Chemical investigation of the marine-derived Streptomyces sp. Act8015 led to the isolation of two cyclic peptide antibiotics, piperazimycins A and B (1a, 1b). Their structures were confirmed on the basis of a detailed HRESI-MS/MS analysis. Additionally, a new butanolide, 4,10-dihydroxy-10-methyl-dodecan-4-olide (2), and the respective acid, 4,10-dihydroxy-10-methyl-dodecanoic acid (3a) were identified. Further isolated compounds were staurosporin, adenine, indole-3-carboxylic acid, ferulic acid, tryptophol, and three g -butyrolactones: virginiae butanolide E (4e) and Graefe's Factors I (4f) and III (4g). The structures of 2 and 3a were confirmed by detailed 1D and 2D NMR studies and MS spectra and by comparison with related structures. A full signal assignment of virginiae butanolide E (4e) is reported here for the first time.Keywords g -butyrolactones, piperazimycins, marinederived Streptomyces sp. The extract from the marine-derived Streptomyces sp. Act8015 exhibited in vitro antitumor activities against a number of cancer cells at very low concentrations. TLC of the crude extract displayed several UV absorbing zones, which turned yellowish-brown and/or reddish-brown with anisaldehyde/sulfuric acid. Further zones without UV absorption appeared as violet-blue and/or greenish-blue spots with the same reagent.
IntroductionA large-scale shaker culture was performed on M 2 ϩ medium [15] for 5 days at 28°C. Chromatography of the ethyl acetate extract afforded 12 compounds, the peptides