Microwave-assisted Extraction Research Articles

Citrus fruit processing, mainly for fresh juice production in the food industry, generates significant amounts of residues and by-products enriched with bioactive components. Peels are the primary waste fraction of citrus fruits, along with discarded pulp and seeds. This study aimed to identify the most fast and sustainable extraction process for flavonoids on a laboratory scale by varying the solvent and extraction methodology, and comparing the yields in order to evaluate their influence on total and individual flavonoid content. A chromatographic analysis was also performed using ultrahigh-performance liquid chromatography (UHPLC) with a 10 min run time. Our focus was on selecting the most user-friendly and cost-effective methodology. Ultrasound- and microwave-assisted extraction equipment were used with green solvents (water and ethanol) and compared for their efficiency in recovering flavonoid compounds from a mixture of peel and pulp. For this study, two widely cultivated Mediterranean citrus varieties were selected: ‘Marsh’ seedless grapefruits (Citrus paradisi Macf.) and ‘Comun’ mandarins (C. deliciosa Ten.). Lab-scale extraction results showed that ultrasound-assisted extraction with a simple ultrasonic bath, using an ethanol–water mixture provided the highest total flavonoid recovery and improved the extraction of key flavanones such as hesperidin, narirutin, and naringin. All ethanol–water mixtures tested (1:1, 7:3, and 3:7) yielded higher flavonoid levels in grapefruit (approximately 2500 mg/100 g DW) and mandarin (approximately 1200 mg/100 g DW) wastes compared with water or ethanol alone. This method offers a scalable and green strategy for valorizing citrus residues.

A comparative study of ultrasound-assisted extraction (UAE) was conducted, and for the first time, microwave-assisted extraction (MAE) was reported for the recovery of bioactive compounds from Justicia spicigera. Among the compounds identified in MAE were kaempferol and peonidin derivatives. In contrast, the extracts obtained via UAE contained cyanidin and kaempferol derivatives. These compounds were associated with the colorimetric changes observed as a function of pH. The results demonstrated that MAE achieved a higher recovery of phenolic compounds (48.93mg GAE/g of dry extract) and total flavonoids (23.46mg catechin/g of dry extract). Regarding antioxidant activity, MAE exhibited an IC50 of 124.47μg of dry extract/mL in the DPPH assay, with no significant differences compared to ABTS and FRAP assays when compared to UAE. This study underscores the role of both extraction technologies in the recovery of bioactive compounds from Justicia spicigera and the potential development of active and intelligent packaging.

Fungal chitosan in focus: a comprehensive review on extraction methods and applications.

Deciphering inulin from Jerusalem artichoke: Extraction, structural characteristics, bioactivities, structure-activity relationship, modifications, pharmacokinetics and applications.

Green extraction of polyphenol compound from walnut green husk by microwave-assisted choline chloride-based deep eutectic solvents: identification, kinetic, comparison and bioactivity.

Microwave-assisted extraction optimization of Hedysarum polybotys polysaccharide and study of their electrochemical fingerprint characteristics

Optimization of microwave-assisted extraction of tannins and phenolic compounds obtained from the pequi tree (Caryocar brasiliense)

Microwave-assisted extraction of Asiatic Pennywort (Centella Asiatica (L.) Urb.) leaves polysaccharides: yield optimization, characterization, in vitro antioxidant and α-amylase inhibitory activities

