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Subcritical Water Extraction of Bioactive Compounds
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Subcritical Water Extraction of Bioactive Compounds

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

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 23775

Special Issue Editors

Prof. Dr. Stela Jokić

E-Mail Website
Guest Editor
Department of Process Engineering, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, 31000 Osijek, Croatia
Interests: extraction; medicinal plants; supercritical carbon dioxide; industrial design; phenolic compounds; response surface methodology
Special Issues, Collections and Topics in MDPI journals
Dr. Jelena Vladić

E-Mail Website
Guest Editor
Faculty of Technology, University of Novi Sad, Novi Sad, Serbia
Interests: Pharmaceutical technologies and chemistry, green extraction technologies (supercritical carbon dioxide, subcritical water, ultrasound- and microwave assisted extraction), production of dry extracts using spray drying technique, physical-chemical, biochemical, and pharmacological analyses of obtained extracts. Valorisation of (food, agricultural, industry, marine, communal) waste/by-products by applying green engineering
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are pleased to invite you to submit original articles or reviews to the Special Issue of Molecules entitled “Subcritical Water Extraction of Bioactive Compounds”.

As a result of a large difference in the structure between different classes of target bioactive components and their natural sources, their physical and chemical properties differ. Therefore, it is very important and necessary to find the most efficient method of extracting selected bioactive components and to optimize the extraction procedure.

Subcritical water extraction (SWE) is currently an attractive research topic in the multidisciplinary areas of pharmaceuticals, food technology, applied chemistry, and biotechnology, as it has shown to be a cleaner, faster, and cheaper method in comparison to conventional extraction methods. SWE can be successfully applied for the extraction of various types of bioactive compounds from materials of different type and origin, and it also represents a way to valorize waste and by-products.

We believe that a Special Issue in the journal Molecules focused on the SWE of bioactives will provide an overview of the current status and future developments.

This Special Issue will cover the following scientific fields:

  • Subcritical water extraction of bioactive compounds from different sources:

Medicinal plants • Food • Food/agricultural waste and by-products • Marine products • Environmental samples;

  • Product characterization, stabilization, and application;
  • Valorization of waste and/or by-products;
  • Innovative extraction process design;

Optimization study • Intensification of extraction

  • Industrial applications of subcritical water.

We would like kindly invite and encourage you to submit your original articles or reviews.

We look forward to receiving your works.

Yours sincerely,
Prof. Dr. Stela Jokić
Dr. Jelena Vladić
Guest Editors

 

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 semimonthly 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 2700 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

  • Subcritical water extraction
  • Bioactive compounds
  • Bioactivity
  • Valorization of waste and by-products
  • Optimization
  • Natural products
  • Separation and purification

Published Papers (7 papers)

