A potent anti-complementary acylated sterol glucoside from Orostachys japonicus.

In order to isolate substances that inhibit the hemolytic activity of human serum against erythrocytes, we have evaluated whole plants of the Orostachys japonicus species with regard to its anti-complement activity, and have identified its active principles following activity-guided isolation. A methanol extract of the O. japonicus, as well as its n-hexane soluble fraction, exhibited significant anti-complement activity on the complement system, which was expressed as total hemolytic activity. A bioassay-guided chromatographic separation of the constituents resulted in the isolation of three known compounds 1-3 from the active n-hexane fraction. The structure of these compounds were analyzed, and they were identified as hydroxyhopanone (1), beta-sitosteryl-3-O-beta-D-glucopyranosyl-6'-O-palmitate (2), and beta-sitosteryl-3-O-beta-D-glucopyranoside (3), respectively. Of these compounds, compound 2 exhibited potent anti-complement activity (IC50= 1.0 +/- 0.1 microM) on the classical pathway of the complement, as compared to tiliroside (IC50= 76.5 +/- 1.1 microM), which was used as a positive control. However, compounds 1 and 3 exhibited no activity in this system.