EFFECT OF OAT SAPONINS AND DIFFERENT TYPES OF DIETARY FIBER ON THE DIGESTION OF CARBOHYDRATES

The effects of oat saponins (a mixture of avenacosides A and B) and di etary fibre (cellulose and guar gum) on the disaccharidase activities in the proximal small intestine of the rat were investigated. The infl uence of avenacosides A and B on the activity of disaccharidases and a lpha-amylase (EC 3.2.1.1) was also studied in vitro. In vivo, oat diet s with three avenacoside contents (negligible, normal and twice normal ) were used. No significant differences in sucrase (EC 3.2.1.48), malt ase (EC 3.2.1.20), trehalase (EC 3.2.1.28) and lactase (EC 3.2.1.21) a ctivities were found between the oat groups after 19 d feeding. The ra ts that were given cellulose tended to have higher disaccharidase acti vities compared with the other groups. The avenacosides inhibited the lactase activity significantly in vitro while no or small effects on t he other disaccharidases were found. In contrast, the in vitro hydroly sis of starch by alpha-amylase was increased in the presence of saponi ns, probably due to their detergent effect. Thus, the in vitro studies showed that the avenacosides could influence the enzyme activities. I n vivo, these effects are probably minor due to the low avenacoside co ncentrations found in oats.