ABSORPTION AND DEGRADATION OF INDIVIDUAL INTACT GLUCOSINOLATES IN THEDIGESTIVE-TRACT OF RODENTS

Degradation of intact glucosinolates or their transformation into othe r products and glucosinolate absorption from the gastrointestinal trac t were investigated by in vivo and in vitro experiments with rats. The absorption of intact glucosinolates in the form of active and passive transport across the intestinal wall was investigated in vitro using the intestine of rat and hamster as everted sacs. Individual glucosino lates as well as rapeseed meal with and without heat inactivation of m yrosinase activity were used for the experiments. Analyses were based on HPLC and HPCE after group separation, purification and concentratio n of intact glucosinolates and their on-column desulfatation products. The in vivo experiments showed 3- to 20-fold lower concentrations of glucosinolates in the content from the stomach and the first parts of the small intestine compared to the concentrations in the applied feed . The glucosinolate concentrations increased again in contents from th e distal part of the small intestine, and were reduced to very low val ues in contents from caecum and colon, with great variations between t he individual animals. In vitro studies of glucosinolate degradation d uring 24 h periods revealed limited degradations when tissue homogenat es of the stomach and small intestine and contents therein were used, whereas appreciable degradations were found when the caecum and / or c olon contents were used. Heat inactivation of myrosinase activity in t he rapeseed meal fed to a group of rats did not affect in vitro glucos inolate degradation in contents from stomach or small intestine, where as the degradation seemed to be prevented in contents from caecum or c olon, indicating an effect from dietary fibres or myrosinase associate d to the dietary fibres. None of the glucosinolates was absorbed activ ely across the intestinal walls in vitro for any parts of the gastroin testinal tract investigated, as found with glucose, whereas passive or facilitated transport was found to be appreciable. The presence of gl ucosinolates did not affect the active glucose transport. The results obtained showed an appreciable in vivo absorption of intact glucosinol ates in the upper gastrointestinal tract and degradation/transformatio n of the remaining glucosinolates in the distal gastrointestinal tract of rats.