Caffeoylquinic acids from aronia juice inhibit both dipeptidyl peptidase IV and α-glucosidase activities

Aronia (Aronia melanocarpa) contains many polyphenols including cyanidin-3,5-diglucoside, and these polyphenols have beneficial effects on lifestyle-related diseases such as type 2 diabetes and obesity. In type 2 diabetes and obesity model KKA(y) mice, drinking water supplemented with aronia juice reduced blood glucose levels partly through inhibition of dipeptidyl peptidase IV (DPP IV) activity by cyanidin-3,5-diglucoside. The objective of this study was to find alpha-glucosidase inhibitors in aronia juice. Polyphenols in aronia juice were first separated using flash chromatography on a reversed-phase column. The fraction with inhibitory activity was further separated using reversed-phase HPLC. Two peak fractions showed inhibitory activity. LC-MS/MS analysis of the fractions indicated that they contained 3-caffeoylquinic acid (3-CQA) and 4-caffeoylquinic acid (4-CQA), respectively. Both CQAs also inhibited DPP IV activity. The results suggest that caffeoylquinic acids in aronia juice are important for the amelioration of type 2 diabetes by the juice.