Effect of different microwave-extraction methods on active components and antimicrobial activities of lemon verbena essential oils

Abstract

In this study, effects of different extraction methods, namely microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME) were investigated in comparison with that of conventional hydrodistillation (HD) in terms of yield, active components, and antimicrobial activities (4 Gram-positive bacteria and 4 Gram-negative bacteria) of lemon verbena leaves essential oils (EOs). Gas chromatography/ mass spectrometry results indicated that geranial (25.54-28.53 %), neral (20.76-23.51 %), and limonene (11.21-12.51 %) were main active components of lemon verbena EOs. There were significant differences among active components of EO obtained by SFME method with those of HD and MAHD methods (P<0.05). Antimicrobial activity of lemon verbena EO obtained by SFME method was higher than those of HD and MAHD methods, which is due to its higher oxygenated components such as geranial (increased by 4.96-11.70%) and neral (increased by 4.09-13.24%). Hence, SFME method can be proposed as a fast, efficient, and selective alternative method for extraction of EO from medicinal plants.

Keywords

• antimicrobial activity
• essential oil
• extraction method
• lemon verbena leaf
• microwave