Phytochemical analysis of some gentianella species and their secondary metabolites' effects on BDNF (brain-derived neurotrophic factor)

Gentianella Moench (Gentianaceae) species contain many secondary metabolites such as xanthones, flavonoids and terpenes. Flavonoids have been reported to contribute to the antidepressant effects of many medicinal plants by increasing the expression level of the brain-derived neurotrophic factor (BDNF). Since xanthones share some structural similarity with flavonoids, they might exhibit analogous biological activity. We used several phytochemical analysis methods to isolate phytochemicals, including: xanthones, flavonoids and iridoid from one endemic species; G. holosteoides Schott & Kotschy and G. caucasea (Lodd. ex Sims) Holub and G. ciliata (L.) Borkh. A total of 28 phytochemicals were isolated from the methanolic extracts of the aerial parts of these plants. Mass spectroscopy, 1D and 2D NMR were used to elucidate the structure of these compounds and accordingly, duplicate compounds were removed and this reduced the total number of isolated compounds to 20 (1 new, 19 known); 9 xanthones (gentiabavaroside, gentiacaulein-1-O-glucoside, decussatin-1-O-primveroside, swertiaperennin, decussatin, norswertianolin, mangiferin, swertianolin, bellidin), 3 benzophenones (2,4,3'-trihydroxy-benzophenone-6-O-β-glucopyranoside, 2,3ꞌ-dihydroxy-4-methoxy-benzophenone-6-O-β-glucopyranoside, 3,4,3'-trihydroxy-benzophenone 6-O-β-glucopyranoside), 3 C-flavones (pakistoside A, isovitexin, isoorientin), 2 iridoids (swertiaside, loganic acid) and 3 secoiridoids (7-O-methylmorroniside, sweroside, svertiamarin). The effects of extracts and pure compounds on BDNF expression in SH-SY5Y cells were investigated. G. holosteoides at 50 µg/mL (148.8%) and G. caucasea at 12.5 µg/mL (145.7%), svertiamarine (39.3%), 7-O-methylmorroniside (36.0%) and sweroside (34.3%) at 30 µM possessed the highest effect by increasing the BNDF expression compared to the control.