Abstract
In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea marine invertebrates, we have investigated the sponge Hemimycale arabica. The antimicrobial fraction of an organic extract of the sponge afforded two new hydantoin alkaloids, hemimycalins A and B (2 and 3), together with the previously reported compound (Z)-5-(4-hydroxybenzylidene)imidazolidine-2,4-dione (1). The structures of the compounds were determined by extensive 1D and 2D NMR (COSY, HSQC and HMBC) studies and high-resolution mass spectral determinations. Hemimycalins A (2) and B (3) represent the first examples of the natural N-alkylated hydantoins from the sponge Hemimycale arabica. Compounds 1–3 displayed variable antimicrobial activities against E. coli, S. aureus, and C. albicans. In addition, compound 1 displayed moderate antiproliferative activity against the human cervical carcinoma (HeLa) cell line. These findings provide further insight into the chemical diversity as well as the biological activity of this class of compounds.
Highlights
The marine environment has proven to be a very rich source of extremely potent compounds with significant activities including antitumor, anti-inflammatory, analgesic, immunomodulatory, anti-allergic, and anti-viral [1]
In the course of our ongoing search for bioactive compounds from Red Sea marine sponges, we have investigated the antimicrobial fraction of an organic extract of the Red Sea sponge
H3-15 a HMBC correlations are from proton(s) stated to the indicated carbons; b Overlapped with the H2O signal of the solvent
Summary
The marine environment has proven to be a very rich source of extremely potent compounds with significant activities including antitumor, anti-inflammatory, analgesic, immunomodulatory, anti-allergic, and anti-viral [1]. Members of the genus Hemimycale are producers of bioactive secondary metabolites including the complex guanidine alkaloids [7,8] and hydantoin derivatives [9] Examples of these compounds include ptilomycalin A. The natural (Z)-5-(4-hydroxybenzylidene) imidazolidine-2,4-dione (1) and its synthetic derivative (Z)-5-(4-(ethylthio)benzylidene)-hydantoin showed potent in vitro anti-growth and anti-invasive properties against PC-3M prostate cancer cells in MTT and spheroid disaggregation [17]. They decreased the orthotopic tumor growth and inhibited the formation of tumor micrometastases in distant organs without apparent cytotoxic effects at the test doses [17]. The purification, structure determination of compounds 1–3 as well as the antimicrobial and antiproliferative activities of the compounds will be discussed
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