THCA

THCA (Δ⁹-tetrahydrocannabinolic acid A, C₂₂H₃₀O₄, MW 358.47) is the non-intoxicating carboxylic acid precursor of Δ⁹-THC and the dominant THC-family molecule in the living plant. It is biosynthesized in glandular trichomes from CBGA by THCA synthase (THCAS), an FAD-dependent oxidocyclase (Sirikantaramas et al., 2004, Journal of Biological Chemistry 279:39767). THCA binds CB1 poorly because the carboxyl group prevents the orientation required for receptor activation; it therefore does not produce a Δ⁹-THC-like intoxication (Rosenthaler et al., 2014, Neurotoxicology and Teratology 46:49). Decarboxylation — loss of CO₂ on heating above ~105 °C — converts THCA to Δ⁹-THC. Preclinical data suggest anti-inflammatory, neuroprotective, and antiproliferative activity at PPARγ and other targets (Moreno-Sanz, 2016, Cannabis and Cannabinoid Research 1:124). Evidence level: in vitro and rodent only. → See also: Decarboxylation, CBGA, THC.