A new antibacterial phenanthrenequinone from Dendrobium sinense.

A new phenanthrenequinone, named denbinobin B (1), together with three known phenanthrenes was isolated from the whole plant of Dendrobium sinense T. Tang et F.T. Wang, an endemic and endangered orchid to Hainan Island. The new compound was elucidated using a combination of 1D, 2D NMR (COSY, HMQC, and HMBC) techniques, and HR-ESI-MS analyses. Compound 1 exhibited moderate antibacterial activity against Staphylococcus aureus with the diameter of the inhibition zone of 16.5 mm.