The reference standards ginkgolide M (3), apigenin-7-O-glucoside (7), bilobalide (8), ginkgolide C (9), quercetin (14), luteolin (15), apigenin (16), kaempferol (17), isorhamnetin (18), ferulic acid (19), ginkgolide A (20), myricetin (22), genistein (23), chlorogenic acid (24), caffeic acid (26), luteolin-7-O-glucoside (33), kaempferol-3-O-glucoside (34), kaempferol-7-O-glucoside (35), quercetin-7-O-rhamnoside (40), isoquercitrin (45) and rutin (65) were purchased from Sichuan Weikeqi Biological Technology Co., Ltd. (Chengdu, China), and their structures are shown in Fig. 1. Purities of all the reference standards were over 98% according to HPLC-DAD analysis. |