Enhancement of antioxidant activities and stabilities of quercetin and isoquercetin through the combination of nanoencapsulation and hydrogel incorporation

This study investigated the possibility of improving the antioxidant activities and solubilities of quercetin (QUE) and isoquercetin (IQUE) through a combination of nanoencapsulation with gel incorporation. QUE- and IQUE-loaded nanoparticles (QUE and IQUE NPs, respectively) were prepared through ionic gelation between chitooligosaccharide and poly-γ-glutamic acid. The antioxidant activities of QUE and IQUE increased by 2.5 and 3.5 times, respectively, after nanoencapsulation. Furthermore, QUE and IQUE NP-filled gelatin gels (G-QUE and G-IQUE NPs, respectively) showed higher antioxidant stabilities than QUE and IQUE NPs, respectively. G-QUE and G-IQUE NPs exhibited significantly (p < 0.05) higher G’ values than free QUE and IQUE in gels, respectively. Moreover, the hardness of G-QUE NPs was significantly (p < 0.05) higher than that of free QUE in gel. In conclusion, combining nanoencapsulation and gel incorporation can improve the antioxidant activities, stabilities, and physical properties of QUE and IQUE.