Thionin
A cysteine-rich plant defence peptide family that disrupts microbial membranes — with metal-binding and anticancer activity in the lab. Research compounds, not drugs
Thionins are among the first antimicrobial peptides ever described: small, cysteine-rich peptides found in wheat, barley, rice and pepper plants, where they help defend against fungi and bacteria. Only about forty-five amino acids long, each is pinned into a compact, amphipathic shape by three or four disulfide bonds; the gamma-thionin subgroup is so like the plant defensins that the two families overlap. Thionins work mainly by binding and breaking microbial membranes, which gives them broad antifungal and antibacterial activity, and research has uncovered other sides to them: some bind toxic metals, some block the blood-vessel-growth signal that tumours rely on, and some push cancer cells toward death while sparing normal cells. Thionins are research peptides and transgenic-plant tools; they are not approved medicines and have not been given to people as an approved treatment.
No established human dose Details ↓
Recommended Dosing
No established human dose
Thionins are plant research peptides and plant-engineering tools; no thionin is an approved treatment. The work here is in plants, cultured cells and microbes at experimental amounts that do not carry over to people, so no amount is printed here.
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What is it?
Plants defend themselves with antimicrobial peptides just as animals do, and the thionins are among the oldest known — first isolated from wheat in the 1940s as 'purothionin'. They are small, only about forty-five to forty-eight amino acids, and unusually rich in cysteine: three or four disulfide bonds pin each peptide into a compact, amphipathic fold. The best-studied subgroup, the gamma-thionins, resemble the plant defensins so closely that the two families are often discussed together. Thionins turn up across cereal and vegetable crops — wheat, barley, rice and pepper among them.
Their core job is antimicrobial. A thionin binds the surface of a microbial membrane and disrupts it, inserting into the phospholipid layer and breaking the cell's barrier. In transgenic trees engineered to make thionins, the peptides bound and disrupted the membranes of attacking fungi, giving the plants resistance to Fusarium and Aspergillus; and a thionin from the mould Aspergillus giganteus, together with the proteins sarcin and chitinase, damaged the spores and membranes of the human fungal pathogen Aspergillus fumigatus, pointing to antifungal potential.
Research has found thionins doing more than killing microbes. A rice thionin sits in the cell wall and binds cadmium, and plants engineered to make more of it carried markedly less of the toxic metal in their grain without losing yield — a route to safer crops. A gamma-thionin from the habanero chile blocked the blood-vessel-growth signal (VEGF) that endothelial cells and tumours depend on, acting as an anti-angiogenic modulator, and the same peptide pushed human chronic-myeloid-leukemia cells toward a calpain-driven, caspase-independent form of cell death while leaving normal blood cells alone.
The family is also woven into the plant's wider biology. A genome-wide survey of rice found dozens of thionin-family genes, and one of them is switched on by drought and by the stress hormone ABA and is needed for the plant to withstand dry conditions — widening the thionins' role well beyond immunity into stress tolerance.
Through all of this, thionins remain research peptides and plant-engineering tools. No thionin is an approved medicine, and material sold online under this name is an unregulated research chemical. Nothing here is a dose or a therapy; this page records what the published science says.
Mechanism of Action
Thionins are small (~45-48 aa) cysteine-rich plant antimicrobial peptides, stabilised by 3-4 disulfide bonds into an amphipathic fold (gamma-thionins resemble plant defensins), that bind and disrupt the membranes of fungi and bacteria. Some also bind toxic metals, block the VEGF blood-vessel-growth signal and push cancer cells toward death.
Plant host defense
A small cysteine-rich peptide stabilised by 3-4 disulfide bonds, from wheat, barley, rice and pepper; the gamma-thionin subgroup overlaps with plant defensins (PMIDs 37054894, 40244412).
Membrane disruption
Binds and breaks the membranes of fungi and bacteria, giving broad antifungal and antibacterial activity (PMIDs 38701959, 35924795).
Metal binding and anticancer activity
Some thionins bind toxic metals such as cadmium, block the VEGF blood-vessel signal, and push cancer cells toward death while sparing normal cells (PMIDs 37218180, 37175071, 37054894).
Published Research
These are studies of thionins read from their PubMed records on November 8, 2026: transgenic trees making thionins resisting fungal infection; a gamma-thionin pushing leukemia cells toward death; a gamma-thionin blocking the endothelial VEGF response; a rice thionin reducing cadmium in grain; a thionin damaging a human fungal pathogen; and a genome-wide survey of the rice thionin family under drought stress. The evidence is in plants, cells and microbes; no thionin is an approved treatment.
Transgenic trees making thionins resist fungal infection
Thionins expressed in transgenic Paulownia trees bound and disrupted the membranes of attacking fungi, delivered with chitosan nanoparticles, giving the trees enhanced resistance to Fusarium and Aspergillus infections (a plant study).
A chile gamma-thionin pushes leukemia cells toward death
A gamma-thionin from the habanero chile drove human chronic-myeloid-leukemia cells into a calpain-mediated, caspase-independent form of cell death and altered their epigenetic marks, while sparing normal blood cells (an in-vitro study).
Gamma-thionin blocks the endothelial VEGF response
The plant peptides PaDef and gamma-thionin blocked VEGF-stimulated proliferation and migration of endothelial cells through a low-oxygen-independent pathway, acting as anti-angiogenic modulators (an in-vitro study).
A rice thionin cuts cadmium in grain
The cell-wall rice thionin OsThi9 binds cadmium; plants engineered to make more of it carried sharply less cadmium in their brown rice grain without losing yield, a route to safer crops (a plant study).
Thionin damages a human fungal pathogen
Thionin, together with sarcin and chitinase from the mould Aspergillus giganteus, damaged the spores and membranes of the human fungal pathogen Aspergillus fumigatus, showing druggable antifungal potential (a pathogen-challenge study).
