Eco-friendly extraction for the recovery of bioactive compounds from Brazilian olive leaves

Abstract The aim of this study was to recover value-added compounds from Brazilian olive tree leaves using organic solvent-free green extraction techniques. The key molecules obtained by microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and maceration were characterized for total phenolic compounds (TP), antioxidant activity (AA), oleuropein (OP) and hydroxytyrosol (HT) contents. In the study, we also determined the lowest concentration of extract that causes growth inhibition of Type 1 Escherichia coli . The results show that green technologies were suitable for the extraction of bioactive compounds from olive tree leaves. MAE was more efficient than UAE and maceration. OP was the predominant phenolic compound found in the extracts. At a concentration of 50 mg.mL −1, the extract produced by MAE inhibited the growth of E . coli by 100%, compared to 80.9% for the extract produced by UAE. As for the inhibition kinetics of the extracts, no bacterial growth was observed up to 75 min after inoculation. This study demonstrates that green technologies can be used successfully to extract compounds with antioxidant and antibacterial properties from olive culture byproducts, and that Brazilian crops are a viable environmental source.