New anthracene glycosides from Rhodomyrtus tomentosa stimulate osteoblastic differentiation of MC3T3-E1 cells

Two new anthracene glycosides (1, 2) were isolated from aerial parts of Rhodomyrtus tomentosa, along with three known compounds (3-5). The structures of two new compounds were established to be 4,8,9,10-tetrahydroxy-2,3,7-trimethoxyanthracene-6-O-beta-D-glucopyranoside (1) and 2,4,7,8,9,10-hexahydroxy-3-methoxyanthracene-6-O-alpha-L-rhamnopyranoside (2) based on spectroscopic and chemical methods. Among them, compound 1, 2, and 5 significantly (P<0.05) increased the alkaline phosphatase activity, collagen synthesis, and mineralization of the nodules of MC3T3-E1 osteoblastic cells compared to those of the control, respectively.