Isolation and Pharmacological Evaluation of Minor Cannabinoids from High-Potency Cannabis sativa
Mohamed M. Radwan, Mahmoud A. ElSohly, Abir T. El-Alfy, Safwat A. Ahmed, Desmond Slade, Afeef S. Husni, Susan P. Manly, Lisa Wilson, Suzanne Seale, Stephen J. Cutler, and Samir A. Ross
Journal of Natural Products, 2015 June 26, 78, (6), 1271–1276.
doi : 10.1021/acs.jnatprod.5b00065
Seven new naturally occurring hydroxylated cannabinoids (1–7), along with the known cannabiripsol (8), have been isolated from the aerial parts of high-potency Cannabis sativa. The structures of the new compounds were determined by 1D and 2D NMR spectroscopic analysis, GC-MS, and HRESIMS as 8α hydroxy-Δ9-tetrahydrocannabinol (1), 8β-hydroxy-Δ9-tetrahydrocannabinol (2), 10α-hydroxy-Δ8 tetrahydrocannabinol (3), 10β-hydroxy-Δ8-tetrahydrocannabinol (4), 10α-hydroxy-Δ9,11 hexahydro-cannabinol (5), 9β,10β-epoxyhexahydrocannabinol (6), and 11-acetoxy-Δ9 tetrahydro-cannabinolic acid A (7). The binding affinity of isolated compounds 1–8, Δ9 tetrahydrocannabinol, and Δ8-tetrahydro-cannabinol toward CB1 and CB2 receptors as well as their behavioral effects in a mouse tetrad assay were studied. The results indicated that compound 3, with the highest affinity to the CB1 receptors, exerted the most potent cannabimimetic-like actions in the tetrad assay, while compound 4 showed partial cannabimimetic actions. Compound 2, on the other hand, displayed a dose-dependent hypolocomotive effect only.
Many natural product classes besides the cannabinoids have been identified from Cannabis sativa L. (Cannabaceae), including monoterpenes, sesquiterpenes, flavonoids, steroids, and nitrogenous compounds. However, the C21 terpenophenolics (cannabinoids) are characteristic structures found in C. sativa. To date, more than 750 constituents have been identified from cannabis, out of which 104 are classified as cannabinoids.1–14
The medicinal properties of cannabis have been much debated from scientific and political points of view, and the subject has gained much interest over the years. After the discovery of the primary active constituent of marijuana, (−)-trans-Δ9-tetrahydrocannabinol (Δ9-THC), in 1964,15 various clinical trials were undertaken to determine its efficacy as an analgesic,16 antiemetic,17 antidepressant,18 and appetite suppressant/stimulant,19 as a treatment of glaucoma,20 and for the management of chemotherapy induced nausea and vomiting.21 Research in the area of the use of C. sativa for medicinal purposes has gained worldwide interest following the discovery of the endogenous endocannabinoid system that interacts with the constituents of this plant.
Features of this endogenous system include cannabinoid receptors, of which there are two types reported (CB1 and CB2), and endogenous ligands that act as receptor agonists and antagonists.22,23 The CB1 receptors, recognized by the cannabinoids, are found in the brain and peripheral tissue of the central nervous system (CNS),24 while CB2 receptors are found primarily outside the CNS in tissues associated with the immune system of the body.25
The availability of high-potency marijuana with unprecedented Δ9-THC concentrations (>20% by dry weight)26 has afforded an opportunity to discover novel constituents from C. sativa. As part of a program to study the constituents of high-potency cannabis and its pharmacological effects,2–5,7,13 reported herein are the isolation and structure elucidation of eight minor cannabinoid constituents, including seven new compounds (1–7) and one known compound (8). Binding affinities of these compounds to both CB1 and CB2 receptors as well as their pharmacological evaluation in a mouse tetrad assay are described.