Comparison of microwave-assisted and conventional hydrodistillation in the extraction of essential oils from mango (Mangifera indica L.) flowers

Microwave-assisted hydrodistillation (MAHD) is an advanced hydrodistillation (HD) technique, in which a microwave oven is used in the extraction process. MAHD and HD methods have been compared and evaluated for their effectiveness in the isolation of essential oils from fresh mango (Mangifera indica L.) flowers. MAHD offers important advantages over HD in terms of energy savings and extraction time (75 min against 4 h). The composition of the extracted essential oils was investigated by GC-FID and GC-MS. Results indicate that the use of microwave irradiation did not adversely influence the composition of the essential oils. MAHD was also found to be a green technology.     

Multivariate optimisation of the microwave-assisted extraction of oleuropein and related biophenols from olive leaves

Microwave assistance is proposed for the first time in order to accelerate the extraction of biophenols from olive leaves. Under optimal working conditions, obtained using a multivariate methodology, complete extraction of the target analytes was achieved in 8 min. The extracts required no clean-up nor concentration prior to injection into a chromatograph–photodiode array detector assembly for individual separation–quantification. The optimal extractant (an 80:20 ethanol–water mixture) was also used in the development of a stirring-based extraction method which required around 24 h for complete extraction of the target compounds. These mixtures can be used as replacements for toxic extractants, with a view to exploiting olive leaves in order to obtain biophenols for human use.     

Optimisation of supercritical fluid extraction of essential oil components of Diplotaenia cachrydifolia: Box-Behnken design

Essential oil of Diplotaenia cachrydifolia cultivated in Iran was obtained by supercritical fluid extraction (SFE) method. The oils were analysed by capillary gas chromatography using flame ionisation and mass spectrometric detections. The compounds were identified according to their retention indices and mass spectra (EI, 70?eV). The effects of different parameters, such as pressure, temperature, modifier volume and extraction times (dynamic and static), on the SFE were inspected by a fractional factorial design (2(5-2)) to identify the significant parameters and their interaction. It showed that static and dynamic times had no effect on the extraction. Finally, a Box-Behnken design was applied to obtain the optimum condition of the significant parameters. The optimal condition was obtained as 30.2?MPa for pressure, 65.6°C for temperature and 258.4?μL for modifier volume. The main components that were extracted with SFE were dillapiole (35.1%), limonene (33.5%) and α-calacorene (25.5%).     

In vitro bioactivity of essential oils and methanol extracts of Salvia reuterana from Iran

The chemical composition of the essential oils, antioxidant activity (DPPH and beta-carotene/linoleic acid assays) and total phenolic content (Foline-Ciocalteu) of the flowers and leaves of Salvia reuterana were determined. Essential oils extracted from the flowers and leaves by hydrodistillation were analyzed by GC and GC/MS. Forty-four constituents, representing 99.7-99.9% of the oils, were identified. The major components were germacrene D, benzoic acid hexyl ester, bicyclogermacrene, beta-gurjunene and ishwarene, constituting 33.7-31.9% of the oils. The highest radical-scavenging activity (DPPH test) was shown by the methanol extract of the flowers (IC50 = 77.6 microg/mL). In the beta-carotene/linoleic acid assay, the methanol extract of the leaves showed the highest inhibition (40.3%) which was only slightly lower than that shown by BHT (82.9%). The total phenolic contents of the methanol extracts of the flowers and leaves as gallic acid equivalents were 81.4 and 88.3 microg/mg, respectively. The plant also showed good antimicrobial activity against three strains of tested microorganisms.     

Application of factorial design in optimization of ultrasonic-assisted extraction of aluminum in juices and soft drinks

