Effect of Solvents on the Extractability of Phenolic Constituents and their Antioxidant Capacity from Irish Seaweed

Seaweeds are being used for human consumption in the Orient and help them live longer with low levels of hypertension, cancer and other ailments. The study aimed at extraction of principle constituents using a wide range of solvents and their mixtures on the basis of polarity, from Irish brown seaweeds namely Himanthalia elongata, Laminaria saccharina and Laminaria digitata. All the extracts were screened for total phenolic content (TPC) and their potential antioxidant capacity, using 2, 2´-diphenyl-1-picrylhydrazyl (DPPH) radical and ferric reducing antioxidant power (FRAP) assay. Among all the solvents tested, 60% methanolic extract and equi-volume mixture of chloroform, diethyl ether and n-hexane (Mix 4) extract exhibited the highest TPC which were in the range of 46.6 ± 2.8 to 156.0 ± 2.4 and 52.7 ± 1.9 to 128.2 ± 1.6 mg gallic acid equivalent/g respectively, among all the seaweed. Interestingly, the same extracts showed the highest antioxidant capacity wherein the value of FRAP ranged from 4.9 ± 0.13 to 11.7 ± 0.23 and 8.3 ± 0.23 to 26.3 ± 0.30 mg trolox equivalent/g, respectively, in all the seaweed studied. Results concluded that different solvents extract different amount of phenolic antioxidant compounds from seaweed. Thus, seaweed can be considered as potential source of natural antioxidants for food and pharmaceuticals purposes.