Lepisanthes alata (Malay cherry) leaves are potent inhibitors of starch hydrolases due to proanthocyanidins with high degree of polymerization

Type-II diabetes has become a health threat globally. One major challenge for diabetes patients is to control their post-prandial hyperglycaemia, which could be achieved through the inhibition of α-amylase and α-glucosidase. Lepisanthes alata (Malay cherry) was discovered as a promising edible plant with high starch hydrolase inhibition activities for corn starch hydrolysis with IC50 of its aqueous extracts at 0.77 ± 0.09 µg/mL (for porcine α-amylase) and 10.83 ± 0.67 µg/mL (for rat intestinal α-glucosidase). Proanthocyanidins were identified to be responsible as active compounds. The proanthocyanidin exhibited high degree (mDP at 27) of polymerization and was composed of (epi)catechins and (epi)gallocatechins linked through B-type 4-8 interflavanyl bonds. Inhibition kinetic study revealed that the proanthocyanidins were a mixed noncompetitive inhibitor against α-amylase but competitive inhibitor against α-glucosidase. Our discovery highlighted the potential of the leaves of L. alata for use in prevention of post prandial hyperglycaemia.