Four novel biscembranes have been isolated from the soft coral Sarcophyton glaucum, collected at Amami Oshima, two of which showed weak activity against proliferation of human promyelocytic leukemia cells (HL-60). Their absolute structures were determined on the basis of the CD spectra.

Seven new tetracyclic biscembranes (1-7) have been isolated from the soft coral Sarcophyton glaucum. Four (1-4) may be formed biogenetically by a Diels-Alder reaction of Delta(4(5)) and Delta(8(9)) geometrical isomers of methyl sarcoate and Delta(21(34), 35(36)) dienes, including two with a tetrahydrofuran ring between C-27 and C-30 (3, 4), and three biscembranes (5-7) are probably derived from methyl sarcoate isomers with Delta(1(14), 4(5), 8(9)) and a cembrane diene. Their structures were established on the basis of spectroscopic methods. Six of them (1-5, 7) exhibited weak cytotoxic activity against proliferation of human promyelocytic leukemia cells (HL-60).

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Seven new isomalabaricane derivatives, rhabdastins A-G (1-7), and a new monocyclic triterpene glycoside, rhabdastoside A (8), have been isolated from the methanol extract of the sponge Rhabdastrella globostellata, collected at Amami-oshima, Japan. Three of them were isolated as their corresponding methyl esters, rhabdastins A-D (1-3). Their structures were determined on the basis of spectroscopic and X-ray diffraction analyses. The isolated compounds were evaluated for their cytotoxicity against the proliferation of promyelocytic leukemia HL-60 cells. Compounds 4, 5, 7, and 11, possessing a cyclopentane side chain, exhibited weak activity, with IC(50) values of 21, 29, 44, and 11 μM, respectively, while compounds 1, 2, and 3, with a 2-substituted-propanoate side chain, were inactive at 100 μM. In addition, the mechanism of cytotoxicity of compounds 4 and 5 was investigated.

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Five novel bis(indole) alkaloids, which were composed of two molecules of aplysinopsin have been isolated from a stony coral, Tubastraea aurea. Their structures were elucidated on the basis of spectroscopic methods.The secondary metabolites of the stony corals have not been studied so extensively as those of soft corals, based on the assumption that their calcareous bodies likely eliminate the requirement for defensive metabolites. However, they have been proven to be a source of many different types of compounds: anthraquinoid derivatives, 1 a phenol, 2 alkaloids, 3 macrolides, 4 and acetylenes. 5 Many of these compounds exhibited interesting biological activities, such as antiviral, 6 antifungal, 6 and cytotoxic activity. 7We examined the chemical constituents of the stony coral, Tubastraea aurea, collected in the Odomari area, Kagoshima Prefecture. A methanol extract of the animal was partitioned between CH 2 Cl 2 and water, and then the aqueous part was extracted with n-BuOH. Neither extract exhibited biological activity (e.g. antibacterial, antifungal, or cytotoxic activity) in our initial screening. Nevertheless, we tried to isolate the aromatic compounds from the dichloromethane extract, because aromtic signals were observed in the 1 H NMR spectrum of the extract. The extract was subjected to silica gel chromatography and reversed-phase HPLC and yielded three unprecedented bis(indole) alkaloids named tubastrindoles A-C (1-3), dimers of aplysinopsin. 8 Further investigation has led to the isolation of five new bis(indole) alkaloids, tubastrindoles D-H (4-8). In this paper, we describe the isolation and structure elucidation of these compounds.

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