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Special Issue "Green Extraction of Natural Product: Innovative Techniques, Alternative Solvents and Original Procedures"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products".

Deadline for manuscript submissions: closed (31 October 2017)

Special Issue Editors

Guest Editor
Prof. Dr. Farid Chemat

Green Extraction Team, Université d'Avignon et des Pays de Vaucluse, INRA, Avignon Cedex 84029, France
Website | E-Mail
Phone: 0033490144465
Interests: green extraction; alternative solvents; innovative technologies; microwave; ultrasound
Guest Editor
Prof. Dr. Giancarlo Cravotto

Dipartimento di Scienza e Tecnologia del Farmaco and NIS - Centre for Nanostructured Interfaces and Surfaces, University of Turin, Via P. Giuria 9, 10125 Torino, Italy
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Interests: key enabling technologies; microwaves; sonochemistry; mechanochemistry; flow chemistry; process intensification
Guest Editor
Prof. Dr. Young Hae Choi

Natural Products Laboratory, Institute of Biology, Leiden University, Leiden, The Netherlands
Website | E-Mail
Interests: metabolomics; phytochemistry; supercritical fluid extraction; natural deep eutectic solvents

Special Issue Information

Dear Colleagues,

The industrial production of perfumes, cosmetics, pharmaceuticals, food ingredients and products, nutraceuticals, biofuel, or fine chemicals, involve extraction processes. In the field of extraction of natural products, conventional methods, mostly using organic solvents have major drawbacks, such as insufficient recovery of extracts, long extraction time, high amounts of by-products and wastes, and high energy consumption. In recent years, the trend of extraction has moved to "sustainability", making a transition to "Green Extraction", to develop more "sustainable" processes using alternative solvents, less energy, and reducing waste, while ensuring the quality of final products.

The present Special Issue, “Green Extraction of Natural Product”, aims to collect and to publish recent advances in this interdisciplinary area. Reviews and research articles dealing with innovative techniques, alternative solvents, original procedures, comprehension of intensification mechanisms, by products valorization, and the green impacts and sustainable footprints. In term of dissemination this Special Issue is aiming to provide some guidelines for good practice and reporting, existing and in conception of reactors or solvents suitable for green extraction. Experts are welcome to give their opinion about how green extraction contributed/contributes/will contribute to natural products area, possible trends, and perspectives.

Prof. Dr. Farid Chemat
Prof. Dr. Giancarlo Cravotto
Prof. Dr. Young Hae Choi
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • green extraction
  • separation and purification
  • intensification
  • enabling technologies
  • deep eutectic solvents
  • natural products
  • supercritical fluids

Published Papers (15 papers)

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Research

Open AccessArticle Identification of Major Flavone C-Glycosides and Their Optimized Extraction from Cymbidium kanran Using Deep Eutectic Solvents
Molecules 2017, 22(11), 2006; doi:10.3390/molecules22112006
Received: 30 October 2017 / Revised: 14 November 2017 / Accepted: 16 November 2017 / Published: 18 November 2017
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Abstract
Cymbidium kanran, an orchid exclusively distributed in Northeast Asia, has been highly valued as a decorative plant and traditional herbal medicine. Here, C. kanran extracts were prepared in 70% aqueous methanol using ultrasound-assisted extraction (UAE) and subjected to liquid chromatography-photodiode array detection
[...] Read more.