The rice thionin family under drought stress
A genome-wide survey identified dozens of rice thionin-family genes; one (OsTHION15) is switched on by drought and the stress hormone ABA and is needed for drought resistance, broadening the thionins' role beyond immunity (a genome-wide survey).
No Established Human Dose
Thionins are plant research peptides and plant-engineering tools; no thionin is an approved treatment. The work here is in plants, cultured cells and microbes at experimental amounts that do not carry over to people, so no amount is printed here.
What this rests on: PMID 38701959, PMID 37175071, PMID 35924795.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Thionin is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Thionin has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Thionin, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Thionin stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Thionin. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
How long it stays in the body: a half-life of not established for humans; disulfide-stabilised and relatively stable. After about five half-lives almost none is left.
When effects appear: unknown; no source on this page gives a time to effect for Thionin. Results reported in the studies are under Published Research.
Source: half-life: PMID 40244412.
Side effects, and when to stop or get help
From the Side Effects section: No approved-treatment human safety data exist for thionins; Thionins disrupt membranes and some are toxic to cells at active concentrations, which is being explored deliberately against cancer cells (PMID 37175071) — research findings, not approved-drug data; Some thionins bind toxic metals and modulate blood-vessel growth (PMIDs 37218180, 37054894), effects to weigh in any development; Material sold online as 'thionin' is an unregulated research chemical of unverified content. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Thionin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“Thionins are research peptides and no thionin is an approved treatment, so there is no established human safety profile; the points below reflect that status and their biology”).
Interactions
Unknown: a PubMed search for human interaction studies of Thionin (reviewed 2026-11-08) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Thionin products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not approved drugs: Drugs@FDA and the openFDA label endpoint hold no record, and FDA GSRS and ChEMBL hold no approved-drug record for thionin (searched November 8, 2026)). Sport: Not on the 2026 List.
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
Thionins are research peptides and no thionin is an approved treatment, so there is no established human safety profile; the points below reflect that status and their biology.
Contraindications & Cautions
Thionins have no approved use and no label. These points reflect their research status.
Legal Status
Thionins are plant antimicrobial peptides used as research compounds; they are not approved drugs in any country.
Frequently Asked Questions
?What is thionin?
A family of small, cysteine-rich plant antimicrobial peptides, first isolated from wheat in the 1940s. Each is about 45-48 amino acids, held by three or four disulfide bonds; the gamma-thionin subgroup resembles the plant defensins (PMID 37054894).
?How does it work?
Mainly by binding and disrupting the membranes of fungi and bacteria, giving broad antimicrobial activity; some thionins also bind toxic metals, block the VEGF blood-vessel signal and push cancer cells toward death (PMIDs 38701959, 37175071).
?Is it approved or available to buy?
No. Thionins are not approved medicines, have no FDA application or label, and are approved nowhere. Material sold online as a thionin is an unregulated research chemical. Grey Peptides lists no sellers and recommends no source; this page records the published science.
References
- [mechanism] Bouqellah NA, et al. "Development of transgenic Paulownia trees expressing antimicrobial thionin genes for enhanced resistance to fungal infections using chitosan nanoparticles." Microb Pathog, 2024;191:106659. PMID: 38701959.
- [mechanism] Flores-Alvarez LJ, et al. "The Antimicrobial Peptide γ-Thionin from Habanero Chile (Capsicum chinense) Induces Caspase-Independent Apoptosis on Human K562 Chronic Myeloid Leukemia Cells and Regulates Epigenetic Marks." Molecules, 2023;28(9). PMID: 37175071.
- [mechanism] Falcón-Ruiz EA, et al. "The plant defensins PaDef and γ-thionin inhibit the endothelial cell response to VEGF." Peptides, 2023;165:171008. PMID: 37054894.
- [mechanism] Liu X, et al. "Plant Defensin-Dissimilar Thionin OsThi9 Alleviates Cadmium Toxicity in Rice Plants and Reduces Cadmium Accumulation in Rice Grains." J Agric Food Chem, 2023;71(22):8367-8380. PMID: 37218180.
- [animal] Ravindhiran R, et al. "Pharmacokinetic profile of sarcin and thionin from Aspergillus giganteus and in vitro validation against human fungal pathogen." Biosci Rep, 2022;42(9). PMID: 35924795.
- [review] Yan M, et al. "Genome-Wide Identification and Expression Analysis of Thionin Family in Rice (Oryza sativa) and Functional Characterization of OsTHION15 in Drought Stress and ABA Stress." Int J Mol Sci, 2025;26(7). PMID: 40244412.
- [other] Thionins are small cysteine-rich plant antimicrobial peptides, first isolated as 'purothionin' from wheat endosperm by Balls, Hale and Harris (1942). Their structure, antimicrobial mechanism and other activities are described in the studies carded on this page (read November 8, 2026).
- [other] US FDA, Drugs@FDA and the openFDA label endpoint, searched November 8, 2026: no application and no label record for thionin. It is a plant research peptide family, not an approved drug; FDA GSRS and ChEMBL hold no approved-drug record for it.
Sources & Citations
The six studies carded above were read from their PubMed records on November 8, 2026. Thionins' plant origin, their small cysteine-rich disulfide-stabilised structure (and the gamma-thionin overlap with plant defensins), their membrane-disrupting antimicrobial mechanism, and their metal-binding, anti-angiogenic and anticancer activities are from the studies carded here; the family was first isolated as purothionin from wheat by Balls, Hale and Harris (1942). The absence of US approval or a drug record from Drugs@FDA, openFDA, FDA GSRS and ChEMBL was checked the same day. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.