Cytotoxic Kendomycins Containing the Carbacylic Ansa Scaffold from the Marine-Derived Verrucosispora sp. SCSIO 07399.

Three new kendomycin analogues, kendomycins B-D ( 1 - 3 ), were discovered from the marine-derived actinomycete Verrucosispora sp. SCSIO 07399. The structures of 1 - 3 were elucidated using diverse spectroscopic data analyses, X-ray crystallography, and semisynthetic derivatization. In vitro antimicrobial assays revealed that 1 - 3 all display good antibacterial activities against six Gram-positive bacteria with MIC values ranging from 0.5 to 8.0 μg/mL. Additionally, 1 - 3 were found to be moderately cytotoxic against MGC803, A549, HeLa, HepG2, MCF-7, and RKO human tumor cell lines; IC ₅₀ values ranged from 2.2 to 44 μM.