foliar treatments: an untreated control, zinc oxide nanoparticles at 100 milligrams per liter, iron oxide nanoparticles at 100 milligrams per liter, and a combined zinc-plus-iron spray delivering 50 plus 50 milligrams per liter. These doses were deliberately selected to reflect concentrations that could plausibly be applied in the field rather than the exaggerated levels sometimes used in laboratory proofs of concept.

A defining feature of the work is the green synthesis route. Instead of relying on synthetic reducing and stabilizing agents, the researchers used an aqueous extract of common sage (Salvia officinalis) to convert metal salt precursors into zinc oxide and iron oxide nanoparticles. Plant extracts are rich in polyphenols, flavonoids, and other biomolecules that can both reduce metal ions and cap the growing particles, making the process cleaner, cheaper, and more compatible with sustainable agriculture. The resulting nanoparticles were characterized using scanning electron microscopy paired with energy dispersive X-ray spectroscopy, which confirmed particle morphology and elemental composition, ensuring that what reached the basil leaves were genuine nano-scale zinc and iron oxide materials rather than aggregated bulk powders.

The growth results were unambiguous. Under the 50 percent field capacity regime, untreated basil plants suffered the expected stunting and tissue loss, but nanoparticle supplementation substantially mitigated the damage. Compared with drought-stressed controls, nanoparticle-treated plants grew up to 26.7 percent taller, produced 30.6 percent more leaves, and accumulated 22.6 percent more biomass. Those are not marginal effects; they represent a meaningful recovery of canopy and yield potential in plants enduring nearly half their normal water allocation. For a high-value herb marketed on leaf quality and aromatic intensity, preserving leaf number and biomass under deficit irrigation has direct agronomic and economic significance.

Beneath the visible growth rescue lies a detailed biochemical story about reactive oxygen species. When stomata close to conserve water, photosynthetic electron transport becomes unbalanced and chloroplasts, mitochondria, and peroxisomes leak electrons onto oxygen, generating superoxide radicals and hydrogen peroxide. Left unchecked, these molecules attack membranes and produce malondialdehyde, a canonical marker of lipid peroxidation. In the nanoparticle-treated drought plants, the oxidative burden dropped dramatically: malondialdehyde and hydrogen peroxide levels each fell by nearly 50 percent relative to untreated drought controls, evidence that the sprays had re-equilibrated the plant’s redox state rather than merely masking stress symptoms.

The mechanism behind that protection differed between the two metals, and this is where the study makes its most interesting contribution. Zinc primarily strengthened the non-enzymatic antioxidant arm of the defense system. Zn-treated plants showed a 135 percent increase in cupric reducing antioxidant capacity, a 48 percent increase in ferric reducing antioxidant power, and a 17 percent increase in DPPH radical-scavenging activity compared with drought controls. These assays collectively indicate an expanded pool of small-molecule antioxidants—phenolics, flavonoids, and related compounds—that can chemically neutralize radicals before they damage cells. Consistent with that, the combined zinc-plus-iron treatment lifted total phenolic content by 53 percent and flavonoid content by 48 percent, effectively arming basil with a denser chemical shield.

Iron, by contrast, emerged as the enzyme specialist. Fe-treated plants recorded a 27 percent increase in superoxide dismutase activity, the front-line enzyme that dismutates superoxide radicals into hydrogen peroxide. Meanwhile, the combined treatment produced the most dramatic enzymatic activation of all: catalase activity surged by 204 percent and ascorbate peroxidase by 86 percent relative to drought controls. Catalase and ascorbate peroxidase are precisely the enzymes responsible for detoxifying the hydrogen peroxide that superoxide dismutase generates, so the combined spray appears to have coordinated a complete detoxification pipeline—converting dangerous radicals into hydrogen peroxide and then efficiently splitting that peroxide into water and oxygen. The two nutrients thus act on complementary arms of the antioxidant system rather than redundantly.

Statistical analysis reinforced this interpretation. Correlation analysis revealed strong positive associations among antioxidant capacity, photosynthetic pigment levels, and growth traits, suggesting that plants with the most robust redox buffering also preserved their chlorophyll and built the most biomass. Principal component analysis separated the treatment groups in multivariate space, with zinc-plus-iron-treated plants clustering distinctly within an antioxidant-rich, high-biomass region. That clustering pattern is the statistical fingerprint of coordinated redox regulation: rather than a scattered collection of independent biochemical changes, the nanoparticle treatments triggered an integrated physiological program linking pigment stability, antioxidant mobilization, and growth maintenance.

The practical implications extend beyond basil. Zinc and iron are essential plant micronutrients whose deficiency is widespread in agricultural soils worldwide, and foliar delivery of them as nanoparticles offers dual benefits: correcting micronutrient nutrition and priming stress defenses in a single intervention. The green synthesis route adds another layer of appeal, since sage extract is inexpensive, non-toxic, and readily available, and the process avoids the hazardous solvents associated with conventional nanomaterial manufacture. The concentrations tested—100 milligrams per liter for single-metal sprays and a 50 plus 50 split for the combination—are within ranges already considered field-applicable, which lowers the barrier to eventual on-farm trials.

Caveats remain, as the authors themselves frame the work as greenhouse-scale evidence rather than a finished field prescription. Open questions include how nanoparticle sprays behave under open-field UV and rainfall, how repeated applications affect soil microbial communities, whether nanoparticles accumulate in the harvested leaves and at what levels, and how the treatment interacts with the essential oil profile that gives basil its market value. Nonetheless, the study provides rigorous physiological and biochemical evidence that nanoparticle-mediated modulation of stress responses is real, measurable, and mechanistically coherent. As droughts deepen and water for irrigation grows scarcer, the idea that a few milligrams of sage-made zinc and iron, misted onto leaves, can cut a plant’s oxidative damage in half while boosting its antioxidant machinery by double digits is precisely the kind of elegant, testable solution that modern stress physiology has been looking for—and it suggests that the future of drought resilience may be not only in the genome, but in a spray bottle.

Subject of Research: Green-synthesized zinc and iron oxide nanoparticles enhancing drought tolerance in basil through antioxidant regulation

Article Title: Green-synthesized zinc and iron nanoparticles enhance basil drought tolerance via antioxidant regulation

Article References: Selvikaya, I., Karataş, R., Karakuş, M., Yilmaz, H., Demirel, F., Güler, E., Tutar, Y., & Yilmaz, A. (2026). Green-synthesized zinc and iron nanoparticles enhance basil drought tolerance via antioxidant regulation. BMC Plant Biology. https://doi.org/10.1186/s12870-026-09935-3

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09935-3

Keywords: basil, drought stress, green synthesis, zinc oxide nanoparticles, iron oxide nanoparticles, antioxidant defense, catalase, superoxide dismutase, foliar application, Ocimum basilicum, redox regulation, stress physiology