Editing Psilocybin (section)

===Physical properties===
[[File:Serotonin.svg|class=skin-invert-image|thumb|200px|The neurotransmitter [[serotonin]] is structurally similar to psilocybin.]]

Psilocybin is a naturally occurring [[substituted tryptamine]] that features an [[indole]] ring linked to an [[ethylamine|aminoethyl]] [[substituent]]. It is structurally related to [[serotonin]], a [[monoamine neurotransmitter]] that is a derivative of the [[amino acid]] [[tryptophan]]. Psilocybin is a member of the general class of tryptophan-based compounds that originally functioned as [[antioxidant]]s in earlier life forms before assuming more complex functions in multicellular organisms, including humans.<ref name=Azmitia2010/> Other related indole-containing psychedelic compounds include [[dimethyltryptamine]], found in many plant species and in trace amounts in some mammals, and [[bufotenin]], found in the skin of certain amphibians, especially the [[Colorado River toad]].<ref name = Wurst2002 />{{rp|10–13}}

Psilocybin is a white, crystalline solid that is soluble in water, [[methanol]] and [[ethanol]] but insoluble in nonpolar organic [[solvent]]s such as [[chloroform]] and [[petroleum ether]].<ref name = Wurst2002 />{{rp|15}} It has a [[melting point]] between {{convert|220|and|228|C|F}},<ref name=Merck13th/> and an [[ammonia]]-like taste.<ref name=HSDB/> Its [[pKa]] values are estimated to be 1.3 and 6.5 for the two successive [[phosphate]] [[hydroxy group]]s and 10.4 for the [[dimethylamine]] nitrogen, so it typically exists as a [[zwitterion]]ic structure.<ref name=HSDB/> There are two known crystalline polymorphs of psilocybin, as well as reported [[Water of crystallization|hydrated phases]].<ref>{{cite journal | vauthors = Sherwood AM, Kargbo RB, Kaylo KW, Cozzi NV, Meisenheimer P, Kaduk JA | title = Psilocybin: crystal structure solutions enable phase analysis of prior art and recently patented examples | journal = Acta Crystallographica, Section C | volume = 78 | issue = Pt 1 | pages = 36–55 | date = January 2022 | pmid = 34982048 | pmc = 8725723 | doi = 10.1107/S2053229621013164 | bibcode = 2022AcCrC..78...36S }}</ref> Psilocybin rapidly oxidizes upon exposure to light—an important consideration when using it as an analytical [[standard solution|standard]].<ref name=Anastos2006/>