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Cytotoxic macrolides from benthic Amphidinium dinoflagellate
Marine dinoflagellates Amphidinium species are known as producers of unique secondary metabolites. In our searches for bioactive substances from symbiotic dinoflagellates, a series of cyototoxic macrolides, named amphidinolides, have been isolated from endosymbiotic dinoflagellates Amphidinium sp. separated from marine acoel flatworms Amphiscolops species, and some of them exhibit potent cytotoxicity and antitumor activity.
Recently, we have developed the rapid searching strategy for the Amphidinium strains with macrolide-producing ability using single-cell PCR protocol, and 250 or more Amphidinium strains isolated from benthic sources collected from South-East Islands, Japan, were tested by the one-cell PCR. The extracts of dinoflagellates positive in the PCR studies were further evaluated by cytotoxic screening and metabolomics analyses using 2D NMR analyses. This led to the discovery of a marine benthic Amphidinium strain HYA024 producing several unknown macrolides with potent cytotoxic activity. From the mass cultured algal cells of this strains, we have discovered a series of novel cytotoxic macrolides, named iriomoteolides.
The discovery of the Amphidinium HYA024 strain, the isolation and structures of iriomoteolides-1a –1c, 2a, 3a, and 4a [1–3] are discussed.
References: 1. Tsuda, M. et al. (2007)J. Org. Chem. 72: 4469–4474. 2. Tsuda, M. et al. (2007)J. Nat. Prod. 70: 1661–1663.
3. Oguchi, K. et al. (2007)J. Org. Chem. 73: 1567–1570.