Tetrahydrocannabinolic acid (THCA, Δ9-THCA, 2-COOH-THC; conjugate base tetrahydrocannabinolate) is a biosynthetic precursor of tetrahydrocannabinol (THC), the active component of cannabis. When purified, it forms a crystal which is unstable in the presence of acids, heat, oxygen, and/or light.
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 or cooked into cannabis edibles.
Tetrahydrocannabinolic acid Wikipedia
THCA does not have any known psychoactive effects on humans in its own right. It does have antiinflammatory, neuroprotective, antiemetic (anti-vomitting) and anti-prostate cancer effects. It inhibits COX-1 and COX-2 enzymes involved in inflammation in human colon cell cultures. It has also been shown to decrease the amount of oxidative stress caused by impairment of mitochondria which is a major mechanism in neural degeneration in mouse mesencephalic cell cultures.
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.
THCA is 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.
THCA is not scheduled by the United Nations' Convention on Psychotropic Substances.
THCA is not scheduled at the federal level in the United States, but it is possible that THCA could legally be considered an analog of THC and sales or possession could potentially be prosecuted under the Federal Analogue Act.
There is also a practical legal issue of potential THC contamination of THCA which should be considered. As mentioned above, THCA decarboxylates to form THC, a Schedule I controlled substance. As such it is somewhat unlikely that any sample of THCA which may be analytically tested will not contain a quantifiable amount of THC, especially if the sampled product was retained at temperatures conducive to decarboxylation. This makes it possible that possession of THCA might lead to prosecution for possession of THC due to the presence of THC breakdown products in bulk THCA.