Structural, physicochemical, and in-vitro release properties of hydrogel beads produced by oligochitosan and de-esterified pectin from yuzu (Citrus junos) peel as a quercetin delivery system for colon target

Abstract The aims of this study were to produce de-esterified pectin from yuzu (Citrus junos) peel by enzymatic treatment, to use de-esterified yuzu peel pectin (DEYPP) to prepare hydrogel beads as quercetin delivery systems for colon target, and to estimate the structural, physicochemical, and in-vitro release properties of the hydrogel beads. Yuzu peel pectin was de-esterified by pectin methylesterase (DE: 34.64%), and oligochitosan-DEYPP hydrogel beads were produced by an ionic gelation method with different concentrations of DEYPP (1, 1.5, and 2%). The new formations of cross-linking (between the ‒COO- of DEYPP and Ca2+) and a polyelectrolyte complex (between the ‒COO- of DEYPP and the ‒NH3+ of oligochitosan) in all the beads were confirmed by Fourier Transform Infrared analysis. The results of X-ray diffraction and differential scanning calorimetry analysis showed that the crystalline quercetin was converted into an amorphous state during the preparation of hydrogel beads. Both the mean particle diameter and the quercetin entrapment efficiency of the beads were significantly increased with increasing DEYPP concentration. For all beads, the cumulative quercetin release after exposure to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was below 1%, because both the cross-linking and the polyelectrolyte complex occurred in the beads were stable in the SGF and SIF. However, when the hydrogel beads were exposed to simulated colonic fluid for 12 h, quercetin was greatly released from the hydrogel beads (65.37–99.54%). These results revealed that oligochitosan-DEYPP hydrogel beads can be effectively used as quercetin delivery systems for colon target.