Mechanochemical extraction of antioxidant phenolic compounds from Mediterranean and medicinal Laurus nobilis: A comparative study with other traditional and green novel techniques

The main objective of this work was to carry out the extraction of antioxidant phenolic compounds from bay leaves (Laurus nobilis L.) through mechanochemical pretreatment (mechanochemical assisted extraction, MCAE). For this purpose, different solid reagents were screened (Na2CO3, BaCO3, Li2CO3, CoCO3, K2CO3 and CaCO3), and the results were compared with other extraction techniques: conventional Soxhlet, ultrasound (UAE) and microwave (MAE). The comparison was carried out based on total dissolved solids (TDS), total phenolic content (TPC) and antioxidant power (AOP). As-obtained extracts were analysed by gas chromatography and gas chromatography-mass spectrometry analysis (GC and GC–MS) to characterize their composition. In conventional Soxhlet extraction different solvents (water, ethanol and methanol) were tested. It was demonstrated that ethanol provided the best results. Mechanochemical processing resulted in comparable TPC (75.54 GAE g−1 extract) to Soxhlet. Therefore, MCAE is a step forward since, for the same TPC as conventional extraction, the total extraction time (mechanochemical pretreatment and extraction in ethanol) is reduced more than 10 times. The main phenolic compounds present in the extracts were identified as eugenol, methyleugenol and elemicin. Although the results obtained by means of UAE and MAE could be better than those of MCAE, the present study proposes the substitution of conventional extraction by mechanochemistry since the same yields were obtained. © 2019 Elsevier B.V.