Abstract
Twelve microalgae species isolated in tropical lagoons of New Caledonia were screened as a new source of antioxidants. Microalgae were cultivated at two light intensities to investigate their influence on antioxidant capacity. To assess antioxidant property of microalgae extracts, four assays with different modes of action were used: 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis (3-éthylbenzothiazoline-6-sulphonique) (ABTS), oxygen radical absorbance capacity (ORAC), and thiobabituric acid reactive substances (TBARS). This screening was coupled to pigment analysis to link antioxidant activity and carotenoid content. The results showed that none of the microalgae studied can scavenge DPPH and ABTS radicals, but Chaetoceros sp., Nephroselmis sp., and Nitzschia A sp. have the capacity to scavenge peroxyl radical (ORAC) and Tetraselmis sp., Nitzschia A sp., and Nephroselmis sp. can inhibit lipid peroxidation (TBARS). Carotenoid composition is typical of the studied microalgae and highlight the siphonaxanthin, detected in Nephroselmis sp., as a pigment of interest. It was found that xanthophylls were the major contributors to the peroxyl radical scavenging capacity measured with ORAC assay, but there was no link between carotenoids and inhibition of lipid peroxidation measured with TBARS assay. In addition, the results showed that light intensity has a strong influence on antioxidant capacity of microalgae: Overall, antioxidant activities measured with ORAC assay are better in high light intensity whereas antioxidant activities measured with TBARS assay are better in low light intensity. It suggests that different antioxidant compounds production is related to light intensity.
Highlights
In the last decade, the demand has increased for sustainable sources of natural antioxidants for nutritional, cosmetic, and pharmaceutical applications as an alternative to controversial synthetic antioxidants
None of the twelve microalgae tested have the capacity to scavenge DPPH and ABTS radicals but they can scavenge peroxyl radical (Chaetoceros sp., Nephroselmis sp., and Nitzschia A sp.) and inhibit lipid peroxidation (Tetraselmis sp., Nitzschia A sp., and Nephroselmis sp.). These antioxidant properties are linked to the biochemical composition of the microalgae: Peroxyl radical scavenging capacity measured with oxygen radical absorbance capacity (ORAC) assay is correlated to xanthophylls whereas lipid peroxidation inhibition measured with
thiobabituric acid reactive substances (TBARS) assay is related to other compounds that may be polyunsaturated fatty acid (PUFA)
Summary
The demand has increased for sustainable sources of natural antioxidants for nutritional, cosmetic, and pharmaceutical applications as an alternative to controversial synthetic antioxidants. Most natural antioxidants available on the market derive from terrestrial plants [1], but new antioxidants from marine origin are getting attention [2,3,4]. Microalgae are a promising source for natural antioxidant products [5,6], as their productivity is greater than terrestrial plant [7], culture conditions could be controlled, and marine microalgae production at a commercial scale does not compete with agriculture for freshwater access and arable land. To be adapted to a large range of environments, microalgae produce a large diversity of secondary metabolites [8,9].
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