In vitro hydrolysis of V-type starch inclusion complexes of alkyl gallates: the controlled two-step release behavior of gallic acid and its beneficial effect on glycemic control.

Abstract

The heat treatment method was used to synthesize starch inclusion complexes from starch and short-chain alkyl gallates (a typical representative of phenololipids), such as butyl gallate, propyl gallate, ethyl gallate and methyl gallate. In an everted rat gut sac model, HPLC-UV analysis revealed that the released alkyl gallates from inclusion complexes were degraded to produce gallic acid. Gallic acids (0.009455-0.014160 nmol min^-1) and alkyl gallates (0.2695-0.9441 nmol min^-1) were both able to pass through intestinal membranes. After transmembrane transfer, alkyl gallates could also be hydrolyzed to produce gallic acid (1.947 × 10^-5-2.290 × 10^-5 min^-1). It was evident that such an inclusion complex demonstrated superior dual sustained-release characteristics for phenolic compounds. Meanwhile, starch inclusion complexes can also slow down starch digestion by raising resistant starch (from 12.2% to 27.2-46.0%) and lowering rapidly digestible starch (from 51.2% to 22.2-51.2%), according to a glucose oxidase-peroxidase analysis. The delayed digestion behavior of starch in inclusion complexes is very beneficial for blood glucose control. Thus, our work effectively established a theoretical foundation for modifying the dual sustained-release behavior of phenolic compounds and the retardation of starch digestion by adjusting the carbon-chain length in starch inclusion complexes.