Inhibitory activity of phenolic-rich pistachio green hull extract-enriched pasta on key type 2 diabetes relevant enzymes and glycemic index

Phenolic compounds as agro-industrial by-products have been associated with health benefits since they exhibit high antioxidant activity and anti-diabetic properties. In this study, polyphenol-rich extract from pistachio green hull (PGH) was evaluated for antioxidant activity and its ability to inhibit alpha-amylase and alpha-glucosidase activity in vitro. The effect of PGH extract powder on in vitro starch digestibility was also evaluated. The results showed that PGH had stronger antioxidant activity than Trolox. The inhibitory effect of PGH extract against a-amylase from porcine pancreas was dose dependent and the IC50 value was similar to 174 mu g GAE/mL. The crude PGH extract was eight times more potent on baker yeast alpha-glucosidase activity (IC50 similar to 6 mu g GAE/mL) when compared to acarbose, whereas the IC50 value of PGH extract against rat intestinal maltase activity obtained similar to 2.6 mg GAE/mL. The non-tannin fraction of PGH extract was more effective against alpha-glucosidase than tannin fraction whereas the alpha-amylase inhibitor was concentrated in the tannin fraction. In vitro starch digestibility and glycemic index (GI) of pasta sample supplemented with PGH extract powder (1.5%) was significantly lower than the control pasta. The IC50 value of PGH extract obtained from cooked pasta against alpha-amylase and alpha-glucosidase was increased. These results have important implications for the processing of PGH for food industry application and therefore could comply with glucose control diets.