Kinetic analysis of hexose transport to determine the mechanism of amygdalin and prunasin absorption in the intestine

Evidence is accumulating that glucose-conjugated compounds may be carried across the gut mucosa via the epithelial sodium-dependent monosaccharide transporter SGLT1. A modification of the everted intestinal sac technique was utilized to study the transport of the cyanogenic glycoside amygdalin (D-mandelonitrile β-D-gentiobioside) and its metabolite D-mandelontrile β-D-glucoside (prunasin). Everted sacs of rat jejunum and ileum were bathed in isotonic oxygenated sodium chloride-potassium phosphate buffer containing 2.8 μCi D-[³H]-mannose and 0.187 μCi D-[¹⁴C] -glucose. For treatment groups, buffers contained phloridzin, galactose, amygdalin or prunasin. The rate constant (k) for the transport process was calculated. Compared with the control (n = 33), phloridzin (n = 25) significantly reduced the rate constants of both D-[¹⁴C]-glucose and D-[³H]-mannose. Substitution of sodium with choline and incremental galactose treatments similarly reduced D-[¹⁴C]-glucose influx, indicating that a fraction of the transport is carrier-mediated. Treatment with amygdalin did not significantly affect the rate constants of D-[¹⁴C]-glucose or D-[³H]-mannose transport. However, treatment with 1 mM prunasin (n = 16) did reduce the influx of D-[¹⁴C]-glucose without affecting D-[³H]-mannose values. This is consistent with the reports finding that glycoside absorption may be mediated by SGLT1.