Four flavonoid compounds from Phyllostachys edulis leaf extract retard the digestion of starch and its working mechanisms.

Bamboo leaf extract as a food additive has been used for preventing the oxidation of food. In the present study, we investigated the influence of Phyllostachys edulis leaf extract on starch digestion. Orientin, isoorientin, vitexin, and isovitexin were determined as its α-amylase inhibitory constituents. An inhibitory kinetics experiment demonstrated that they competitively inhibit α-amylase with Ki values of respectively 152.6, 11.5, 569.6, and 75.8 μg/mL. Molecular docking showed the four flavones can interact with the active site of α-amylase, and their inhibitory activity was greatly influenced by the glucoside linking position and 3'-hydroxyl. Moreover, the results of starch-iodine complex spectroscopy, X-ray diffraction, and scanning electron microscopy indicated that P. edulis flavonoids retard the digestion of starch not only through interaction with digestive enzymes, but also through interaction with starch. Thus, P. edulis leaf extract can be potentially used as a starch-based food additive for adjusting postprandial hyperglycemia.