Chemical constituents from the seeds of Cassia obtusefolia and their in vitro α-glucosidase inhibitory and antioxidant activities

Basing on chromatographic separation techniques, fifteen aglycones (1-15), including two new anthraquinone aglycones (1, 2) and thirteen known compounds (3-15), were isolated from the small polar fraction of Cassia obtusefolia (petroleum ether extract). Structural elucidations were performed by 1D/2D NMR spectroscopy and mass spectrometry. The in vitro antioxidant and alpha-glucosidase inhibitory activities of these fifteen compounds were determined. Except compounds 12 (IC50 3.03 +/- 0.31 mu g/mL, stronger than ascorbic acid, which IC50 was 6.48 +/- 2.30 mu g/mL) and 13 (IC50 78.40 +/- 2.39 mu g/mL), the free radical scavenging capacities of other compounds were weak. Compounds 4, 5, 6 and 13 exhibited inhibitory activities on alpha-glucosidase with IC50, values of 50.60 +/- 1.10, 22.57 +/- 0.07, 60.09 +/- 1.40, and 80.01 +/- 2.66 mu g/mL separately, however, all the alpha-glucosidase inhibitory activities were weaker than positive control (acarbose).