Two new pyrrolo-2-aminoimidazoles from a Myanmarese marine sponge, Clathria prolifera
Marine organisms such as marine sponges and soft corals are valuable sources of pharmacologically active secondary metabolites. In our ongoing research on the discovery of new secondary metabolites from marine organisms, two new pyrrolo-2-aminoimidazoles, clathriroles A (1) and B (2), were isolated from the water-soluble portion prepared from the methanol and acetone (2:1) extract of the marine sponge, Clathria prolifera, collected in Myanmar. The chemical structures of the isolated compounds were determined using extensive spectroscopic techniques, including NMR, HRESIMS, IR, and optical rotation, and comparisons with the reported literature. The spectroscopic analyses of 1 and 2 suggested that 1 is an enantiomer of antifungal N-methylmanzacidin C isolated from the marine sponge Axinella brevistyla, whereas 2 is a diastereomer of manzacidin D at C-11 isolated from the marine sponge Astrosclera willeyana. To the best of our knowledge, this is the first report of the isolation of the pyrrolo-2-aminoimidazole compounds from C. prolifera. Furthermore, in contrast to the potency of N-methylmanzacidin C against Saccharomyces cerevisiae, the antifungal assay revealed that 1 and 2 lack any activity against this strain. Thus, these observations may suggest that the absolute configurations at both C-9 and C-11 play an important role in controlling the antifungal activity of this type of compound.
KeywordsClathria prolifera Pyrrole derivatives Alkaloids Marine sponge Saccharomyces cerevisiae
This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan (JSPS KAKENHI Grants JP17K08333, JP15H05138, JP17H02203, JP26303005, and JP17H05435) and Grants from the Kobayashi International Scholarship Foundation (H.M.) and from the Kanae Foundation for the Promotion of Medical Science (H.M.).
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