Effect of oat saponins and different types of dietary fibre on the digestion of carbohydrates

Abstract

The effects of oat saponins (a mixture of avenacosides A and B) and dietary fibre (cellulose and guar gum) on the disaccharidase activities in the proximal small intestine of the rat were investigated. The influence of avenacosides A and B on the activity of disaccharidases and α-amylase (EC3·2·1·1) was also studiedin vitro. In vivo, oat diets with three avenacoside contents (negligible, normal and twice normal) were used. No significant differences in sucrase (EC3·2·1·48), maltase (EC3·2·1·20), trehalase (EC3·2·1·28) and lactase (EC3·2·1·21) activities were found between the oat groups after 19 d feeding. The rats that were given cellulose tended to have higher disaccharidase activities compared with the other groups. The avenacosides inhibited the lactase activity significantlyin vitrowhile no or small effects on the other disaccharidases were found. In contrast, thein vitrohydrolysis of starch by α-amylase was increased in the presence of saponins, probably due to their detergent effect. Thus, thein vitrostudies showed that the avenacosides could influence the enzyme activities.In vivo, these effects are probably minor due to the low avenacoside concentrations found in oats.