Cymbidium kanran, an orchid exclusively distributed in Northeast Asia, has been highly valued as a decorative plant and traditional herbal medicine. Here, C. kanran extracts were prepared in 70% aqueous methanol using ultrasound-assisted extraction (UAE) and subjected to liquid chromatography-photodiode array detection and ultra-high performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry analysis, which were used for quantitative and qualitative analysis, respectively. It was found that the extracts were rich in flavone C-glycosides including vicenin-2, vicenin-3, schaftoside, vitexin, and isovitexin. Ten deep eutectic solvents (DESs) were synthesized by combining choline chloride (hydrogen bond acceptor) with various polyols and diols (hydrogen bond donors) and were tested as a medium for the efficient production of extracts enriched with potentially bioactive flavone C-glycosides from C. kanran. A DES named ChCl:DPG, composed of choline chloride and dipropylene glycol at a 1:4 molar ratio, exhibited the best extraction yields. Then, the effects of extraction conditions on the extraction efficiency were investigated by response surface methodology. Lower water content in the extraction solvent and longer extraction time during UAE were desirable for higher extraction yields. Under the statistically optimized conditions, in which 100 mg of C. kanran powder were extracted in 0.53 mL of a mixture of ChCl:DPG and water (74:26, w/w) for 86 min, a total of 3.441 mg g−1 flavone C-glycosides including 1.933 mg g−1 vicenin-2 was obtained. This total yield was 196%, 131%, and 71% more than those obtained using 100% methanol, water, and 70% methanol, respectively. Full article
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Open AccessArticle Optimization of the Extraction Conditions for Buddleja officinalis Maxim. Using Response Surface Methodology and Exploration of the Optimum Harvest Time
Molecules 2017, 22(11), 1877; doi:10.3390/molecules22111877
Received: 30 September 2017 / Accepted: 29 October 2017 / Published: 1 November 2017
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Abstract
The Box-Behnken design was used to evaluate the effects of the methanol concentration (60–100%), liquid to solid ratio (20:1 to 40:1 mL/g) and extraction time (20–40 min) on the yield of 11 constituents from Buddleja officinalis Maxim using ultrasound-assisted extraction. The Derringer’s desirability
[...] Read more.
The Box-Behnken design was used to evaluate the effects of the methanol concentration (60–100%), liquid to solid ratio (20:1 to 40:1 mL/g) and extraction time (20–40 min) on the yield of 11 constituents from Buddleja officinalis Maxim using ultrasound-assisted extraction. The Derringer’s desirability function approach showed that the modified optimum extraction conditions were: 76% methanol concentration, 33 min extraction time and a 34:1 mL/g solvent to solid ratio. Under these conditions, the experimentally measured yields of the compounds were in good agreement with the predicted values. An accurate and sensitive method was also established using high-performance liquid chromatography with diode-array detection for the simultaneous determination of the 11 compounds in Buddleja officinalis. The newly developed method was used to determine the amounts of bioactive components in Buddleja officinalis during four different growth stages. According to these results, we recommend that the full blossom stage is the best time for harvesting this plant to obtain the highest yield of crude materials. Full article
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Open AccessArticle Recovery of Oil with Unsaturated Fatty Acids and Polyphenols from Chaenomelessinensis (Thouin) Koehne: Process Optimization of Pilot-Scale Subcritical Fluid Assisted Extraction
Molecules 2017, 22(10), 1788; doi:10.3390/molecules22101788
Received: 13 September 2017 / Revised: 17 October 2017 / Accepted: 19 October 2017 / Published: 22 October 2017
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Abstract
The potential effects of three modern extraction technologies (cold-pressing, microwaves and subcritical fluids) on the recovery of oil from Chaenomelessinensis (Thouin) Koehne seeds have been evaluated and compared to those of conventional chemical extraction methods (Soxhlet extraction). This oil contains unsaturated fatty acids
[...] Read more.
