Iriomoteolide-12a, a 12-membered macrolide from dinoflagellate Amphidinium species

Marine dinoflagellates of the genus Amphidinium are well-known as a producer of unique cytotoxic metabolites. We have isolated a new 12-membered macrolide, iriomoteolide-12a, from the benthic dinoflagellate Amphidinium species collected off Iriomote Island, Japan. In this symposium, we will discuss the isolation and structural elucidation of this new macrolide.

The dinoflagellate Amphidinium sp. (strain KCA09053) was cultivated in 50 L of 1% Provasoli's enriched seawater (PES) medium, 16h light and 8h dark. The algal cells obtained from 50 L of the medium were extracted with MeOH/toluene (3:1). The toluene-soluble materials of the extract were subjected to a SiO₂ column, C18 column and one of a macrolide containing fractions were separated by C18 HPLC to afford a new compound, iriomoteolide-12a. Iriomoteolide-12a was obtained as colorless amorphous solid, and the molecular formula of C₂₅H₄₀O₅ was revealed by HRESIMS data. ¹³C NMR data disclosed the presence of a total of 25 carbon atoms due to five quaternary carbons, one of which is three carbonyl carbons, eight methine carbons, five methylene carbons, and seven methyl carbons. The planar structure of iriomoteolide-12a was elucidated on the basis of detailed analyses of 2D NMR data and MS spectra.

Iriomoteolide-12a is a new 12-membered macrolide with six one-carbon branches, two ketone carbonyls, and a hydroxyl group. The skeleton is related to that of amphidinolide Q [1,2].

References: 1. Kobayashi J, Takahashi M, Ishibashi M (1996) Tetrahedron Lett 37: 1449–1450.

2.Takahashi Y, Kubota T, Fukushi E, Kawabata J, Kobayashi J (2008) Org Lett 10: 3709–37111.