Antioxidant, Antiacetylcholinesterase, and Hypoglycemic Properties of Aqueous Extracts of Five Seaweeds

Abstract

The biochemical compositions and bioactive properties of red seaweed species Gelidiella acerosa, Gelidiella papillosa, Kappaphycus alvarezii, Sargassum pachycarpum, and Sargassum wightii were characterized. The crude protein (13.9 ± 0.28%) and dry matter (91.4 ± 2.1%) contents were highest in K. alvarezii and G. acerosa, respectively. The ash content was high in S. pachycarpum (28.9 ± 0.22%). The highest phenolic (3.27 ± 0.019 gallic acid equivalents (GAE)/g dry wt) and flavonoid (3.372 ± 0.002 catechin equivalents (CAE)/g dry wt) contents were detected in S. wightii. The antioxidant activity ranged from 58.5 ± 0.44 to 81.5 ± 1.1% in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The half maximal inhibitory concentration values (IC₅₀ values) of the seaweed extracts ranged from 0.61 ± 0.021 mg/mL to 0.79 ± 0.027 mg/mL according to the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, which were lower than those of the ferric reducing antioxidant power (FRAP) method (0.76 ± 0.027 to 1.39 ± 0.015 mg/mL). The seaweed extracts exhibited moderate acetylcholinesterase enzyme inhibition activity. The highest inhibition activity was observed for the K. alvarezii extract (49.3 ± 1.3%), while S. wightii presented the highest α-glucosidase (83.2 ± 1.8%) inhibition activity. The G. papillosa extract exhibited the highest a-amylase inhibition activity (57.4 ± 2.4%).