The potential effects of three modern extraction technologies (cold-pressing, microwaves and subcritical fluids) on the recovery of oil from Chaenomelessinensis (Thouin) Koehne seeds have been evaluated and compared to those of conventional chemical extraction methods (Soxhlet extraction). This oil contains unsaturated fatty acids and polyphenols. Subcritical fluid extraction (SbFE) provided the highest yield—25.79 g oil/100 g dry seeds—of the three methods. Moreover, the fatty acid composition in the oil samples was analysed using gas chromatography–mass spectrometry. This analysis showed that the percentages of monounsaturated (46.61%), and polyunsaturated fatty acids (42.14%), after applying SbFE were higher than those obtained by Soxhlet, cold-pressing or microwave-assisted extraction. In addition, the oil obtained under optimized SbFE conditions (35 min extraction at 35 °C with four extraction cycles), showed significant polyphenol (527.36 mg GAE/kg oil), and flavonoid (15.32 mg RE/kg oil), content, had a good appearance and was of high quality. Full article
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Open AccessArticle Complex Enzyme-Assisted Extraction Releases Antioxidative Phenolic Compositions from Guava Leaves
Molecules 2017, 22(10), 1648; doi:10.3390/molecules22101648
Received: 13 September 2017 / Revised: 26 September 2017 / Accepted: 26 September 2017 / Published: 30 September 2017
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Abstract
Phenolics in food and fruit tree leaves exist in free, soluble-conjugate, and insoluble-bound forms. In this study, in order to enhance the bioavailability of insoluble-bound phenolics from guava leaves (GL), the ability of enzyme-assisted extraction in improving the release of insoluble-bound phenolics was
[...] Read more.
Phenolics in food and fruit tree leaves exist in free, soluble-conjugate, and insoluble-bound forms. In this study, in order to enhance the bioavailability of insoluble-bound phenolics from guava leaves (GL), the ability of enzyme-assisted extraction in improving the release of insoluble-bound phenolics was investigated. Compared to untreated GL, single xylanase-assisted extraction did not change the composition and yield of soluble phenolics, whereas single cellulase or β-glucosidase-assisted extraction significantly enhanced the soluble phenolics content of PGL. However, complex enzyme-assisted extraction (CEAE) greatly improved the soluble phenolics content, flavonoids content, ABTS, DPPH, and FRAP by 103.2%, 81.6%, 104.4%, 126.5%, and 90.3%, respectively. Interestingly, after CEAE, a major proportion of phenolics existed in the soluble form, and rarely in the insoluble-bound form. Especially, the contents of quercetin and kaempferol with higher bio-activity were enhanced by 3.5- and 2.2-fold, respectively. More importantly, total soluble phenolics extracts of GL following CEAE exhibited the highest antioxidant activity and protective effect against supercoiled DNA damage. This enzyme-assisted extraction technology can be useful for extracting biochemical components from plant matrix, and has good potential for use in the food and pharmaceutical industries. Full article
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Open AccessArticle Ultrasonic Assisted Extraction of Paclitaxel from Taxus x media Using Ionic Liquids as Adjuvants: Optimization of the Process by Response Surface Methodology
Molecules 2017, 22(9), 1483; doi:10.3390/molecules22091483
Received: 1 August 2017 / Revised: 25 August 2017 / Accepted: 4 September 2017 / Published: 11 September 2017
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Abstract
(1) Background: Ionic liquids (ILs) are considered “green” solvents and have been widely used in the extraction and separation field in recent years; (2) Methods: In this study, some common ILs and functionalized magnetic ionic liquids (MILs) were used as adjuvants for the
[...] Read more.
(1) Background: Ionic liquids (ILs) are considered “green” solvents and have been widely used in the extraction and separation field in recent years; (2) Methods: In this study, some common ILs and functionalized magnetic ionic liquids (MILs) were used as adjuvants for the solvent extraction of paclitaxel from Taxus x media (T. x media) using methanol solution. The extraction conditions of methanol concentration, IL type and amount, solid–liquid ratio, extraction temperature, and ultrasonic irradiation time were investigated in single factor experiments. Then, three factors of IL amount, solid–liquid ratio, and ultrasonic irradiation time were optimized by response surface methodology (RSM); (3) Results: The MIL [C4MIM]FeCl3Br was screened as the optimal adjuvant. Under the optimization conditions of 1.2% IL amount, 1:10.5 solid–liquid ratio, and 30 min ultrasonic irradiation time, the extraction yield reached 0.224 mg/g; and (4) Conclusions: Compared with the conventional solvent extraction, this ultrasonic assisted extraction (UAE) using methanol and MIL as adjuvants can significantly improve the extraction yield, reduce the use of methanol, and shorten the extraction time, which has the potentiality of being used in the extraction of some other important bioactive compounds from natural plant resources. Full article
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Open AccessArticle Microwave-Assisted Extraction of Natural Antioxidants from the Exotic Gordonia axillaris Fruit: Optimization and Identification of Phenolic Compounds
Molecules 2017, 22(9), 1481; doi:10.3390/molecules22091481
Received: 12 August 2017 / Revised: 30 August 2017 / Accepted: 3 September 2017 / Published: 6 September 2017
Cited by 1 | PDF Full-text (3037 KB) | HTML Full-text | XML Full-text
Abstract
Our previous study reported that the fruit of Gordonia axillaris, an edible wild fruit, possessed strong antioxidant activity. In this study, a microwave-assisted extraction (MAE) method was established to extract antioxidants from the fruit of Gordonia axillaris. The influence of five
[...] Read more.
