Pectin substances were extracted from food plants: sweet pepper Capsicum annuum L., carrot sowing Daucus sativus L., bulb onion Allium cepa L., white cabbage Brassica oleracea L. by two methods with acid solutions similar to gastric environment. The pectins that were extracted were characterized by Monosaccharide composition and quantitative contents of uronic acids, neutral monosaccharides, methoxy groups, protein. The inhibitory effect of all extracted pectin-protein complexes on activity of pharmaceutical drugs of human pancreatic alpha-amylase was detected. It was found that the inhibitory effect of isolated pectin substances was dependent upon the species of plant source, the manner of pectin substance extraction, the chemical composition and acting concentrations. The ability of pectin substances to suppress enzyme activity was found in a range of pectin concentrations from 0.5 up to 1.5 %. It was revealed that extracted pectin substances from bulb onion and white cabbage by acid solution with pepsin had a 2.4-3.4 times greater inhibiting effect on the human pancreatic alpha-amylase activity in comparison with pectin substances extracted by solution without pepsin from the same plant sources in high concentrations.