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Research

13 pages, 1046 KiB  
Article
Valorization of Cork Using Subcritical Water
by Mónica Cunha, Ana Lourenço, Susana Barreiros, Alexandre Paiva and Pedro Simões
Molecules 2020, 25(20), 4695; https://doi.org/10.3390/molecules25204695 - 14 Oct 2020
Cited by 12 | Viewed by 2417
Abstract
Granulated cork was submitted to subcritical water extraction/hydrolysis in a semi-continuous reactor at temperatures in the range of 120–200 °C and with a constant pressure of 100 bar. The influence of temperature on the composition of the cork extracts obtained was assessed—namely, their [...] Read more.
Granulated cork was submitted to subcritical water extraction/hydrolysis in a semi-continuous reactor at temperatures in the range of 120–200 °C and with a constant pressure of 100 bar. The influence of temperature on the composition of the cork extracts obtained was assessed—namely, their content of carbohydrates and phenolics. The extraction yield increased with the temperature, and this was associated with the decrease in the dielectric constant of water and the increase in its ionic product. Extracts composed of up to 36% phenolics were obtained at temperatures of up to 120 °C, with an antioxidant activity only two times lower than that of pure gallic acid, but in low amounts. Assays at higher temperatures generated extracts richer in carbohydrates and with a phenolics content of ca. 20 wt.% in comparatively far higher amounts. Neither the amount of suberin nor its structure were affected by the subcritical water treatment. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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20 pages, 2401 KiB  
Article
Towards Higher Oil Yield and Quality of Essential Oil Extracted from Aquilaria malaccensis Wood via the Subcritical Technique
by M. Samadi, Z. Zainal Abidin, H. Yoshida, R. Yunus and D. R. Awang Biak
Molecules 2020, 25(17), 3872; https://doi.org/10.3390/molecules25173872 - 26 Aug 2020
Cited by 18 | Viewed by 4995
Abstract
A method that delivers a high yield and excellent quality of essential oil, which retains most of its value-added compounds, and undergoes least change after the extraction process, is greatly sought after. Although chemical free methods are acceptable, they call for an extensive [...] Read more.
A method that delivers a high yield and excellent quality of essential oil, which retains most of its value-added compounds, and undergoes least change after the extraction process, is greatly sought after. Although chemical free methods are acceptable, they call for an extensive processing time, while the yield and quality from these methods are often disappointing. This work utilizes subcritical water technology to address these issues. In this undertaking, essential oil was extracted from Aquilaria malaccensis wood by way of subcritical conditions, and characterized through gas chromatography/mass spectroscopy (GC/MS). Optimization through response surface methodology revealed temperature to be the most critical factor for the extraction process, while the optimum conditions for temperature, sample-to-solvent ratio, and time for subcritical water extraction was revealed as 225 °C, 0.2 gr/mL, and 17 min, respectively. The subcritical water extraction technique involves two simultaneous processes, which are based on good fitting to the two-site kinetic and second order model. In comparison to the hydrodistillation method, GC/MS results indicated that the quality of A. malaccensis’ wood oils, derived through the subcritical water technique, are of significantly better quality, while containing many constructive value-added compounds, such as furfural and guaiacol, which are useful for the production of pesticides and medicines. Pore size, functional groups, and morphology analysis revealed the occurrence of substantial damage to the samples, which facilitated an improved extraction of bio-products. In comparison to conventional methods, the use of the subcritical method not only involves a shorter processing time, but also delivers a higher oil yield and quality. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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17 pages, 871 KiB  
Article
Vine-Canes as a Source of Value-Added Compounds for Cosmetic Formulations
by Manuela M. Moreira, Francisca Rodrigues, Olena Dorosh, Diana Pinto, Paulo C. Costa, Jaroslava Švarc-Gajić and Cristina Delerue-Matos
Molecules 2020, 25(13), 2969; https://doi.org/10.3390/molecules25132969 - 28 Jun 2020
Cited by 17 | Viewed by 2608
Abstract
The majority of works about vine-canes are focused on the evaluation of their chemical composition and antioxidant potential. To the best of our knowledge, the possible applications of produced extracts in cosmetic formulations have never been explored. The aim of the present study [...] Read more.
The majority of works about vine-canes are focused on the evaluation of their chemical composition and antioxidant potential. To the best of our knowledge, the possible applications of produced extracts in cosmetic formulations have never been explored. The aim of the present study was to evaluate the antioxidant properties of vine-canes subcritical water extracts for use as active ingredients in the cosmetic industry. For that, the phenolic content and antioxidant activity of six vine-cane varieties, namely Alvarinho and Loureiro from the Minho region and Touriga Nacional and Tinta Roriz (TR) from both the Douro and Dão regions, were evaluated through spectrophotometric and chromatographic methods. All extracts presented similar antioxidant activity and the highest phenolic content was reported for TR variety from the Douro region (33.7 ± 1.9 mg GAE/g dw). The capacity of vine-cane extracts to capture reactive oxygen species superoxide (O2∙−) was also studied, with the highest IC50 value being obtained for Loureiro variety (56.68 ± 2.60 µg/mL). Furthermore, no adverse effects on HaCaT and HFF-1 dermal cell lines in concentrations below 100 and 1000 μg/mL, respectively, were determined. Finally, Loureiro vine-cane extract was incorporated into a topical formulation, and physical and microbiological properties were within expected values, demonstrating that vine-canes extracts can be successfully incorporated in cosmetic products. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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23 pages, 7501 KiB  
Article
Subcritical Water Extraction of Chestnut Bark and Optimization of Process Parameters
by Tanja Gagić, Željko Knez and Mojca Škerget
Molecules 2020, 25(12), 2774; https://doi.org/10.3390/molecules25122774 - 16 Jun 2020
Cited by 13 | Viewed by 2487
Abstract
The aim of the work was the optimization of the subcritical water extraction process of chestnut bark using Box–Behnken response surface methodology. The influence of process parameters, such as temperature, extraction time and solvent-solid ratio, on extraction yield, yield of the main compounds, [...] Read more.
