Characterization of flavonoid and quinic acid derivatives from Calystegia soldanella with antioxidant activities

Calystegia soldanella is a species broadly used in an edible source and traditional herb in South Korea and China. It has diverse bioactivities, such as dropsy, antipyretic, and diuretic effect. In this study, we investigated the main components with antioxidant activities from the 70% EtOH extract of C. soldanella. The structural determination of compounds was achieved by nuclear magnetic resonance and HR-ESI-MS spectroscopic data. The main components from C. soldanella were identified as flavonoids and quinic acid derivatives. Furthermore, the 70% EtOH extract, partitioned layers, and compounds (1–8) of C. soldanella were evaluated for their antioxidant effects. The most active compound 8 (isochlorogenic acid C) exhibited the IC50 values of 12.4 ± 0.1 (2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical) and 37.9 ± 0.5 μM (2,2-diphenyl-1-picrylhydrazyl radical), respectively. Two active compounds (7 and 8) displayed higher activities than ascorbic acid (positive control). In addition, we also confirmed the antioxidant effects on the intracellular reactive oxygen species production of compound 8. Therefore, the present study suggests extract of C. soldanella is a promising natural antioxidative candidate.