Cannabigerolic acid: the acid form the cannabinoids come from

In short

Cannabigerolic acid, or CBGA, is the form the plant actually produces. It carries a carboxyl group that the neutral cannabinoids lack. The acid precursors of THC, CBD and CBC all derive from it, which makes it the branch point of the entire pathway.

How it is made

Assembly runs in two stages. First a short-chain fatty acid is extended over several steps into olivetolic acid. Then an enzyme transfers the geranyl group from geranyl pyrophosphate onto that acid, and cannabigerolic acid is complete.

A second, narrower branch runs through divarinic acid and yields cannabigerovarinic acid. From it come the varins, the relatives shortened by two carbon atoms such as THCV and CBDV.

The difference from CBG

Neutral cannabigerol arises from the acid through decarboxylation, the loss of the carboxyl group as carbon dioxide. Heat, light or simply time drive that reaction; no enzyme is involved. CBG is therefore a conversion product and never the starting material of a reaction inside the plant.

In practice this means that what a laboratory reports as CBG depends on how it measured. Methods with a hot inlet strip the carboxyl group inside the instrument and can only report the combined figure. Only methods that separate at low temperature report acid and neutral form apart. Comparing studies without checking this means comparing partly different quantities.

Relevance to cannabis

At harvest, what counts is how much cannabigerolic acid has not yet been converted. In plants with a working synthase that is a remainder; in chemotype IV plants it is the main constituent. After the cut there is no enzymatic route left to THCA or CBDA, so drying and curing only shift the balance between acid and neutral form within the same pool. What follows from that for harvest timing is covered in the article on cannabigerol.

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