Inhibitory effect of Hibiscus rosa-sinensis L. flower extract on α-glucosidase and α-amylase activities

Hibiscus rosa-sinensis flowers had traditionally been used in folk medicine to manage diabetes; however, the mechanisms underlying their glucose-lowering effects remained unclear. The aim of this study was to investigate phytochemical properties and in vitro inhibitory activity of Hibiscus rosa-sinensis flower extracts on starch-hydrolyzing enzymes. Ethanol (70 %) and aqueous extracts (EE and AE respectively) were prepared using an ultrasound-assisted extraction method. The phytochemical properties of the extracts were determined by colorimetric reactions. The antidiabetic activity of these extracts was examined via α-glucosidase and α-amylase inhibitory assays. The extracts were found to contain bioactive phytochemicals, including flavonoids, mucilage, tannins and reducing compounds. Moreover, the inhibitory effect of aqueous and ethanol 70 % extracts on α-glucosidase activity was observed at IC50 values of 1.40 ± 0.02 mg/mL and 0.92 ± 0.02 mg/mL, respectively. On the other hand, α-amylase activity was also inhibited by aqueous extract and ethanol 70 % extract at IC50 values of 1.39 ± 0.09 mg/mL and 0.95 ± 0.06 mg/mL, respectively. These findings suggested that the inhibitory activity of H. rosa-sinensis flower extracts on α-glucosidase and α-amylase might have contributed to the reduction of blood glucose levels, indicating potential for diabetes management.