In vitro antioxidant and antidiabetic activities of some South African seaweeds via digestive enzyme inhibition and glucose uptake

Seaweeds are increasingly recognized as a potential source of bioactive compounds with applications in metabolic disorders. This study evaluated the antioxidant, digestive enzyme inhibitory, and yeast glucose uptake activities of seven South African seaweeds, including Dictyota dichotoma, Plocamium corallorhiza, Ptilophora pinnatifida, Gelidium pristoides, Ceramium capense, Jania intermedia , and Hymenena venosa . Antioxidant activity was assessed using DPPH and nitric oxide assays, while antidiabetic potential was evaluated through inhibition of α-amylase, α-glucosidase, and pancreatic lipase, as well as glucose uptake using a yeast cell model. All extracts exhibited concentration-dependent activity across assays, with notable variability among species. D. dichotoma demonstrated the most consistent activity, showing moderate nitric oxide scavenging and the strongest inhibition of α-amylase, α-glucosidase, and pancreatic lipase. In contrast, the ethanolic extract of P. pinnatifida exhibited the highest glucose uptake activity. Other seaweeds showed limited or assay-specific effects. These findings identify selected seaweed extracts as candidates for further investigation of bioactivities relevant to metabolic dysfunction. Further studies are required to identify active compounds and validate these effects using advanced in vitro and cell-based models.