Tetrahydrocannabinol (THC) is a cannabinoid found in cannabis. It is the principal psychoactive constituent of cannabis and one of at least 113 total cannabinoids identified on the plant. Its chemical formula C21H30O2 includes compounds, the term THC usually refers to the delta-9-THC isomer with chemical name (−)-trans-Δ9-tetrahydrocannabinol. It is a colorless oil.
Cannabinoids are several structural classes of compounds found in the cannabis plant primarily and most animal organisms or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoactive compound in cannabis. Cannabidiol (CBD) is also a major constituent of temperate cannabis plants and a minor constituent in tropical varieties. At least 113 distinct phytocannabinoids have been isolated from cannabis, although only four have been demonstrated to have a biogenetic origin. It was reported in 2020 that phytocannabinoids can be found in other plants such as rhododendron, licorice and liverwort, and earlier in Echinacea.
Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system of vertebrates– a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid receptors contain seven transmembrane spanning domains. Cannabinoid receptors are activated by three major groups of ligands:
Cannabinol (CBN) is a mildly psychoactive cannabinoid that acts as a low affinity partial agonist at both CB1 and CB2 receptors. This activity at CB1 and CB2 receptors constitutes interaction of CBN with the endocannabinoid system (ECS).
Cannabidiol (CBD) is a phytocannabinoid discovered in 1940. It is one of 113 identified cannabinoids in cannabis plants, along with tetrahydrocannabinol (THC), and accounts for up to 40% of the plant's extract. As of 2022, clinical research on CBD included studies related to the treatment of anxiety, addiction, psychosis, movement disorders, and pain, but there is insufficient high-quality evidence that cannabidiol is effective for these conditions. CBD is also sold as a herbal dietary supplement promoted with unproven claims of particular therapeutic effects.
Tetrahydrocannabivarin is a homologue of tetrahydrocannabinol (THC) having a propyl (3-carbon) side chain instead of pentyl (5-carbon), making it non-psychoactive in lower doses. It has been shown to exhibit neuroprotective activity, appetite suppression, glycemic control and reduced side effects compared to THC, making it a potential treatment for management of obesity and diabetes. THCV was studied by Roger Adams as early as 1942.
Δ9-Tetrahydrocannabutol is a phytocannabinoid found in cannabis that is a homologue of tetrahydrocannabinol (THC), the main active component of Cannabis. Structurally, they are only different by the pentyl side chain being replaced by a butyl side chain. THCB was studied by Roger Adams as early as 1942
Onternabez (also known as HU-308, HU308, PPP-003, and ARDS-003) is a synthetic cannabinoid that acts as a potent cannabinoid agonist. It is highly selective for the cannabinoid-2 receptor (CB2 receptor) subtype, with a selectivity more than 5,000 times greater for the CB2 receptor than the CB1 receptor. The synthesis and characterization of onternabez took place in the laboratory of Raphael Mechoulam at the Hebrew University of Jerusalem (the HU in HU-308) in the late 1990s. The pinene dimethoxy-DMH-CBD derivative onternabez was identified as a potent peripheral CB2-selective agonist in in vitro and animal studies in 1990 and 1999.
A cannabinoid receptor antagonist, also known simply as a cannabinoid antagonist or as an anticannabinoid, is a type of cannabinoidergic drug that binds to cannabinoid receptors (CBR) and prevents their activation by endocannabinoids. They include antagonists, inverse agonists, and antibodies of CBRs. The discovery of the endocannabinoid system led to the development of CB1 receptor antagonists. The first CBR inverse agonist, rimonabant, was described in 1994. Rimonabant blocks the CB1 receptor selectively and has been shown to decrease food intake and regulate body-weight gain. The prevalence of obesity worldwide is increasing dramatically and has a great impact on public health. The lack of efficient and well-tolerated drugs to cure obesity has led to an increased interest in research and development of CBR antagonists. Cannabidiol (CBD), a naturally occurring cannabinoid and a non-competitive CB1/CB2 receptor antagonist, as well as Δ9-tetrahydrocannabivarin (THCV), a naturally occurring cannabinoid, modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. CBD is a very low-affinity CB1 ligand, that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant.
