Callophycoic Acids and Callophycols from the Fijian Red Alga Callophycus serratus

Abstract

Callophycoic acids A-H (1-8) and callophycols A and B (9 and 10) were isolated from extracts of the Fijian red alga Callophycus serratus, and identified by NMR, X-ray, and mass spectral analyses. These natural products represent four novel carbon skeletons, providing the first examples of diterpene-benzoic acids and diterpene-phenols in macroalgae. Compounds 1-10 exhibited antibacterial, antimalarial, and anticancer activity, although they are less bioactive than diterpene-benzoate macrolides previously isolated from this red alga.

Desorption electrospray ionization mass spectrometry reveals surface-mediated antifungal chemical defense of a tropical seaweed

“…When natural products within algal extracts were quantified by LC-MS, bromophycolides were found to be associated exclusively with 4 algal collections, whereas callophycoic acids and callophycols were observed in 6 other collections (Table S1), consistent with previous reports of 2 chemically-distinct genotypes (''chemotypes'') of C. serratus on Fijian coral reefs (32)(33)(34). Sequencing of 18S rRNA (Ϸ1.2 kb) from these algal samples revealed 3 unique haplotypes differing by 1-13 bp.…”

Iodinated Meroditerpenes from a Red Alga Callophycus sp.

“…The halogenation-decarboxylation-halogenation sequence of reactions is also likely in the formation of callophycoic acid H and callophycols A–B, previously isolated from another member of the Callophycus genus, likely Callophycus densus . 27 For the bromophycoic acids, a coumaran ring system is first predicted to be obtained through the oxidation of an alkenic methyl group followed by the formation of the furan ring fused with the phenol group (Figure 7c). This step is required to obtain bromophycoic acids A–D ( 12–15 ), F ( 6 ), and bromophycoic acid A methyl ester ( 7 ), more specifically, with the 4-hydroxybenzoic acid moiety bonded at position 2 of the decalin system rather than at position 1 as for callophycoic acids G and H (Figure 7d).…”

“…This step is required to obtain bromophycoic acids A–D ( 12–15 ), F ( 6 ), and bromophycoic acid A methyl ester ( 7 ), more specifically, with the 4-hydroxybenzoic acid moiety bonded at position 2 of the decalin system rather than at position 1 as for callophycoic acids G and H (Figure 7d). 27 The decalin rings can then be formed by a reaction cascade initiated by the bromination of one double bond (Figure 7e). The loss of a proton, preceded or not by the addition of water, allows the formation of bromophycoic acids A ( 12 ) and F ( 6 ).…”

“…Interestingly, the closest analogs of 1 , callophycoic acids C–E, did not show any activity against these human pathogens. 27 The lack of bioactivity of iodocallophycols A–D ( 2–5 ) suggested that the carboxylic acid on the phenol ring is crucial to inhibit bacterial growth. The same phenomenon was observed with the bioactive callophycoic acids G–H, which possess a hydroxybenzoic acid ring, whereas the inactive callophycols A–B have a phenol but not carboxylic acid functional group.…”

Marine and Freshwater Microalgae as a Potential Source of Novel Herbicides

“…Hassan and Ghareib, 2009) and terpenoids (e.g. Lane et al, 2007;Arunkumar et al, 2010), have been characterized. Although the potential of these compounds as herbicides remains to well-studied, based on the apparent importance of allelopathy among photoautotrophs in aquatic habitats, the chemical diversity of the macroalgae, like the microalgae, represents a wealth of secondary metabolites to be explored to this end.…”