Three novel pterosin dimers form Pteris obtusiloba.

Three novel pterosin dimmers, named as obtupterosin A (1), B (2) and C (3), together with eight known pterosins (4-11) were isolated from Pteris obtusiloba. Their structures were elucidated on the basis of ESI-MS, 1D and 2D NMR spectral data, CD, X-ray and literature comparisons. Compounds 1 and 2 were a pair of isomers. Compounds 1 and 3 were the novel type of pterosin dimer. The new compounds (1-3) were assessed for their cytotoxic activities and their α-glucosidase inhibition activity. Compounds 1-3 exhibited cytotoxic activity against HCT-116 cells with IC50 value of 27.5 μM, 30.6 μM and 12.8 μM, respectively. However, all were found to be inactive at 200 μM for α-glucosidase inhibition.