ABSTRACT
The chemical investigation of the Caribbean sponge Agelas citrina revealed four new pyrrole-imidazole alkaloids (PIAs), the citrinamines A-D (1-4) and the bromopyrrole alkaloid N-methylagelongine (5). All citrinamines are dimers of hymenidin (6) which was also isolated from this sponge as the major metabolite. Citrinamines A (1) and B (2) are derivatives of the PIA dimer mauritiamine (7), whereas citrinamine C (3) is derived from the PIA dimer nagelamide B (8). Citrinamine D (4) shows an uncommon linkage between the imidazole rings of both monomeric units as it is only observed in the benzocyclobutane ring moiety of benzosceptrins A-C (9-11). Compound 5 is the N-methyl derivative of agelongine (12) which consist of a pyridinium ring and an ester linkage instead of the aminoimidazole moiety and the common amide bond in PIAs.
ABSTRACT
The chemistry of the burrowing sponge Aka coralliphagum was investigated to identify chemically labile secondary metabolites. The HPLC-MS analysis of the two growth forms typica and incrustans revealed different metabolites. The previously unknown sulfated compounds siphonodictyals B1 to B3 (6-8), corallidictyals C (9) and D (10), and siphonodictyal G (11) were isolated, and their structures were elucidated by NMR and MS experiments. The compounds were tested in a DPPH assay, in antimicrobial assays against bacteria, yeasts, and fungi, and in antiproliferation assays using cultures of mouse fibroblasts. The biological activity was linked to the presence of the ortho-hydroquinone moiety.
Subject(s)
Porifera/chemistry , Sesquiterpenes , Animals , Aspergillus fumigatus/drug effects , Biphenyl Compounds , Caribbean Region , Chromatography, High Pressure Liquid , Drug Screening Assays, Antitumor , Escherichia coli/drug effects , Fibroblasts/drug effects , Mice , Microbial Sensitivity Tests , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , Picrates/pharmacology , Sesquiterpenes/chemistry , Sesquiterpenes/isolation & purification , Sesquiterpenes/pharmacology , Staphylococcus aureus/drug effectsABSTRACT
Two new bromopyrrole alkaloids were isolated from the Caribbean sponge Stylissa caribica. The new natural products, 4-bromopyrrole-2-carboxyarginine (1) and 4-bromopyrrole-2-carboxy-N(epsilon)-lysine (2), are derivatives of amino acids linked with a 4-bromopyrrole-2-carboxylic acid. The structures were elucidated on the basis of NMR and MS/MS data and their absolute configurations assigned via synthesis.
