This one is for the budtenders out there. We’ve all had the experience of comparing products, trying to figure out for our customers which cartridge has the most THC. Depending on the company, THC percentage might be accompanied by it’s buddy, THC-A. It’s a common misconception and easy to see that A and think “active”, but the truth is the complete opposite. In fact, THC-A is non-reactive, the molecule being unable to attach to the receptor in the brain that causes the effects of cannabis to manifest. The A, in fact, stands for “acid”.
Time for SCIENCE!
THC-A is Δ9-tetrahydrocannabinolic acid, THC before it is “decarbed”; that is, before the removal of a carboxyl group. The carboxyl group is just a chunk of atoms at one end of the molecule that makes up the cannabinoid. This group makes the molecule stable, meaning it has no chemical reason to interact with any other molecules. Decarbing releases that chunk of atoms, destabilizing the molecule and converting it to Δ9-tetrahydrocannabinol (THC). Once that carboxyl group is out of the way, the THC can attach to the receptor in the brain, and you are off to your happy place.
Removing the carboxyl group is done easily through heat, which is part of why smoking the product has such a quick effect. Conversion to THC is also done in the liver, allowing edibles to have effects once they have reached that point in digestion and head on up to the brain. This is a less efficient conversion than burning, but also creates a secondary chemical, 11 hydroxy THC, a far more potent “metabolite” of THC, resulting in the longer-lasting effects associated with edibles.
The presence of both THC and THC-A on a label is why the percentages don’t always add up to 100. The THC value includes BOTH converted THC and unconverted THC-A, meaning you are accounting for the A twice if you add all of the percentages together.
Prior to heating or eating, THC-A is the opposite of active, and won’t cause any psychoactive effects.