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Microwave and Ultrasound-Assisted Extraction for Plant Bioactive Compounds

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

Deadline for manuscript submissions: 15 June 2025 | Viewed by 1293

Special Issue Editors


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Guest Editor
Department of Food Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia
Interests: polyphenols; pigments; extraction techniques; encapsulation; spray drying; fruit and vegetable processing; chromatographic techniques; antioxidant activity; bioavailability
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Department of Food Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia
Interests: fruit; vegetable and herb composition and processing; fresh-cut processing; plant bioactive compounds (polyphenols, pigments, sterols, fatty acids); conventional and advanced extraction techniques; antioxidant capacity; high-performance liquid chromatography; gas chromatography; volatiles; essential oils
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Plants are a rich source of various bioactive compounds, such as polyphenols, pigments, sterols, and essential oil constituents, which possess a wide range of health-promoting effects, including antioxidant, antimicrobial, and anti-inflammatory properties. As awareness of health and nutrition grows, the demand for these bioactives in the food, pharmaceutical, and cosmetic industries has surged. To maximize the benefits of these plant bioactives, selecting a suitable extraction method is crucial.

Microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) are two advanced techniques developed to efficiently isolate these valuable compounds. MAE employs microwave energy to rapidly heat the plant material and solvent, causing the breakdown of plant cell walls and enhancing the release of bioactives. This method offers advantages such as reduced extraction time, lower solvent usage, and higher yields. On the other hand, UAE uses high-frequency sound waves to create cavitation bubbles in the solvent, which collapse and generate localized high pressure and temperature, disrupting the plant cells. UAE is ideal for extracting heat-sensitive plant bioactives, offering benefits such as shorter extraction times and energy efficiency. Both MAE and UAE are eco-friendly, cost-effective, and tailored to meet the increasing demand for plant bioactives in health-related industries, ensuring maximum retention of their positive properties.

This Special Issue therefore aims at gathering the most recent contributions and findings concerning the employment of these two extraction techniques for the isolation of different plant bioactive compounds.

Dr. Ivona Elez Garofulić
Dr. Maja Repajić
Guest Editors

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Keywords

  • microwave-assisted extraction
  • ultrasound-assisted extraction
  • plant bioactive compounds
  • polyphenols
  • pigments
  • volatiles
  • antioxidants

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Published Papers (3 papers)

