改进的微波辅助无溶剂法提取薄荷和陈皮中的挥发油组分

An improved solvent free microwave extraction, in which a kind of microwave absorption medium （carbonyl iron powder） was used, was applied to the extraction of essential oil from dried menthol mint and orange peel without addition of any solvent and pretreatment. It took much less time of extraction （30 min） than microwave-assisted hydrodistillation （90 min） and conventional hydrodistillation （180 min）. The kinds of chemical compositions in essential oil extracted by different methods were almost the same and such improved solvent free microwave extraction can be a feasible way in extraction of essential oil from dried plant materials.     

Rapid analysis of the essential oils from dried Illicium verum Hook. f. and Zingiber officinale Rosc. by improved solvent-free microwave extraction with three types of microwave-absorption medium

A new method of extracting essential oils from dried plant materials has been studied. By adding a microwave-absorption medium (MAM) to a reactor, solvent-free microwave extraction (SFME) was improved and can be used to extract essential oils from dried plant material without pretreatment. With a microwave irradiation power of 85 W it took only approximately 30 min to extract the essential oils completely. The whole extraction process is simple, rapid, and economical. Three types of MAM, iron carbonyl powder (ICP), graphite powder (GP), and activated carbon powder (ACP), and two types of dried plant material, Illicium verum Hook. f. and Zingiber officinale Rosc., were studied. The results were compared with those obtained by use of conventional SFME, microwave-assisted hydrodistillation (MAHD), and conventional hydrodistillation (HD), and the conclusion drawn was that improved SFME was a feasible means of extracting essential oils from dried plant materials, because there were few differences between the composition of the essential oils extracted by improved SFME and by the other methods.     

Non-polar Solvent Microwave-Assisted Extraction of Volatile Constituents from Dried Zingiber Officinale Rosc.

A new method, non-polar solvent microwave-assisted extraction （NPSMAE）, was applied to the extraction of essential oil from Zingiber officinale Rosc. in closed-vessel system. By adding microwave absorption mediumcarbonyl iron powders （CIP） into extraction system, the essential oil was extracted by the non-polar solvent （ether） which can be heated by CIP. The constituents of essential oil obtained by NPSMAE were comparable with those obtained by hydrodistillation （HD） by GC-MS analysis, which indicates that NPSMAE is a feasible way to extract essential oil from dried plant materials. The NPSMAE took much less extraction time （5 min） than HD （180 min）, and its extraction efficiency was much higher than that of conventional polar solvent microwave-assisted extraction （PSMAE） and mixed solvent microwave-assisted extraction （MSMAE）. It can be a good alternative for the extraction of volatile constituents from dried plant samples.     

固体微波介质加热快速提取新鲜橘皮中挥发油组分

对传统微波加热模式进行了改进,以具有良好微波吸收性能的微波吸收固体介质取代传统溶剂和水,将其加入到新鲜样品的提取体系,达到快速升温的目的.将改进的微波辅助无溶剂法应用于提取新鲜植物样品中挥发油组分,并考察了3种微波吸收介质(羰基铁粉、石墨粉和活性炭粉)对提取结果的影响.结果证明:对于新鲜样品,除活性炭粉无法使用外,羰基铁粉和石墨粉均适用.在20 g微波吸收介质及85 W微波功率的加热作用下,仅需30 min即可将100 g样品中的挥发油提取完全.通过与传统微波辅助无溶剂法、微波辅助水蒸馏法和传统水蒸馏法比较,改进的微波辅助无溶剂法具有提取时间短(30 min)、耗电量小(0.43 kW · h/kg)等优点,且所得挥发油组分无明显差别.此外,还考察了烘干过程对橘皮挥发油组成的影响,发现橘皮挥发油的组成受烘干影响较大.     

A surprising method for green extraction of essential oil from dry spices: Microwave dry-diffusion and gravity

Without adding any solvent or water, we proposed a novel and green approach for the extraction of secondary metabolites from dried plant materials. This "solvent, water and vapor free" approach based on a simple principle involves the application of microwave irradiation and earth gravity to extract the essential oil from dried caraway seeds. Microwave dry-diffusion and gravity (MDG) has been compared with a conventional technique, hydrodistillation (HD), for the extraction of essential oil from dried caraway seeds. Essential oils isolated by MDG were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by HD, but MDG was better than HD in terms of rapidity (45min versus 300min), energy saving, and cleanliness. The present apparatus permits fast and efficient extraction, reduces waste, avoids water and solvent consumption, and allows substantial energy savings.     

