To investigate the relationship between the intestinal bacterial metabolism of kalopanaxsaponin B and H from Kalopanax pictus (Araliaceae), and their antidiabetic effect, kalopanaxsaponin B and H were metabolized by human intestinal microflora and the antidiabetic activity of their metabolites was measured. Human intestinal microflora metabolized kalopanaxsaponin B to kalopanaxsaponin A, hederagenin 3-O-alpha-L-arabinopyranoside and hederagenin. The main metabolites of kalopanaxsaponin B were kalopanaxsaponin A and hederagenin. Kalopanaxsaponin H was metabolized to kalopanaxsaponin A and I, hederagenin 3-O-alpha-L-arabinopyranoside and hederagenin. The main metabolites of kalopanaxsaponin H were kalopanaxsaponin I and hederagenin. Among kalopanaxsaponin B, H and their metabolites, kalopanaxsaponin A showed the most potent antidiabetic activity, followed by hederagenin. However, the main components, kalopanaxsaponin B and H, in K. pictus were inactive.

By human intestinal bacteria, saikosaponin c was transformed to four metabolites, prosaikogenin E1 (E1) prosaikogenin E2 (E2), prosaikogenin E3 (E3) and saikogenin E. Metabolic time course of saikosaponin c was as follows; in early time, saikosaponin c was converted to E1 and E2, and then these were transformed to saikogenin E via E3. Also, this metabolic pathway was similar to the metabolism of saikosaponin c by rat intestinal bacteria.Bacteroides JY-6 andBacteroides YK-4, the bacteria isolated from human intestinal bacteria, could transform saiko-saponin c to E via E1 (or E2) and E3. However, these bacteria were not able to directly transform E1 and E2 to saikogenin E. Naringin was mainly transformed to naringenin by human intestinal bacteria. The minor metabolic pathway transformed naringin to naringenin via prunin. By JY-6 or YK-4, naringin was metabolized to naringenin only via prunin.