Highly Efficient Extraction Of Essential Oil From Dryopteris Fragrans And Its Effect On The Oxidation Stability Of Edible Oils

Dryopteris fragrans, known as Xianglinmaojue in China, is a deciduous perennial aromatic herb belonging to the family of Dryopteridaceae. It normally tends to occur on the lava and molten rocks resulting from volcanic eruptions. Due to hard cultivation and over-exploitation, the wild D. fragrans resources have depleted increasingly. Essential oil is one of main active ingredients in D. fragrans, which possesses outstanding antioxidant potential and strong bactericidal effect. Thus, studying the efficient extraction technique is the important scientific support for ensuring the sustainable development of D. fragrans resources. In this paper, on the basis of the strong dissolution abilities of ionic liquids to plant cell walls under microwave irradiation conditions, we combined ionic-liquid-assisted microwave distillation with headspace single drop microextraction for the fast analysis of DEO on one hand; on the other hand, we proposed microwave-assisted ionic liquids pretreatment followed by hydro-distillation for the efficient extraction of DEO. In addition, we assessed the effect of DEO as a natural antioxidant additive on the oxidative stability of sunflower oil for the first time. The main studies and conclusions were exhibited as follows:1. Establishment of ionic liquids-assisted microwave distillation coupled with headspace single-drop microextraction (ILAMp-HSDME) followed by gas chromatography-mass spectrometry for the rapid analysis of essential oil in Dryopteris fragrans.Ionic liquids can be used as the destruction agent of plant cell walls and microwave absorption medium for accelerating the release and distillation of essential oil. Subsequently, essential oil can be simultaneously isolated, extracted and concentrated through the HSDME approach. Various influential parameters of the proposed method were optimized systematically by Box-Behnken design (BBD). Optimal sample preparation conditions were presented as follows:Ionic liquids:[C2mim]OAcSuspended solvent:n-Heptadecape (2.0μL)Microwave irradiation power:300WSample mass:0.9gExtraction temperature:79℃Extraction time:3.6minMass ratio of ionic liquids to sample:2.8In comparison to the previous reports, the proposed technique could equally monitor all the essential oil components with no significant differences in a simple way, which was more rapid and required a much lower amount of sample. Additionally, due to its good stability and repeatability (RSD≤7.67%), the simple, green, rapid and effective ILAMD-HSDME method exhibits a very promising prospect for the rapid analysis of DEO.2. Optimization of microwave-assisted ionic liquids pretreatment followed by hydro-distillation (MILP-MHD) for the efficient extraction of essential oil from D.fragrans.Combining the versatile features of ILs with the beneficial properties of microwave irradiation for the pretreatment of plant matrices followed by hydro-distillation can achieve the high efficient isolation of the essential oil from D. fragrans. The operational parameters of this novel extraction technique were optimized by central composite design (CCD) and first order kinetic model. Optimal extraction conditions were shown as follows:Microwave-assisted ionic liquids pretreatment (MILP) process:Microwave irradiation power:300WPretreatment temperature:76℃Mass concentration of [C2mim]OAc:67.1%Pretreatment time:2.2minMicrowave-assisted hydro-distillation (MHD) process:Microwave irradiation power:700WHydro-distillation time:12minUnder optimized extraction conditions, the yield of DEO obtained by MILP-MHD was0.91%, which significantly increased by175.76%on the basis of the reported solvent-free microwave extraction (SFME) technique. Additionally, the extraction duration taken to the equilibrium yield of essential oil by MILP-MHD was only14.2min, which remarkably decreased by84.89%on the basis of SFME. Additionally, GC-MS results showed that there were no considerable modifications in their chemical compositions. Moreover, SEM result demonstrated that MILP-MHD technique could disintegrate plant matters efficiently thus significantly increasing the release of essential oil. In addition, the recovered [C2mim]OAc could be reused five cycles and0.47%of DEO could still be obtained at the fifth run under the optimal condition. Therefore, it is strongly believed that this green and novel MILP-MHD technique has a great potential for the extraction of DEO.3. Evaluation of DEO as a potent natural antioxidant additive in sunflower oil storage.The antioxidant effectiveness of DEO compared with BHT and VE on the stabilization of sunflower oil under60℃accelerated storage condition was investigated. Parameters of peroxide values (PV), conjugated dienes (CD), free fatty acids (FFA), thiobarbituric acid-reactive substances (TBARS) and p-anisidine values (PAV) were measured as the indices to evaluate the oxidation degree of sunflower oil. During the accelerated oxidation storage of sunflower oil, results showed that the inhibitory effect on the primary and secondary oxidation products formation decreased in the order of BHT> DEO> VE. Therefore, DEO can be explored as an alternative antioxidant additive from the plant origin to prevent the oxidation of edible oils during the storage process.