Superheated liquid extraction of oleuropein and related biophenols from olive leaves

Oleuropein and other healthy olive biophenols (OBPs) such as verbacoside, apigenin-7-glucoside and luteolin-7-glucoside have been extracted from olive leaves by using superheated liquids and a static-dynamic approach. Multivariate methodology has been used to carry out a detailed optimisation of the extraction. Under the optimal working conditions, complete removal without degradation of the target analytes was achieved in 13 min. The extract was injected into a chromatograph-photodiode array detector assembly for individual separation-quantification. The proposed approach - which provides more concentrated extracts than previous alternatives - is very useful to study matrix-extractant analytes partition. In addition, the efficacy of superheated liquids to extract OBPs, the simplicity of the experimental setup, its easy automation and low acquisition and maintenance costs make the industrial implementation of the proposed method advisable.     

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.     

Supercritical fluid extraction of phenol compounds from olive leaves

A clean, highly selective supercritical fluid extraction (SFE) method for the isolation of phenols from olive leaf samples was examined. Total phenol extracts were determined using the Folin-Ciocalteu reagent. Dried, ground, sieved olive leaf samples (30 mg) are subjected to SFE, using carbon dioxide modified with 10% methanol at 334 bar, 100 degrees C (CO(2) density 0.70 g ml(-1)) at a liquid flow-rate of 2 ml min(-1) for 140 min. Diatomaceous earth is used to reduce the void volume of the extraction vessel. The influence of extraction variables such as modifier content, pressure, temperature, flow-rate, extraction time, and collection/elution variables, were studied. Supercritical fluid extracts were screened for acid compounds such as carboxylic acids and phenols using Electrospray-MS (in the negative ionization mode). SFE was found to produce higher phenol recoveries than sonication in liquid solvents such as n-hexane, diethyl ether and ethyl acetate. However, the extraction yield obtained was only 45%, using liquid methanol.     

The recovery of biophenols from wastewaters of olive oil production

In this article, the phenolic composition of wastewaters prepared from different cultivars of Olea europaea have been described. The main aim is the recovery of these compounds for technological utilization.     

Dynamic ultrasound-assisted extraction of polyphenols in tobacco

A novel extraction method, namely dynamic ultrasound-assisted extraction, is investigated. This technique is efficient with respect to both time and solvent consumption because it utilizes ultrasonic energy in dynamic mode during extraction. Polyphenols (chlorogenic acid, esculetin, rutin, scopoletin, and quercitrin) are extracted from a tobacco (Nicotina tobaccum L.) sample for 10 min with 6 mL of solvent. Fresh solvent is continuously pumped through the sample, with which the analytes can be rapidly extracted, and the possibility of degradation efficiently avoided. Methanol involving 0.5% w/v ascorbic acid was used as extraction solvent; optimal flow rate and extraction time were investigated. The extract was cleaned up by C18 disposable cartridge. The spiked and nonspiked tobacco samples were used for the evaluation of the proposed method. Recoveries obtained were varied from 96 to 108% and RSDs from 2.0 to 4.6%. This extraction technique was revealed to recover larger amounts of polyphenols from tobacco, compared to the static ultrasound-assisted extraction method.     

Dynamic ultrasound-assisted extraction of cadmium and lead from plants prior to electrothermal atomic absorption spectrometry

A dynamic ultrasound-assisted extraction step is proposed for the quantitative extraction of Cd and Pb from plant leaves prior to determination by electrothermal atomic absorption spectrometry (ETAAS). Beech leaves (a certified reference material—CRM 100—where the target analytes were not certified) were used for optimizing the extraction step by a multivariate approach. The samples (0.25 g) were subjected to dynamic ultrasound-assisted extraction with dilute nitric acid as extractant. The method was validated with a certified reference material BCR-062 (olive leaves) where both Cd and Pb are certified. The good agreement between the certified values and those found using the proposed method demonstrates its usefulness. The repeatability was 2.0 and 0.9% and the within-laboratory reproducibility was 7.1 and 2.8% for Cd and Pb, respectively. The precision of the method, together with its efficiency, rapidity, low cost and environmental acceptability makes it a good alternative for the determination of trace metals from plant material.     

