Inhibitory effects of chlorophylls and its derivative on starch digestion in vitro

Chlorophylls (Chls) have been shown to help regulate blood glucose levels. In this study, the effects of Chls and its derivative, pheophytin a (Phe a), on starch digestion in vitro were investigated. Chls significantly decreased starch hydrolysis while increasing resistant starch content (p < 0.05). SEM revealed that Chls either existed in free form or was absorbed and embedded on the surface of starch granules. Spectroscopic analysis and molecular docking demonstrated that Chls had a dual effect: (1) the phytol chain of Chls formed a double helix structure with starch, which may hinder the starch-enzyme contacts; and (2) the porphyrin ring of Chls interacted with amino acid residues of alpha-amylase and alpha-glucosidase to change the characteristics of enzymes, thereby inhibiting their activities. The investigation may serve as motivation for developing healthful starchy foods rich in Chls and enhancing the selection of foods for diabetics and hyperglycemias.