Natural α-glucosidase and α-amylase inhibitors from raspberry (Rubus corchorifolius L.) leaf-tea: Screening, identification and molecular docking analysis

Raspberry leaf as a tea substitute has been consumed in China for long time. In this work, the inhibitory activities of raspberry leaf-tea (RLT) extract on α -glucosidase ( α -GLU)/ α -amylase ( α -AMY) were measured, and the effects of the RLT extract on the glucose consumption of 3T-3L1 cells were also investigated. Results confirmed that RLT 70% ethanol extract (REE) exhibited strong inhibitory activities on α -GLU/ α -AMY in vitro . In addition, REE remarkably improved the glucose consumption of 3T-3L1 cells. Subsequently, eight major inhibitors including epigallocatechin gallate (EGCG), delphinidin-3- O -glucoside, cyanidin-3-rutinoside, isoorientin, procyanidin C3, dihydromyricetin, rutin, and isovitexin were screened and identified through affinity ultrafiltration combined with HPLC-MS/MS. Confirmation tests verified that these major compounds were responsible the inhibitory activities of the REE on α -GLU/ α -AMY. Molecular docking studies revealed that these inhibitors can well interact with α -GLU/ α -AMY via van der Waals force or hydrogen bonding, thus inhibiting their activities. In a short, raspberry leaf can be exploited as a promising anti-hypoglycemic material. This study provides a theoretical basis for discovering active components from medicinal plants using affinity ultra-filtration with multi-targets.