Abnormal cannabidiol (Abn-CBD) is a synthetic regioisomer of cannabidiol, which unlike most other cannabinoids produces vasodilator effects, lowers blood pressure, and induces cell migration, cell proliferation and mitogen-activated protein kinase activation in microglia, but without producing any psychoactive or sedative effects.
HU-320 (7-nor-7-carboxy-CBD-1,1-DMH) is a drug related to cannabidiol, which has strong antiinflammatory and immunosuppressive properties while demonstrating no psychoactive effects.
4'-Fluorocannabidiol is a fluorinated cannabidiol derivative that has more potent anxiolytic, antidepressant, antipsychotic and anti-compulsive activity in mice compared to its parent compound. It was first synthesized in 2016, alongside 10-fluorocannabidiol diacetate and 8,9-dihydro-7-fluorocannabidiol, which showed much weaker activity.
Cannabidiol-dimethylheptyl (CBD-DMH or DMH-CBD) is a synthetic homologue of cannabidiol where the pentyl chain has been replaced by a dimethylheptyl chain. Several isomers of this compound are known. The most commonly used isomer in research is (−)-CBD-DMH, which has the same stereochemistry as natural cannabidiol, and a 1,1-dimethylheptyl side chain. This compound is not psychoactive and acts primarily as an anandamide reuptake inhibitor, but is more potent than cannabidiol as an anticonvulsant and has around the same potency as an antiinflammatory. Unexpectedly the “unnatural” enantiomer (+)-CBD-DMH, which has reversed stereochemistry from cannabidiol, was found to be a directly acting cannabinoid receptor agonist with a Ki of 17.4nM at CB1 and 211nM at CB2, and produces typical cannabinoid effects in animal studies, as does its 7-OH derivative.
8,9-Dihydrocannabidiol is a synthetic cannabinoid that is closely related to cannabidiol (CBD) itself. that was first synthesized by Alexander R. Todd in 1940 derived from the catalytic hydrogenation of cannabidiol.
Δ-8-tetrahydrocannabinol is a psychoactive cannabinoid found in the Cannabis plant. It is an isomer of delta-9-tetrahydrocannabinol, the compound commonly known as THC, with which it co-occurs in hemp; natural quantities of ∆8-THC found in hemp are low.
7-Hydroxycannabidiol (7-OH-CBD) is an active metabolite of cannabidiol, generated in the body from cannabidiol by the action of the enzyme CYP2C19. While methods have been developed for its synthetic production, and measurement of levels in the body following consumption of cannabidiol, its pharmacology has been relatively little studied, though it has been found to possess similar anticonvulsant effects to cannabidiol itself, as well as lowering blood triglyceride levels. Like its precursor CBD, it is not known to exhibit any psychoactive effects on the body and is known to counter the psychoactive effects of THC if it is present at the same time. This mode of action in 2015 was discovered to be at least contributing in part by being a non competitive negative allosteric modulator of the Cannabinoid receptor type 1.
Hexahydrocannabinol (HHC) is a hydrogenated derivative of tetrahydrocannabinol (THC). It is a naturally occurring phytocannabinoid that has rarely been identified as a trace component in Cannabis sativa, but can also be produced synthetically by firstly acid cyclization of cannabidiol and then hydrogenation of tetrahydrocannabinol. The synthesis and bioactivity of HHC was first reported in 1940 by Roger Adams.
11-Hydroxyhexahydrocannabinol is an active metabolite of tetrahydrocannabinol (THC) and a metabolite of the trace cannabinoid hexahydrocannabinol (HHC).
H2CBD are cannabinoids that were first synthesized by Alexander R. Todd in 1940 by catalytic hydrogenation of cannabidiol.
Hexahydrocannabivarin is a semi-synthetic cannabinoid derivative, the hydrogenated derivative of tetrahydrocannabivarin (THCV). It was first synthesised by Roger Adams in 1942 and produces only weak cannabinoid-like effects in animals. More recently it has been sold as an ingredient in grey-market cannabinoid products. It has been investigated for potential antineoplastic activity in vitro.
