Three siderophores mirubactins B―D (4―6) were identified as the degradation products of previously isolated mirubactin (1). Their structures were revealed by HR-ESI-MS/MS, NMR analyses, and density function calculations, in which...
Lobophorins (LOBs) are a growing family of spirotetronate natural products with significant cytotoxicity, anti-inflammatory, and antibacterial activities. Herein, we report the transwell-based discovery of Streptomyces sp. CB09030 from a panel of 16 in-house Streptomyces strains, which has significant anti-mycobacterial activity and produces LOB A (1), LOB B (2), and LOB H8 (3). Genome sequencing and bioinformatic analyses revealed the potential biosynthetic gene cluster (BGC) for 1–3, which is highly homologous with the reported BGCs for LOBs. However, the glycosyltransferase LobG1 in S. sp. CB09030 has certain point mutations compared to the reported LobG1. Finally, LOB analogue 4 (O-β-D-kijanosyl-(1→17)-kijanolide) was obtained through an acid-catalyzed hydrolysis of 2. Compounds 1–4 showed different antibacterial activities against Mycobacterium smegmatis and Bacillus subtilis, which revealed the varying roles of different sugars in their antibacterial activities.
A Tripterygium wilfordii endophyte, Streptomyces sp. CB04723, was shown to produce an unusually
highly reduced cytotoxic
cinnamoyl lipid, tripmycin A (1). Structure–activity
relationship studies revealed that both the cinnamyl moiety and the
saturated fatty acid side chain are indispensable to the over 400-fold
cytotoxicity improvement of 1 against the triple-negative
breast cancer cell line MDA-MB-231 compared to 5-(2-methylphenyl)-4-pentenoic
acid (2). Bioinformatical analysis, gene inactivation,
and overexpression revealed that Hxs15 most likely acted as an enoyl
reductase and was involved with the side chain reduction of 1, which provides a new insight into the biosynthesis of cinnamoyl
lipids.
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