SMALL-INTESTINAL TRANSFER MECHANISM OF PRUNASIN, THE PRIMARY METABOLITE OF THE CYANOGENIC GLYCOSIDE AMYGDALIN

1 The small-intestinal transfer of prunasin (D-mandelo-nitrile-beta-D- glucoside), the primary metabolite of amygdalin which is not absorbed in the small intestine as such, was studied in rat jejunum and ileum i n vitro. 2 As shown by high pressure liquid chromatography, prunasin i s transferred essentially intact across the intestinal wall, without c leavage of the glycosidic bond and thus no formation of benzaldehyde o r cyanide during the mucosal passage. 3 Only the jejunal transfer of p runasin followed saturation kinetics (v(max) = 1.6 mu mol cm(-1) min(- 1); K-T = 460 mu mol l-1) and exhibited a clearsodium-ion dependence. As indicated by the temperature dependence, only the jejunal mucosa-to -serosa transfer and the corresponding tissue uptake of prunasin requi red apparently high activation energies. Transfer in the terminal ileu m showed diffusion characteristics. 4 Jejunal methyl alpha-D-glucoside transfer was inhibited by the presence of prunasin. Furthermore, the tissue uptake of methyl alpha-D-glucoside in rat jejunum was competiti vely inhibited by prunasin. 5 The results indicate that prunasin is ab sorbed unmetabolised in the jejunum of the rat via the transport syste m of glucose.