Acarbose-chlorogenic acid interaction: Kinetics studies on α-glucosidase reveals mixed-type inhibition and denaturant effect of chlorogenic acid

Abstract: Chlorogenic acid is a promising compound for the treatment of diabetes. This phenolic compound from the class of hydroxycinnamic acids exhibits anti-diabetic effects through the inhibition of α-glucosidase activity. In this study, the mechanism of inhibition by chlorogenic acid on α-glucosidase activity was explored via enzyme kinetics and fluorescence quenching. Furthermore, the role of chlorogenic acid in dual inhibition with acarbose was explored. Through enzyme kinetics, the mode of inhibition of chlorogenic acid was identified as mixed inhibition with an IC₅₀ of 2.31 ± 0.36 mM. Furthermore, chlorogenic acid exhibits concentration-dependent denaturant effects on α-glucosidase, which was confirmed by fluorescence quenching. As a dual inhibitor, a simultaneous decrease in acarbose ratio and subsequent increase in chlorogenic acid ratio results in the maintenance of the degree of α-glucosidase inhibition relative to acarbose-only inhibition or equal concentration. Fluorescence quenching experiments confirmed the increased affinity of chlorogenic acid in the presence of acarbose, with an effective quenching constant increasing from 1.6 ± 0.11 x 10⁴ M^-1 to 3.9 ± 0.32 x 10⁴ M^-1. Furthermore, the binding interactions between chlorogenic acid and α-glucosidase are static in nature with the number of chlorogenic acid molecules bound per α-glucosidase, n, value at approximately 1 in the presence and absence of acarbose. Overall, the dynamic inhibitory mechanism of chlorogenic acid, coupled with its increased inhibition potency when added to acarbose confirm its strong potential as adjuvant therapy for type II diabetes treatment.