Optimising extraction of antioxidants from roasted Moringa oleifera Lam. leaves using response surface methodology

Abstract

Optimal conditions for alcoholic extraction of antioxidants from roasted leaves of Moringa oleifera Lam. were determined using response surface methodology and the phenolic profile of optimised extract determined by HPLC-PDA. The experimental results adequately fitted the second-order polynomial models as indicated by regression coefficient (.90–.95), lack-of-fit >.05, and absolute deviation .01–.04). Using multiple responses optimization and desirability function, the optimal conditions needed to maximize simultaneously antioxidant activity, phenolic content and extract yield were 65%–75% ethanol, 55–65°C and 40 min. The experimental values were not significantly different (p > .05) from those predicted, indicating the suitability of the models in the studied range. HPLC analysis of the extract revealed the presence of quercetin, isoquercetin, caffeic acid, and rutin. Rutin (45 mg/g), a flavonoid, was the major phenolic. The extract exhibited significant antioxidant potential IC50 2,2-diphenyl-2-picryl hydrazyl 1.28 mg/L, ferric reducing antioxidant power 236 mg AAE/g, total phenolic content 176 mg GAE/g and could be used as nutraceuticals. Practical applications Moringa oleifera L. leaves were roasted to improve antioxidant function and optimum conditions for the preparation of extract with optimal antioxidant potential determined using the multiple response optimization procedure. The resulting extract was freeze-dried and its phenolic profile characterized by HPLC-PDA. The powdered extract has good antioxidant (radical scavenging and ferric reducing) potential and contained rutin as the major phenolic flavonoid followed by quercetin, isoquercetin caffeic acid, and vanillin. The extract has potential for use in nutraceutical formulations for the prevention and management of oxidative stress and chronic diseases (diabetes, cardiovascular diseases, cancer).