In vitro bioaccessibility of citrus pomace compounds possessing health promoting properties with potential to reduce the risk of diabetes

This article belongs to the Proceedings of First International Electronic Conference on Nutrients, Microbiota and Chronic Disease.

Citrus (mandarin and orange) pomace is an agro-food industrial waste rich in polyphenols and dietary fiber with great potential as a functional ingredient. In this work, the chemical composition and in vitro bioaccessibility of health-promoting compounds present in raw citrus pomaces (Clemenule and Ortanique mandarins and Navel and Valencia oranges) were studied. In addition, the by-products were employed as food ingredients in cookies and the effect of the food matrix on the bioaccessibility of their bioactive compounds was evaluated. Nobiletin, hesperidin/neohesperidin, tangeretin, heptamethoxyflavone, tetramethylscutellarein, and naringin/narirutin were detected in the citrus samples by UHPLC-MS. Citrus pomaces were in vitro digested mimicking the human oral gastrointestinal conditions and the bioactivity of the digests (antioxidant, carbohydrases modulation, and anti-inflammatory effects) was assessed. The bioaccessibility of the antioxidants in the by-products was confirmed by Total Polyphenol Content (TPC) (6.6–11.0 mg GAE/g digest), ABTS (65.5–97.1 µmol TE/g digest), ORAC-FL assays (135.5–214.8 µmol TE/g digest), and inhibition of Reactive Oxygen Species (ROS) formation induced by treatment with tert-butyl hydroperoxide 1 mM in intestinal IEC-6 (19–45%) and CCD-18Co (28–45%) cells pretreated with the digests at concentrations ranging between 5 and 25 µg/mL. Inhibitors of the enzymatic activity of α-glucosidase (IC50 3.97–11.42 mg/mL) and α-amylase (IC50 58.04–105.68 mg/mL) also remained bioaccessible after in vitro digestion of citrus pomaces. In addition, the bioaccessible compounds in orange pomace samples significantly reduced (p < 0.05) the lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages. The digests of orange pomace cookies with the nutrition claims “no-added sugars” and “source of fiber” presented antioxidant and anti-diabetic properties, and good sensory quality (6.9–6.7 on a scale of 1 to 9). The results obtained support the feasibility of unfractionated orange pomace as a functional ingredient for reducing the risk of diabetes. The health-promoting benefits observed in the present research might be, at least partially, associated with flavonoids.

This research was funded by ANII (grant POS_NAC_2016_1_130292), program EMHE-CSIC (grant MHE-200003) and PEDECIBA-UdelaR.

Peer reviewed