Comparison of Major Constituents and Antioxidant Activity of Polygonum cuspidatum Root with Polygonum afghanicum Root

Polygonum species are belonging to Polygonaceae family and they have various uses in the traditional medicine of Asian countries such as China, Japan and Iran. In this study, antioxidant activities of two methanolic extracts of root of Polygonum afghanicum, one collected in spring and the other in fall, and the one methanolic extract of root of Polygonum cuspidatum were measured and compared with each other. So, the antioxidant activities of the extracts were evaluated using various antioxidant tests, including total phenolic content TPC), total flavonoid content TFC), radical scavenging activity RSA), ferric ion chelating FIC), and beta-carotene bleaching. The results showed the highest values of TPC 347.2 ± 3.1) and TFC 165.2 ± 1.6) for P. cuspidatum, while the P. afghanicum, collected in spring, exhibited slightly higher antioxidant activity than the others for RSA IC50 = 14.5 ± 1.5 µg/mL), FIC 96.7 ± 1.7%), and BCB 50.9 ± 3.6%) tests. According to the obtained results, the P. afghanicum collected in spring, as a local species, showed the better activity in the some of the antioxidant tests, probably due to the presence of other active metabolites in this plant.