Bioactive Clitoria ternatea L. Flower extract for the glycemic control to carbohydrate foods and sugary beverages

Abstract

Clitoria ternatea L. flower, an edible plant containing anthocyanins, has been currently used as the source of natural colorant in foods, beverages and desserts worldwide. The previous report demonstrated its biological properties including antioxidant and antihyperglycemic activity. However, the various concentrations of Clitoria ternatea were used in food and beverages but the effective concentration of Clitoria ternatea on the digestibility of starch and glycemic response remains unknown. In this study, the effects of foods and beverage containing Clitoria ternatea L. flower extract (CTE) on starch digestibility in vitro, postprandial glycemic response and antioxidant capacity in human as well as sensory acceptability were investigated. The results showed that CTE (1 and 2 g) significantly suppressed postprandial plasma glucose and insulin levels with enhanced antioxidant status after consumption of sucrose beverage. Moreover, CTE did not cause hypoglycemia in the fasting state. Likewise, the 1% and 2% (w/v) CTE inhibited the pancreatic a-amylase activity when using potato, cassava, rice, corn, wheat and glutinous rice flours as a substrate. Consequently, 0.5%, 1% and 2% (w/v) CTE showed a significant reduction in the glucose release, hydrolysis index (HI) and predicted glycemic index (pGI) of all flours. Statistical analysis demonstrated strong positive significant correlation between the percentage of CTE and the undigested starch of wheat and cassava flours. The addition of 5%, 10% and 20% (w/w) CTE significantly reduced the rate of starch digestion of wheat bread. Finally, the incorporation of 2.5% (w/v) CTE caused a reduction in starch digestibility of cooked rice with a good overall acceptability using an electric rice cooker and a microwave oven. Interestingly, CTE decreased the glycemic index (GI) of cooked rice by 13%. Consumption of cooked rice with CTE caused a reduction in postprandial blood glucose in healthy subjects Therefore, CTE may potentially be a useful ingredient to reduce glycemic response in high carbohydrate foods and beverages.