A sample preparation method based on ultrasound-assisted pseudo-digestion of Al from Juices and soft drink samples under ultrasonic effect has been described. A Plackett-Burman experimental design was used as a multivariate strategy for the evaluation of the effects of varying several variables at once. The effects of five different variables preintensification time (without ultrasonic stirring), intensification time in ultrasonic bath (UB), temperature of UB, two acid mixtures (HNO(3)-H(2)SO(4)-H(2)O(2) and HNO(3)-H(2)O(2)), on the recovery of Al have been investigated. From these studies, certain variable showed up as significant, and they were optimized by a using 2(3)+star central composite design, which involved 16 experiments. The best conditions for pseudo-digestion were as follows: a preintensification time 10min, intensification time 20min, volume of acid mixtures 3.0ml and temperature of ultrasonic bath 80 degrees C. A conventional acid digestion on electric hot plate was used to obtain total Al for comparative purpose. Final solutions obtained from both methods, were analysed by electrothermal atomic absorption spectrometry. Analytical results for the Al by ultrasound-assisted pseudo-digestion, and conventional wet digestion methods showed a good agreement, thus indicating the possibility of using ultrasonic-assisted digestion sample preparation instead of intensive treatments inherent with the acid digestion methods on electric hot plate. The procedure proposed allowed the determination of Al with detection limit (3alpha/s) 10mugl(-1).     

Application of non-ionic surfactant in the microwave-assisted extraction of alkaloids from Rhizoma Coptidis

The feasibility of employing non-ionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) as an alternative and effective solvent for the microwave-assisted extraction of alkaloids from Rhizoma Coptidis was demonstrated. When compared with commonly used solvents, 5% Genapol X-080 enhanced the extraction efficiency. Under optimal conditions, i.e. 5% acidified Genapol X-080 (v/v), microwave-assisted extraction for 10 min at 100 °C, the extraction recovery of alkaloids reached 92.8% in a one-step extraction. The efficiency of cloud-point preconcentration of three alkaloids was in the range 93.6-94.7% with relative standard deviation lower than 3.3% by the proposed procedure. Furthermore, the combination of microwave-assisted extraction and cloud-point extraction was shown to be a green, rapid and effective approach for alkaloids preconcentration of Rhizoma Coptidis samples.     

Application of a fractionary factorial design to the determination of tin in lubricating oils by continuous flow hydride generation-atomic absorption spectrometry

The determination of wear metals and metalloids in used lubricating oils allows the prediction of equipment failure. A number of procedures to determine wear metals in lubricating oils by atomic spectrometry has been published. Industry has lately shown a special interest in the determination of tin, since its appearance at certain levels in used oils indicates severe engine wear. Therefore, a method for the determination of the total tin content in used lubricating oils by hydride generation-atomic absorption spectrometry (HG-AAS) is described. Unused marine lubricating oils spiked with the analyte were digested in closed vessels in a microwave oven and the diluted product was used for continuous stannane generation. There are many factors that influence effective SnH₄ generation; therefore, fractionary factorial design was used to obtain an adequate sensitivity and also to stabilize the signal. Six variables were taken into account and a 2^6–2 _IV design was used with spiked samples containing 30 ng g^–1 Sn. The reproducibility, stability, calibration curve and limit of detection were established. The method was applied to different kinds of used lubricating oils. In all cases, the results were higher than those obtained in the industry by simple dilution.     

Application of a fractionary factorial design to the determination of tin in lubricating oils by continuous flow hydride generation-atomic absorption spectrometry

The determination of wear metals and metalloids in used lubricating oils allows the prediction of equipment failure. A number of procedures to determine wear metals in lubricating oils by atomic spectrometry has been published. Industry has lately shown a special interest in the determination of tin, since its appearance at certain levels in used oils indicates severe engine wear. Therefore, a method for the determination of the total tin content in used lubricating oils by hydride generation-atomic absorption spectrometry (HG-AAS) is described. Unused marine lubricating oils spiked with the analyte were digested in closed vessels in a microwave oven and the diluted product was used for continuous stannane generation. There are many factors that influence effective SnH₄ generation; therefore, fractionary factorial design was used to obtain an adequate sensitivity and also to stabilize the signal. Six variables were taken into account and a 2^6–2 _IV design was used with spiked samples containing 30 ng g^–1 Sn. The reproducibility, stability, calibration curve and limit of detection were established. The method was applied to different kinds of used lubricating oils. In all cases, the results were higher than those obtained in the industry by simple dilution. Received: 30 September 1998 / Revised: 22 January 1999 / Accepted: 27 January 1999     

Application of ionic liquids based microwave-assisted simultaneous extraction of carnosic acid, rosmarinic acid and essential oil from Rosmarinus officinalis

