What is cordycepin? It's a small molecule found in Cordyceps militaris, closely related to adenosine, one of the building blocks of RNA. It's the compound most often named on cordyceps labels and in cordyceps research. But the body breaks it down within minutes, nearly all the research on it comes from cells and animals, and no clinical trial has tested purified cordycepin as a supplement. This guide explains what cordycepin is, where it comes from, what the research shows and what a cordycepin figure on a label does and doesn't tell you.
Cordycepin (3'-deoxyadenosine) was first isolated from Cordyceps militaris cultures in 1950 (Cunningham 1950). It's abundant in cultivated militaris but found only at low levels in wild Ophiocordyceps sinensis, and not detected at all in cultured sinensis (Yang 2009). The fungus makes it together with pentostatin, which protects it from an enzyme called adenosine deaminase (Xia 2017). In the body, that same enzyme breaks cordycepin down quickly, which limits how much reaches the tissues (Chen 2023). Lab and animal studies show anti-inflammatory and anticancer activity (Tan 2020), but human trials have used whole Cordyceps militaris products, not cordycepin alone (Kang 2015, Ontawong 2024). A cordycepin percentage on a label tells you about the product's composition, not how well it works.
What Is Cordycepin, Chemically?
Cordycepin is a nucleoside, the same kind of molecule as adenosine. Adenosine is part of RNA and plays many roles in the body as a signalling molecule. Cordycepin's full chemical name is 3'-deoxyadenosine. It's identical to adenosine except that it lacks one oxygen-containing group at a position on its sugar ring called the 3' carbon.
That small difference matters. Because cordycepin looks so much like adenosine, cells can take it up and try to use it where adenosine belongs. When it's built into a growing RNA chain, the missing group means the chain can't be extended further. This is why cordycepin has interested researchers in cancer and viral infections, where cells or viruses make large amounts of RNA. It also mimics adenosine at some of its receptors and enzymes.
Where Does Cordycepin Come From?
British researchers first isolated cordycepin in 1950 from cultures of Cordyceps militaris (Cunningham 1950). It's sometimes described as "the active compound of Cordyceps sinensis", but that's misleading. When researchers measured nucleosides in different cordyceps samples, they found cordycepin abundant in cultivated Cordyceps militaris, present only at low levels in natural Cordyceps sinensis (now called Ophiocordyceps sinensis) and undetectable in cultured sinensis (Yang 2009).
So if cordycepin is what you're interested in, militaris is the relevant species. Our comparison of Cordyceps militaris vs sinensis covers the other differences between the two.
Why Does the Fungus Make Pentostatin Too?
A 2017 study found that Cordyceps militaris makes cordycepin and another adenosine-like molecule, pentostatin, from a single cluster of genes (Xia 2017). Pentostatin blocks adenosine deaminase, the enzyme that would otherwise break cordycepin down. In effect, the fungus produces its own bodyguard for cordycepin. When cordycepin reaches levels that are toxic to the fungus itself, the protection is lifted and the excess is broken down into an inactive form.
Pentostatin is also a prescription chemotherapy drug, originally isolated from a bacterium. The amounts in cordyceps products are not usually measured or listed. This doesn't mean cordyceps supplements are dangerous, but it's a reminder that militaris contains more than one biologically active nucleoside.
What Happens to Cordycepin in the Body?
Adenosine deaminase is plentiful in human blood and tissues. It converts cordycepin into 3'-deoxyinosine, which is far less active. A review of cordycepin's pharmacology describes this rapid breakdown as the main obstacle to its use: it shortens cordycepin's half-life and reduces how much reaches the tissues (Chen 2023).
Researchers have tried three ways around this: giving cordycepin together with an adenosine deaminase inhibitor, changing its structure to make it more stable, and packaging it in new delivery systems such as nanoparticles (Chen 2023). None of these is a supplement you can buy. They're drug-development strategies.
For a cordyceps supplement, this means you can't assume that the cordycepin in a capsule arrives intact in your tissues. Whether the small amounts in whole-mushroom products have any effect on their own is unknown.
What Does the Research Show?
Cell and animal studies. Most cordycepin research is in the lab. A review of its anti-inflammatory effects describes protective effects in animal and cell models of lung injury, asthma, arthritis, liver inflammation, atherosclerosis and skin inflammation, acting through several inflammatory signalling pathways (Tan 2020). Other work has looked at effects on cancer cells and on viral RNA. These are early-stage findings and often use concentrations that are hard to reach by mouth.
Human trials. No published clinical trial has tested purified cordycepin as a supplement. Human trials have tested whole Cordyceps militaris products. In a Korean trial of 79 healthy men, 1.5 g a day of militaris for four weeks increased natural killer cell activity and lymphocyte proliferation compared with placebo (Kang 2015). A small Thai trial gave 40 healthy adults a fermented militaris drink providing 2.85 mg of cordycepin a day for eight weeks and found increases in natural killer cell activity (Ontawong 2024).
