Pyridapeptides F‒I, Cyclohexapeptides from Marine Sponge-derived Streptomyces sp. OUCMDZ-4539

Abstract

Four new cyclohexapeptides, pyridapeptides F–I (1–4), were isolated from the fermentation broth of marine sponge-derived Streptomyces sp. OUCMDZ-4539. The pyridapeptides F–H (1–3) are composed of β-hydroxyleucine, alanine, O-methylthreonine, hexahydropyridazine-3-carboxylic acid, 5-hydroxytetrahydropyridazine-3-carboxylic acid, and (2S,3R,4E,6E)-2-amino-3-hydroxy-4,6-dienoic acid residues. Pyridapeptide I (4) contains (2S,3R,4E,6E)-2-amino-3-hydroxy-8-methylnona-4,6-dienoic acid residue and a very rare glycose residue, aculose. Their structures were determined based on spectroscopic analysis and chemical methods. Pyridapeptides G–I (2–4) have the 2,3,6-trideoxyhexose units glycosylated at the γ-OH-TPDA residue, displayed significant antiproliferative activity against four (PC9, MKN45, HepG2, K562) or two (PC9, MKN45) human cancer cell lines.