Comparative study on physicochemical characteristics, α‐glucosidase inhibitory effect, and hypoglycemic activity of pectins from normal and Huanglongbing‐infected navel orange peels

This study aimed at comparing the physicochemical characteristics, α-glucosidase inhibitory effect, and hypoglycemic activity of pectins (N-NOP and H-NOP) from peels of normal and Huanglongbing (HLB)-infected Navel oranges. Results indicated the pectins were high methoxy pectins mainly composed of homogalacturonan and rhamnogalacturonan-I. The pectins exhibited similar functional groups, surface morphology, and particle size, and had no triple-helical conformation in solution. They exerted fat and glucose absorption capacities and were mixed-type noncompetitive α-glucosidase inhibitors with IC50 values of 1.182 and 2.524 mg/ml, respectively. Both N-NOP and H-NOP showed hypoglycemic activity in alloxan-induced diabetic mice. Administration of them could promote the synthesis of hepatic glycogen and/or serum insulin to lower blood glucose levels and enhance antioxidant status to alleviate oxidative stress injury in diabetic mice. Moreover, N-NOP had higher yield, molecular weight, ζ-potential, oil holding capacity, α-glucosidase inhibitory effect and in vivo hypoglycemic activity, whereas H-NOP possessed higher uronic acid, degree of esterification, thermal stability, water holding capacity, swelling capacity, and fat absorption capacity. It could be concluded that some similarities and differences existed between N-NOP and H-NOP in physicochemical characteristics, functional properties, α-glucosidase inhibitory effects, and hypoglycemic activity. This study provides references for the basic research and application of pectins from peels of normal and HLB-infected Navel oranges. Practical applications Pectin has been widely used in the food and pharmaceutical industries for several decades due to its health benefit, gelling, thickening, and emulsification performances. Diabetes mellitus is a worldwide concern in recent years. Pectins (N-NOP and H-NOP) from peels of normal and Huanglongbing (HLB)-infected Navel oranges possessed in vitro and in vivo hypoglycemic activities, indicating they were potential anti-antidiabetic substitutes of chemical drugs. Moreover, comparative understanding on the physicochemical characteristic, α-glucosidase inhibitory effect and hypoglycemic activity of pectins from peels of normal and Huanglongbing-infected Navel oranges was conducive to the recycling and utilization of Navel orange peels. Recently, the biological activity of pectin from peels of normal Navel oranges has been rarely reported, and the information on pectin from peels of Huanglongbing-infected Navel orange is rare. This study provides references for the basic research and application of pectins from peels of normal and HLB-infected Navel oranges.