Hypoglycemic activity evaluation and chemical study on hollyhock flowers

Hollyhock (Althaea rosea (Linn.) Cavan) belongs to Althaea genus, Malvaceae family, is a perennial garden plant distributed throughout the world in warm temperate and tropical regions, which was used as anti-diabetes ingredient in traditional Chinese medicine. In the process of our research, ethanolic extract of hollyhock flower (HFE) was found to decrease serum triglyceride and glucose levels significantly in KK-Ay mice after oral administration for 8 weeks. Meanwhile, gene expressions on AMPK, IRS2, PI3K, AKT and GLUT4 in liver were remarkably up-regulated. Three new dihydroflavonol glycosides, named as roseaflavanonolosides A (1), B (2), and C (3), together with two known ones were obtained from HFE. Their structures were elucidated by chemical and spectroscopic methods. Hepatic cell glucose uptake experiment was performed using 2-NBDG as a glucose uptake indicator. At the dosage of 20 μg/mL for 1–5, the glucose uptake increasing level was nearly 30%–40% in HepG2 cells. We partly revealed the glucose metabolism regulation effect may relate to dihydroflavonols in hollyhock flower.