Mohangic Acid H and Mohangiol: New p-Aminoacetophenone Derivatives from a Mudflat-Derived Streptomyces sp.

Streptomyces sp. AWH31-250, isolated from a tidal mudflat in the Nakdong River estuary in Busan, Republic of Korea, was found to produce two novel p-aminoacetophenone derivatives, mohangic acid H (1) and mohangiol (2). Their planar structures were established by comprehensive 1D and 2D NMR spectroscopy, mass spectrometry, and UV analysis, possessing a shorter carbon-chain with a diene moiety, whereas known mohangic acids A-F bear a longer carbon-chain with a triene moiety. The absolute configurations of the key stereogenic centers were determined via computational DP4+ calculations and bioinformatic analysis of the ketoreductase domain sequence from the biosynthetic gene cluster. Based on the careful gene analysis along with whole-genome sequencing, the first plausible biosynthetic pathway of mohangic acids A-G and mohangiol was proposed. Mohangic acid H (1) and mohangiol (2) displayed moderate inhibitory activity against Candida albicans isocitrate lyase with IC50 values of 21.37 and 21.12 µg/mL, respectively.