The water layer was further partitioned with water-saturated BuOH three times, yielding the BuOH and water fractions (0.20 and 4.4 g, respectively). Ginsenosides F1, F2, Rd, Rg3, Rh1, Rh2, protopanaxadiol, and protopanaxatriol were obtained from Sichuan Weikeqi Biological Technology (Chengdu, Sichuan, China); ginsenosides Rg1 and Rb1 were obtained from Wako Pure Chemical Industries (Osaka, Japan)

Ginsenosides Rg1 and Rb1 were obtained from Wako Pure Reagents (Osaka). Compound K was obtained from ChromaDex (Irvine, CA, USA). Ginsenosides F1, F2, Rd, Rg3, Rh1, Rh2, protopanaxadiol and protopanaxatriol were obtained from Sichuan Weikeqi Biological Technology (Chengdu, Sichuam, China). Chemical structures of ginsenosides used in the present study are shown in Fig. 1.

Recombinant human UGT isoforms (UGT1A1, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, UGT2B15) expressed in baculovirus-infected insect cells were obtained from BD Gentest Corp. (Woburn, MA, USA). Ginsenosides Rb1, Rb2, Rc, Rd, Rg3, Rh2, C-K, ppd, ppt, Re, Rg1, Rh1, F1, and F2 were purchased from Sichuan Weikeqi Biotechnology Company (Chengdu, Sichuan, China). The purity of these compounds was above 95%. All other reagents were of HPLC grade or of the highest grade commercially available.