Solvent-free microwave extraction of essential oil from aromatic herbs: comparison with conventional hydro-distillation

Solvent-free microwave extraction (SFME) is a combination of microwave heating and dry distillation, performed at atmospheric pressure without added any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. SFME has been compared with a conventional technique, hydro-distillation (HD), for the extraction of essential oil from three aromatic herbs: basil (Ocimum basilicum L.), garden mint (Mentha crispa L.), and thyme (Thymus vulgaris L.). The essential oils extracted by SFME for 30min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by conventional hydro-distillation for 4.5 h. The SFME method yields an essential oil with higher amounts of more valuable oxygenated compounds, and allows substantial savings of costs, in terms of time, energy and plant material. SFME is a green technology and appears as a good alternative for the extraction of essential oils from aromatic plants.     

Rapid Extraction and Analysis of Essential Oil from Cinnamomum Cassia Presl.

An improved solvent-free microwave extraction（ISFME） was used for the extraction of essential oil from dried Cinnamomum cassia Presl. Two kinds of solid microwave absorption media[carbonyl iron powder（CIP） and graphite powder（GP）] were used. When ISFME was applied, the heating rate was enhanced and the extraction time was obviously shorter than that consumed in conventional solvent-free microwave extraction（CSFME）. Twenty-eight kinds of compounds in the essential oil were identified, and the total content fractions of the compounds obtained by CIP-ISFME, GP-ISFME, CSFME, and hydrodistillation（HD） were 96.65%, 96.06%, 97.22%, and 96.29%, respectively. The compounds in the essential oil obtained from Cinnamomum cassia Presl. by ISFME, CSFME, and HD were compared and the quantity of the essential oil was almost the same. The ISFME has been proved to be a feasible way to extract essential oil from dried samples, and there are several obvious advantages in ISFME over those of HD and CSFME, for example, shorter extraction time（30 min） and lower energy consumption.     

Rapid Extraction of Essential Oil from Dried Cinnamomum cassia Presl and Forsythia suspensa(Thunb.)Vahl by Ionic Liquid Microwave Extraction

Ionic liquid (IL) was used as the microwave absorption medium to extract essential oils from dried Cinnamomum cassia Presl and Forsythia suspensa (Thunb.) Vahl, and the ionic liquid microwave extraction (ILME) was developed. Some experimental parameters for ILME were examined. The proposed method was compared with other methods, including hydrodistillation (HD), microwave hydrodistillation (MHD), solvent‐free microwave extraction (SFME) and improved solvent‐free microwave extraction (ISFME). Experimental results showed that compared with other extraction methods the ILME had some advantages, such as time‐saving, simplicity and usage of green solvents. The extraction time was less than 18 min at the microwave power of 440 W and 1.5 mL of ionic liquid was required. The constituents of essential oils obtained by the five methods are not obviously different.     

Effects of solvent-free microwave extraction on the chemical composition of essential oil of Calamintha nepeta (L.) Savi compared with the conventional production method

The essential oil of Calamintha nepeta has been obtained by solvent-free microwave extraction (SFME) and by classical hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 38 compounds, constituting 97.6% of the oil, were identified in the oil obtained by SFME, whereas 46 compounds, representing 95.4% of the oil, were characterized in the HD oil. SFME-distilled oil is richer in lightly oxygenated monoterpenes (LOM) than HD oil. It also has a higher amount of sesquiterpenes and a lower quantity of hydrocarbon monoterpenes. HD oil seems to be affected by chemical changes more than SFME oil.     

Headspace single drop microextraction coupled with microwave extraction of essential oil from plant materials

Headspace single drop microextraction (HS-SDME) coupled with microwave extraction (ME) was developed and applied to the extraction of the essential oil from dried Syzygium aromaticum (L.) Merr. et Perry and Cuminum cyminum L. The operational parameters, such as microdrop volume, microwave absorption medium (MAM), extraction time, and microwave power were optimized. Ten microliters of decane was used as the microextraction solvent. Ionic liquid and carbonyl iron powder were used as MAM. The extraction time was less than 7 min at the microwave power of 440 W. The proposed method was compared with hydrodistillation (HD). There were no obvious differences in the constituents of essential oils obtained by the two methods.     

莪术中挥发性成分的微波辅助固相顶空气相色谱法分析

将微波无溶剂提取(SFME)与顶空气相色谱(HS-GC)在线联用,建立了中药材的微波辅助固相顶空气相色谱法(MASP-HSGC),并用该方法快速直接分析了莪术药材中的挥发性成分。研究中对色谱条件、微波作用时间、微波作用功率等因素进行了考察,并以莪术醇为标准品考察了回收率和检出限,同时测定了莪术醇在莪术药材中的含量。对采用水蒸气蒸馏法(HD)和SFME法获得的莪术挥发油进行了气相色谱-质谱（GC-MS）分析,所得结果与所建立方法的结果进行对比。结果表明: HD-GC、SFME-GC和MASP-HSGC法所测得的化合物分别为35、33和40种;3种方法测得的莪术醇含量分别为（0.294±0.015）、（0.331±0.023）和（0.297±0.009） mg/g。该法简便快速,可用于莪术中挥发性成分的分离分析。     

