The double-distilled water was prepared in the laboratory by using a Milli-Q system (Millipore, Bedford, MA, USA). Schaftoside (1), isoschaftoside (2), 2,4,7-trihydroxy-9,10-dihydrophenanthrene (3), dihydroresveratrol (4), coelonin (5), nudol (6), gigantol (7), 4-methoxy-2,5- phenanthrenediol (8), 3-hydroxy-3,4,5-trimethoxybibenzy (9), erianin (10), and tristin (11) were purchased from Sichuan Weikeqi Biological Technology Co., Ltd. (Sichuan province, Chengdu, China). The purity of all the reference standards was above 98%. The structures of these standards are shown in Figure 1. |