Proximate composition and antioxidant property, anti-inflammatory and anti-diabetic efficacies of brown seaweed extracts

The proximate compositions of seaweeds, namely Sargassum boveanum, Padina gymnospora, and Dictyota dichotoma, were analyzed. The dried powder was further extracted via ethanol, acetone, ethyl acetate, and chloroform, and the phenolic and flavonoid contents of the extracts were determined. The ethanolic extracts presented greater yields than the other solvents did, and the values ranged from 5.1±0.9 to 25.2±1.3, 2.2±0.4 to 35.3±1.1, and 3.3±0.5 to 20.6±1.2, for S. boveanum, P. gymnospora, and D. dichotoma, respectively. The highest total flavonoid and phenolic contents were found in the ethyl acetate extract of P. gymnospora, with values of 91.5±1.2 mg QE/g and 178.3±1.1 mg GAE/g, respectively. The 2,2-diphenyl-1-picrylhydrazyl (DPPH)-scavenging assay, ferric reduction activity powder (FRAP) assay, and ABTS method were used. The ethyl acetate extract of P. gymnospora presented the maximum DPPH activity (65.3±1.1 TE/g), whereas the ethanol extract presented 27.6±0.5 AAE/g in the FRAP assay, and the ethyl acetate extract presented 37.3±0.8 TE/g activity. The ethyl acetate extract of P. gymnospora presented higher α-amylase inhibitory activity (0.28±0.04 mg/mL), whereas the ethanol extract of S. boveanum presented higher α-glucosidase inhibitory activity (0.31±0.02 mg/mL). The maximum human red blood cell protection activity (43.7±1.2%) and cyclooxygenase enzyme -2 inhibition(37.1±0.2%) activity were observed in the ethyl acetate fraction of S. boveanum.