Heronamides G-L, polyene macrolactams from Streptomyces niveus .

Six new polyene macrolactams, heronamides G-L (1-6), one new polyenoic acid derivative, niveamide B (10), together with four known compounds, BE-14106-6 (7), BE-14106 (8), GT32-B (9), and niveamide (11), were isolated from the fermentation broth of Streptomyces niveus . Their planar structures were elucidated by detailed analysis of spectroscopic data. The absolute configurations of compounds 1-6 were determined by calculated ECD spectra and analysis of the possible biosynthetic pathways. Compounds 1-6 and 8-11 did not exhibit any significant antimicrobial activities, cytotoxicities, or inhibitory effects on lipopolysaccharide-induced NO production in BV2 microglial cells.