Our previous study reported that the fruit of Gordonia axillaris, an edible wild fruit, possessed strong antioxidant activity. In this study, a microwave-assisted extraction (MAE) method was established to extract antioxidants from the fruit of Gordonia axillaris. The influence of five parameters, including ethanol concentration, solvent/material ratio, extraction time, extraction temperature and microwave power, was investigated by single-factor experiments. Three factors, namely ethanol concentration, solvent/material ratio, extraction time, were found to exert a major influence on extraction efficacy, and were further studied by response surface methodology to investigate their interactions. Ethanol concentration of 36.89%, solvent/material ratio of 29.56 mL/g, extraction time of 71.04 min, temperature of 40 °C, and microwave power of 400 W were found to be the optimal condition. The TEAC value was 198.16 ± 5.47 µmol Trolox/g DW under the optimal conditions, which was in conformity to the predicted value (200.28 µmol Trolox/g DW). In addition, the MAE method was compared with two conventional methods (Soxhlet extraction and maceration extraction). Results showed that the antioxidant capacity of the extract obtained by MAE method was stronger than that obtained by maceration (168.67 ± 3.88 µmol Trolox/g DW) or Soxhlet extraction (114.09 ± 2.01 µmol Trolox/g DW). Finally, several phenolic compounds in the extract were identified and quantified by UPLC-MS/MS, which were rutin, gallic acid, protocatechuic acid, epicatechin, epicatechin gallate, 2-hydrocinnamic acid, p-coumaric acid, quercetin, chlorogenic acid and ferulic acid. Full article
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Open AccessArticle Optimization of the Ultrasound-Assisted Extraction of Phenolic Compounds from Brosimum alicastrum Leaves and the Evaluation of Their Radical-Scavenging Activity
Molecules 2017, 22(8), 1286; doi:10.3390/molecules22081286
Received: 17 July 2017 / Revised: 29 July 2017 / Accepted: 31 July 2017 / Published: 7 August 2017
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Abstract
In order to maximize the yield of the total phenolic content (TPC) and total monomeric anthocyanin (TMA) from Brosimum alicastrum leaf and to study the radical-scavenging activity, a three-level three-factor Box–Behnken design (BBD) was used to determine the optimal points for ultrasound-assisted extraction
[...] Read more.
