Antidiabetic and antioxidant activities of brown and red macroalgae from the Persian Gulf

The inhibition of pancreatic α-amylase and the prevention of pancreatic oxidative damage are considered possible strategies for the management of type 2 diabetes. The aim of our study was to evaluate in vitro the antioxidant properties and α-amylase inhibition of ten brown and red macroalgal species from the Persian Gulf. The α-amylase inhibition was tested using the chromogenic dinitrosalicylic acid (DNS) method, and the antioxidant properties were evaluated using the ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) radical scavenging and ferric reducing antioxidant power (FRAP) methods. The results of our study showed that all analyzed macroalgal species revealed antioxidant effects and α-amylase inhibitory activities. Among the studied species, the highest α-amylase inhibition was shown by the brown algae Sirophysalis trinodis (IC50 0.42 mg mL−1, 32–97% inhibition), Polycladia myrica (IC50 = 0.72 mg mL−1, 32–97% inhibition), and the red alga Palisada perforata (IC50 = 1.1 mg mL−1, 27–91%). Sirophysalis trinodis (125.4 μg ASA mg−1) and Sargassum angustifolium (IC50 = 0.40 mg mL−1) had the highest FRAP-reducing power and ABTS radical scavenging activities, respectively. In addition to the species, α-amylase inhibition and the antioxidant effects depended on the type of solvent used for algal extraction; the best properties were generally presented by methanol and ethyl acetate. In conclusion, the enzyme inhibition and antioxidant activities of S. trinodis, P. myrica, P. perforata, and S. angustifolium suggest that they may have potential for antidiabetic and antioxidant use and could therefore be studied further for potential pharmaceutical use.