Inhibition of starch hydrolysis during in vitro co-digestion of pasta with phenolic compound-rich vegetable foods

The ability of phenolic compounds to inhibit amylolytic enzymes activities has been investigated, suggesting their possible role in type-2 diabetes management. However, these studies have been carried out with purified enzymes and synthetic substrates and are distant from simulating a real physiological situation. The objective of the present research was to evaluate the ability of phenolic-rich vegetable foods to inhibit starch hydrolysis during in vitro co-digestion with pasta resulting in a potential anti-diabetic effect and mimicking as closely as possible a real scenario. Some tested vegetable foods, such as capers, red-skinned onion, red radish, and olives, determined a decrease in starch hydrolysis by 21.5%-31.7% during in vitro co-digestion with pasta. The qualiquantitative phenolic profiles of in vitro co-digested samples were elucidated and selected standard compounds were tested for their ability to inhibit porcine pancreatic alpha-amylase and mammalian alpha-glucosidase. The inhibitory potential of these compounds, especially against alpha-glucosidase, explained the effect observed during co-digestion experiments. The most active phenolic compounds against alpha-glucosidase were quercetin-4'-Oglucoside, quercetin-3-O-rutinoside, luteolin-7-O-glucoside and quercetin-3-O-glucoside-4'-O-glucoside with IC50 values of 20.67, 52.23, 68.84 and 87.58 mu mol/L, respectively. This is the first report suggesting that these compounds are potent inhibitors of mammalian alpha-glucosidase. This study indicates that consuming starchy foods (i.e., pasta) with phenolic-rich vegetable foods may result in an inhibition of starch digestion possibly reducing the post-prandial glucose levels.