Phlorotannins Composition, Radical Scavenging Capacity and Reducing Power of Phenolics from the Brown AlgaCystoseira sauvageauana

The aim of this study was to assess the phenolic composition extracted from the brown alga Cystoseira sauvageauana collected from the Algerian coast through high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) analysis and their antioxidant activity based on free radical scavenging and reducing power. The crude extract was obtained from dried biomass using ethanol/water and then fractionated (liquid-liquid) using solvents of increasing polarity. The ethyl acetate fraction contained the largest amount of phenolic compounds (59.27 ± 0.20 g of phloroglucinol equivalents per 100 g of fraction dry weight) and showed strong radical scavenging and reducing capacity. HPLC-ESI-MS/MS analysis using the multiple reactions monitoring scan mode showed that this fraction was mostly composed of phlorotannins (41 compounds) with a degree of polymerization ranging from 3 to 12. The most abundant compounds were two phloroglucinol nonamer isomers (deprotonated molecular ion [M-H]− at m/z 1117). The results suggest that Cystoseira sauvageauana represents an important natural source of antioxidants that could be valorized for human health.