Studies on the metabolic fate of sucrose esters in rats.
The metabolism in rats of sucrose esters of stearic acid and palmitic acid was studied in vivo and in vitro using esters labelled with 14C at the sucrose of fatty-acid moiety. In excretion studies, the ratio of expired radioactivity to absorbed radioactivity after oral administration of the sucrose esters labelled at the sucrose moiety was similar to that after the administration of [14C]sucrose. A similar correlation between the ester labelled at the fatty-acid moiety and the free [14C]fatty acid was also observed. No intact sucrose ester was detected in the urine. Studies in vitro using everted intestinal sacs showed that there was virtually no transport of 14C-labelled sucrose esters from the mucosal to the serosal solution through the intestinal tissues, and that the enzymes in the intestinal mucosa played a more important role in the hydrolysis of sucrose esters than did those in the digestive fluid. In studies of intestinal absorption through the mesenteric lymphatic system, during the 24 hr after ingestion 1.8% of the administered radioactivity was recovered in the lymph after dosing with [U-14C]sucrose monostearate whereas 20% was recovered in the lymph after dosing with sucrose [1-14C]monostearate. This difference in levels of recovery of administered radioactivity indicated that sucrose monostearate was absorbed only after hydrolysis. No intact ester was detected in the lymph or in the portal or femoral blood. The results of all of these experiments show that the sucrose esters are hydrolysed to sucrose and fatty acids prior to intestinal absorption.