Dynamic ultrasound-assisted extraction of colistin from feeds with on-line pre-column derivatization and liquid chromatography-fluorimetric detection

A dynamic ultrasound-assisted extraction (UAE) method with on-line pre-column derivatization/high performance liquid chromatography (HPLC) and fluorimetric detection is proposed for the analysis of colistin in feed. A flow injection manifold is used for the development of the extraction and derivatization steps and for interfacing them with the separation/detection step, thus providing an on-line approach with the advantage of minimum sample handling. The derivatization was performed with ortho-phthaldialdehyde and 2-mercaptoethanol. The optimum conditions for colistin extraction and formation of the fluorescent derivative have been obtained by experimental design methodology. The use of a high-intensity probe sonication makes UAE an expeditious (7 min versus > 1 h) and efficient (93.1-98.2% versus 87.5-94% of recovery) alternative as compared with extraction using an ultrasonic bath. The within-laboratory reproducibility and repeatability, expressed as percentage of relative standard deviation, were 5.2 and 5.8, respectively.     

Dynamic ultrasound-assisted extraction of catechins and caffeine in some tea samples

A novel dynamic ultrasound-assisted extraction (DUAE) device has been constructed for extraction of five catechins and caffeine in solid sample. The accurate, simple, reproducible and sensitive method for the determination of five catechins and caffeine has been developed and validated. A comparison has been made of the efficiencies by employing DUAE and conventionally static ultrasound-assisted extraction (UAE). The proposed method can not only improve extraction efficiency but also decrease time and solvent consumption. The commercial Chinese tea samples, involving green and black teas, are rapidly analyzed by the proposed DUAE method. The linearity, range, selectivity, precision, accuracy, and robustness also showed acceptable values.     

Separation and purification of hydroxytysol and oleuropein from Olea europaea L. (olive) leaves using macroporous resins and a novel solvent system

The separation and purification of hydroxytysol and oleuropein from Olea europaea L. (olive) using a macroporous resin with a novel solvent system was systematically investigated. Static adsorption experiments with BMKX–4 resin revealed that the experimental data of both hydroxytysol and oleuropein fitted best to the pseudo‐second‐order kinetic and Freundlich isotherm models. The thermodynamic parameters indicated spontaneous and exothermic adsorption processes. The novel solvent system, composed of n–hexane:ethyl acetate:methanol:water in a (v/v/v/v) ratio of 1:9:1:9, had two phases (upper and lower). The separation and purification parameters of hydroxytysol and oleuropein were optimized using dynamic adsorption/desorption on a column packed with BMKX–4 resin. The effects of flow rates and volumes of the upper and lower phases on the separation efficiency were systematically studied. Under optimal conditions, the fraction of hydroxytysol in the final product increased by 6.34‐fold from 0.46 to 2.96%, with a yield rate of 88.58% w/w, while that of oleuropein increased 4.17‐fold from 11.40 to 47.59%, with a 93.31% w/w yield rate. These results may be help in selecting a suitable eluent for improved separation of macroporous adsorption resins.     

Microwave-assisted extraction of coumarin and related compounds from Melilotus officinalis (L.) Pallas as an alternative to Soxhlet and ultrasound-assisted extraction

Soxhlet extraction, ultrasound-assisted extraction (USAE) and microwaves-assisted extraction (MAE) in closed system have been investigated to determine the content of coumarin, o-coumaric and melilotic acids in flowering tops of Melilotus officinalis. The extracts were analyzed with an appropriate HPLC procedure. The reproducibility of extraction and of chromatographic analysis was proved. Taking into account the extraction yield, the cost and the time, we studied the effects of extraction variables on the yield of the above-mentioned compounds. Better results were obtained with MAE (50% v/v aqueous ethanol, two heating cycles of 5 min, 50 degrees C). On the basis of the ratio extraction yield/extraction time, we therefore propose MAE as the most efficient method.     

