Phenolic compounds recovered from ora-pro-nobis leaves by microwave assisted extraction

Abstract

Ora-pro-nobis is an ornamental plant, often used as food in some regions of Brazil, and Pereskia grandifolia is one of the less explored specie of this nutritional plant. To understand the antioxidant potential and phenolic profile of ora-pro-nobis leaves, the micro-wave assisted extraction (MAE) was held using the green solvents ethanol and water. An optimization was made using Box-Behnken experimental design (3 2 ), with process time, temperature and solvent (% of water/ethanol) as variables. The evaluated responses were the process yield, combined with antioxidant capacity (DPPH, ABTS and FRAP methods) and total phenolic content (TPC) of the recovered extracts. Soxhlet method with ethanol was performed for comparison purpose. The phenolic profile of extract samples was assessed by LC-ESI-MS/MS analysis. High yield values were provided by 50% ethanol as solvent at 150 °C. Best antioxidant potential from DPPH and FRAP methods were provided by ethanolic extracts at 110 °C, while water extracts at 150 °C provided best ABTS results. High TPC recovery was found in 50% ethanol samples at 70 °C. Overall, 24 phenolic compounds were identified, within caffeic acid, ellagic acid, p -anisic acid, p-coumaric acid kaempferol and quercetin as the main components. Ellagic acid and p-anisic acid were firstly reported associated to ora-pro-nobis leaves. The optimization of the results indicates that 150 °C, 12.5 min of MAE and ethanol as solvent provided the best combined responses. The use of MAE for ora-pro-nobis leaves is a novelty that must be followed to explore green methods to value natural products. • MAE was efficient to recover phenolic-rich extracts from ora-pro-nobis. • MAE water extracts provided phenolic-rich and flavonoid-rich fraction. • Ellagic acid and p -anisic acid were firstly identified from ora-pro-nobis leaves.