Nanosupplements based on protein-polysaccharide coacervates loaded with essential oils: Evaluation of antioxidant and antidiabetic properties

Abstract

Essential oils (EOs) have demonstrated potential in food products to prevent complications related to diabetes. Nevertheless, the physicochemical characteristics of pure EOs, including high volatility and low chemical stability, face significant challenges when considering their utilization as functional ingredients. Thus, this study aimed to develop nanosupplements based on protein-polysaccharide coacervates loaded with EOs, thyme (THY) and oregano (ORE), and to evaluate their colloidal, antioxidant, and α-glucosidase and α-amylase inhibitory properties following an in vitro gastrointestinal digestion process. First, heat-induced egg white protein nanoparticles (EWPn) were used to encapsulate both EOs as nanocomplexes. Second, the process to obtain nanosupplements involved the electrostatic deposition of high methoxyl pectin (HMP) onto the surface of pre-formed nanocomplexes, resulting in the production of EWPn-THY-HMP and EWPn-ORE-HMP powders through a freeze-drying process. The effects of in vitro digestion on particle size, zeta potential, stability, and bioaccessibility of systems were analyzed. HMP exhibited a slight ability to protect EWPn from gastric digestion, while encapsulation within the EWPn-HMP system prevented the chemical degradation of EOs during gastrointestinal digestion. Subsequently, the antioxidant properties and the inhibitory effects of digested systems on α-glucosidase and α-amylase activities were examined. After in vitro digestion, EWPn-THY-HMP and EWPn-ORE-HMP systems showed higher ABTS+ radical scavenging than pure EOs (around 70% vs. 30%, respectively). Additionally, reducing power activities (expressed as mg of ascorbic acid equivalents-AAE mL−1) of EWPn-THY-HMP and EWPn-ORE-HMP systems were higher (1.6 ± 0.0 mg and 1.8 ± 0.1 mg of AAE mL−1, respectively) compared to pure THY and ORE (approximately 1.5 mg of AAE mL−1 for both) after in vitro digestion. The α-glucosidase inhibitory activity of EOs decreased upon encapsulation within EWPn-HMP system from an IC50 value of 0.3–1.0 μg mL−1, approximately. However, the effect of encapsulation on α-amylase inhibitory activity was EOs-dependent, and it was higher for the EWPn-ORE-HMP system, with an IC50 value of 8.6 ± 0.2 μg mL−1. The results highlight the potential of EOs encapsulation within EWPn-HMP coacervate nanosupplements as a promising strategy to facilitate their incorporation into food matrices while preserving their antioxidant and α-glucosidase and α-amylase inhibitory properties.