In order to maximize the yield of the total phenolic content (TPC) and total monomeric anthocyanin (TMA) from Brosimum alicastrum leaf and to study the radical-scavenging activity, a three-level three-factor Box–Behnken design (BBD) was used to determine the optimal points for ultrasound-assisted extraction (UAE). In this study, we analyzed the extraction time (10, 20, and 30 min), temperature (28, 30, and 32 °C), and probe sonication power (40%, 28 W/cm2; 60%, 51 W/cm2; and 80%, 74 W/cm2). Analysis of variance (ANOVA) indicated that the sonication power plays a significant role in the extraction of phenolic compounds. An increase in time and temperature resulted in a decrease in the yield, in particular, of the TMA group. DPPH was found to be a better indicator of radical-scavenging activity than ABTS. The predicted TPC and TMA optimum levels (45.18 mg GAE/g and 15.16 mg CyE/100 g) were obtained at 28 °C, 80%, and 20–10 min. DPPH obtained a maximum value (67.27 μmol TE/g) under same optimization conditions. The RSM confirmed that TPC and TMA enhanced the antioxidant activity when subjected to low temperature (28 °C), extraction time less than 20 min, and higher sonication power (74 W/cm2), and hence achieving the better DPPH scavenging activity. Full article
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Open AccessArticle Homogenate-assisted Vacuum-powered Bubble Extraction of Moso Bamboo Flavonoids for On-line Scavenging Free Radical Capacity Analysis
Molecules 2017, 22(7), 1156; doi:10.3390/molecules22071156
Received: 5 June 2017 / Revised: 5 July 2017 / Accepted: 5 July 2017 / Published: 11 July 2017
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Abstract
A homogenate-assisted vacuum-powered bubble extraction (HVBE) method using ethanol was applied for extraction of flavonoids from Phyllostachys pubescens (P. pubescens) leaves. The mechanisms of homogenate-assisted extraction and vacuum-powered bubble generation were discussed in detail. Furthermore, a method for the rapid determination of flavonoids
[...] Read more.
A homogenate-assisted vacuum-powered bubble extraction (HVBE) method using ethanol was applied for extraction of flavonoids from Phyllostachys pubescens (P. pubescens) leaves. The mechanisms of homogenate-assisted extraction and vacuum-powered bubble generation were discussed in detail. Furthermore, a method for the rapid determination of flavonoids by HPLC was established. HVBE followed by HPLC was successfully applied for the extraction and quantification of four flavonoids in P. pubescens, including orientin, isoorientin, vitexin, and isovitexin. This method provides a fast and effective means for the preparation and determination of plant active components. Moreover, the on-line antioxidant capacity, including scavenging positive ion and negative ion free radical capacity of different fractions from the bamboo flavonoid extract was evaluated. Results showed that the scavenging DPPH˙ free radical capacity of vitexin and isovitexin was larger than that of isoorientin and orientin. On the contrary, the scavenging ABTS+˙free radical capacity of isoorientin and orientin was larger than that of vitexin and isovitexin. Full article
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Open AccessArticle Subcritical Water Technology for Extraction of Phenolic Compounds from Chlorella sp. Microalgae and Assessment on Its Antioxidant Activity
Molecules 2017, 22(7), 1105; doi:10.3390/molecules22071105
Received: 31 May 2017 / Revised: 21 June 2017 / Accepted: 22 June 2017 / Published: 3 July 2017
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Abstract
Chlorella sp. microalgae is a potential source of antioxidants and natural bioactive compounds used in the food and pharmaceutical industries. In this study, a subcritical water (SW) technology was applied to determine the phenolic content and antioxidant activity of Chlorella sp.
[...] Read more.
Chlorella sp. microalgae is a potential source of antioxidants and natural bioactive compounds used in the food and pharmaceutical industries. In this study, a subcritical water (SW) technology was applied to determine the phenolic content and antioxidant activity of Chlorella sp. This study focused on maximizing the recovery of Chlorella sp. phenolic content and antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay as a function of extraction temperature (100–250 °C), time (5–20 min) and microalgae concentration (5–20 wt. %) using response surface methodology. The optimal operating conditions for the extraction process were found to be 5 min at 163 °C with 20 wt. % microalgae concentration, which resulted in products with 58.73 mg gallic acid equivalent (GAE)/g phenolic content and 68.5% inhibition of the DPPH radical. Under optimized conditions, the experimental values were in close agreement with values predicted by the model. The phenolic content was highly correlated (R² = 0.935) with the antioxidant capacity. Results indicated that extraction by SW technology was effective and that Chlorella sp. could be a useful source of natural antioxidants. Full article
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Open AccessArticle Ultrasonic Assisted-Reflux Synergistic Extraction of Camptothecin and Betulinic Acid from Camptotheca acuminata Decne. Fruits
Molecules 2017, 22(7), 1076; doi:10.3390/molecules22071076
Received: 28 May 2017 / Revised: 26 June 2017 / Accepted: 26 June 2017 / Published: 27 June 2017
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Abstract
A novel and efficient ultrasonic assisted-reflux synergistic extraction (UARSE) method for extracting camptothecin (CPT) and betulinic acid (BA) from Camptotheca acuminata Decne. fruits has been developed in this study. The advantages of the ultrasonic and reflux extraction methods have been combined in the
[...] Read more.
