Extraction Optimization of Essential Oil from Medicago hispida and Preliminary Inhibitory Mechanism Against Escherichia coli

Abstract

In this study, the extraction optimization, characterization, antioxidant evaluation and preliminary inhibitory mechanism against Escherichia coli of the essential oil from dried Medicago hispida (EOMH) were explored to uncover the pending questions that had been raised in our previous work and to enlarge the industrial potential of EOMH production. The optimal parameters for EOMH extraction were: Extraction time of 7 h, particle size of 20 mesh and liquid-to-solid ratio of 30: 1 (mL/g), under which the highest yield of EOMH reached 0.31%. Nineteen constituents were identified in EOMH by gas chromatography mass spectrometry analysis, among which phytol content was up to 53.6%. These structures were further confirmed by infrared spectroscopy analysis. EOMH exerted similar scavenging capacities against Diphenyl Picryl Hydrazinyl (DPPH) and hydroxyl radicals with those of phytol. However, EOMH elicited stronger inhibitory effect on E. coli than that of phytol via shrinking E. coli cells, indicating that other factors, in addition to the antioxidant mechanism would equally affect the inhibitory effect of EOMH against E. coli, which should be deepened in the near further. In summary, present work would provide evidence for the industrial production and application of EOMH.