An ionic liquid based microwave-assisted simultaneous extraction and distillation (ILMSED) method has been developed for the effective extraction of carnosic acid (CA), rosmarinic acid (RA) and essential oil (EO) from Rosmarinus officinalis. A series of 1-alkyl-3-methylimidazolium ionic liquids differing in composition of anion and cation were evaluated for extraction yield in this work. The results obtained indicated that the anions and cations of ionic liquids had influences on the extraction of CA and RA, 1.0M 1-octyl-3-methylimidazolium bromide ([C8mim]Br) solution was selected as solvent. In addition, the ILMSED procedures for the three target ingredients were optimized and compared with other conventional extraction techniques. ILMSED gave the best result due to the highest extraction yield within the shortest extraction time for CA and RA. The novel process developed offered advantages in term of yield and selectivity of EO and shorter isolation time (20 min in comparison of 4h of hydrodistillation), and provides a more valuable EO (with high amount of oxygenated compounds). The microstructures and chemical structures of rosemary samples before and after extraction were also investigated. Moreover, the proposed method was validated by the stability, repeatability and recovery experiments. The results indicated that the developed ILMSED method provided a good alternative for the both extraction of non-volatile compounds (CA and RA) and EO from rosemary as well as other herbs.     

Application of ionic liquids in the microwave-assisted extraction of podophyllotoxin from Chinese herbal medicine

A micelle-mediated extraction technique, i.e. ionic liquid-based microwave-assisted extraction (ILs-MAE) technique has been developed for the effective extraction of podophyllotoxin from three Chinese medicinal plants. Several operating parameters were successively optimized by single-factor and L(9) (3(4)) orthogonal array experiments. 1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]), 1-decyl-3-methylimidazolium tetrafluoroborate ([demim][BF(4)]) and 1-allyl-3-methylimidazolium tetrafluoroborate ([amim][BF(4)]) were selected as the optimal surfactants for Dysosma versipellis, Sinopodophyllum hexandrum and Diphylleia sinensis, respectively. Compared with other extraction techniques, such as ionic liquids-based maceration extraction (ILs-ME), heat extraction (ILs-HE) and ultrasound-assisted extraction (ILs-UAE), the ILs-MAE technique not only took a shorter time but also afforded a higher extraction rate of podophyllotoxin from the herbs. Reversed phase high performance liquid chromatography was employed for the analysis of podophyllotoxin. The results showed that the linearity for analyzing podophyllotoxin in all three herbs was in the concentration range of 0.005-0.4 mg mL(-1) with the correlation coefficient between 0.9993 and 0.9996. LODs were 2.05-2.58 μg mL(-1) and RSDs of inter-day stability were less than 5.8%. Repeatability and intermediate precision were separately lower than 3.3% and 6.3%. The recoveries for podophyllotoxin extracted with the ILs-MAE technique were in the range of 97.1-102% and all RSDs were lower than 3.0%. Furthermore, the mechanism of ILs-MAE was preliminarily studied by means of kinetic mechanism, surface structures and chemical compositions of samples before and after different extraction techniques. On the basis of the destruction of herb surface microstructures and high solubility of ILs, the ILs-MAE technique eventually got the maximum yield value.     

Isolation of essential oils from tobacco by gas co-distillation/solvent extraction

Summary The essential oils have been isolated from tobacco leaves using a simple gas co-distillation apparatus. The method involves co-distillation with water under the continuous stream of an inert gas with subsequent single solvent extraction of the distillate. The extract is analysed on GC and GC/MS in splitless injection mode without further concentration. The method was evaluated for reproducibility using n-octadecane as an internal standard. The distillation-extraction procedure was reporducible with an average deviation of ±3% for the major constituents. The present method was applied to the analyses of the essential oils of other agricultural products.Dedicated to Dr. L. S. Ettre on the occasion of his 60th birthday.     

