Microwave-assisted extraction of essential oils from herbs ( Epazote, pretreated Lavender)

The aim of this study was to characterize and analyze the physical and chemical properties in the Microwave-assisted extraction (MAE) process of essential oils (EOs) from herbs. Microwaves are a form of non-ionizing electromagnetic energy at frequencies ranging from 300 MHz to 300 GHz. This energy is transmitted as waves, which can penetrate in biomaterials and interact with polar molecules into materials, such as water to generate heat. Fast heating is the main advantage of microwaves. EOs, which are isolated by physical means only, are defined as products obtained from raw plant materials. The conventional methods for EOs extraction are distillation (steam, steam/water and water), squeezing (also known as cold pressing for citrus peel oils) or dry distillation of natural products. Advances in microwave-assisted extraction (MAE) have led in the development of various techniques such as compressed air microwave (CAMD), microwave hydro distillation (MWHD), solvent free microwave extraction. Also using of MWHD methods is an appropriate alternative to conventional techniques due to the reduced extraction time, more effective and selective heating, simplified equipment, reduce volume of solvent required and high purity of the final product. The material that we use for microwave assisted is a domestic microwave oven.100g of sample (dried leaves of epazote) were placed in a 1000 ml flat-bottomed flask and the solvent amount (distilled water) to analyze was added (400 or 500 ml).the flask introduced to microwave and adjusted to condenser connected to a cold water recirculation system. And for MWHD experiment, lavender flowers (50gr) were mixed with 500 ml pretreatment solution. For comparison the extraction of the EOs was performed using steam distillation method. In MWHD, the EOs were extracted using multimode microwave reactor with using bubbling nitrogen gas to avoid oxidation of the components. The chemical composition of EOs were analyzed by GC-MS. The physical properties of EOs was determined using a digital refractometer .In the extraction of EOs of epazote (microwave assisted) higher yields(0.39%) were obtained with the combination of 70% of power, 30min of microwave heating and400 ml of water. Epazote essential oil yield was found to be significantly different in comparison with the oil obtained by steam distillation (SD) extraction. (0.20±0.008%). The major components of epzote were limonene oxide cis, and 4-carene.The last one was the most abundant compound in the essential oil obtained by SD, meanwhile, 4-trimethyl-acetate was the main component in the oil extracted by MAE. MWHD methods assures a greater content in comparison to conventional methods. The influence of MWHD should be more evident in plant material where the EOs are less superficially located and more difficult to distill out conventionally. Due to the significant reduction of time, solvent and changes in the yields of EOs was shown with respect to SD, the MAE is a good alternative in the extraction process of essential oil from herbs.

کلیدواژه ها:

Epazote ، Microwave-assisted extraction ، essential oils ، steam distillation ، energy reduction