Coal tailings represent a promising secondary resource of rare earth elements (REEs), yet efficient extraction is limited by their complex mineralogy. This study investigated the impact of alkali pretreatment on aluminosilicate structures in coal tailings and its implications for REE extraction via acid digestion. Precombustion coal refuse was treated with 5 M NaOH at varying solid-to-liquid (S/L) ratios (5, 50 g/L) and reaction times (5, 15 min), including a multistep (five-cycle) treatment under microwave conditions. At 180 °C, XRD, 29Si NMR, and thermodynamic modeling showed kaolinite transformed to hydrosodalite at high S/L ratios, while kaolinite completely dissolved at low S/L ratios. Quartz maintained crystallinity but slowly transformed to amorphous silica during prolonged alkaline treatment. Compared to untreated tailings, light REE extraction was enhanced by a factor of ∼3 when kaolinite dissolved and by ∼2 when it converted to hydrosodalite; heavy REE extraction increased by ∼2 and ∼1.5, respectively. Extending pretreatment time produced minimal additional enhancement, indicating that under microwave conditions, kaolinite concentration in alkaline solutions and hydrosodalite solubility in acidic solutions are the primary factors controlling REE release. Alkali pretreatment also promoted uranium removal prior to acid digestion, while REE extraction correlated strongly with Mg, Ca, Fe, and Ti release.

Abstract: Agricultural waste, once considered an inevitable by-product of global farming practices, is now emerging as a goldmine of untapped potential. With the planet grappling with escalating waste production, the transformation of agricultural residues into high-value products represents a revolutionary shift toward sustainable development. This review delves into the multifaceted world of agricultural waste management, exploring its vast potential in industries ranging from biofuels and biodegradable plastics to the burgeoning field of pharmaceutical excipients. We highlight cutting-edge technologies such as enzymatic hydrolysis, microwave-assisted extraction, and advanced bioconversion processes that are redefining the role of waste in global supply chains. By uncovering the hidden value within crop residues, animal by-products, and agro-industrial waste, we showcase the promise of a circular economy that converts waste into resources. Particularly compelling is the conversion of agricultural by-products into pharmaceutical excipients, where substances like cellulose, starch, and lignin are transformed into crucial components that enhance drug formulations. The environmental and economic implications of such innovations are profound, with potential reductions in carbon footprints, pollution, and resource depletion. As we stand on the cusp of a bioeconomic revolution, this review paints a vivid picture of how waste valorisation not only addresses critical environmental challenges but also spurs economic growth, scientific innovation, and sustainable practices that could redefine industries, reshape economies, and unlock new frontiers of scientific discovery.

Ultrasound-Assisted green extraction and resin purification of Hypaphorine from Nanhaia speciosa using deep eutectic solvents.

Solvent-free microwave extraction (SFME) is a clean and advanced method of extracting essential oils. In this study, it was compared to conventional hydrodistillation (HD) and steam-water distillation (SD), which are commonly used to extract essential oils from fresh ylang-ylang flowers. The yield and density of essential oils extracted via SFME within 40 min after the appearance of the first oil drop were higher than those obtained via conventional HD and SD within 3 h after the appearance of the first drop. Analysis of chemical compounds in the essential oils showed a high degree of variability in volatile compounds between the three extraction methods. Light oxygenated compounds are odor-active constituents. They comprised 81.23% of the SFME extract, whereas their levels were lower in the HD (69.94%) and SD extracts (57.98%). Total aromatic compounds were also higher in the essential oils obtained via SFME than in those obtained via HD and SD. These results support the use of SFME for ylang-ylang essential oil extraction, as it offers promising energy-/time-saving characteristics, along with higher quality.

Brown seaweeds are rich in bioactive polysaccharides such as laminarin, fucoidan, and alginate, which exhibit a wide range of biological activities and hold great potential for applications in the functional food and nutraceutical industries. In recent years, there has been a growing interest in developing advanced and sustainable extraction techniques to improve the recovery of these valuable compounds. While conventional methods – including Soxhlet extraction, hydrodistillation, and maceration – are still commonly used, they are often time-consuming, inefficient, and environmentally taxing. In contrast, innovative techniques such as enzyme-assisted extraction (EAE), microwave-assisted extraction, and ultrasound-assisted extraction offer faster, more selective, and eco-friendly alternatives. Among these, EAE has emerged as a particularly promising approach due to its efficiency, mild operating conditions, and ability to preserve the integrity of thermolabile compounds. However, challenges related to enzyme stability and reusability limit its industrial application. To address these issues, enzyme immobilisation has been explored, with magnetic nanoparticles (MNPs) gaining considerable attention as effective supports due to their large surface area, biocompatibility, and ease of magnetic separation. This review provides an overview of the biology of brown seaweeds and their major bioactive polysaccharides, followed by a critical evaluation of enzyme immobilisation methods. Particular emphasis is placed on the use of MNPs as supports for immobilised enzymes in the context of polysaccharide extraction. The integration of immobilised enzymes with green extraction technologies offers a promising route toward more efficient, sustainable, and scalable recovery of marine-derived bioactives.

