We present the isolation and characterization of seven novel [natural] pyrroloiminoquinones, the makaluvamines A-F (1-6), makaluvone (7), and the known compounds discorhabdin A (8) and damirone B (9) from the Fijian sponge Zyzzya cf. marsailis. The makaluvamines exhibit potent in vitro cytotoxicity toward the human colon tumor cell-line HCT 116, show differential toxicity toward the topoisomerase II sensitive CHO cell-line xrs-6, and inhibit topoisomerase II in vitro. This activity may be mediated by intercalation into DNA and single-stranded breakage. Makaluvamine A and C exhibited in vivo antitumor activity against the human ovarian carcinoma Ovcar3 implanted in athymic mice. The makaluvamines suggest a plausible interrelationship between the batzelline/isobatzelline and discorhabdin/prianosin classes of compounds.f American Cyanamid Co.
An examination of organic extracts of four new species of South African latrunculid sponges, Tsitsikamma pedunculata, T. favus, Latrunculia bellae, and Strongylodesma algoaensis, yielded 13 known and eight new pyrroloiminoquinone alkaloids, 3-dihydro-7,8-dehydrodiscorhabdin C (4), 14-bromo-3-dihydro-7,8-dehydrodiscorhabdin C (5), discorhabdin V (6), 14-bromo-1-hydroxydiscorhabdin V (7), tsitsikammamine A N-18 oxime (10), tsitsikammamine B N-18 oxime (11), 1-methoxydiscorhabdin D (12), and 1-aminodiscorhabdin D (13). Standard spectroscopic methods provided the structures of the pyrroloiminoquinone metabolites, while chiral GC-MS analysis of the acylated ozonolysis products of 21 confirmed the stereochemistry of the l-histidine residue in this compound. The anticancer activity of 20 pyrroloiminoquinone compounds was explored in the HCT-116 cancer cell line screen, and the DNA intercalation of the tsitsikammamines, together with their ability to cleave DNA through topoisomerase I inhibition, is discussed.
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