Vegetable polyphenols inhibit starch digestibility and phenolic availability from composite carbohydrate foods in-vitro

Abstract

The interaction of Phenolic compounds with carbohydrate has been observed to reduce postprandial glucose released from carbohydrate foods. This study investigates the chemical composition of eight species of vegetable; the vegetables (raw and blanched) were subjected to phytochemical screening, phenolic and antioxidant potential analyses. The phenolic compounds profile of Amaranthus hybridus was also determined using high performance liquid chromatography (HPLC).Composite foods containing A. hybridus vegetable with either rice or wheat were prepared, digested in-vitro using a multienzyme simulated method and the digestates dialyzed. The dialysates were analyzed for phenolic and glucose availability. The results indicated that the total phenol, tannin and flavonoids ranged from 21.1 to 106 mg gallic acid equivalent/g, 1.89 to 14.4 and 3.5–20.5 mg catechin equivalent/g, respectively. Crude and neutral detergent fibres varied between 0.02 - 16.7% and 10.8–79.2%, respectively. Reducing sugar, total sugar and Uronic acid ranged from 0.84 to 9.40 mg/g, 5.00–11.12 mg/g and 136.8–498.4 mg/g, respectively. Blanching was observed to cause reduction in phenolic compounds in A. hybridus. The in-vitro available phenolics and glucose were inhibited in the composite diets, and the percentage inhibition varied between 37.5 and 53.3% for phenolics, and 11.3 and 51.5% for glucose. The study revealed that interaction between phenolic compounds and carbohydrates could impair starch digestibility hence the inclusion of vegetable with high glycemic index foods could serve as an alternative nutrition therapy in the management of diabetes.

Keywords

• Antioxidant
• Simulated digestion
• Nutrients
• Phenolics
• Vegetable