The scientific rationale for looking inside plants rather than at them rests on a decades-old insight: endophytes, the fungi and bacteria that colonize plant tissues without causing visible disease, are often the true chemical factories behind a plant’s medicinal reputation. These microorganisms can synthesize bioactive secondary metabolites that help the host defend itself against pathogens, and many of those molecules have proven promising starting points for drug and agrochemical discovery. Medicinal plants, in particular, tend to harbor one or more endophytic fungi capable of producing such compounds. Ginger has a rich ethnopharmacological pedigree, used traditionally across Asia and Africa against ailments ranging from catarrh and rheumatism to asthma and diabetes, and its well-known pungent principles, including gingerols, shogaols, paradols and zingerone, have been extensively studied. Yet the microbes living inside the rhizome remain far less explored, and earlier work has already yielded intriguing metabolites such as epidithiodiketopiperazine, epicorazine A and pretrichodermamide A from fungi associated with ginger.

The urgency of the search is difficult to overstate. According to the World Health Organization, an estimated 263 million malaria cases and 597,000 deaths were recorded globally in 2023, with the African region shouldering roughly 94 percent of cases and 95 percent of deaths. Children under five account for about 76 percent of malaria deaths in that region. More than 400 species of Anopheles are known to affect humans, but only around 30 play a major role in transmitting the Plasmodium parasite, and Anopheles gambiae sits at the top of that short list in Nigeria. Widespread resistance to synthetic insecticides has made vector control increasingly difficult, which is precisely why natural products with larvicidal activity are attracting renewed attention from researchers and public health planners alike.

The journey from farm to molecule began in Kafanchan, in Nigeria’s Kaduna State, where fresh, healthy ginger rhizomes were collected and authenticated at the herbarium of Bayero University Kano, with a voucher specimen deposited for reference. Back in the laboratory, the plant material was washed, surface sterilized through a sequential bath of 70 percent ethanol, 0.5 percent sodium hypochlorite and 96 percent ethanol, then rinsed with sterile distilled water. Small segments of tissue were plated onto potato dextrose agar supplemented with chloramphenicol to suppress bacterial growth and incubated for a week at 27 degrees Celsius. Fungal hyphae were purified by hyphal tipping, and the isolate was identified through colony morphology and microscopic examination of its reproductive structures. The culture showed white to cream colonies with a yellowish-brown reverse, septate antler hyphae, intercalary chlamydospores, and clavate to cylindrical macroconidia with rounded ends, features consistent with an Arthroderma species.

With the fungus in hand, the team turned to fermentation chemistry. Mycelial plugs were inoculated into potato dextrose broth and incubated at room temperature for three weeks, after which the culture was filtered and extracted with ethyl acetate, while the mycelial mat was separately macerated with methanol. The combined organic extract, weighing 15 grams, was purified by column chromatography on silica gel using an escalating polarity gradient from n-hexane through chloroform to ethyl acetate. From the chloroform-ethyl acetate fraction at a 9:1 ratio emerged a brown amorphous solid, coded TC23, which would turn out to be the study’s headline compound. The entire pipeline, from a few grams of rhizome to a purified natural product, illustrates why endophytes are increasingly viewed as a sustainable alternative to harvesting large quantities of plant biomass, a particular advantage for slow-growing medicinal species where land and harvest time impose real constraints.

Characterizing TC23 required a full battery of spectroscopic techniques. Electrospray ionization mass spectrometry in negative mode produced a pseudo-molecular ion at m/z 269.2578, matching the calculated value of 269.2587 for the formula C17H34O2. Carbon-13 NMR revealed seventeen carbon signals, dominated by a carbonyl carbon at 179.15 parts per million downfield, while the DEPT 135 experiment resolved one methyl and fifteen methylene carbons. Proton NMR showed the classic signature of a long saturated fatty acid: a triplet at 0.88 parts per million for the terminal methyl group, a dense multiplet at 1.28 for the methylene bulk, a beta-position multiplet at 1.63, and a triplet at 2.34 for the methylene adjacent to the carbonyl. Two-dimensional experiments, including COSY, HSQC and HMBC, mapped the proton-proton and long-range proton-carbon connectivities along the chain. Infrared spectroscopy sealed the identification, with a broad carboxylic acid O-H stretch spanning 2500 to 3500 inverse centimeters, a strong carbonyl peak at 1707, and C-H stretches at 2920 and 2851. The data matched heptadecanoic acid, or margaric acid, reported in the literature.

