chapter  5
14 Pages

Mechanism of the Inhibition by Chlorogenic Acids against Postprandial Increase in Blood Glucose Level

Chlorogenic acids (CGAs) are a family of esters that are structural analogs of quinic acid (QA) that carry either one or multiple cinnamate derivatives such as caffeic (CA), ferulic (FA), and p-coumaric acids. CGAs are widely distributed among plants such as apple, prune, yacon, blueberry, broccoli, burdock, and sweet potato,1-5 and are one of the most commonly consumed polyphenols in diets worldwide. QA has a chemical structure with an equatorial hydroxyl group at the 4-and 5-positions and an axial hydroxyl group at the 1-and 3-positions (Figure 5.1).6-8 The nomenclature of CGAs follows the preferred IUPAC numbering system with QA as the parent structure.6-8 In general, 5-caffeoylquinic acid (5-CQA) is called chlorogenic acid (CGA). The UV-visible absorption spectra of CGA in distilled water at room temperature shows two absorption peaks at 324 and 217 nm, two shoulders at 296 and 240 nm, and one trough at 262 nm.9 Commonly, quantitative and qualitative analysis of CGAs from coffee is performed using reverse-phase high-performance liquid chromatography (HPLC) with a UV or photodiode array detector.10-13 Green coffee

5.1 Chlorogenic Acids .......................................................................................... 89 5.2 Coffee Drinking and Risk of Type 2 Diabetes ...............................................90 5.3 Inhibitory Effects of CGAs on Postprandial Blood Glucose Elevation in

Clinical Studies ...............................................................................................92 5.4 Inhibition of α-Amylase and α-Glucosidase by CGAs ...................................95 5.5 Inhibition of Glucose Absorption in Small Intestine by CGAs ......................96 5.6 Conclusion ......................................................................................................98 References ................................................................................................................98