Forward-and-back dynamic ultrasound-assisted extraction of fat from bakery products

A dynamic ultrasound-assisted extraction method prior to the gravimetric determination of total fat content in bakery products is proposed. An open approach in which forward-and-back extractant steps and cycles of extract draining and filling of the sample chamber with fresh extractant was used, which provided the best results as compared with both an open system with forward-and-back of a single extractant volume and an one-direction open system. Recoveries from 99.7 to 100.7% compared with Sohxlet extraction were obtained. The repeatability and within laboratory reproducibility, expressed as relative standard deviation (R.S.D.), were 2.04 and 2.74%, respectively. As compared with conventional Soxhlet, the extraction time was shortened more than five times—from 16 to 3 h—in the case of cookies and more of eight times—from 8 to 1 h—in the case of snacks. Thirteen or 25 ml of hexane was required for total extraction in 10 or 20 cycles, depending on the sample.     

Optimization of ultrasound-assisted extraction of phenolic compounds from Sesamum indicum

Abstract

Effective extraction of phyto-biomolecules insures retaining maximum functionality along with higher recovery. In this study, ultrasound-solvent assisted extraction (USAE) was employed for optimal extraction of phyto-biomolecules from Sesamum indicum (sesame) leaves using the approach of Response Surface Methodology (RSM). The optimized condition of 200?W power, 59% methanol concentration with 1:14?g/mL solid–liquid ratio and 15?min of extraction time yielded 367.39?±?1.85?mg GAE/100?g of total phenolic content, 96.72?±?3.27% of free radical scavenging activity and 81.20?±?2.87% of iron chelating activity respectively. The extract consist of essential phytocomponents like gallic acid, chlorogenic acid, and quercetin with lipid peroxidation activities of >50% over incubation time of 48?h. Also, showed antimicrobial activity against various Gram’s negative and positive food borne pathogens. The results of this study implied the importance of USAE for effective and optimum recovery of phyto-biomolecules from Sesame leaves with retained functional properties.     

Polyethylene glycol-based ultrasound-assisted extraction of magnolol and honokiol from Cortex Magnoliae Officinalis

In this study, a kind of green solvent named polyethylene glycol (PEG) was developed for the ultrasound-assisted extraction (UAE) of magnolol and honokiol from Cortex Magnoliae Officinalis. The effects of PEG molecular weight, PEG concentration, sample size, pH, ultrasonic power and extraction time on the extraction of magnolol and honokiol were investigated to optimise the extraction conditions. Under the optimal extraction conditions, the PEG-based UAE supplied higher extraction efficiencies of magnolol and honokiol than the ethanol-based UAE and traditional ethanol-reflux extraction. Furthermore, the correlation coefficient (R²), repeatability (relative standard deviation, n = 6) and recovery confirmed the validation of the proposed extraction method, which were 0.9993–0.9996, 3.1–4.6% and 92.3–106.8%, respectively.     

Dynamic ultrasound-assisted extraction of environmental pollutants from marine sediments for comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection

A dynamic ultrasound-assisted extraction (UAE) of marine sediments has been optimized using experimental design methodology. Comprehensive two-dimensional gas chromatography (GC x GC) using a cryogenic modulator, and time-of-flight-mass spectrometry (TOF-MS) were used to separate and identify environmental pollutants. Six compounds from three different chemical classes were used to optimize the extraction parameters.     

Determination of cadmium in leaves by ultrasound-assisted extraction prior to hydride generation, pervaporation and atomic absorption detection

A flow injection-pervaporation approach, where the samples – beech or olive leaves – were introduced as slurry, has been used for continuous derivatization hydride generation and separation of cadmium prior to determination by atomic absorption spectrometry. The removal of the analyte is achieved with an 1 mol/l HCl + 16% H₂O₂ aqueous solution with the help of an ultrasound probe acting for 17 min. Thiourea and cobalt were also added to the slurry for kinetic catalysis of hydride generation. A CRM – beech leaves – where the analyte had not been certified but estimated was used for optimisation of the leaching step. The results obtained using direct calibration against aqueous standards demonstrated the reliability of the method. The linear concentration range of the calibration curve was from pg/ml to ng/ml, with a correlation coefficient, r², better than 0.99. The detection and quantification limits were 0.3 and 0.9 ng/ml, respectively. The relative standard deviation for within-laboratory reproducibility was 5.7%. Olive leaves CRM was used for validation.     