These trials show that militaris products can change immune markers. They can't show how much of that comes from cordycepin, because the products also contain polysaccharides, adenosine, other nucleosides and more. Our article on Cordyceps militaris and immunity covers the immune trials in more detail.
What Doesn't the Research Show?
Cordycepin is often marketed with claims about energy, stamina, hormones or sexual function. Those claims aren't supported by human research on cordycepin. Our article on cordyceps and libido explains why animal results in this area don't transfer to people, and our cordyceps benefits overview covers the evidence for militaris more broadly.
Similarly, the anticancer research is lab research. Our article on the antitumour effects of Cordyceps militaris explains what those studies did. If you have cancer, don't use cordyceps or cordycepin in place of treatment, and tell your oncology team about any supplement.
What Does a Cordycepin Figure on a Label Mean?
Some products state their cordycepin content, often as a percentage or in milligrams. That can be useful as a marker that the product really is Cordyceps militaris, since sinensis-type and mycelium products contain little. Keep these points in mind:
- Check the method. A figure measured by HPLC, a standard lab method, is more reliable than an unspecified claim. Ask for a certificate of analysis. Our guide on how to read a certificate of analysis explains what to look for.
- More isn't proven better. No trial has compared different cordycepin levels for any health outcome.
- It's one compound among many. Polysaccharides, other nucleosides and other compounds also differ between products.
Our Cordyceps militaris capsules contain a 10:1 dual extract of the fruiting body. Our guide on how to read a mushroom supplement label covers the other details worth checking.
Is Cordycepin Safe?
Cordyceps militaris products were well tolerated in the human trials above. The Korean trial reported no significant adverse reactions (Kang 2015), and the Thai trial found no signs of liver, kidney or blood toxicity (Ontawong 2024). Purified cordycepin is a different matter: it's a drug-like nucleoside that acts on RNA, and it hasn't been tested for long-term safety as a supplement. Practical cautions:
- Avoid cordyceps products during pregnancy and breastfeeding, as there's no safety data.
- Ask your doctor first if you take immunosuppressants, blood thinners or diabetes medicines, or if you have an autoimmune condition.
- Don't use purified cordycepin powders sold as research chemicals.
- Stop if you notice stomach upset, rash or unusual bleeding.
Our cordyceps dosage guide covers typical amounts of whole militaris products.
Frequently Asked Questions
What is cordycepin?
A nucleoside found mainly in Cordyceps militaris. It's 3'-deoxyadenosine, a near copy of adenosine that lacks one chemical group, which lets it interfere with RNA production in cells.
Does Cordyceps sinensis contain cordycepin?
Only at low levels in wild material, and it wasn't detected in cultured sinensis in one analysis. Cultivated Cordyceps militaris is the main source.
How much cordycepin should I take?
No effective or safe dose of purified cordycepin has been established in people. Human trials used whole Cordyceps militaris products, such as 1.5 g a day of mushroom or a drink providing 2.85 mg of cordycepin a day.
Is cordycepin absorbed well?
Not very. The enzyme adenosine deaminase breaks it down quickly in the body, which shortens its half-life and limits how much reaches the tissues.
Is a higher cordycepin content better?
It hasn't been shown to be. Cordycepin content is a useful identity marker for militaris, but no trial has linked higher levels to better results.
Related Articles
- Cordyceps Militaris vs Sinensis
- Cordyceps Militaris and Immunity
- Cordyceps Dosage Guide
- Cordyceps Benefits
- How to Read a Certificate of Analysis
Sources
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- Yang FQ, Ge L, Yong JW, Tan SN, Li SP. Determination of nucleosides and nucleobases in different species of Cordyceps by capillary electrophoresis-mass spectrometry. J Pharm Biomed Anal. 2009;50(3):307-314. PubMed 19497699
- Xia Y, Luo F, Shang Y, et al. Fungal cordycepin biosynthesis is coupled with the production of the safeguard molecule pentostatin. Cell Chem Biol. 2017;24(12):1479-1489. PubMed 29056419
- Chen M, Luo J, Jiang W, et al. Cordycepin: a review of strategies to improve the bioavailability and efficacy. Phytother Res. 2023;37(9):3839-3858. PubMed 37329165
- Tan L, Song X, Ren Y, et al. Anti-inflammatory effects of cordycepin: a review. Phytother Res. Published online 2020. PubMed 33090621
- Kang HJ, Baik HW, Kim SJ, et al. Cordyceps militaris enhances cell-mediated immunity in healthy Korean men. J Med Food. 2015;18(10):1164-1172. PubMed 26284906
- Ontawong A, Pengnet S, Thim-Uam A, et al. A randomized controlled clinical trial examining the effects of Cordyceps militaris beverage on the immune response in healthy adults. Sci Rep. 2024;14(1):7994. PubMed 38580687