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

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 degrees C. Best antioxidant potential from DPPH and FRAP methods were provided by ethanolic extracts at 110 degrees C, while water extracts at 150 degrees C provided best ABTS results. High TPC recovery was found in 50% ethanol samples at 70 degrees 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 degrees 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.

Automated summary

The study focused on the microwave-assisted extraction of ora-pro-nobis leaves, showing high yield with 50% ethanol at 150 degrees C. Ethanol extracts at 110 degrees C exhibited the best antioxidant potential in DPPH and FRAP methods, while water extracts at 150 degrees C showed the best ABTS results. High total phenolic content recovery was found in 50% ethanol samples at 70 degrees C.