The aim of the work was the optimization of the subcritical water extraction process of chestnut bark using Box–Behnken response surface methodology. The influence of process parameters, such as temperature, extraction time and solvent-solid ratio, on extraction yield, yield of the main compounds, total phenol content, total tannin content and antioxidant activity has been investigated. The identified compounds were ellagic and gallic acids, ellagitannins (vescalagin, castalagin, 1-o-galloyl castalagin, vescalin and castalin), sugars (maltose, glucose, fructose and arabinose) and sugar derivatives (5-HMF, furfural and levulinic acid). Finally, the optimal process conditions for obtaining the bark extract highly rich in ellagic acid and with satisfactory levels of total phenols and total tannins have been determined. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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12 pages, 7711 KiB  
Article
Subcritical Water Extraction of Valuable Metals from Spent Lithium-Ion Batteries
by Jenni Lie, Stefani Tanda and Jhy-Chern Liu
Molecules 2020, 25(9), 2166; https://doi.org/10.3390/molecules25092166 - 6 May 2020
Cited by 24 | Viewed by 3393
Abstract
The leaching of valuable metals (Co, Li, and Mn) from spent lithium-ion batteries (LIBs) was studied using subcritical water extraction (SWE). Two types of leaching agents, hydrochloric acid (HCl) and ascorbic acid, were used, and the effects of acid concentration and temperature were [...] Read more.
The leaching of valuable metals (Co, Li, and Mn) from spent lithium-ion batteries (LIBs) was studied using subcritical water extraction (SWE). Two types of leaching agents, hydrochloric acid (HCl) and ascorbic acid, were used, and the effects of acid concentration and temperature were investigated. Leaching efficiency of metals increased with increasing acid concentration and temperature. Ascorbic acid performed better than HCl, which was attributed to ascorbic acid’s dual functions as an acidic leaching agent and a reducing agent that facilitates leaching reactions, while HCl mainly provides acidity. The chemical analysis of leaching residue by X-ray photoelectron spectroscopy (XPS) revealed that Co(III) oxide could be totally leached out in ascorbic acid but not in HCl. More than 95% of Co, Li, and Mn were leached out from spent LIBs’ cathode powder by SWE using 0.2 M of ascorbic acid within 30 min at 100 °C, initial pressure of 10 bar, and solid-to-liquid ratio of 10 g/L. The application of SWE with a mild concentration of ascorbic acid at 100 °C could be an alternative process for the recovery of valuable metal in spent LIBs. The process has the advantages of rapid reaction rate and energy efficiency that may benefit development of a circular economy. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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10 pages, 1624 KiB  
Article
Conversion and Hydrothermal Decomposition of Major Components of Mint Essential Oil by Small-Scale Subcritical Water Treatment
by Tai-Ying Chiou, Shiori Nomura, Masaaki Konishi, Chien-Sen Liao, Yasutaka Shimotori, Miki Murata, Naofumi Ohtsu, Yoshihito Kohari, Wei-Ju Lee, Tsung-Yu Tsai, Yuichi Nagata and Tohru Saitoh
Molecules 2020, 25(8), 1953; https://doi.org/10.3390/molecules25081953 - 22 Apr 2020
Cited by 6 | Viewed by 3189
Abstract
Thermal stabilities of four major components (l-menthol, l-menthone, piperitone, and l-menthyl acetate) of Japanese mint essential oil were evaluated via subcritical water treatment. To improve experimental throughput for measuring compound stabilities, a small-scale subcritical water treatment method using ampoule [...] Read more.
Thermal stabilities of four major components (l-menthol, l-menthone, piperitone, and l-menthyl acetate) of Japanese mint essential oil were evaluated via subcritical water treatment. To improve experimental throughput for measuring compound stabilities, a small-scale subcritical water treatment method using ampoule bottles was developed and employed. A mixture of the four major components was treated in subcritical water at 180–240 °C for 5–60 min, and then analyzed by gas chromatography. The results indicated that the order of thermal resistance, from strongest to weakest, was: l-menthyl acetate, l-menthol, piperitone, and l-menthone. In individual treatments of mint flavor components, subsequent conversions of l-menthyl acetate to l-menthol, l-menthol to l-menthone, l-menthone to piperitone, and piperitone to thymol were observed in individual treatments at 240 °C for 60 min. As the mass balance between piperitone and thymol was low, the hydrothermal decomposition of the components was considered to have occurred intensely during, or after the conversion. These results explained the degradation of mint essential oil components under subcritical water conditions and provided the basis for optimizing the extraction conditions of mint essential oils using subcritical water. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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15 pages, 1500 KiB  
Article
Valorization of Yarrow (Achillea millefolium L.) By-Product through Application of Subcritical Water Extraction
by Jelena Vladić, Martina Jakovljević, Maja Molnar, Senka Vidović, Milan Tomić, Zorica Drinić and Stela Jokić
Molecules 2020, 25(8), 1878; https://doi.org/10.3390/molecules25081878 - 18 Apr 2020
Cited by 21 | Viewed by 3415
Abstract
In the present study, valorization of yarrow (Achillea millefolium) by-product from the filter tea industry was investigated through the application of subcritical water for the extraction of bioactive compounds. The influence of different process parameters (temperature 120–200 °C, extraction time 10–30 [...] Read more.
In the present study, valorization of yarrow (Achillea millefolium) by-product from the filter tea industry was investigated through the application of subcritical water for the extraction of bioactive compounds. The influence of different process parameters (temperature 120–200 °C, extraction time 10–30 min, and HCl concentration in extraction solvent 0–1.5%) on extract quality in terms of content of bioactive compounds and antioxidant activity was investigated. Optimal conditions of the extraction process (temperature 198 °C, extraction time 16.5 min, and without acidifer) were determined and, when applied, the most efficient exploitation of by-products is achieved, that is, attainment of extracts rich in total phenols and flavonoids and high antioxidant activity. In addition, by applying the high performance liquid chromatographic analysis, the content of chlorogenic acid was determined as well as the hydroxymethylfurfural content in obtained extracts. The results demonstrated that subcritical water can be successfully used for utilization of yarrow by-products for obtaining extracts rich in antioxidants. Full article
(This article belongs to the Special Issue Subcritical Water Extraction of Bioactive Compounds)
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