Application Of Microwave Assisted Technology In Extraction Of Plant Essential Oil Based On Novel Solvents

Essential oils(EOs)have been gaining much attention in recent years due to its various biological activities(antibacterial,antioxidation,anticancer and insecticidal activities).Currently,EOs have been widely used in many interesting applications,especially in pharmaceutical,sanitary,cosmetic,agricultural and food industries.Hydrodistillation is the most simplest and oldest method that is used for the extraction of EOs,however,the degradation of some unsaturated compounds may occur due to thermal effects of hydrodistillation.Furthermore,this method have some disadvantages in relatively longer extraction time and lower extraction efficiency.The combination of microwave into the process of hydrodistillation can solve these problems due to the characteristics of microwave in rapid heating,heating uniformity and selective heating.The experimental results of this paper are as follows:(1)A method for the extraction of volatile EO from Schisandra sphenanthera by microwave assisted simplified simultaneous distillation extraction(MASSDE)based on ionic liquid(IL)was established.The yield of EO obtained by microwave assisted simplified simultaneous extraction was 0.575%,while that of MASSDE based on IL was 0.850%.As for the EO components,IL-MASSDE resulted in more volatile components than MASSDE.The experimental results show that IL-MASSDE is a novel green pretreatment technology for efficient extraction of volatile EO from Schisandra sphenanthera.(2)A novel deep eutectic solvent(DES)-based microwave hydrodistillation(MHD)coupled with GC-MS was developed to determine the volatile EO from three Amomum species.Under the optimum conditions,the EO yields of Amomum kravanh,Amomum tsaoko and Amomum villosum were 3.64%,2.16%and 1.62%,respectively.GC-MS analysis achieved identification of totally 63 compounds from three Amomum species,of which 33,51 and 43 compounds belonged to Amomum kravanh,Amomum tsaoko and Amomum villosum,respectively.Compared with the traditional extraction technique,the novel extraction method can result in more volatile components,especially high boiling point substances.The precision of DES-MHD in the three Amomum species was 7.3%,8.2%and 8.7%,respectively(n = 6).In summary,DES-MHD is a method that can quickly extract the volatile components of Amomum species plants.(3)A novel DES-based microwave hydrodistillation coupled with GC-MS was developed to determine the volatile EO from white pepper and black pepper.Under the optimum conditions,the yields of EOs from white and black pepper were 1.78%and 1.77%,respectively.The volatile compounds extracted from black pepper and white pepper were analyzed by GC-MS.54 compounds were obtained.The novel method brought about more identified compounds than conventional hydrodistillation.The methodological precision of DES-MHD extraction of volatile EOs from white pepper and black pepper was expressed by RSD,which turned out to be 7.2%and 8.3%,respectively(n = 6).Therefore,DES-MHD is a method that can quickly extract EOs from white pepper and black pepper.The volatile components in plants are mainly present in the cells of plants,which have network structures formed by cellulose.Therefore,the volatile components will be blocked by such structures when extraction is performed.By pretreating plant samples with strongly polar ILs and DESs,the yield of EOs and the components of EOs can be significantly increased.It is possible that the IL and DES can dissolve the plant cell wall and destruct the network structure formed by cellulose to promote the release of volatile components within the cells.