Pasta fortified with C-glycosides-rich carob (Ceratonia siliqua L.) seed germ flour: Inhibitory activity against carbohydrate digesting enzymes

Abstract

Carob (Ceratonia siliqua L.) seed germ flour (SGF) is a by-product resulting from the extractionextraction of locust bean gum (E410), which is a texturing and thickening ingredient used for food, pharmaceutical and cosmetic preparations. SGF is a protein-rich edible matrix and contains relatively high amounts of apigenin 6,8-C-di- and poly-glycosylated derivatives. In this work, we prepared durum wheat pasta containing 5 and 10 % (w/w) of SGF and carried out inhibition assays against type-2 diabetes relevant carbohydrate hydrolysing enzymes, namely porcine pancreatic α-amylase and α-glycosidases from jejunal brush border membranes. Nearly 70–80% of the SGF flavonoids were retained in the pasta after cooking in boiling water. Extracts from cooked pasta fortified with 5 or 10% SGF inhibited either α-amylase by 53% and 74% or α-glycosidases by 62 and 69%, respectively. The release of reducing sugars from starch was delayed in SGF-containing pasta compared to the full-wheat counterpart, as assessed by simulated oral-gastric-duodenal digestion. By effect of starch degradation, the SGF flavonoids were discharged in the water phase of the chyme, supporting a possible inhibitory activity against both duodenal α-amylase and small intestinal α-glycosidases in vivo. SGF is a promising functional ingredient obtained from an industrial by-product for producing cereal-based foods with reduced glycaemic index.