Composition of Dithyrea wislizenii fruit extract and free-radical scavenging activity of its constituents

Glucolesquerellin (2), glucohesperin (3), quercetin 3-O-sophoroside (4), and quercetin 3-O-sophoroside-7-O-glucoside (5), isolated from the fruit of Dithyrea wislizenii, were quantified by HPLC. The fruit extract and flavonoids were not found to be toxic by using a brine shrimp lethality assay. The fruit extract and the flavonoids and glucosinolates were submitted to a free-radical scavenging activity assay with the diphenylpicrylhydrazyl radical (DPPH center dot). The concentration of quercetin (6) (a positive control for the flavonoids) able to scavenge 50% of DPPH center dot (SC50) was 32 +/- 2 mu mol/L (or 4 +/- 1 mu g/mL), which was about 27 times more potent than the crude extract. Compounds 4 and 5 had a SC50, the concentration of the compound required to scavenge 50% of the DPPH center dot, of 78 +/- 1 mu mol/L and 113 +/- 10 mu mol/L, respectively. The positive control for the glucosinolates, glucoraphasatin, (1) had a SC50 of 1768 +/- 60 mu mol/L. The glucosinolates 2 and 3 had a SC50 of 7819 +/- 1968 and 970 +/- 63 mu mol/L, respectively.