A novel and efficient ultrasonic assisted-reflux synergistic extraction (UARSE) method for extracting camptothecin (CPT) and betulinic acid (BA) from Camptotheca acuminata Decne. fruits has been developed in this study. The advantages of the ultrasonic and reflux extraction methods have been combined in the UARSE method and used to extract CPT and BA for the first time. The parameters influencing the efficiency of UARSE were optimized using the Box-Behnken design (BBD) to obtain the maximum extraction yield of CPT and BA. The optimal extraction conditions were as follows: 225 W for the ultrasonic power; 24 min for the extraction time; and 32 mL/g for the liquid–solid ratio. The extraction yields obtained by UARSE were 2.386 ± 0.112 mg/g for CPT and 17.192 ± 0.808 mg/g for BA, which were 1.43-fold and 1.33-fold, respectively, higher than by using heating reflux extraction (HRE) and ultrasonic-assisted extraction (UAE). In addition, the 24-min extraction time using UARSE was 80% and 60% less than those provided by HRE and UAE, respectively. Therefore, UARSE can be considered a rapid and efficient method for extracting CPT and BA from the fruits of C. acuminata Decne. Full article
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Open AccessArticle Magnetic Solid-phase Extraction with Fe3O4/Molecularly Imprinted Polymers Modified by Deep Eutectic Solvents and Ionic Liquids for the Rapid Purification of Alkaloid Isomers (Theobromine and Theophylline) from Green Tea
Molecules 2017, 22(7), 1061; doi:10.3390/molecules22071061
Received: 4 June 2017 / Revised: 24 June 2017 / Accepted: 24 June 2017 / Published: 25 June 2017
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Abstract
Different kinds of deep eutectic solvents (DES) based on choline chloride (ChCl) and ionic liquids (ILs) based on 1-methylimidazole were used to modify Fe3O4/molecularly imprinted polymers (Fe3O4/MIPs), and the resulting materials were applied for the rapid purification of alkaloid isomers (theobromine and theophylline)
[...] Read more.
Different kinds of deep eutectic solvents (DES) based on choline chloride (ChCl) and ionic liquids (ILs) based on 1-methylimidazole were used to modify Fe3O4/molecularly imprinted polymers (Fe3O4/MIPs), and the resulting materials were applied for the rapid purification of alkaloid isomers (theobromine and theophylline) from green tea with magnetic solid-phase extraction (M-SPE). The M-SPE procedure was optimized using the response surface methodology (RSM) to analyze the maximum conditions. The materials were characterized by Fourier transform infrared spectroscopy (FI-IR) and field emission scanning electron microscopy (FE-SEM). Compared to the ILs-Fe3O4/MIPs, the DESs-Fe3O4/MIPs were developed for the stronger recognition and higher recoveries of the isomers (theophylline and theobromine) from green tea, particularly DES-7-Fe3O4/MIPs. With RSM, the optimal recovery condition for theobromine and theophylline in the M-SPE were observed with ratio of methanol (80%) as the washing solution, methanol/acetic acid (HAc) (8:2) as the eluent at pH 3, and an eluent volume of 4 mL. The practical recoveries of theobromine and theophylline in green tea were 92.27% and 87.51%, respectively, with a corresponding actual extraction amount of 4.87 mg•g−1 and 5.07 mg•g−1. Overall, the proposed approach with the high affinity of Fe3O4/MIPs might offer a novel method for the purification of complex isomer samples. Full article
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Open AccessArticle Solvent-Free Microwave-Assisted Extraction of Polyphenols from Olive Tree Leaves: Antioxidant and Antimicrobial Properties
Molecules 2017, 22(7), 1056; doi:10.3390/molecules22071056
Received: 27 May 2017 / Revised: 16 June 2017 / Accepted: 19 June 2017 / Published: 24 June 2017
Cited by 4 | PDF Full-text (4241 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Response surface methodology (RSM) and artificial neural networks (ANN) were evaluated and compared in order to decide which method was the most appropriate to predict and optimize total phenolic content (TPC) and oleuropein yields in olive tree leaf (Olea europaea) extracts,
[...] Read more.
