Investigating the Potential Anti-Diabetic Mechanisms of Water-Soluble Palm Fruit Extract

Water-Soluble Palm Fruit Extract (WSPFE) obtained from the aqueous vegetation liquor of oil palm (Elaeis guineensis) fruit milling demonstrated anti-diabetic effects in Nile rats, but the related mechanisms were unknown. Here, we investigated the potential effects of WSPFE samples on glucose uptake and enzymes involved in carbohydrate hydrolysis and incretin degradation. Glucose uptake assays were performed using spray dried (SD) WSPFE, freeze dried (FD) WSPFE, WSPFE ethyl acetate fraction (EAF) and seven individual WSPFE fractions obtained from WSPFE EAF on everted mouse intestinal sacs ex vivo and Caco-2 cell monolayers in vitro. α-glucosidase, α-amylase and dipeptidyl peptidase-4 (DPPIV) enzymatic assays were performed in vitro. Glucose uptake assays revealed that all the WSPFE samples tested did not inhibit glucose absorption. However, WSPFE EAF consistently had stronger inhibitory effects on α-glucosidase, α-amylase and DPPIV enzymes compared to SD WSPFE and FD WSPFE. SD WSPFE inhibited α-amylase better than FD WSPFE. In terms of individual fractions, F2 demonstrated the strongest inhibitory effects against α-glucosidase and DPPIV. Hence, although WSPFE samples did not inhibit glucose uptake, they showed inhibitory effects on the three enzymes tested, especially WSPFE EAF and F2. Further studies to investigate their effects on carbohydrate digestion and postprandial hyperglycaemia are warranted. (author)