Nondigestibility of a New Sweetener, “Neosugar,” in the Rat

Abstract

The digestion of Neosugar, a mixture of 1^F-(1-β-fructofuranosyl)_n-1 sucrose [n = 2, 1-kestose (GF₂); n = 3, nystose (GF₃); n = 4, 1^F-β-fructofuranosyl nystose (GF₄)] was investigated in vitro and in vivo by using the rat. The results obtained were as follows. GF₂ and GF₃ were not hydrolyzed by a pancreatic homogenate. The GF₂- and GF₃-hydrolyzing activities of the enzymes in the intestinal mucosa homogenate were negligible compared with the activities of maltase and sucrase. GF₂ and GF₃ added to the incubation mixture did not affect the activities of sucrase and maltase in the intestinal mucosa. Long-term ingestion of Neosugar did not cause induction or suppression of GF₂- and GF₃-hydrolyzing enzymes in the small intestine. [U-¹⁴C]Neosugar injected intravenously was rapidly excreted in the urine without having undergone any degradation. These results indicate that Neosugar, which consists of GF₂, GF₃ and GF₄, is scarcely hydrolyzed by the digestive enzymes of the gastrointestinal tract and internal organs, and that suggests to us that Neosugar is not utilized as an energy source in the body.