Extraction optimisation, hydrolysis, antioxidant properties and bioaccessibility of phenolic compounds in Natal plum fruit (Carissa Macrocarpa)

The phenolic content and antioxidant properties of fruits would be underestimated if the extraction method is not optimised and bound phenolic content are not considered. A Central Composite Design and Response Surface Methodology were used to optimize sonication time and ethanol concentration to obtain a food-grade phenolic extract from Natal plum fruit (Carissa Macrocarpa). The free and bound phenolics of Natal plum fruit were extracted, and their release was simulated by in vitro digestion. Optimal conditions (38% ethanol and 16.7 min of ultrasonication) yielded 863.99 mg kg(-1) fresh weight of total phenolics and 421.52 mg kg(-1) fresh weight of total anthocyanins. There were strong correlations between ferric reducing capacity to cyanidin 3-sambubioside (Cy-3-Sa) (R-2 = 0.948), and cyanidin 3-O-glucoside (Cy-3-G) (R-2 = 0.901). Compared to alkaline hydrolysis, acid hydrolysis produced more bound phenolic compounds. The optimum extract still had low anthocyanin bioaccessibility. The optimal extract of the Natal plum fruit may serve as a functional ingredient due to its high antioxidant capacity.

Automated summary

Optimizing the extraction conditions can yield a high antioxidant extract from Natal plum fruit, rich in phenolics and anthocyanins.