Antiviral and antioxidant activities of flavonoids of Ficus virens: Experimental and theoretical investigations

Abstract

A phytochemical investigation of Ficus virens leaves led to isolation of six flavonoids (1–6). On the basis of 2D and/or 1D NMR, and mass data, together with the comparison with the literature values, the flavonoids were identified as quercetin (1), quercetin-3-O-I±-D-arabinopyranoside (2), quercetin-3-O-I²-D-galactopyranoside (3), kaempferol-3-O-I±-D-arabinopyranoside (4), kaempferol-3-O-I²-D-galactopyranoside (5), and vogelin J (6). The procedures for simultaneous isolation of the glycosides 2–5 are described. The antioxidant activity of the isolated flavonoids were experimentally evaluated. The structural characteristics and structure-antioxidant activity relationship of these isolates are studied by quantum mechanical calculations on the molecules and on the free radicals derived from each compound by an abstraction of single hydrogen from the various aromatic OH groups. The calculations are performed at the B3LYP/6-31+G(d,p) level of theory, and show that glycosylation of quercetin and kaempferol distorts the planar geometry of the aromatic moiety of both the molecular and radical compounds. The viral inhibitory effects of the isolated flavonoids on Coxsackie B4 (CVB4), and hepatitis A virus (HAV) are also investigated. The flavonoids 1, 3, and 6 exerted mild anti CVB4 inhibitory effects, while 2, and 3 exerted mild inhibitory activities against HAV.