In vitro antioxidant potential and inhibitory effect of seaweed on enzymes relevant for hyperglycemia

Hizikia fusiforme , Capsosiphon fulvescens , Undaria pinnatifida sporophyll, and Undaria pinnatifida blade extracts were evaluated for in vitro antioxidant and antihyperglycemic activities. Seaweed extracts contained high levels of phenolic compounds (12.44 to 39.01 mg of gallic acid equivalents/g of extract) and exhibited multiple antioxidant activities. Extracts showed weak inhibition of α-amylase. However, all extracts showed pronounced inhibition of α-glucosidase with EC 50 values from 2.56 to 18.81 mg/mL. U. pinnatifida sporophyll and U. pinnatifida blade extracts both contained protocatechuic and syringic acids. p -Coumaric and ferulic acids were detected only in the H. fusiforme extract. Caffeic acid and epicatechin were the dominant phenoilc acids found in C. fulvescens extracts. A basis for further research is provided to establish the capability of seaweed extracts as hypoglycemic agents or functional food ingredients.