Free radical scavengers from Goniothalamus tenuifolius leaves

Abstract

Phytochemical study of the leaves of Goniothalamus tenuifolius led to the isolation of nine pure compounds, which included a new natural product namely 3'-hydroxy-3,5,7,4'-tetramethoxyflavone and eight known compounds including trans-cinnamic acid, retusine, pachypodol, kumatakenin, 5,7,3',4'-tetrahydroxy-3-methoxyflavone, 3',4'-dihydroxy-3,5,7-trimethoxyflavone, 3,5,7,3',4'-pentamethoxyflavone, 4'-hydroxy-3,5,7,3'-tetramethoxyflavone. The structures of all of these isolates were determined by interpretation of their spectroscopic data (UV, IR, MS and NMR) and comparison of the spectral properties with previously reported values. Each of these compounds was evaluated for free radical scavenging activity on DPPH decoloration test. The active compounds were kumatakenin, 5,7,3',4'-tetrahydroxy-3-methoxyflavone and 3',4'-dihydroxy-3,5,7-trimethoxyflavone with IC50 values of 5.8, 6.4 and 6.7 M, respectively, whereas quercetin (positive control) showed an IC50 value of 6.6 M