What is CBN? CBN (or cannabinol) is produced when the cannabis or hemp plant ages. Enzymes, ultraviolet light and heat produce changes at various stages of the plant's life to transform CBGA (or cannabigerolic acid) ultimately into the CBN cannabinoid. More precisely, most cannabinoids start off as CBGA in the hemp plant. As the hemp plant matures, enzymes transform the CBGA into CBG (cannabigerol), CBDA (cannabidiolic acid), THCA (tetrahydrocannabinolic acid), and CBCA (cannabichromenic acid). THCA, on being exposed to heat, becomes THC. On being exposed to ultraviolet light, such as from sunlight, THCA transforms into CBNA (cannabinolic acid). This CBNA, when exposed to heat, decarboxylates into CBN (cannabinol).