Functional assessments of Psidium guajava L. and Morus alba L. leaf extracts on postprandial glucose control

Diabetes is a leading cause of death, according to statistics published by the Department of Health, Executive Yuan of Taiwan. In modern medicine, diabetes can be controlled using various medications; however, some drugs often have undesirable side effects. It therefore became a goal to find plant-based material that can reduce glucose concentration in the blood while reducing the incidence of complications and not causing side effects. Alpha-glucosidase inhibitors (AGIs) are effective glucose-lowering medicines and are enzymes essential to carbohydrate digestion. Inhibition of α-glucosidase leads to a delayed and reduced rise in postprandial blood glucose levels. This study evaluates the inhibitory effect of mixed extracts of Psidium guajava L. and Morus alba L. leaves on α-glucosidase activity and postprandial hyperglycemia in normal and diabetic rats. The inhibition of α-glucosidase activity was assayed in vitro. Half maximal inhibitory concentration (IC₅₀) values of Psidium guajava L. and Morus alba L. were 2.25 and 0.1 mg/mL, respectively. The IC₅₀ value of a commercial anti-hyperglycemic agent (Glucobay) is 6.41 mg/mL. The IC₅₀ value of a mixture of extracts of Psidium guajava L. and Morus alba L. was 0.07 mg/mL. In cytotoxicity tests, survival percentages and shape did not significantly affect the murine embryonic liver cell line (BNL CL.2) when treated with varying concentrations of mixture extracts for varying periods of time. In summary, Psidium guajava L. and Morus alba L. showed positive anti-diabetes activity and suggested promising potential for alternative functional foods for diabetes mellitus (DM) patients.