Hypoglycemic activity in vivo and in vitro of the Lotus (Nelumbo nucifera Gaertn.) seed skin (testa) phenolic-rich extracts

Lotus (Nelumbo nucifera Gaertn.) seed, a traditional Chinese herbal medicine, exhibits good hypoglycemic activities. However, the bioactive components that are responsible for the biological effects and their underlying mechanisms remain obscure. This study aimed to identify the bioactive components of lotus seed skin phenolic-rich extract (LSSE) and investigate their α-glucosidase inhibitory activity. In vivo study showed that LSSE could significantly decrease the fasting blood glucose levels and the area under the curves with dose-dependent manners in diabetes mellitus mice. And the α-glucosidase activity was decreased by 39.4% after intervention with LSSE. The results also demonstrated that LSSE possessed up to 77.53% rat intestinal maltase inhibitory activity and general sucrase and isomaltase inhibitory activity. A total of 38 phenolic compounds were first quantified in LSSE. Molecular docking analysis further revealed that the bioactive components in LSSE bind with α-glucosidase by hydrogen bonding Van der Waals and hydrophobic interactions. These results indicate the potential use of LSSE for natural hypoglycemic functional foods.