Tetrahydrocannabinolic acid (THCA, 2-COOH-THC; conjugate base tetrahydrocannabinolate) is a precursor of tetrahydrocannabinol (THC), an 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 or cooked into cannabis edibles. THCA is often the majority constituent in cannabis resin concentrates, such as hashish and hash oil, when prepared from high-THC cannabis fresh plant material, frequently comprising between 50% and 90% by weight. Uses THCA is rarely directly used, but its presence is commonly analyzed when cannabis or hemp-based products are screened for THC; some countries require that it be measured in such screens. THCA in its isolated form is available for purchase in select medical and recreational cannabis dispensaries in the form of a white crystalline powder. It can be smoked or vaporized in typical smoking devices, such as a bong or dab rig (device used for vaporizing hash oil). These methods convert the THCA to THC and so are used for their psychoactive benefits. THCA is also sometimes encapsulated and taken as a supplement for a variety of illnesses, although there are currently no established medical applications. Pharmacological effects Conversion of THCA to THC in vivo appears to be very limited, giving it only very slight efficacy as a prodrug for THC. In receptor binding assays it is promiscuous; there are papers showing it being an inhibitor of PC-PLC, COX-1, COX-2, TRPM8, TRPV1, FAAH, NAAA, MGL, and DGLα, and an inhibitor of anandamide transport, as well as an agonist of TRPA1 and TRPV2. Many THCA reagents used in biochemistry experiments are contaminated with THC due to THCA's instability. A study found THCA and unheated Cannabis sativa extracts exert immuno-modulating effect, not mediated by the cannabinoid CB1 and CB2 receptor coupled pathways like THC. THCA were able to inhibit the tumor necrosis factor alpha (TNF-alpha) levels in U937 macrophages and peripheral blood macrophages, an inhibition that persisted over a longer period of time, whereas after prolonged exposure time THC and heated extract tend to induce the TNF-alpha level. THCA and THC show distinct effects on phosphatidylcholine specific phospholipase C (PC-PLC) activity, as THCA and unheated extracts inhibit the PC-PLC activity in a dose-dependent manner, but THC only induced PC-PLC activity at high concentrations, suggest THCA and THC exert their immuno-modulating effects via different metabolic pathways. The anti-inflammatory activity