Isolation and Structure Elucidation of Nazumazoles A-F from the Marine Sponge Theonella swinhoei

Fukuhara Kazuya, Takada Kentaro, Okada Shigeru, Matsunaga Shigeki

doi:10.24496/tennenyuki.57.0_oral18

Marine sponges of the genus Theonella have been shown to be a rich source of structurally unique and biologically active secondary metabolites. We have isolated more than 40 bioactive polyketides and modified peptides from T. swinhoei with yellow interior (T. swinhoei Y) collected at Hachijo Island. Recently, a symbiotic filamentous bacterium, ‘CandidatusEntotheonella sp.’, was identified as the sole producer of a variety of natural products from this sponge. We have analyzed the extracts of marine invertebrates by LCMS and found that the extract of T. swinhoei Y contained unidentified metabolites, among which were extraordinarily broad peaks in ODS-HPLC. We determined the components of the peaks, novel peptides nazumazoles A–C (1–3) and their analogues, nazumazoles D–F (4–6).The structures of the peptides were determined by interpretation of the MS and NMR data, and chemical degradations. 1–3 were cyclic pentapeptides dimerized through a disulfide bond, and 4–6 were monomer-like analogues of 1–3. They contain one residue each of alanine-derived oxazole and a-keto-b-amino acid residue. The absolute configuration of the amino acid residues in 1–6 were determined by Marfey’s method.While the mixture of 1–3exhibited cytotoxicity against P388 murine leukemia cells with an IC₅₀value of 0.83 mM, the mixture of 4–6 exhibited only moderate cytotoxicity against same cells (IC₅₀ > 50 mM).

Isolation and Structure Elucidation of Nazumazoles A-F from the Marine Sponge Theonella swinhoei

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