A new actinomycin Z analogue with an additional oxygen bridge between chromophore and β-depsipentapeptide from Streptomyces sp. KIB-H714.

Actinomycin Z6 (1), a new member of the actinomycin family, along with three congeners of the Z-type (Z1 , Z3 , Z5 ) actinomycins, are produced from Streptomyces sp. KIB-H714. Their structures were authenticated by comprehensive spectroscopic data interpretation. Different from all the reported Z-type actinomycins, the β-ring of the new compound actinomycin Z6 includes an additional ring linked between the actinoyl chromophore and β-peptidolactone. In Z3 and Z5 , the L-threonine in β-depsipeptide is replaced by the unusual 4-chlorothreonine, an amino acid rarely found in actinomycin family. All isolates were evaluated for cytotoxicity against five human tumor cell lines and for inhibitory activity against Candida albicans and Staphylococcus aureus.