Both the
caps and the
stems contain the psychoactive compounds, although the caps consistently contain more. The
spores of these mushrooms do not contain psilocybin or psilocin.
[36][37][38] The total
potency varies greatly between species and even between specimens of a species collected or grown from the same strain.
[39]Because most psilocybin biosynthesis occurs early in the formation of
fruit bodies or
sclerotia, younger, smaller mushrooms tend to have a higher concentration of the drug than larger, mature mushrooms.
[40] In general, the psilocybin content of mushrooms is quite variable (ranging from almost nothing to 1.5% of the
dry weight)
[41] and depends on species, strain, growth and drying conditions, and mushroom size.
[42] Cultivated mushrooms have less variability in psilocybin content than wild mushrooms.
[43] The drug is more stable in dried than fresh mushrooms; dried mushrooms retain their potency for months or even years,
[44] while mushrooms stored fresh for four weeks contain only traces of the original psilocybin.
[45] The psilocybin contents of dried
herbarium specimens of
Psilocybe semilanceata in one study were shown to decrease with the increasing age of the sample: collections dated 11, 33, or 118 years old contained 0.84%, 0.67%, and 0.014% (all dry weight), respectively.
[46] Mature
mycelia contain some psilocybin, while young mycelia (recently
germinated from spores) lack appreciable amounts.
[47] Many species of mushrooms containing psilocybin also contain lesser amounts of the analog compounds
baeocystin and
norbaeocystin,
[48] chemicals thought to be biogenic
precursors.
[49] Although most species of
psilocybin-containing mushrooms bruise blue when handled or damaged due to the oxidization of phenolic compounds, this reaction is not a definitive method of identification or determining a mushroom's potency.[39][50]
