Organisms living in the sea are known to contain a considerable amount of compounds belonging to the classes of phenols and quinoids [1]. Representatives of these classes possess a broad spectrum of biological activity, the antimicrobial effect being the most common property of these compounds.The purpose of this work was to study the cytotoxic and antimicrobial activity of polybrominated diphenyl esters [2] and sesquiterpenequinones [3][4][5] isolated previously from some marine sponges.The cytotoxic activity was studied by measuring the degree of inhibition of the inclusion of labeled thymidine into an acid-insoluble fraction of Ehrlich ascites tumor cells. The cytotoxic effect of sesquiterpenequinones was evaluated from the inhibiting dose (ID50) of these compounds producing a 50~ inhibition of the label inclusion. According to the results of our experiments, the IDs0 values of sesquiterpenequinones I-IX are 22.4, 16.2, 12.8, 100, 31.1, 33.2, 34.8, 6.5, and 15.8gg/ml, respectively. Acetylation of the hydroxyl groups and reductive acetylation of the quinoid carbonyl groups in compounds I and IV led to an increase in the activity. The cytotoxic activities of diphenyl esters X-XII, estimated as the degree of inhibition at a compound concentration of 50 gg/mi, are 33.8, 46.7, and 78.3%.The results of investigation of the antimicrobial activity are presented in Table 1.Polybrominated diphenyl esters X-XII exhibit a high activity with respect to St. aureus and T. mentographytes while being inactive toward other microbial strains studied. All the natural quinones (I, IV, VI-IX) also produce a significant antistaphylococcal effect but show no activity toward Gram-negative species and fungi. Acetylation of the hydroxyl group in sesquiterpenequinones leads to a significant decrease or complete loss of antimicrobial activity.I Pacific-Ocean Institute of Bioorganic Chemistry, Far-East Division, Russian Academy of Sciences, Vladivostok. Russia.
EXPERIMENTAL CHEMICAL PARTThe IH NMR spectra were measured on a Bruker WM-250 spectrometer using TMS as the internal standard. The mass spectra were obtained with an LKB-9000S spectrometer operated at an electron impact energy of 70 eV.The extraction, chromatography, and properties of compounds I, VI, VII, were described in [3], IV-in [5], , and X, XI, and XII -in [2].
