Bromophycoic Acids: Bioactive Natural Products from a Fijian Red Alga Callophycus sp.

Abstract

Bioassay-guided fractionation of extracts from a Fijian red alga in the genus Callophycus resulted in the isolation of five new compounds of the diterpene-benzoate class. Bromophycoic acids A-E (1–5) were characterized by NMR and mass spectroscopic analyses and represent two novel carbon skeletons, one with an unusual proposed biosynthesis. These compounds display a range of activities against human tumor cell lines, malarial parasite, and bacterial pathogens including low micromolar suppression of MRSA and VREF.

Iodinated Meroditerpenes from a Red Alga Callophycus sp.

“…Examination of the NMR spectroscopic data (Table 4) showed that 6 possessed a 1,2,4-trisubstituted aromatic ring as well as 4-methylpent-3-enyl and bromomethine moieties, similar to bromophycoic acids A–E ( 12–16 ) previously described from the same alga. 19 The spin group composed of H-2 and H 2 -1 correlates with C-3′, C-3, and C-4′, as shown by the HMBC spectrum, suggesting that a double bond was present on the decalin ring system where the coumaran moiety was attached. The double bond was ascertained at C-3 because of COSY correlations between H-4 and H 2 -5.…”

“…Because of this spectroscopic evidence, 7 was identified as the methyl ester of bromophycoic acid A. 19 …”

“…The absolute stereochemistries of 6 and 7 , respectively 2 S ,6 R ,7 R ,10 S ,11 S -bromophycoic acid F and 2 S ,3 R ,6 R ,7 R ,10 S ,11 S -bromophycoic acid A methyl ester, are inverted relative to that originally depicted for bromophycoic acid A ( 12 ). 19 The chirality of the latter and its analogs were not previously formally assigned. Since all these compounds are related biosynthetically, it is now reasonable to consider that bromophycoic acid F ( 6 ) and bromophycoic acid A methyl ester ( 7 ) share the same absolute stereochemistry as bromophycoic acids A–E ( 12–16 ), depicted correctly below.…”

Peroxy natural products

“…102 Bioassay-guided fractionation of extracts from a Fijian red alga in the genus Callophycus provided one new compound of the diterpene-benzoate class, bromophycoic acid C 183, which exhibited modest activities against methicillin-resistant Staphylococcus aureus and the human malaria parasite Plasmodium falciparum. 103 Two xeniaphyllane peroxides gibberosins B and C 184 and 185 were isolated from a Taiwanese soft coral Sinularia gibberosa. 104 Six further members of this family containing the unusual cyclic peroxyhemiketal moiety, sinugibberosides A-F 186-191, have been reported from the same species, S. Gibberosa.…”

Comparative mass spectrometry-based metabolomics strategies for the investigation of microbial secondary metabolites

“…Natural product extracts are commonly divided into multiple fractions which are then screened to identify the components underlying the desired biological activity. 222-225 However, low abundance compounds can often be overlooked in complex extracts, and recently MVSA have been utilized to help link observed fraction bioactivity to detectable features from metabolomic analyses. 39,226 Even after correlating metabolites with biological activity, determining the mode of action for active compounds can be difficult and expensive.…”