Metabolism of sitosteryl β‐D‐glucoside and its nutritional effects in rats

Abstract

[4-14C]Sitosteryl beta-D-glucoside, intragastrically administered to rats, was not absorbed by the intestinal mucosa. At three hr after the application, radioactivity was concentrated almost exclusively in the digesta of stomach, small intestine as well as cecum and colon, whereas only low proportions of radioactively labeled compounds were found in the various tissues of the gastrointestinal tract. Minor proportions of labeled metabolites of [4-14C]sitosteryl beta-D-glucoside, such as sitosterol and sitosteryl esters, were formed in the small intestine in vivo and in slices of small intestine in vitro. In the tissues of cecum and colon as well as the digesta derived from them, high proportions of labeled coprositostanol, i.e. 24 alpha-ethyl-5 beta-cholestan-3 beta-ol, that obviously had been formed by bacterial degradation of the substrate were detected. The feeding of sitosteryl beta-D-glucoside (0.5 g/kg body weight X day) over a period of four weeks did not alter significantly body weights or organ weights of rats. Analyses of steryl lipids of the various organs and tissues confirmed the findings obtained with the radioactive substrate: neither sitosteryl beta-D-glucoside nor sitosterol or sitosteryl esters derived therefrom had been transported in appreciable amounts to organs and tissues outside the alimentary canal during the feeding period. Minor proportions of unmetabolized sitosteryl beta-D-glucoside were detected in the tissues of stomach and intestine, whereas large proportions of the substrate were found in feces of rats that had received the sitosteryl beta-D-glucoside-containing diet; coprositostanol was found in feces of these animals in high proportions as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Phytosterol glycosides reduce cholesterol absorption in humans

“…Explanations of the mechanism by which such glycosides are active would need to take account of the reports that phytosterol glycosidic bonds are not cleaved by mammalian pancreatic enzymes in vitro (9). Furthermore, a study in rats showed that [4-14 C]sitosteryl ␤-D-glucoside remains unhydrolyzed and unabsorbed in rat stomach and small intestine (23). This suggests that phytosterol glycosides may be active with the glycosidic bond intact and not necessarily hydrolyzed to yield free phytosterols.…”

“…Although literature on the physiology of phytosterol glycosides is sparse, previous workers have shown that fatty acids are cleaved from glycosylated phytosterols in vitro by pancreatin, but the sugar moiety itself is not removed (9). This was confirmed by another study in which [ 14 C]sitostanol glucoside was not cleaved in the stomach or small bowel after intragastric administration (23). If cleavage of the sugar from glycosylated phytosterols is needed for bioactivity, or if poor solubility limits physiological interactions, then phytosterol glycosides might not necessarily be biologically active.…”

Glycosidic Bond Cleavage is Not Required for Phytosteryl Glycoside‐Induced Reduction of Cholesterol Absorption in Mice

“…Previous work has shown that fatty acids are cleaved from glycosylated phytosterols in vitro by pancreatin and cholesterol esterase but the sugar moiety itself is not removed [20]. Acetylated 14 C-sitosteryl glucoside was not absorbed in the stomach or small bowel of rats after intragastric administration [21]. However, the 14 C label was located in the phytosterol moiety, which did not enable the authors to answer whether or not any cleavage had occurred in vivo.…”

Animal models of BMAA neurotoxicity: A critical review

“…In general, low intestinal absorption (5-10%) and rapid clearance through the liver are characteristics of the majority of plant sterols (Ling and Jones, 1995;Plat and Mensink, 2001). Particularly, β-sitosterol β-D-glucoside (identified as the most toxic component of cycad seed flour by Wilson et al (2002) is reported to have a very limited absorption by the intestinal mucosa upon intragastric administration to rats (Weber, 1988).…”