Anti-osteoporotic and antioxidant activities of chemical constituents of the aerial parts of Ducrosia ismaelis

A new pterocarpan glycoside, glycinol-3-O-β-d-glucopyranoside (1), and a new dihydrochalcone glycoside, ismaeloside A (2), were isolated together with 13 known compounds, including several flavonoids (3-8), lignans (9-11), and phenolic compounds (12-15), from the methanol extract of the aerial parts of Ducrosia ismaelis. The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. The anti-osteoporotic and antioxidant activities of the isolated compounds were assessed using tartrate-resistant acid phosphatase (TRAP), oxygen radical absorbance capacity (ORAC), and reducing capacity assays. Compound 15 exhibited a dose-dependent inhibition of osteoclastic TRAP activity with a TRAP value of 86.05 ± 6.55% of the control at a concentration of 10 μM. Compounds 1, 3-5, and 8 showed potent peroxyl radical-scavenging capacities with ORAC values of 22.79 ± 0.90, 25.57 ± 0.49, 20.41 ± 0.63, 26.55 ± 0.42, and 24.83 ± 0.12 μM Trolox equivalents (TE) at 10 μM, respectively. Only compound 9 was able to significantly reduce Cu(I) with 23.44 μM TE at a concentration of 10 μM. All of the aforementioned compounds were isolated for the first time from a Ducrosia species.