5-Hydroxyindole-type Alkaloids from Marine Organisms

Abstract

Much attention has been focused on indole alkaloids owing to their potential utility and significant biological activity, including cytotoxic, antiviral, antimicrobial, antiparasitics, and anti-inflammatory. A variety of marine sources including sponges, tunicates, red alga, and symbiotic bacteria have been shown to generate indole alkaloids, which represent the largest number and most complicated of the marine alkaloids [1]. The alkaloids obtained from marine organisms frequently possess novel frameworks while in other cases terrestrially related compounds clearly exist. Their structure elucidation, chemical modification, and synthesis have received a great deal of interdisciplinary attention from areas of research other than chemistry and include pharmacology and medicine.In the course of our study on the chemical investigation of marine organisms [2], we found indol alkaloids from the Micronesian sponge Hyrtios sp. collected in Chuuk State, Federated States of Micronesia and Korean sponge Scalarispongia sp. collected in Dokdo Island, Korea. Bioassay-guided separation of the crude extracts using various chromatographic techniques yielded a new ？-carboline alkaloid together with known 5-hydroxyindol alkaloids. From the extracts of Hyrtios sp., 1-carboxy-6-hydroxy-3,4-dihydro-b-carboline (1), 6-hydroxy-3,4-dihydro-1-oxo-？-carboline (2), 5-hydroxy-1H-indole-3-carboxylic acid methyl ester (3), serotonin (4), hyrtiosin A (5), 5-hydroxyindole-3-carbaldehyde (6), and hyrtiosin B (7) were isolated. And from the extracts of Scalarispongia sp., bis-indole alkaloid, hyrtinadine A (8) together with the known metabolites were isolated. Their structures were elucidated on the basis of mass spectrometry and detailed 2D NMR spectroscopic data.