Two new alkaloids, strepchazolins A (1) and B (2), together with a previously reported compound, streptazolin (3), were isolated from a marine actinomycete, Streptomyces chartreusis NA02069, collected in the Coast of Hainan Island, China. The structures of new compounds were determined by extensive NMR, mass spectroscopic and X-ray crystallographic analysis, as well as modified Mosher's method. Compound 1 showed weak anti-Bacillus subtilis activity with the MIC value of 64.0 μM, and weak inhibitory activity against acetylcholinesterase (AChE) in vitro with IC50 value of 50.6 μM, while its diastereoisomer, Compound 2, is almost inactive.
Keywords: Streptomyces chartreusis; acetylcholinesterase inhibitory activity; alkaloid; antimicrobial activity; marine natural product; strepchazolin; streptazolin.