This study is the first report on the effectiveness and specificity of α-acarviosinyl-(1→4)-α-d-glucopyranosyl-(1→6)-d-glucopyranosylidene-spiro-thiohydantoin (PTS-G-TH) inhibitor on the 2-chloro-4-nitrophenyl-4-O-β-d-galactopyranosyl-maltoside (GalG 2 CNP) and amylose hydrolysis catalysed by human salivary α-amylase (HSA). Synthesis of PTS-G-TH was carried out by transglycosylation using acarbose as donor and glucopyranosylidene-spiro-thiohydantoin (G-TH) as acceptor. This new compound was found to be a much more efficient HSA inhibitor than G-TH. The inhibition is a mixed-noncompetitive type on both substrates and only one molecule of inhibitor binds to the enzyme. Kinetic constants calculated from secondary plots are in micromolar range. Values of K EI and K ESI are very similar in the presence of GalG 2 CNP substrate; 0.19 and 0.24μM, respectively. Significant difference can be found for K EI and K ESI using amylose as substrate; 8.45 and 0.5μM, respectively. These values indicate that inhibition is rather uncompetitive than competitive related to amylose hydrolysis.