Bitter taste of monosaccharide pentaacetate esters

The pentaacetate esters of several, but not all, monosaccharides were recently found to stimulate insulin release from rat pancreatic islets. We have now compared the taste of solutions of either these esters or the corresponding unesterified monosaccharides. The sweet taste of the latter monosaccharides (0.22 M) ranged as follows: D‐glucose ≅D‐galactose ≅D‐mannoheptulose > L‐glucose. None of the esters (1.7 mM) displayed a sweet taste. However, the α‐ and β‐anomer of D‐glucose pentaacetate, the α‐anomer of D‐mannose pentaacetate and the β‐anomer of L‐glucose pentaacetate all displayed a bitter taste, whilst both α‐ and β‐D‐galactose pentaacetate yielded doubtful results. Since such a situation is comparable to that characterizing the islet B‐cell response to these esters, it is proposed that the intracellular interaction between the esters or their hydrolytic products and a protein involved in the recognition of bitter taste in taste buds may participate in their insulinotropic action.