Baeocystin and norbaeocystin are close relatives of psilocybin that differ by methyl groups on the side-chain nitrogen: norbaeocystin has none, baeocystin has one and psilocybin has two. They are intermediates on the mushroom’s assembly line, where the enzyme PsiM adds those methyl groups one at a time (Hudspeth et al., 2024).
Both names come from Psilocybe baeocystis. Baeocystin was described in 1967 as a “mono-methyl analog of psilocybin” from laboratory cultures of that species (Leung and Paul, 1967), and norbaeocystin was reported with it in 1968 (Leung and Paul, 1968).
What they do in the body is much less clear. In mice, baeocystin did not produce the head-twitch response used as a marker of psychedelic-like activity (Sherwood et al., 2020). A 2025 rat study found that baeocystin and norpsilocin, its likely breakdown product, barely crossed the blood-brain barrier (Danda et al., 2025). No human study has tested them, so the idea that they change a mushroom’s effects is unproven.
Sources
- Leung and Paul, 1968, Journal of Pharmaceutical Sciences: baeocystin and norbaeocystin
- Hudspeth et al., 2024, Nature Communications: PsiM and the pathway order
- Sherwood et al., 2020, Journal of Natural Products: synthesis and testing
- Danda et al., 2025, Progress in Neuro-Psychopharmacology & Biological Psychiatry: baeocystin in rats
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