Response surface methodology (RSM) and artificial neural networks (ANN) were evaluated and compared in order to decide which method was the most appropriate to predict and optimize total phenolic content (TPC) and oleuropein yields in olive tree leaf (Olea europaea) extracts, obtained after solvent-free microwave-assisted extraction (SFMAE). The SFMAE processing conditions were: microwave irradiation power 250–350 W, extraction time 2–3 min, and the amount of sample 5–10 g. Furthermore, the antioxidant and antimicrobial activities of the olive leaf extracts, obtained under optimal extraction conditions, were assessed by several in vitro assays. ANN had better prediction performance for TPC and oleuropein yields compared to RSM. The optimum extraction conditions to recover both TPC and oleuropein were: irradiation power 250 W, extraction time 2 min, and amount of sample 5 g, independent of the method used for prediction. Under these conditions, the maximal yield of oleuropein (0.060 ± 0.012 ppm) was obtained and the amount of TPC was 2.480 ± 0.060 ppm. Moreover, olive leaf extracts obtained under optimum SFMAE conditions showed antibacterial activity against S. aureus and S. epidermidis, with a minimum inhibitory concentration (MIC) value of 1.25 mg/mL. Full article
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Open AccessArticle Response Surface Optimized Infrared-Assisted Extraction and UHPLC Determination of Flavonoid Types from Flos Sophorae
Molecules 2017, 22(6), 1000; doi:10.3390/molecules22061000
Received: 21 March 2017 / Revised: 11 June 2017 / Accepted: 13 June 2017 / Published: 15 June 2017
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Abstract
Single-factor experiment and Box-Behnken design were applied to optimize the infrared-assisted extraction (IRAE) of rutin, quercetin, kaempferol, and isorhamnetin from Flos sophorae. Four factors (extract solvent, solid-liquid ration, extraction time, infrared power) affecting the extraction yield of flavonoids were studied. Under optimized conditions
[...] Read more.
Single-factor experiment and Box-Behnken design were applied to optimize the infrared-assisted extraction (IRAE) of rutin, quercetin, kaempferol, and isorhamnetin from Flos sophorae. Four factors (extract solvent, solid-liquid ration, extraction time, infrared power) affecting the extraction yield of flavonoids were studied. Under optimized conditions the extraction yield was 33.199 ± 0.24 mg/g, which substantially improved, compared with heating reflux extraction (HRE) and ultrasonic-assisted extraction (UAE), while extraction time was only 9 min. The eluents were rich in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azobis (2-methyl-propionamidine) dihydrochloride radical scavenging potential (IC50 of DPPH: 53.44 ± 0.01 μg/mL, oxygen radical absorbance capacity (ORAC): 3785.83 ± 52 μmol/g) than the extracts obtained by HRE and UAE. In addition, an ultra-high performance liquid chromatography method was optimized for the identification and quantification of the tested flavonoids, and the method was validated based on its correlation coefficient (r), reproducibility (RSD, n = 5), and recovery values, which were 0.9994–0.9998, 0.74–1.83%, and 97.78–102.94%, respectively. These results confirmed that high extraction yield of flavonoids results in stronger antioxidant values and response surface methodology optimization of IRAE is a promising alternative to traditional extraction techniques for flavonoids from medicinal plants. Full article
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Open AccessArticle Optimization of Ultrasonic-assisted Extraction of Fatty Acids in Seeds of Brucea Javanica (L.) Merr. from Different Sources and Simultaneous Analysis Using High-Performance Liquid Chromatography with Charged Aerosol Detection
Molecules 2017, 22(6), 931; doi:10.3390/molecules22060931
Received: 3 May 2017 / Revised: 24 May 2017 / Accepted: 1 June 2017 / Published: 4 June 2017
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Abstract
Our research aimed to optimize the oil extraction process and determine the fatty acids in Brucea javanica (L.) Merr. seeds. The extraction technology was optimized using response surface methodology. A Box-Behnken design was employed to investigate the effects of three independent variables on
[...] Read more.
