NMR assignments of the major cannabinoids and cannabiflavonoids isolated from flowers of Cannabis sativa.

The complete 1H- and 13C-NMR assignments of the major Cannabis constituents, delta9-tetrahydrocannabinol, tetrahydrocannabinolic acid, delta8-tetrahydrocannabinol, cannabigerol, cannabinol, cannabidiol, cannabidiolic acid, cannflavin A and cannflavin B have been determined on the basis of one- and two-dimensional NMR spectra including 1H- and 13C-NMR, 1H-1H-COSY, HMQC and HMBC. The substitution of carboxylic acid on the cannabinoid nucleus (as in tetrahydrocannabinolic acid and cannabidiolic acid) has a large effect on the chemical shift of H-1" of the C5 side chain and 2'-OH. It was also observed that carboxylic acid substitution reduces intermolecular hydrogen bonding resulting in a sharpening of the H-5' signal in cannabinolic acid in deuterated chloroform. The additional aromaticity of cannabinol causes the two angular methyl groups (H-8 and H-9) to show identical 1H-NMR shifts, which indicates that the two aromatic rings are in one plane in contrast to the other cannabinoids. For the cannabiflavonoids, the unambiguous assignments of C-3' and C-4' of cannflavin A and B were determined by HMBC spectra.

Cloning and over-expression of a cDNA encoding a polyketide synthase from Cannabis sativa.

A polyketide synthase has been suggested to play an important role in cannabinoid biosynthesis in Cannabis sativa L. This enzyme catalyzes the biosynthesis of olivetolic acid, one of the precursors for cannabinoid biosynthesis. Using a reverse transcriptase-polymerase chain reaction (RT-PCR) based on the DNA homology of chalcone synthase (EC 2.3.1.156) and valerophenone synthase (EC 2.3.1.156) of hop (Humulus lupulus), a cDNA encoding a polyketide synthase in C. sativa was identified. The coding region of the gene is 1170 bp long encoding a 389 amino acid protein of a predicted 42.7 kDa molecular mass and with a pI of 6.04. The gene shares a high homology with a chalcone synthase gene of H. lupulus, 85% and 94% homology on the level of DNA and protein, respectively. Over-expression of the construct in Escherichia coli M15 resulted in a 45 kDa protein. The protein has chalcone synthase activity as well as valerophenone synthase activity, a chalcone synthase-like activity. Using n-hexanoyl-CoA and malonyl-CoA as substrates did not give olivetol or olivetolic acid as a product.