Evaluation of effective factors on the extraction efficiency of phenolic and flavonoid compounds of lemon verbena (Aloysia citriodora Palau) under ultrasonic waves and evaluation of its antibacterial properties

One of the major challenges in application of medicinal plants is to improve the extraction efficiency of bioactive materials. Therefore, the study of factors affecting the extraction of these materials is one of the important attractive subject for researchers. Lemon verbena due to the presence of high active substances in its leaves and nutritional properties has always been noticed by researchers of medicinal and aromatic plants. In this study, the effect of solvent type, extraction temperature, extraction time and solid to solvent on the extraction efficiency of phenolic compounds, flavonoid compounds and antioxidant activity of plant leaves under ultrasonic waves was investigated based on designed experiments using response surface methodology (RSM). Our result showed that the extraction temperature and solid to solvent ratio are two effective extraction variables on bioactive compounds extraction of lemon verbena leaves under ultrasonic waves. Also our results showed that aqueous- alcoholic extract has a higher efficiency for extraction of phenolic and flavonoid compounds, and trapping free radicals when compared with pure water. The antibacterial properties of aqueous-alcoholic extract showed a significant difference compared to pure aqueous extract. The susceptibility of Escherichia coli to both aqueous-alcoholic extracts and aqueous extracts was higher than that of Staphylococcus aureus.