Determination of Total Antioxidant Capacities of Algal Pigments in Seaweed by the Combination of High-Performance Liquid Chromatography (HPLC) with A Cupric Reducing Antioxidant Capacity (CUPRAC) Assay

Abstract

This study mainly aimed to analyze the essential antioxidant algal pigments present in marine algae to quantify the total antioxidant capacity (TAC) of these pigment constituents with CUPRAC (cupric ion reducing antioxidant capacity) and ABTS spectrophotometric methods, and to correlate the TAC values combined with high-performance liquid chromatography (HPLC) results. S. vulgare, C. barbata brown and F. petiolata green algae species demonstrated the highest antioxidant activity with the values of 12.11 ± 0.01; 18.56 ± 0.01; and 13.98 ± 0.02 (mmol trolox (TR) g−1 dw) obtained by the CUPRAC method. The individual antioxidant constituents of acetonic seaweed extracts were detected and quantified by HPLC on a C30 column using a modified mobile phase of gradient elution comprised of methanol-acetonitrile (50:50, v/v) with 0.1% (v/v) triethylamine (TEA) and acetone and ultraviolet detection for caroteneoids at 450 nm and for chlorophylls at 650 nm. The theoretical TAC values of seaweed samples were calculated by multiplying individual concentrations of pigments determined by HPLC with the spectrophotometric trolox equivalent or β-carotene equivalent antioxidant capacity (TEAC or CEAC) coefficient of each identified pigment and summing up this values. Among the studied seaweeds, those with the highest carotenoid content determined by HPLC were S. vulgare (51.77 µg/g), H. incurva (32.89 µg/g) and F. petiolata (200.12 µg/g), respectively. On the other hand, those with the highest total chlorophyll content were F. petiolata (1694.67 µg/g), S. vulgare (127.07 µg/g), and C. barbata (100.78 µg/g), respectively. As expected, fucoxanthin was present as the main carotenoid accumulated in the brown algae species presented in the study.