Securidacaxanthone D: a new xanthone with free radical scavenging activity from the roots of Securidaca longepedunculata (Polygalaceae)

A previously unpublished xanthone named securidacaxanthone D (1) and five known analogues: 1,7-dihydroxyxanthone (2), 7-hydroxy-1,2-dimethoxy-xanthone (3), 1,5-dihydroxy-6,7-dimethoxyxanthone (4), 1,7-dihydroxy-3-methoxyxanthone (5), 1,7-dihydroxy-4-methxyxanthone (6) were isolated from the ethyl acetate soluble fraction obtained from the liquid-liquid partition of the crude hydro-ethanolic extract of the roots of Securidaca longipedunculata. Their structures were determined by analysis of 1D -(1H and 13C), 2D-(COSY, HSQC and HMBC) NMR data in conjunction with mass spectrometry (TOF-ESI-MS) and by comparison with reported data. Free radical scavenging activity were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) as a free radical. Crude extract, ethyl acetate and n-butanol fractions as well as isolated compounds showed different degrees of free radical scavenging activity. Among the extract and fractions tested, the hydro-ethanolic extract was the most active with an IC50 value of 32 μg/mL. Among the compounds, compound 2 was the most active with an IC50 value of 282 μg/mL.