RETRACTED: Jejupeptins A and B: Polyketide–Cyclic Peptide Hybrids with Anti-Corticosterone Activity from Streptomyces sp. KCB15JA151

Two new polyketide–cyclic peptide hybrids jejupeptins A (1) and B (2), together with a known compound eurystatin B (3), were isolated from a culture of Streptomyces sp. KCB15JA151. The chemical structures of the compounds were elucidated using a combination of 1D and 2D NMR spectroscopy and DP4+ probability analyses. Comprehensive spectroscopic analysis revealed that 1 and 2 are the first examples of hybrid peptide–polyketides possessing an unprecedented 4-amino-3-hydroxymethyl-3-methyl-2-oxopentanoic acid moiety. A plausible biosynthetic pathway for these compounds was proposed. Biological evaluation demonstrated that compounds 1 and 2 exhibit protective effects against corticosterone-induced apoptosis and cellular oxidative stress without any associated cytotoxicity.