Decarboxylation is a chemical reaction in which a carboxylic acid group (-COOH) leaves a molecule as carbon dioxide. In cannabis it converts the acid cannabinoids the plant makes (THCA, CBDA, CBGA and others) into their neutral counterparts (THC, CBD, CBG). The reaction is driven mainly by heat; it also happens slowly at room temperature during drying, curing and storage.
In practice
Smoking and vaporising decarboxylate THCA almost instantly. Raw, cured flower is still mostly THCA, which is why a COA shows THCA high and Δ9-THC low. Over long storage, slow decarboxylation raises the Δ9-THC line a little while oxidation pushes some THC on toward CBN. Gas chromatography decarboxylates samples in its hot inlet, which is why GC cannot measure the acids directly. GenetixBay doesn't publish processing temperatures or times.
Mass is lost as CO2: 1 g THCA gives at most 0.877 g THC; 1 g CBDA gives at most 0.877 g CBD. Real conversions fall short of that because of side reactions and degradation.
Don't confuse with
- Oxidation: a different reaction that degrades THC to CBN.
- Curing: a controlled moisture decline; any decarboxylation during it is minor.
Acid cannabinoids (THCA, CBDA, CBGA) are the carboxylated forms the plant makes; neutral cannabinoids (THC, CBD, CBG) form when heat or time removes the carboxyl group.THCA (tetrahydrocannabinolic acid) is the acid cannabinoid that drug-type cannabis makes in its trichomes; heat or time decarboxylates it into THC, losing about 12% of its mass.CBDA (cannabidiolic acid) is the acid cannabinoid made by CBDA synthase from CBGA; it dominates hemp-type and CBD-type cannabis and decarboxylates to CBD.THC (Δ9-tetrahydrocannabinol) is the neutral, decarboxylated cannabinoid mainly responsible for cannabis's reported intoxicating effects; the living plant makes it almost entirely as THCA.CBD (cannabidiol) is a non-intoxicating neutral cannabinoid formed when CBDA decarboxylates; hemp-type and CBD-dominant cannabis make it mainly as CBDA in their trichomes.CBG (cannabigerol) is the neutral, decarboxylated form of CBGA, the cannabinoid precursor; most plants convert nearly all of it onward, but some cultivars are bred to accumulate it.CBN (cannabinol) is a cannabinoid formed mainly when THC or THCA oxidises after harvest, so high CBN readings usually signal age, heat, light or air exposure, not plant ripeness.Total THC is a calculated figure, Δ9-THC plus 0.877 × THCA, estimating the maximum THC a sample could yield after full decarboxylation.Gas chromatography (GC) separates volatile compounds in a heated gas stream; it is used for terpenes and residual solvents and decarboxylates acid cannabinoids in its hot inlet.