Application of central composite design to the optimisation of aqueous two-phase extraction of human antibodies

The partition of human antibodies in aqueous two-phase systems (ATPSs) of polyethylene glycol (PEG) and phosphate was systematically studied using first pure proteins systems and then an artificial mixture of proteins containing 1mg/ml human immunoglobulin G (IgG), 10mg/ml serum albumin and 2mg/ml myoglobin. Preliminary results obtained using pure proteins systems indicated that the PEG molecular weight and concentration, the pH value and the salts concentration had a pronounced effect on the partitioning behaviour of all proteins. For high ionic strengths and pH values higher than the isoelectric point (pI) of the contaminant proteins, IgG could be selectively recovered on the top phase. According to these results, a face centred composite design was performed in order to optimise the purification of IgG from the mixture of proteins. The optimal conditions for the isolation of IgG were observed for high concentrations of NaCl and low concentrations of both phase forming components. The best purification was achieved using an ATPS containing 8% (w/w) PEG 3350, 10% (w/w) phosphate pH 6 and 15% (w/w) NaCl. A recovery yield of 101+/-7%, a purity of 99+/-0% and a yield of native IgG of 97+/-4% were obtained. Back extraction studies of IgG to a new phosphate phase were performed and higher yields were obtained using 10% phosphate buffer at pH 6. The total extraction yield was 76% and the purity 100%.     

Application of ionic liquids in the microwave-assisted extraction of polyphenolic compounds from medicinal plants

Ionic liquids (ILs) solutions as solvents were successfully applied in the microwave-assisted extraction (MAE) of polyphenolic compounds from medicinal plants. ILs, its concentration and MAE conditions were investigated in order to extract polyphenolic compounds effectively from Psidium guajava Linn. (P. guajava) leaves and Smilax china (S. china) tubers. The results obtained indicated that the anions and cations of ILs had influences on the extraction of polyphenolic compounds as well as the ILs with electron-rich aromatic π-system enhanced extraction ability. Under the optimized conditions, the extraction yields of the polyphenolic compounds were in the range of 79.5-93.8% with one-step extraction, and meanwhile the recoveries were in the range of 85.2-103% with relative standard deviations (R.S.D.s) lower than 5.6%. Compared to conventional extraction procedures, the results suggested that the proposed method was effective and alternative for the extraction of polyphenolic compounds from medicinal plants. In addition, the extraction mechanisms and the structures of samples before and after extraction were also investigated. ILs solutions as green solvents in the MAE of polyphenolic compounds from medicinal plant samples showed a great promising prospect.     

Application of ionic liquids in the microwave-assisted extraction of trans-resveratrol from Rhizma Polygoni Cuspidati

In this paper, the application of 1-n-butyl -3-methylimidazolium-based ionic liquids aqueous solutions as solvents in the microwave-assisted extraction (MAE) technique was first developed for the extraction of trans-resveratrol from Rhizma Polygoni Cuspidati. 1-butyl-3-methylimidazolium bromide ([bmim]Br) solution was selected as solvent; the conditions of MAE including the size of sample, liquid/solid ratio, extraction temperature and time were optimized by means of an orthogonal design L(9)(3(4)). Under optimized conditions, the extraction yield value of trans-resveratrol was 92.8% in a one-step extraction. The recovery was in the range 93.7-103.2% with relative standard deviation lower than 3.0% by the proposed procedure. The method was applied to extract trans-resveratrol from several different region samples. On the basis of extraction solvent and time, the proposed extraction technique was a green, rapid and alternative technique to extract and analyze trans-resveratrol in Rhizma Polygoni Cuspidati samples.     

Effects of operating variables on the extraction of uranium from phosphoric acid by factorial design

Extraction of uranium from aqueous phosphoric acid by DEHPA/TOPO is carried out commercially and in pilot plants. The operating variables followed are temperature, concentration of phosphoric acid, and the ratio of DEHPA/TOPO. This study investigates the influence of these operating variables by the statistical method of 2³ Factorial Design on extraction of uranium from phosphoric acid. The mathematical model suggested (K=242.31–7.34C–4.784T+0.164C.T) predicts the effect of variables on the distribution ratio (extraction coefficient). The model is tested by a significance test and represented graphically.     

