Inhibitory effects of chlorogenic acids from green coffee beans and cinnamate derivatives on the activity of porcine pancreas α-amylase isozyme I

Nine kinds of chlorogenic acids (CGAs) account for 80% of the total CGA content in green coffee beans. They consist of three subgroups of caffeoylquinic acids (CQAs), feruloylquinic acids (FQAs), and dicaffeoylquinic acids (diCQAs). We previously reported the inhibitory effects of 5-CQA on porcine pancreas α-amylase (PPA) isozymes, PPA-I and PPA-II. In this paper, we investigated the PPA-I inhibition by eight kinds of CGAs. The IC50 values of CQAs, FQAs, and diCQAs against the PPA-I-catalysed hydrolysis of p-nitrophenyl-α-D-maltoside were 0.08–0.23 mM, 1.09–2.55 mM, and 0.02–0.03 mM, respectively. All CQAs and FQAs and 3,5-diCQA showed mixed-type inhibition with binding to the enzyme–substrate complex (ES) being stronger than to the enzyme (E). 3,4-DiCQA and 4,5-diCQA showed mixed-type inhibition, but, conversely are suggested to bind to E stronger than ES.