Anti‐hyperglycaemic effects of Burdock (Arctium lappa L.) leaf flavonoids through inhibiting α‐amylase and α‐glucosidase

Abstract

SummaryBurdock (Arctium lappa L.) leaves are a polyphenol‐rich and underutilised by‐product of burdock. To exploit the use of burdock leaves, inhibitory effects of burdock leaf flavonoids (BLF) on α‐amylase (α‐A) and α‐glucosidase (α‐G) activities and starch digestion were investigated. The findings revealed that BLF exhibited promising α‐A (IC50 value of 92.01 μg mL−1) and α‐G (IC50 value of 29.49 μg mL−1) inhibitions in a mixed‐type manner. Fourteen compounds in BLF were identified, and apigenin glycosides, morin, kaempferol and quercetin 3‐O‐rhamnoside were the predominant compounds in BLF. The key active compound existing in BLF was morin which possessed the highest inhibition of α‐A and α‐G activities followed by quercetin 3‐O‐rhamnoside and kaempferol. Kinetic and spectroscopic studies verified that morin could bind to the two carbohydrate digestive enzymes to form the complexes, causing declines in α‐A and α‐G activities. The results of starch digestion in vitro showed that the addition of 4% BLF and morin significantly reduced the content of rapidly digestible starch in wheat flour. The above results suggest that BLF can become a new functional ingredient which may help in the design of lower glycaemic‐response foods.