Inhibitory effect on aldose reductase activity of standardized extracts of Cannabis sativa L. chemotypes.

Cannabis sativa L. chemotypes distinction is based mainly on the content of ∆9-tetrahydrocannabinol (∆9-THC), cannabidiol (CBD), cannabigerol (CBG) and their acidic forms (THCA, CBDA, CBGA). The well-known psychotropic effects of ∆9-THC, have greatly limited its clinical use. On the other hand, CBD is a non-psychotropic cannabinoid with therapeutic potential in inflammation, diabetes, cancer and neurodegenerative diseases. Cannabidiol has also been proven useful for possible complications of diabetes. Aldose reductase has been implicated in the etiology of diabetic complications, including blindness. The aim of this study was to investigate in vitro inhibition of aldose reductase activity by hexane extracts and their fractions from Cannabis sativa CBD-type (I) and CBG-type (II). The hexane extracts of cannabis type-I and type-II (HxExI, HxExII) were subjected to chromatography MPLC yielding three fractions. An HPLC method was performed for the simultaneous identification and quantification of both free cannabinoids and their acids in extracts and the fractions were also confirmed by 1H NMR analysis. HxExI, HxExII and their fractions were assayed at different concentrations for aldose reductase inhibitory activity on porcine liver homogenate and on human recombinant aldose reductase. The hexane extracts showed significant dose-dependent inhibitory activity (≥ 60%). The inibitory activity of the fractions was substantially lower than that of extracts and greater for cannabinoid acid rich fraction.