In vitro antioxidative activities of extract and semi-purified fractions of the marine red alga, Rhodomela confervoides (Rhodomelaceae)

The methanol-chloroform extract of the marine red alga, Rhodomela confervoides, was measured for antioxidant activity, using the alpha,alpha-diphenyl-beta-picrylhydrazyl radical-scavenging assay and the beta-carotene-linoleate bleaching assay systems, and compared with those of the positive Controls of butylated hydroxytoluene, gallic acid and ascorbic acid, The active extract was further purified by liquid-liquid partition to afford four fractions, of which the ethyl acetate-soluble (EA) fraction exhibited the strongest antioxidant activity in both assay systems. This fraction was further divided into seven subfractions, designated as EA1-EA7, by silica gel vacuum liquid chromatography. in most cases, EA1 and EM Were found to possess the strongest activity. The total phenolic contents and reducing powers of the extract, fractions, and subfractions were also determined. Significant associations between the antioxidant potency and the total phenolic content, as well as between the antioxidant potency and the reducing power, were found for the tested fractions and subfractions. (c) 2008 Elsevier Ltd. All rights reserved.

Biosynthesis of fluorescent allophycocyanin alpha-subunits by autocatalysis in Escherichia coli

APC (allophycocyanin) is widely used for fluorescence tagging and may be a promising antioxidant agent for use within the food and pharmaceutical industries. Chromophore attachment to apo-ApcA (apo-APC alpha-subunit without chromophore) can be auto-catalysed both in vitro and in vivo. In the present study, a plasmid containing genes of apo-ApcA and chromophore synthetases (HOI (ferredoxin-dependent haem oxygenase) and PcyA (phycocyanobilin:ferredoxin oxidoreductase)] was constructed and expressed in Escherichia coli. The results show that holo-ApcA (APC alpha-subunit with chromophore) can be synthesized by autocatalysis in E. coli. Recombinant holo-ApcA showed the same spectral and fluorescent properties as PC (phycocyanin) and could serve as a good substitute for native PC for fluorescent tagging. Moreover, recombinant ApcA can inhibit hydroxyl and peroxyl radicals more strongly than holo-ApcA and native APC. The EC50 values were 296.4 +/- 22.4 mu g/ml against hydroxyl radicals and 38.5 +/- 2.6 mu g/ml against peroxyl radicals.