Microwave extraction of essential oils from dried fruits of Illicium verum Hook. f. and Cuminum cyminum L. using ionic liquid as the microwave absorption medium

Ionic liquid was used as microwave absorption medium and applied to the extraction of essential oils from dried fruits of the Illicium verum Hook. f. and Cuminum cyminum L. by microwave‐assisted extraction. The extraction time is less than 15 min at the microwave power of 440 W. The constituents of essential oils obtained by the proposed method were compared with those obtained by hydrodistillation. There is no obvious difference in the constituents of essential oils obtained by the two methods.     

Chemical composition and antibacterial activity of Origanum saccatum P.H. Davis essential oil obtained by solvent-free microwave extraction: comparison with hydrodistillation

The components of the essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum saccatum P.H. Davis were identified by using GC/MS. The main constituents of both EOs obtained by SFME and HD, respectively, from O. saccatum were p-cymene (72.5 and 70.6%), thymol (9.32 and 8.11%), and carvacrol (7.18 and 6.36%). The EO obtained by SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than did the EO obtained by HD. The antibacterial activities of the EOs obtained by SFME and HD were evaluated with the disc diffusion method by comparison with 10 different bacterial strains. The antibacterial activity of the EO extracted by SFME was found to be more effective than that of the EO extracted by HD against seven of the tested bacteria.     

Water as a green solvent combined with different techniques for extraction of essential oil from lavender flowers

Using water as a green solvent with a variable geometry makes use of physical and chemical phenomena that are fundamentally different from those applied in conventional extraction techniques such as hydro-distillation, steam distillation or solvent extraction. Advantages and drawbacks of using water as a solvent with different physical and chemical states have been compared. A total of ten extraction techniques: hydro-distillation (HD), steam distillation (SD), turbo-hydro-distillation (THD), salt-hydro-distillation (NaCL-HD), enzyme-hydro-distillation (Enzyme-HD), micelle-hydro-distillation (Micelle-HD), ultrasound-hydro-distillation (US-HD) or subcritical water-hydro-distillation (SW-HD), solvent-free microwave extraction (SFME) and microwave steam distillation (MSD) were used to extract the essential oil from lavender (Lavandula L.) and their results were compared. The quantity was measured by the yield of essential oil and the quality was evaluated using the oil composition especially the content of linalyl acetate, linalool and terpin-4-ol compared with the corresponding control sample: Hydro-distillation. For environmentally friendly of the process: extraction time, total energy consumption and CO₂ emission were considered and compared with conventional hydro-distillation. The mechanism explaining the linalyl acetate degradation has been resolved by using COSMO-RS software. Based on the present experimental conditions, it is recommended that lavender oil may be produced preferably by steam distillation assisted by microwave extraction to reduce the by-product formation by various chemical reactions and to get better oil recoveries.     

A comparison between different techniques for the isolation of rosemary essential oil

Traditional hydrodistillation (HD), supercritical fluid extraction (SFE), organic solvent extraction (SE), and water microwave assisted hydrodistillation (MAHD) techniques were compared and evaluated for their effectiveness in the isolation of rosemary essential oil. The microwave assisted hydrodistillation technique was optimized in terms of both delivered power and time duration. The extracts/distillates were analyzed by GC and GC-MS. Microwave distillation, which exploits the physical action of microwaves on plants, showed a series of advantages over the other approaches: low cost, use of water in sample pre-treatment step, greatly reduced isolation time, and attainment of high quality essential oil distillate. Moreover, the absence of environmental impact of this innovative technique was also emphasized.     

Solvent-free microwave extraction and hydrodistillation of essential oils from endemic Origanum husnucanbaseri H. Duman, Aytac & A. Duran: comparison of antibacterial activity and contents

The essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum husnucanbaseri H. Duman, Aytac & A. Duran were investigated using the gas chromatography-mass spectrometry system. The main constituents of both oils obtained from SFME and HD from O. husnucanbaseri are borneol (15.2-12.8%), α-terpineol (12.3-10.8%) and trans-sabinene hydrate (11.8-9.92%). The EO obtained from SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than that from HD. The antibacterial activities of the EOs from SFME and HD were evaluated by the disc diffusion method against six bacterial strains. The EO extracted by SFME was more effective than the EO extracted by HD against the tested bacteria, except for Klebsiella pneumoniae American type culture collection (ATCC) 13883. Streptococcus pyogenes ATCC 19615 and Staphylococcus aureus ATCC 25923 in particular were more sensitive against the EO extracted by SFME.     

