Antioxidant and DPP-IV inhibitory activities of <i>Sargassum cristaefolium</i> extract: A therapeutic potential agent for type-2 diabetes

Diabetes mellitus (DM) is a metabolic disorder characterized by elevated blood glucose levels due to impaired insulin function. Dipeptidyl peptidase 4 (DPP-IV) inhibitors are potential agents for managing type-2 DM. This study evaluates the total phenolic and flavonoid content, antioxidant activity, and DPP-IV inhibitory potential of the ethanolic extract and ethyl acetate fraction of Sargassum cristaefolium . Antioxidant activity was assessed using the DPPH assay, while DPP-IV inhibition was compared with sitagliptin. Gas Chromatography-Mass Spectrometry (GC-MS) was used to identify active compounds. The total phenolic content in the ethanol extract and ethyl acetate fraction was 1.04% and 7.33% GAE, respectively, while total flavonoid content was 1111.70 and 3529.01 µgQE/g. Antioxidant activity increased in a concentration-dependent manner, with IC₅₀ values of 1.38 mg/mL (ethanol extract) and 0.71 mg/mL (ethyl acetate fraction). The ethanolic extract (500 ppm) and ethyl acetate fraction (62.5 ppm) exhibited DPP-IV inhibitory activity of 92.07% and 95.87%, respectively. GC-MS identified hexadecenoic acid, methyl ester, and trans-13-octadecenoic acid, methyl ester as dominant compounds. S. cristaefolium exhibits promising antioxidant and DPP-IV inhibitory activity, supporting its potential role in type-2 DM management.