Cannabis Chemistry: Cannabinoids, Acids and Terpenes Explained

In short

Cannabis makes a large family of compounds. The best known are cannabinoids such as THC and CBD, and aromatic terpenes. This page explains the building blocks, the acid forms, and the "entourage effect" idea. Evidence labels used: established, preclinical (cells/animals only), mixed and insufficient evidence.

Cannabinoids

Cannabinoids are a group of substances found in the plant. THC and CBD are the main ones, and more than 100 others have been identified. [1] THC is mainly responsible for intoxicating effects, while CBD is not intoxicating in the same way. [2] Individual minor cannabinoids are covered in CBG, CBN, CBC, THCV and other minor cannabinoids.

One starting molecule

Cannabigerol (CBG) is the precursor of the most abundant phytocannabinoids. [3] In the plant, the acid form of CBG is the starting point for the acid forms of THC and CBD. [4] Terpenoids share a precursor with phytocannabinoids too. [5]

Acid forms: THCA and CBDA

• What they are. The plant makes acid forms first: THCA, CBDA, CBGA and CBCA. These are the biosynthetic precursors of THC and CBD. [6]
• Not the same as THC. A 2026 review says acidic cannabinoids are not intoxicating like THC, but that this applies mainly to non-heated use. [6]
• Decarboxylation. This is the loss of a carbon dioxide group that turns an acid form into the neutral form. WHO describes CBD as formed by decarboxylation from its acid precursor, CBDA. [7] A laboratory study found that acid cannabinoids break down with light, air and heat. [8]
• Evidence for the acids as medicine. The 2026 review reports instability, low bioavailability and a dearth of controlled human trials. [6] Label: insufficient evidence in people.
• Why you may see "THCA" on labels. A product listing a large THCA number is not the same as a product listing THC. How much of each a product contains is shown on a certificate of analysis; see how to read a certificate of analysis. We did not read a regulator's page on how THCA is counted, so legal treatment is not verified.

Terpenes

Terpenes are aromatic compounds that give cannabis its smell. More than 100 have been identified. [9] Russo notes they are flavor and fragrance components common in the human diet and designated Generally Recognized as Safe by the FDA and other regulatory agencies. [5] That food-safety status is not the same as proof of safety when they are inhaled from concentrated products. Details are on terpenes in cannabis. For aromatherapy with essential oils, see aromatherapy.

The entourage effect

The entourage effect is the idea that cannabis compounds work together to produce effects different from, or stronger than, any one alone.

• The proposal. In 2011 Russo reviewed possible synergy between cannabinoids and terpenoids, which he said could contribute to the effects of cannabis-based extracts. [5]
• A lab test. A 2020 study tested five cannabis terpenes, alone and in mixtures. Apart from a possible weak interaction of beta-caryophyllene with CB2, it found no direct effects at CB1 or CB2 and no change to the action of THC, CBD or 2-AG. [10] That does not rule out other mechanisms.
• A 2024 systematic review. It concluded that additive or synergistic enhancement of cannabinoid effects by terpenes remains unproven and needs clinical trials. [11]
• A 2026 review. It reports demonstrated synergistic interactions, but calls the findings promising preclinical results with limited clinical translation. [12]
• Label: preclinical, insufficient evidence in people. Product claims that a "full-spectrum" or "whole-plant" product works better than a single compound are a marketing claim unless backed by a clinical trial. The FDA warns that unapproved cannabis products have not been evaluated for whether they work. [13]

Why chemistry matters for safety

THC, CBD and other compounds differ in risk, so labels matter. Products have been found to contain different amounts of CBD than labeled, and some CBD products contain THC. [2] Delta-8 THC, for example, is typically made from hemp-derived CBD through chemical conversion, and the FDA warns about by-products. [14] See minor cannabinoids and CBD quality and certificates of analysis.