Antioxidant activity and major constituents of methanol extract of Polygonum hyrcanicum
The genus Polygonum (Polygonaceae) is one of the widely grown medicinal plants in Iran. Different species of Polygonum were shown to possess various medicinal activities such as anti inflammation, neuro protection, reduction of age-related degenerative changes, cardiovascular protection and treatment of hepatic disorders. It is considered that the beneficial effects afforded by Polygonum treatments, are partly mediated by their antioxidant properties. This study is designed to investigate radical scavenging activity of Polygonum hyrcanicum Rech. f. and to identify major constituents of the effective fraction. P. hyrcanicum.
Aerial parts of the plant were extracted with hexane, ethyl acetate and methanol respectively. DPPH free radical scavenging assay was employed to study antioxidant activities. Major constituents of methanol extract, as the most antioxidant containing fraction, were purified using different chromatographic methods. Finally, 7 flavonols involving myricetin (1), myricetin-3-O- rhamnopyranoside (2), myricetin-3-O- α-L-arabinofuranoside (3), quercetin (4), quercetin-3-O-α-L-arabinofuranoside (5), quercetin-3-O-galactopyranoside (6), quercetin-3-O-(3“-O-acetyl- arabinofuranoside) (7), and 2 structurally related flavanols, catechin (8) and gallocatechin (9), were identified.
Among different extracts of Polygonum hyrcanicum which were tested for their radical scavenging properties in this study, methanol extract exhibited noticeable antioxidant activity (IC50=68.6µg/ml) which is comparable with 16µg/ml vitamin E. Main constituents of the mentioned fraction involved highly hydroxylated flavonols, myricetin and quercetin, their glycosilated derivatives and their structurally related catechins which are known as potent antioxsidants and possess various interesting medicinal properties.