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•). The concentration of quercetin (6) (a positive control for the flavonoids) able to scavenge 50% of DPPH• (SC50) was 32 ± 2 µmol/L (or 4 ± 1 µg/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•, of 78 ± 1 µmol/L and 113 ± 10 µmol/L, respectively. The positive control for the glucosinolates, glucoraphasatin, (1) had a SC50 of 1768 ± 60 µmol/L. The glucosinolates 2 and 3 had a SC50 of 7819 ± 1968 and 970 ± 63 µmol/L, respectively.