In-Vitro Antioxidant Properties of Lipophilic Antioxidant Compounds from 3 Brown Seaweed

Lipophilic compounds of seaweed have been linked to their potential bioactivity. Low polarity solvents such as chloroform, diethyl ether, n-hexane and their various combinations were used to extract the lipophilic antioxidants from brown seaweed namely Himanthalia elongata, Laminaria saccharina and Laminaria digitata. An equal-volume mixture of chloroform, diethyl ether and n-hexane (Mix 4) gave the highest total phenol (52.7 ± 1.93 to 180.2 ± 1.84 mg gallic acid equivalents/g), flavonoid (31.9 ± 2.65 to 131.3 ± 4.51 mg quercetin equivalents/g), carotenoid (2.19 ± 1.37 to 3.15 ± 0.91 μg/g) and chlorophyll content (2.88 ± 1.08 to 3.86 ± 1.22 μg/g) in the tested seaweeds. The extracts were screened for their potential antioxidant capacity and the extracts obtained from the selected solvents system exhibited the highest radical scavenging capacity against 2,2′-diphenly-1-picrylhydrazyl radical (EC₅₀ 98.3 ± 2.78 to 298.8 ± 5.81 mg/L) and metal ions (EC₅₀ 228.6 ± 3.51 to 532.4 ± 6.03 mg/L). Similarly, the same extract showed the highest ferric reducing antioxidant power (8.3 ± 0.23 to 26.3 ± 0.30 mg trolox equivalents/g) in all the seaweeds. Rapid characterization of the active extracts by liquid chromatography coupled with photodiode array detector and electrospray ionization tandem mass spectrometry (LC-PDA–ESI-MS/MS) identified cyanidin-3-O-glucoside, fucoxanthin, violaxanthin, β-carotene, chlorophyll a derivatives and chlorophyll b derivatives in the tested seaweed. The study demonstrated the use of tested brown seaweed as potential species to be considered for future applications in medicine, cosmetics and as nutritional food supplement.