The biological results were the most eye-catching part of the study. In a brine shrimp lethality test against larvae of Artemia salina, margaric acid achieved a median lethal concentration of just 3.010 micrograms per milliliter, with mortality rising from 70 percent at 10 micrograms per milliliter to 100 percent at 1000, and no deaths in the solvent control. Under the widely used Meyer’s criteria, extracts with LC50 values below 1000 micrograms per milliliter are considered toxic, placing margaric acid firmly in the highly toxic category. The authors contrasted this with earlier work on endophytic fungi from red ginger, in which isolates resembling Mucor and Trichoderma species were essentially nontoxic to brine shrimp, with LC50 values of 2300 and 1747 micrograms per milliliter respectively, a discrepancy they attribute to differences in fungal species and environmental conditions.

Against the malaria vector itself, the compound performed respectably. Following the World Health Organization’s standard larvicidal testing protocol, third instar larvae of Anopheles gambiae were exposed to concentrations of 1000, 500, 250 and 125 micrograms per milliliter in triplicate. Margaric acid achieved 70 percent mortality at the highest dose after 24 hours and an LC50 of 79.63 micrograms per milliliter. The crude fungal extract actually outperformed the pure compound, with an LC50 of 51.13 micrograms per milliliter and complete mortality at 1000 micrograms per milliliter, hinting at synergistic effects among the extract’s constituents. For context, the synthetic larvicide pylarvex used as a positive control killed 100 percent of larvae at 125 micrograms per milliliter, where margaric acid managed 45 percent. The compound also compared favorably with other natural products: it was more potent than the anthraquinone derivative 13-hydroxyversicolorin B from an endophytic Podospora species, which had an LC50 of 294.5 micrograms per milliliter, and outperformed an Aspergillus extract with an LC50 of 143.88, though it fell short of sterigmatocystin, that study’s most potent metabolite at 13.3 micrograms per milliliter.

The authors are candid about the study’s limitations. Identification of the fungus relied on macroscopic and microscopic morphology, which constrains resolution to roughly the genus level; molecular barcoding would be needed for a definitive species assignment. The mechanism by which margaric acid kills brine shrimp larvae also remains unexplored, leaving open questions about whether the fatty acid disrupts membranes, interferes with molting, or acts through some other pathway. Whether the compound’s high cytotoxicity in the brine shrimp assay would translate to hazards for non-target aquatic organisms, or conversely to useful pharmaceutical activity, will require dedicated follow-up. These caveats are typical of early natural product chemistry, where a single paper establishes identity and preliminary bioactivity while leaving the deeper biology to future work.

Even so, the findings carry a certain viral appeal: a saturated fatty acid, chemically unremarkable at first glance, produced by a fungus hiding inside the world’s most familiar spice, capable of killing the larvae of the mosquito that transmits Africa’s deadliest disease. The authors suggest that margaric acid could serve as a potential biodegradable natural larvicide in mosquito control programs, and that its pronounced cytotoxicity warrants investigation for other bioactivities. As resistance to synthetic insecticides continues to erode conventional vector control, molecules sourced from the endophytic microbiome of medicinal plants offer a renewable and environmentally gentler pipeline. Ginger’s hidden fungus may be only the first of many such discoveries waiting inside the tissues of the world’s medicinal flora.

Subject of Research: Larvicidal and cytotoxic margaric acid isolated from an endophytic fungus of ginger rhizome

Article Title: Isolation and characterization of margaric acid from an endophytic fungus of Zingiber officinale rhizome, its cytotoxicity and larvicidal activity against Anopheles gambiae

Article References: Muhammad, N. A., Muhammad, A. J., Adoum, O. A., Abubakar, S., & Salihu, A. S. (2026). Isolation and characterization of margaric acid from an endophytic fungus of Zingiber officinale rhizome, its cytotoxicity and larvicidal activity against Anopheles gambiae. Discover Chemistry, 3(1), Article 561. https://doi.org/10.1007/s44371-026-01009-5

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01009-5

Keywords: margaric acid, endophytic fungus, Zingiber officinale, Anopheles gambiae, malaria, larvicide, natural products, Arthroderma, brine shrimp lethality, heptadecanoic acid, vector control, NMR characterization