Brown macroalgae or seaweeds have recently been in the focus of many researches due to their composition and the accumulation of specific metabolites with great antioxidant potential. They represent a valuable source of bioactive compounds: polyphenols, pigments, peptides and polysaccharides that are associated with several health benefits and biological activities. Food, cosmetics and pharmaceutical industries are constantly working to find natural, non-toxic compounds that can be used in their products.
In this study, we evaluated the antioxidant activity of two (methanolic F3 and dichlormethane F4) different fractions from macroalga Halopteris scoparia in order to determine differences between harvesting season. Total protein content, chlorophyll and carotenoid content were determined. Also, several methods were used for evaluation of antioxidant activity. The semipurified fractions were also tested for antimicrobial activity using broth microdilution method for quantitative assessment and the toxicity of samples was determined using the zebrafish embryotoxicity test up to 96 h of embryonal development in order to reveal the safety of their usage and further implementation. Pearson’s correlation coefficient was used to correlate obtained results for antioxidant activity.
All methanolic fractions showed higher antioxidant activity than the dichloromethane fractions of same season by implementing 3 different antioxidants assays, namely reduction of the radical cation (ABTS), the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and the oxygen radical absorbance capacity (ORAC) assays. April sample of H. scoparia (HASC) methanolic fraction (F3) showed the highest activity (268.6±20.6 mg AAE/g fraction) followed by HASC F4 April and HASC F3 February samples by DPPH method (Fig.1a). By using ABTS assay, the highest activity was observed for HASC F3 February followed by F3 April and F3 July fractions (Fig.1b). The highest protein value was observed for Halopteris scoparia April sample (20.5%) followed by HASC July (19.7%) and February (14.3%) samples. Chloropyll a and its derivate pheophytin a are dominant pigments in all three samples and the highest pigment content (chloropyll a and b, pheophytine a and b and carotenoids) was observed for HASC February sample.
Obtained results indicate that harvesting season has a crutial role in obtaining samples with best properties that have a potential to be used as a source of natural antioxidants in food, pharmaceutical and cosmetic industry.