Hepatoprotective, Gastroprotective, Antioxidant Activity and Phenolic Constituents of Quercus robur Leaves

Phytochemical investigation of the 80% aqueous methanol extract (AME) of Quercus robur leaves using chromatographic techniques, led to isolation of ten phenolic compounds, namely gallic acid (1), methyl gallate (2), strictinin (3), 4-O-galloyl-2,3-(S)hexahydroxydiphenoyl-(α/β)-D-glucopyranose (4), 2,3-(S)-hexahydroxydiphenoyl-(α/β)-D-glucopyranose (5), casuarinin (6), casuariin (7), kaempferol 3-O-(6′′-O-galloyl)-β-D-C1-galactopyranoside (8), ellagic acid (9) and ellagic acid 3-O-methyl ether (10). Compounds 4, 5 and 8 were isolated from Quercus genus for the first time, while 2, 3, 6, 7, 9 and 10 were isolated for the first time from Q. robur. Structures of the isolated compounds were established using chemical and physical methods and by comparison with compounds reported in literature. The AME of Q. robur was found to be nontoxic to mice up to 5000 mg /kg b.wt. It exhibited a significant hepatoprotective activity, as compared to paracetamol treated group and gastroprotective activity, as compared to ethanol treated group in dose dependent manner. The results are supported by histopathological data in the current study. Both AME and its tannin fractions exhibited marked in vitro antioxidant activity, as compared to pyrogallol and ascorbic acid using DPPH method.