Identification of the Antioxidant Principles of Polyalthia longifolia var. pendula using TEAC assays

Abstract

Activity guided fractionation of the ethanolic extract of the leaves of the P. longifolia var. pendula led to the identification of quercetin 1, quercetin-3-O-ß-glucopyranoside 2, kaempferol-3-O-α-rhamnopyranosyl-(1→6)-ß-galactopyranoside 3, kaempferol-3-O-α-rhamnopyranosyl-(1→6)-ß-glucopyranoside 4, rutin 5 and allantoin 6 as the active constituents from butanol fraction. Compound 2, 3 and 4 are reported for the first time from this natural source. Structures of the compounds were confirmed on the basis of their 1D and 2D NMR coupled with other spectroscopic methods. All the isolated compounds and the fractions were evaluated for their antioxidant potential using the TEAC assays and it was found that activity of the active fraction was due to quercetin 1 and its glycosides 2 and 5 with their TEAC values of 4.10 mM, 1.91 mM, and 2.38 mM, respectively while kaempferol glycosides were found to be inactive. This is also the first study on the antioxidant activity of this plant species.