Synthesis of Phloretin 2'-O-β-L-Glycosides and Their Inhibitory Action against Sugar Transport in Rat Small Intestine

To investigate the inhibitory potency of phloretin 2′-O-β-l-glycodides, phloretin 2′-O-(6-deoxy-β-l-galactoside) (1), -2′-O-(6-deoxy-β-l-galactoside) (2) and -2′-O-β-l-glucoside (3) were syn-thesized. The appropriate phloracetophenone 4′-O-β-l-glycosides were coupled with p-hydroxy-benzaldehyde in aq. alkali to yield the respective chalcone glycosides, which were catalytically hydrogenated to give 1–3.Compounds 1–3 as well as phloretin 2′-O-(6-deoxy-α-l-mannopyranoside) (glycyphyllin) each exhibited dose-dependent inhibition of 3-O-methyl-d-glucose-evoked ΔPD (transmural potential difference), using the everted jejunal segment of rats. A kinetic study revealed that the mode of action of 1–3 was non-conpetitive and that their Ki values were more than 400 times smaller than the Km value, indicating that they possess strong inhibitory potency toward the Na+ co-transporter.