Our research aimed to optimize the oil extraction process and determine the fatty acids in Brucea javanica (L.) Merr. seeds. The extraction technology was optimized using response surface methodology. A Box-Behnken design was employed to investigate the effects of three independent variables on an ultrasonic-assisted extraction technique, namely, sonication time (X1: 20–40 min), liquid–solid ratio (X2: 16:1 mL/g–24:1 mL/g), and ethanol concentration (X3: 90%–100%). The optimum conditions of sonication time, liquid–solid ratio, and ethanol concentration were 40 min, 24:1 mL/g, and 100%, respectively. The content of fatty acids and the oil yield were 14.64 mg/g and 16.87%, respectively, which match well with the predicted models. The optimum number of extraction times was eventually identified as two. A new rapid method for the qualitative and quantitative analysis of the fatty acids of B. javanica (L.) Merr. seed oil using HPLC with a charged aerosol detector was described. The fatty acid contents of 14 batches of B. javanica (L.) Merr. seed oil were determined, and the relevance and difference were analyzed by fingerprint analysis. The fingerprint has five common peaks, and the similarity was greater than 0.991. HPLC analysis represents a specialized and rational approach for the quality identification and comprehensive evaluation of B. javanica (L.) Merr. seed oils. Full article
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Open AccessArticle Optimization of Ultrasound-Assisted Extraction of Antioxidants from the Mung Bean Coat
Molecules 2017, 22(4), 638; doi:10.3390/molecules22040638
Received: 13 March 2017 / Revised: 9 April 2017 / Accepted: 12 April 2017 / Published: 15 April 2017
Cited by 2 | PDF Full-text (1064 KB) | HTML Full-text | XML Full-text
Abstract
Mung bean (Vigna radiata) sprout is commonly consumed as a vegetable, while the coat of the germinated mung bean is a waste. In this paper, an ultrasound-assisted extraction method has been developed to extract natural antioxidants from the seed coat of
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Mung bean (Vigna radiata) sprout is commonly consumed as a vegetable, while the coat of the germinated mung bean is a waste. In this paper, an ultrasound-assisted extraction method has been developed to extract natural antioxidants from the seed coat of mung bean. Several experimental parameters—which included ethanol concentration, solvent/material ratio, ultrasound extraction time, temperature, and power—were studied in single-factor experiments. The interaction of three key experimental parameters (ethanol concentration, solvent/material ratio, and ultrasonic extraction time) was further investigated by response surface method. Besides, traditional extracting methods, including maceration and Soxhlet extraction methods, were also carried out for comparison. The results suggested that the best extracting condition was 37.6% (v/v) of ethanol concentration, 35.1:1 mL/g of solvent/material ratio and ultrasonic extraction of 46.1 min at 70 °C under 500 W ultrasonic irradiation. The antioxidant capacity (178.28 ± 7.39 µmol Trolox/g DW) was much stronger than those obtained by the maceration extraction process (158.66 ± 4.73 µmol Trolox/g DW) and the Soxhlet extraction process (138.42 ± 3.63 µmol Trolox/g DW). In addition, several antioxidant components in the extract were identified and quantified. This study is helpful for value-added utilization of the waste from germinated mung bean. Full article
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