Ionic liquid-based microwave-assisted extraction of essential oil and biphenyl cyclooctene lignans from Schisandra chinensis Baill fruits

Ionic liquid-based microwave-assisted extraction (ILMAE) has been successfully applied in extracting essential oil and four kinds of biphenyl cyclooctene lignans from Schisandra chinensis Baill. 0.25 M 1-lauryl-3-methylimidazolium bromide ionic liquid is selected as solvent. The optimum parameters of dealing with 25.0 g sample are 385 W irradiation power, 40 min microwave extraction time and 1:12 solid-liquid ratio. The yields of essential oil and lignans are 12.12±0.37 ml/kg and 250.2±38.2 mg/kg under the optimum conditions. The composition of the essential oil extracted by hydro-distillation, steam-distillation and ILMAE is analyzed by GC-MS. With ILMAE method, the energy consumption time has not only been shortened to 40 min (hydro-distillation 3.0 h for extracting essential oil and reflux extraction 4.0 h for extracting lignans, respectively), but also the extraction efficiency has been improved (extraction of lignans and distillation of essential oil at the same time) and reduces the environmental pollution. S. chinensis materials treated by different methods are observed by scanning electronic microscopy. Micrographs provide more evidence to prove that ILMAE is a better and faster method. The experimental results also indicate that ILMAE is a simple and efficient technique for sample preparation.     

Orthogonal test design for optimisation of extraction of trans-resveratrol from Pinot Noir-grape pomace

Yield of trans-resveratrol from Pinot Noir-grape pomace obtained by microwave-assisted extraction (MAE) through an orthogonal experiment (16 (4(4))) was investigated to get the best extraction conditions. In this method, the highest yield was obtained when the extraction solvent used ethanol; the ratio of raw material to solvent, the extraction time, the extraction temperature and microwave irradiation power were 1:20 (g mL(-1)), 30 min, 55°C and 1.0 kW, respectively. The average yield of trans-resveratrol was 90.87%, and the recovery was in the range of 85.49-89.04% with relative standard deviation lower than 1.39%. Then, the extract of MAE was separated by NKA-9 macroporous resin and re-crystallisation. Finally, the purity of trans-resveratrol was 97.47%.     

Use of factorial design and Doehlert matrix for multivariate optimisation of an on-line preconcentration system for lead determination by flame atomic absorption spectrometry

A system for on-line preconcentration and determination of lead by flame atomic absorption spectrometry (FAAS) was proposed. It was based on the sorption of lead(II) ions on a minicolumn of polyurethane foam loaded with 2-(2-thiazolylazo)-5-dimethylaminophenol (TAM). The optimisation step was carried out using two-level full factorial and Doehlert designs for the determination of the optimum conditions for lead preconcentration. The proposed procedure allowed the determination of lead with a detection limit of 2.2 microg L(-1), and a precision, calculated as relative standard deviation (RSD), of 2.4 and 6.8 for a lead concentration of 50.0 and 10.0 microg L(-1), respectively. A preconcentration factor of 45 and a sampling frequency of 27 samples per hour were obtained. The recovery achieved for lead determination in the presence of several cations demonstrated that this procedure has enough selectivity for analysis of environmental samples. The validation was carried out by analysis of certified reference material. This procedure was applied to lead determination in natural food.     

Microwave hydrodiffusion and gravity, a new technique for extraction of essential oils

A new process design and operation for the extraction of essential oils was developed. Microwave hydrodiffusion and gravity (MHG) is a combination of microwaves for hydrodiffusion of essential oils from the inside to the exterior of biological material and earth gravity to collect and separate. MHG is performed at atmospheric pressure without adding any solvent or water. MHG has been compared with a conventional technique, hydrodistillation (HD), for the extraction of essential oil from two aromatic herbs: spearmint (Mentha spicata L.) and pennyroyal (Mentha pulegium L.) belonging to the Labiatae family. The essential oils extracted by MHG for 15 min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by conventional hydrodistillation for 90 min. MHG also prevents pollution through potential 90% of energy saved which can lead to greenhouse gas emission benefits.     

Features of the extraction of essential oils from plant raw material in the presence of surface-active agents

It has been established that the influence of surface-active agents (SAAs), on the extraction of essential oils (EOs) is connected with a fall in the surface tension of water, which facilitates the process of steeping, wetting, and swelling of plant raw material and also the solubilization of the EOs in micellar solutions of SAAs. A. Sultanov Uzbek Scientific Research Institute of Pharmaceutical Chemistry, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 648–652, September–October, 1998.