Indole alkaloids from Kopsia hainanensis and evaluation of their antimicrobial activity.

Three new indole alkaloids, named kopsihainin D (1), kopsihainin E (2), and kopsihainin F (3), along with nine known compounds (4-12) were isolated from the twigs of Kopsia hainanensis. The structures of the new compounds were elucidated by spectroscopic methods including HRESIMS, UV, IR, and NMR. Compounds 1 - 3 and 5 showed inhibitory activity against Staphylococcus aureus with an antibacterial circle diameter of 11.2, 9.1, 10.3 and 9.7 mm, respectively.