Water solubility-based Rutin encapsulation by HPCD improves its bioavailability, antioxidant capacity and enzyme inhibitory functions

The water solubility of food bioactives is one of the crucial factors influencing their bioavailability and biological functions. The encapsulation and cellular bioavailability of Rutin, as a representative of bioactive compounds with poor water solubility, was studied. The results showed that Rutin encapsulation by hydroxypropyl-β-cyclodextrin (HPCD) formed an inclusion complex in a molar ratio of 1:1. The encapsulation of Rutin by HPCD exhibited a semi-edged form in which the pyran glucose unit and part of the aromatic ring of Rutin are in the cavity of HPCD through hydrogen bonding and hydrophobic interactions. Rutin encapsulation by HPCD substantially increased the water solubility of Rutin by 51 times. The formed nanoscale inclusion complex (IC) also significantly increased the thermal stability of Rutin with a release kinetics fitting the Korsmeyer-Peppas model. The Rutin encapsulation increased the antioxidant property of Rutin (∼50%) and the inhibitory function on glycolytic enzymes of α-amylase. IC also significantly reduced the postprandial glycemic response to cooked starch (peak glucose level of starch, starch + Rutin, starch + IC are 10.3, 7.2 and 4.7 mmol/L) in mice. Further study using a cell model revealed a significantly increased bioavailability (∼10%). Thus, Rutin encapsulation by HPCD significantly increased its water solubility, bioavailability and biological functions, and high water solubility-induced increase of contact opportunities between Rutin and other components (free radicals, and enzymes) in the reaction system might be the underlying mechanism.