Impact of the Food Matrix on the Antioxidant and Hypoglycemic Effects of Betalains from Red Prickly Pear Juice After In Vitro Digestion

Abstract

This study evaluated the impact of the food matrix on the bioaccessibility and hypoglycemic potential and antioxidant potential of betalains from red prickly pear juice (Opuntia spp.) after in vitro gastrointestinal digestion. Six aqueous model systems (AMSs) were formulated using a betalain extract combined with glucose, citric acid, mucilage, pectin, or all components, alongside three complex matrices, the fresh juice (FJ), a formulated beverage (BF), and a pasteurized formulated beverage (BP). In vitro digestion simulated the gastric and intestinal phases. The results showed that complex matrices (FJ, BF, and BP) enhanced betalain bioaccessibility, with FJ exhibiting the highest bioaccessibility (59%). Mucilage and pectin provided the strongest protection, reducing betalain degradation by 30% and 25%, respectively, while citric acid had a destabilizing effect. Pasteurization (BP) reduced betalain stability compared to FJ and BF. Antioxidant activity decreased post-digestion but remained higher in BF. Notably, FJ showed the highest inhibition of α-amylase (72%) and α-glucosidase (68%), surpassing acarbose (50-60% inhibition). These findings highlight the critical role of the food matrix, particularly mucilage and pectin, in stabilizing betalains through non-covalent interactions and enhancing their hypoglycemic potential. Red prickly pear juice emerges as a promising functional food for managing postprandial glucose levels, offering valuable insights for developing betalain-rich foods to address type 2 diabetes.

Keywords: antidiabetic compounds; gastrointestinal stability; interactions; nutraceuticals; synergy.

Figure 1

Antioxidant potential of different complex aqueous model systems before and after digestion. (a) ABTS assay. (b) DPPH assay. BE, betalain extract, S1, BE in water; S2, BE + glucose; S3, BE + citric acid; S4, BE + pectin: S5, BE + mucilage, S6, BE + glucose, citric acid, pectin, and mucilage; JF, fresh juice; BF, formulated beverage; and BP, pasteurized beverage. The data are presented as the means ± SDs from three independent replicates. Uppercase letters indicate statistically significant differences (p < 0.05) between antioxidant activities (DPPH and ABTS) before digestion, while lowercase letters indicate differences after digestion (p < 0.05) according to Tukey’s test.

Figure 2

Chemical structures of betalains and their possible functional groups involved in radical reduction. Red circle: diazapolymethine system. Dotted green circle: phenol group. Adapted from “Estudio preliminar de los pigmentos presentes en cáscara de pitaya de la región mixteca” by Mandujano, 2006 Tesis de licenciatura, maestría, Universidad Tecnológica de la Mixteca.

Figure 3

Free betalain contents in aqueous model systems during in vitro digestion quantified by spectrophotometry UV/vis. BE, betalain extract; S1, BE in water; S2, BE + glucose; S3, BE + citric acid; S4, BE + pectin; S5, BE + mucilage; FJ, fresh juice; FB, formulated beverage; BP, pasteurized beverage. Uppercase letters indicate statistically significant differences between samples in the initial digestion phase, lowercase letters indicate differences in the gastric phase, and lowercase letters from the end of the alphabet indicate differences between samples in the intestinal phase (p < 0.05) according to Tukey’s test.

Figure 4

α-Amylase inhibition by the aqueous model systems after in vitro digestion. C-, starch (negative control); AP, pharmaceutical-grade acarbose (1 mg/mL) (positive control); AR, reagent-grade acarbose (1 mg/mL) (positive control); BE, betalain extract (1.7 mg/g); P, pectin (0.9%); M, mucilage (0.2%); CA, citric acid (0.03%); G, glucose (13.7%); S1, BE in water; S2, BE + glucose; S3, BE + citric acid; S4, BE + pectin; S5, BE + mucilage; FJ, fresh juice; BF, formulated beverage; BP, pasteurized beverage. Each bar represents three determinations, while the error bar represents the standard deviation. Uppercase letters indicate statistically significant differences between samples before digestion, and lowercase letters indicate differences between samples after digestion (p < 0.05), as determined by Tukey’s test.

Figure 5

α-Glucosidase inhibition by aqueous model systems after in vitro digestion. C-, starch (negative control); AP, pharmaceutical-grade acarbose (1 mg/mL) (positive control); AR, reagent-grade acarbose (1 mg/mL) (positive control); BE, betalain extract (1.7 mg/g); P, pectin (0.9%); M, mucilage (0.2%); CA, citric acid (0.03%); G, glucose (13.7%); S1, BE in water; S2, BE + glucose; S3, BE + citric acid; S4, BE + mucilage; S5, BE + pectin; FJ, fresh juice; FB, fresh beverage; BP, pasteurized beverage. Each bar is the mean of three determinations while the error bar represents standard deviation. Different letters indicate significantly different values between samples in each phase (p < 0.05) according to Tukey’s test.