Comparison of microwave-assisted extraction of aloe-emodin in aloe with Soxhlet extraction and ultrasound-assisted extraction

This paper reports the extraction of aloe-emodin from aloe by microwave-assisted extraction.The effects of various factors,including the solvent,the ratio (mL/g) of the solvent to the sample,microwave irradiation time and microwave power,were discussed in the experiments.The yield of aloe-emodin was determined by HPLC.The optimized conditions for microwave-assisted extraction of aloe-emodin were concluded as follows: the solvent is 80% ethanol (V/V) solution,microwave irradiation time is 3 min and microwave...     

Monitoring the oleuropein content of olive leaves and fruits using ultrasound‐ and salt‐assisted liquid–liquid extraction optimized by response surface methodology and high‐performance liquid chromatography

A novel and rapid ultrasound‐ and salt‐assisted liquid–liquid extraction coupled with high‐performance liquid chromatography has been optimized by response surface methodology for the determination of oleuropein from olive leaves. Box–Behnken design was used for optimizing the main parameters including ultrasound time (A), pH (B), salt concentration (C), and volume of miscible organic solvent (D). In this technique, a mixture of plant sample and extraction solvent was subjected to ultrasound waves. After ultrasound‐assisted extraction, phase separation was performed by the addition of salt to the liquid phase. The optimal conditions for the highest extraction yield of oleuropein were ultrasound time, 30 min; volume of organic solvent, 2.5 mL; salt concentration, 25% w/v; and sample pH, 4. Experimental data were fitted with a quadratic model. Analysis of variance results show that BC interaction, A², B², C², and D² are significant model terms. Unlike the conventional extraction methods for plant extracts, no evaporation and reconstitution operations were needed in the proposed technique.     

Development of a simple green extraction procedure and HPLC method for determination of oleuropein in olive leaf extract applied to a multi-source comparative study

A simple, green and inexpensive water-based procedure was developed to extract oleuropein from olive leaf samples. Extraction was optimized in terms of the solvent, pH of the solvent, temperature and time of extraction. The experimental results revealed that deionised water adjusted to pH 3, at 60 °C for 4 h had the highest extraction efficiency. Samples were lyophilized and stored in tight containers at ?18 °C until the analysis. Oleuropein was identified by comparing the retention time of the extracts with standard compound using UV detector at 280 nm. The method of analysis was based on RP-HPLC, with a mobile phase of water (adjusted to pH 3):acetonitrile (80:20 v/v) with a flow rate of 1 ml min^?1. Linear dynamic range and limit of detection were found to be 50?C900 ??g ml^?1 and 9.5 ??g ml^?1, respectively. Intra- and inter-day precision of the method were calculated as RSD% of 1.2 and 5.7, respectively. Olive leaves gathered from various cultivars of Iran were analyzed by the method and results showed that olive leaves from Shiraz had the highest oleuropein content (about 13 mg g^?1). The developed method can be used in industry for proper mass production of this compound that is of great significance in medicine as well as food and cosmetics industry.     

Ethanol production from lignocellulosic byproducts of olive oil extraction

The recent implementation of a new two-step centrifugation process for extracting olive oil in Spain has substantially reduced water consumption, thereby eliminating oil mill wastewater. However, a new high sugar content residue is still generated. In this work the two fractions present in the residue (olive pulp and fragm ented stones) were assayed as substrate for ethanol production by the simultaneous saccharification and fermentation (SSF) process. Pretreatment of fragmented olive stones by sulfuric acid-catalyzed steam explosion was the most effective treatment for increasing enzymatic digestibility; however, a pretreatment step was not necessary to bioconvert the olive pulp into ethanol. Theolive pulp and fragmented olive stones were tested by the SSF process using a fed-batch procedure. By adding the pulp three times at 24-h intervals, 76% of the theoretical SSF yield was obtained. Experiments with fed-batch pretreated olive stones provided SSF yields significantly lower than those obtained at standard SSF procedure. The preferred SSF conditions to obtain ethanol from olives stones (61% of theoretical yield) were 10% substrate and addition of cellulases at 15 filter paper units/g of substrate.