Aleppo tannin: structural analysis and salivary amylase inhibition Original Research Article

The effectiveness and specificity of a tannin inhibition on human salivary amylase (HSA) catalyzed hydrolysis was studied using 2-chloro-4-nitrophenyl 4-O-β-d-galactopyranosyl-α-maltoside (GalG2-CNP) and amylose substrates. Aleppo tannin was isolated from the gall nut of Aleppo oak. This tannin is a gallotannin, in which glucose is esterified with gallic acids. This is the first kinetic report, which details the inhibitory effects of this compound on HSA. A mixed non-competitive type inhibition has been observed on both substrates. The extent of inhibition is markedly dependent on the substrate-type. Kinetic constants were calculated from Lineweaver–Burk secondary plots for GalG2-CNP (KEI 0.82 μg mL−1, KESI 3.3 μg mL−1). This indicates a 1:1 binding ratio of inhibitor–enzyme and/or inhibitor–enzyme–substrate complex. When amylose was the substrate the binding ratio of inhibitor to enzyme–substrate complex was found to be 2:1, with the binding constants of KEI 17.4 μg mL−1, KESI 14.9 μg mL−1, KESI2 9.6 μg mL−1. Presumably, the tannin inhibitor can bind not only to HSA, but to the amylose substrate, as well. Kinetic data suggest that Aleppo tannin is a more efficient amylase inhibitor than the recently studied other tannin with quinic acid core (GalG2-CNP: KEI 9.0 μg mL−1, KESI 47.9 μg mL−1).