Last updated November 17, 2022

Most cannabis consumers have heard of the compound delta9-Tetrahydrocannabinol, or THC. It is famously responsible for the intoxicating feeling associated with the consumption of cannabis products and is likely the most well-known of the more than 100 cannabinoids found in cannabis. However, fewer people are probably familiar with the precursor of THC, which is aptly named Tetrahydrocannabinolic Acid (THCA). While they are similar in name, there are some key differences between these two compounds that cannabis consumers should understand.

What is THC?

An active ingredient in cannabis, THC is a cannabinoid well known for its ability to produce intoxicating effects. It is often a primary measure of the potency of cannabis and cannabis-derived products.

Legally, THC is also the barometer for whether cannabis flower or a cannabis-derived product is considered industrial hemp or marijuana. The distinction was created in the 2014 Farm Bill, which defined industrial hemp as varieties of Cannabis sativa L. containing 0.3% or lessTHC by volume. Then, under the 2018 Farm Bill, industrial hemp was de-scheduled under the federal Controlled Substances Act, effectively classifying it as any other ordinary agricultural commodity. Any Cannabis sativa L. products containing more than 0.3% THC are considered marijuana under federal law and remain illegal Schedule I substances under the Controlled Substances Act.

While THC is often in the spotlight, it wouldn't exist if it weren't for its acidic parent compound THCA. Despite their shared namesake, there is a significant difference between the two compounds, even though one is formed by a chemical change in the other.

What is THCA?

Closely related to THC is its precursor, THCA. Unlike THC, THCA does not produce any intoxicating effects, nor does it bind to the endocannabinoid system. THCA, however, is present in large quantities in cannabis flower, especially while it is still on the plant or immediately after harvest.

As the cannabis flower dries following harvest, THCA begins to "decarboxylate." This means the acid is eliminated from the compound and the levels of THC begin to increase. Decarboxylation occurs at even higher levels when the flower is subjected to heat, either during cooking, combustion, or vaporization.

Decarboxylation is a natural process but encouraging further decarboxylation and expediting the process is a necessary step for the creation of certain value-added cannabis-derived products, such as edibles. Failure to "decarb" cannabis flower prior to baking or cooking edible products significantly reduces potency.

Unlike THC, THCA is not scheduled as an illicit substance under U.S. law. However, because it spontaneously decarboxylates into THC, there is no way to have a pure sample of THCA without any THC present. Moreover, it could potentially be considered an analog to THC as well even though it is not classified as federally illegal itself.

Cannabinoid acids and the origins of cannabinoids

THC is not unique as a product of a decarboxylated cannabinoid acid. In fact, all cannabinoids have a precursor acid like THCA. Each cannabinoid forms from its acidic precursor in a similar manner as well. But where do each of these cannabinoid acids come from?

It all begins with Cannabigerolic acid (CBGA), which decarboxylates into a compound called Cannabigerol (CBG). CBG is affectionately known amongst botanists as "the mother of all cannabinoids" because it ultimately converts into THC, CBD, and other cannabinoids during the growth of the cannabis plant.
While CBG is present in large amounts during early growth stages, it is a minor compound in a mature cannabis plant, having largely changed into other cannabinoids. In fact, most mature plants have less than 1 percent CBG content.

While humans are seldom interested in cannabis plants for their cannabinoid acid quantities, these compounds do serve important roles in facilitating the growth and the development of the plant. For example, some cannabinoid acids provide antibiotic defenses against disease as the plant grows. Others offer insecticidal properties. These roles could explain why different cultivars of cannabis plants vary so widely in their compound profiles; plants native to certain areas would require specific quantities of cannabinoid acids to fight off local diseases and insect populations.

Extraction Process for THC Concentrates

During the creation of cannabis-derived concentrates, THC is often a highly sought-after compound. Concentrates are made through a process called extraction, which is intended to draw a cannabis plant's naturally occurring compounds out from the plant material.

To achieve this, extractors use solvents including butane and carbon dioxide. The resulting solution is a mix of cannabis-based compounds, lipids, and the solvent. Extractors then subject the solution to heat and/or pressure to remove the solvents and other unwanted compounds. The result is a concentrated material that mimics the proportions of compounds found in the plant.

However, there are cases when extractors want to isolate or emphasize a specific cannabinoid like THC. In these cases, extractors can further refine the concentrate, removing additional cannabinoids and terpenes. A wide range of concentrates can be made this way, from hash oil to wax to isolate powders.

Concentrates, whether they are potent in THC or some other cannabinoid, are popular among consumers for vaping, dabbing, and use as an ingredient in baking or cooking in legal markets. Some concentrates are also used in the creation of topical skincare products.

Acids: The Precursor to Cannabinoids

Whether you enjoy cultivars of cannabis that are potent in THC or you'd rather use products derived from CBD-heavy industrial hemp, a cannabis plant's compound profile is all thanks to the acids that form as the plant grows. Humans might have a closer relationship with the decarboxylated cannabinoids than those acids from which they originate, but if it weren't for cannabinoid acids it's unlikely that a cannabis plant would survive to maturity.

The harvesting, drying, and curing of cannabis flower is not just about making flower more manageable. These processes encourage the decarboxylation that is necessary for cannabinoids to interact with the endocannabinoid system. These interactions are the reason humans have consumed cannabis for centuries, but none of them would be possible if it weren't for the acids that started it all.

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