Antibacterial activities of essential oils extracted from leaves of Murraya koenigii by solvent-free microwave extraction and hydro-distillation

Solvent-free microwave extraction (SFME) for the isolation of essential oil from leaves of Murraya koenigii L. (Rutaceae) has been compared with the conventional hydro-distilled oil (HD) in terms of yield, composition, antioxidant activity, and antibacterial activity against Listeria innocua. The yield of essential oil obtained from 30 min of SFME was similar to that of HD for 180 min. By GC-MS analysis, the major compounds of the essential oil extracted by SFME, which were obtained in somewhat lower amounts than in the essential oil obtained by HD, were alpha-copaene (44.3%), beta-gurjunene (25.5%), isocaryophyllene (12.1%), beta-caryophyllene (8.7%) and germacrene D (2.9%). The content of oxygenated terpenes, slightly higher for the SFME-essential oil (2.3%) than the HD-essential oil (1.4%), were much lower than that of nonoxygenated terpenes in both oils. DPPH radical scavenging activities of both essential oils were relatively low (10%-24%). Complete inhibition of growth of L. innocua was observed with both SFME and HD essential oils, at 400 and 600 microg/mL (minimum inhibitory concentration), respectively. The SFME-essential oil at 300 microg/mL provided 92% inhibition, indicating its potential as a natural antimicrobial agent.     

Microwave assisted extraction of essential oils from enzymatically pretreated lavender (<Emphasis Type="Italic">Lavandula angustifolia</Emphasis> Miller)

In this study, microwave assisted a hydrodistillation process (MWHD) of essential oils from lavender (Lavandula angustifolia Miller) was investigated. In order to examine any potential differences in essential oil extraction, the lavender flowers underwent enzymatic pretreatment.A 2³ factorial design of experiments, combined with statistical methods of data analysis were used to optimize enzymatic pretreatment and to evaluate the influence of major variables (enzyme concentration, temperature and pH) on the performance of the microwave assisted extraction.Under optimal conditions, an extraction yield of 24 mg oil g^?1 substrate was achieved (an increase by approximately 25% in comparison with the classic extraction conditions of conventional hydrodistillation).The main compounds of the essential oils obtained were analyzed and identified by gas chromatography coupled to mass spectrometry (GC-MS). Analyzing the data obtained indicated that the content of main compounds (linalool and linalyl acetate ? 73%) was greater than that obtained by conventional extraction (67%).

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Comparison of continuous subcritical water extraction and hydrodistillation of marjoram essential oil.

Continuous subcritical water extraction (CSWE) and hydrodistillation were compared for the extraction of essential oil from marjoram leaves. Ground marjoram leaves (0.4 g) were subjected to dynamic extraction with water at 50 bar, 150 degrees C and 2 ml/min for 15 min. Hydrodistillation was performed treating 140 g of marjoram leaves with 1000 ml of water for 3 h. When CSWE was used the compounds were removed from the aqueous extract by a single extraction with 5 ml of hexane, detected by gas chromatography-flame ionization detection (GC-FID) and identified by mass spectrometry, electronic impact. The CSWE method is quicker (15 min versus 3 h), provides a more valuable essential oil (with higher amounts of oxygenated compounds and no significant presence of terpenes) and allows substantial savings of costs, in terms both of energy and plant material. The efficiency (in terms of volume of essential oil/1 g of plant) of CSWE is 5.1 times higher than that provided by hydrodistillation. The precision of the overall method (CSWE combined with GC-FID) is good (RSD less than 7.5%) for n = 5.     

Rapid analysis of the essential oil components of dried Zanthoxylum bungeanum Maxim by Fe2O3‐magnetic‐microsphere‐assisted microwave distillation and simultaneous headspace single‐drop microextraction followed by GC–MS

In this work, microwave distillation assisted by Fe₂O₃ magnetic microspheres (FMMS) and headspace single‐drop microextraction were combined, and developed for determination of essential oil compounds in dried Zanthoxylum bungeanum Maxim (ZBM). The FMMS were used as microwave absorption solid medium for dry distillation of dried ZBM. Using the proposed method, isolation, extraction, and concentration of essential oil compounds can be carried out in a single step. The experimental parameters including extraction solvent, solvent volume, microwave power, irradiation time, and the amount of added FMMS, were studied. The optimal analytical conditions were: 2.0 μL decane as the extraction solvent, microwave power of 300 W, irradiation time of 2 min, and the addition of 0.1 g FMMS to ZBM. The method precision was from 4 to 10%. A total of 52 compounds were identified by the proposed method. The conventional steam distillation method was also used for the analysis of essential oil in dried ZBM and only 31 compounds were identified by steam distillation method. It was found that the proposed method is a simple, rapid, reliable, and solvent‐free technique for the determination of volatile compounds in Chinese herbs.