Tetrahydrocannabinolic acid (THCA, 2-COOH-THC), is a biosynthetic precursor of tetrahydrocannabinol (THC), the active component of Cannabis. THCA is found in variable quantities in fresh, undried cannabis, but is progressively decarboxylated to THC with drying, and especially under intense heating such as when cannabis is smoked. While THCA does not have psychoactive effects in its own right, it does have antiinflammatory and neuroprotective effects. Despite the ready decarboxylation by drying or heating ex vivo, conversion of THCA to THC in vivo appears to be very limited, giving it only very slight efficacy as a prodrug for THC. Consequently it is believed to be important in less-psychoactive preparations of cannabis used for medical use, such as cannabis tea. It is also commonly used as a biomarker in drug testing along with THCV, to distinguish between prescribed synthetic Delta-9-tetrahydrocannabinol, such as Marinol, and cannabis plant material which may also be used by patients.
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