Kofumicins A−D, Antibacterial Glycosylated Linear Polyene Polyketides from Kutzneria kofuensis , Identified via Bacterial Activity Metabolomics

Abstract

Four previously unreported glycosylated linear polyene polyketides, kofumicins A−D (1−4), were isolated from Kutzneria kofuensisNRRL 24061 and were found to inhibit Staphylococcus aureus growth. The kofumicins were identified from the crude extract using a bacterial activity metabolomics-guided approach, which employs split-flow HPLC-UV/MS to generate microtiter plate arrays enabling dereplication and bioactivity assessment prior to isolation. The structures were determined using NMR data, HR-ESI-MS, and biosynthetic gene cluster inference, establishing the kofumicins as new members of a family of glycosylated amphoteric linear polyene polyketides. Kofumicins A−C (1−3) share a conserved polyketide chain but differ in disaccharide composition and glycosidic regiochemistry, while kofumicin D (4) exhibits a truncated polyketide chain with a monosaccharide. Distance-constrained molecular dynamics calculations suggest that the kofumicins adopt a bent bolaamphiphilic conformation. Kofumicin C (3), bearing 6-deoxyglucose as the polyketide-linked sugar, was the most potent glycovariant tested, with MICs of 2−4 μg/mL against S. aureus strains including MRSA, while kofumicin B (2), bearing a glucose at the same position, exhibited MICs of 16−32 μg/mL. These results identify the C-6 substituent of the polyketide-linked sugar as an important determinant of antibacterial potency in this compound class.