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Research

13 pages, 4365 KiB  
Article
Optimization of Ultrasonic-Assisted Extraction of Diene Urushiol from Lacquer Tree Leaves Using Response Surface Methodology
by Fengming Xia, Haojiang He, Jize Ma, Yutian Jin, Qing Qiao, Peng Long, Ping Li and Rui Sun
Molecules 2025, 30(8), 1663; https://doi.org/10.3390/molecules30081663 - 8 Apr 2025
Viewed by 94
Abstract
Lacquer trees are an important economic tree species in China, and raw lacquer is its main secondary metabolite. Polyphenolic compounds are the primary components of raw lacquer, among which diene urushiol exhibits high inhibitory activity against the reverse transcriptase of acquired immunodeficiency syndrome [...] Read more.
Lacquer trees are an important economic tree species in China, and raw lacquer is its main secondary metabolite. Polyphenolic compounds are the primary components of raw lacquer, among which diene urushiol exhibits high inhibitory activity against the reverse transcriptase of acquired immunodeficiency syndrome (AIDS). Therefore, this study established and optimized the ultrasound-assisted extraction process of diene urushiol from lacquer tree leaves. Based on single-factor experiments on the number of extractions, extraction time, extraction temperature, and solvent to solid ratio, the Box–Behnken Design response surface methodology was employed to obtain the optimal extraction process, which included three extractions, an extraction time of 55 min, an extraction temperature of 50 °C, and a solvent to solid ratio of 10:1 mL/g. Under these conditions, the content of diene urushiol was 4.56 mg/g (FW), which bore no significant difference from the theoretical value of 4.69 mg/g (FW), indicating a good model fit. Therefore, response surface methodology (RSM) can be used to optimize the extraction process of diene urushiol from lacquer leaves. This method lays a solid foundation for the comprehensive development and utilization of lacquer tree resources. Full article
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13 pages, 652 KiB  
Article
Optimization of Deep Eutectic Solvent-Based Ultrasound-Assisted Extraction of Bioactive Compounds from Maca Leaves Using the Taguchi Method
by Eun Ji Lee and Kyung Young Yoon
Molecules 2025, 30(7), 1635; https://doi.org/10.3390/molecules30071635 - 6 Apr 2025
Viewed by 91
Abstract
This study was conducted to identify the optimal conditions and evaluate the feasibility of deep eutectic solvent (DES)-based ultrasound-assisted extraction (UAE) for utilizing maca (Lepidium meyenii) leaves, an agricultural by-product, as functional materials. The extraction parameters influencing the recovery of saponins [...] Read more.
This study was conducted to identify the optimal conditions and evaluate the feasibility of deep eutectic solvent (DES)-based ultrasound-assisted extraction (UAE) for utilizing maca (Lepidium meyenii) leaves, an agricultural by-product, as functional materials. The extraction parameters influencing the recovery of saponins and polyphenols, which are major bioactive compounds, were analyzed using the Taguchi method. Results: Signal-to-noise ratios and analysis of variance indicated that the liquid–solid ratio was the most critical factor for optimizing the extraction process. The optimal extraction conditions were determined to be a liquid–solid ratio of 40 mL/g, a water content in DES of 30%, an extraction time of 30 min, and an ultrasonic power of 300 W in the DES system consisting of choline chloride and glycerin in the molar ratio of 1:2. Maca leaf extract obtained under optimized DES-based UAE conditions exhibited higher bioactive compounds content and antioxidant activity compared with that obtained by hot water extraction. Therefore, the DES-based UAE method is a promising, eco-friendly alternative for extracting bioactive compounds from maca leaves. Full article
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26 pages, 2742 KiB  
Article
High-Power Ultrasound and High-Voltage Electrical Discharge-Assisted Extractions of Bioactive Compounds from Sugar Beet (Beta vulgaris L.) Waste: Electron Spin Resonance and Optical Emission Spectroscopy Analysis
by Josipa Dukić, Anet Režek Jambrak, Jurica Jurec, Dalibor Merunka, Srećko Valić, Rafaela Radičić, Nikša Krstulović, Marinela Nutrizio and Igor Dubrović
Molecules 2025, 30(4), 796; https://doi.org/10.3390/molecules30040796 - 9 Feb 2025
Viewed by 829
Abstract
To achieve sustainable extractions, this study examines the impact of different extraction methods to utilize waste from the sugar industry. In addition to conventional thermal extraction, the impact of high-power ultrasound (US) and high-voltage electrical discharge (HVED)-assisted extractions on the yield of bioactive [...] Read more.
To achieve sustainable extractions, this study examines the impact of different extraction methods to utilize waste from the sugar industry. In addition to conventional thermal extraction, the impact of high-power ultrasound (US) and high-voltage electrical discharge (HVED)-assisted extractions on the yield of bioactive compounds and the antioxidant capacity (AC) value of sugar beet leaf extracts was determined. US extraction proved to be an excellent method for extracting bioactive compounds, while HVED extraction proved to be an excellent method for extracting Vitexin. AC was measured both spectrophotometrically (DPPH and FRAP) and spectroscopically via electron spin resonance (ESR). The AC results correlate with each other, and the highest AC values were found in the US-treated samples with 25% ethanol solution as the extraction solvent. Characterization of the plasma via optical emission spectroscopy (OES) showed that neither the solvent nor the sample influenced the plasma spectra, only the gas used (nitrogen/argon). All of the obtained results provide an excellent basis for future research into the utilization of food waste and by-products. Full article
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