Antioxidant and Anti-glycation Properties of <i>Rehmannia glutinosa</i> Leaves

The root of Rehmannia glutinosa is an ingredient in herbal medicine used for tonifying blood in Japanese Kampo medicine and traditional Chinese medicine. Biological investigations of the roots have been well reported; however, those of the leaves are limited. In this study, we examined the potential value of R. glutinosa leaves, focusing on their antioxidant activity and inhibition of advanced glycation end product formation. The leaf extract exhibited both antioxidant and anti-glycation activities in all assay systems, and the potencies of the leaves were stronger than those of the roots. The bioassay-guided fractionation led to the isolation of eight compounds from the ethyl acetate fraction. Among them and their related compounds, acteoside (3), luteolin (6), and echinacoside (12) exhibited DPPH radical scavenging, copper ion reduction, and SOD-like activities. Furthermore, compound 6, apigenin (7), and chrysoeriol (8) exhibited anti-glycation activities. The leaf extract tended to contain higher amounts of most analytes, especially compounds 3, 6, and 7, suggesting that these compounds contributed to the antioxidant or anti-glycation activities of R. glutinosa leaves. These findings will aid in the effective use of R. glutinosa leaves.