Abstract Ulva represents an important raw material due to its nutritional value. In addition, it contains cell wall polysaccharides, attractive for various applications. Ulva ohnoi is commercially cultivated in Baja California (México) and successfully marketed as human food. The valorization of this biomass as a source of ulvans and cellulose is proposed through a sequential extraction approach. As a first step, an ulvan with a 22.7% yield dry weight, high sulfate and uronic acids content, and with antioxidant capacity was obtained directly from the biomass. From the residual biomass, a semi-crystalline cellulose was recovered (3.8%) with potential for use in encapsulation and biocomposites. Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analysis confirmed the structure of ulvans and cellulose and characterized the crystalline structure of the polysaccharides. Furthermore, using environmentally friendly technology through microwave-assisted extraction (MAE) and ionic liquid (IL), a cellulose derivative (CD) was isolated in the form of microcellulose, as observed by scanning electron microscopy. The results reinforced the potential of this species to diversify its use.

Role of model equations and energy dynamics in understanding bioactive compounds of olive leaf extract by LC-MS/MS; their evaluation using a cluster approach.

First evidence of nitroaromatic compounds in indoor dust: determination of nitrophenols, nitroguaiacols, and nitrocatechols by microwave-assisted extraction combined with solid-phase microextraction gas chromatography-tandem mass spectrometry.

The Lempuyang plant is one of the medicinal plants in Indonesia. One of the plants of the Lempuyang family that has not been widely researched is Lempuyang Gajah Zingiber zerumbet (L.). The commonly used method of extraction of phenolic compounds is maceration with organic solvents. The disadvantages are the amount of organic solvents that must be used and the long extraction time (days). An environmentally friendly solvent that has been successfully developed in the 21st century is eutectic or known as Natural deep eutectic solvent (NADES). In addition, NADES can also be used in conjunction with other extraction methods such as (UAE), and microwave aid (MAE). The results obtained were the synthesis of NADES with HBA (Choline Chloride) and HBD variations (Glucose, Lactic Acid, and Ethylene Glycol) with ratios of 1:1 and 1:2. In the maceration process, variations in time (2, 4, 6 hours) and variations in extraction methods (maceration, UAE and UAE-MAE) are carried out. The best TFC (Total Flavonoid Content) value data was obtained by NADES D (choline chloride: glycerol 1:2) of 697.24 mg QE/g extract through a combined ultrasonic and microwave method (UAE-MAE) while the best TPC (Total Phenolic Content) was NADES C (choline chloride: glycerol 1:1) of 2491.88 mg GA/g extract through a combined ultrasonic and microwave method (UAE-MAE). Meanwhile, the characterization of NADES synthesis to see the interaction of hydrogen bonds through FTIR analysis, and the content of phenolic compounds and flavonoids was carried out through HPLC-DAD.

Vegetable and fruit waste (VFW) is generated in large quantities worldwide and contains valuable antioxidants such as phenolics, flavonoids, carotenoids, and vitamins. Efficient and environmental friendly extraction of these molecules is of great importance for applications in food, medicine, and cosmetics. It involves various sustainable methods for the isolation of antioxidants from VFW, including pressurized liquid extraction (PLE), enzyme-assisted extraction (EAE), supercritical fluid extraction (SFE), ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), green solvent extraction (GSE), deep eutectic solvents (DESs/NADES), and ionic liquids (ILs). Among these, UAE and MAE were found to be highly efficient in extraction with less energy consumption, whereas DESs/NADES yielded eco-friendly procedures with high selectivity. Despite such advancements, challenges such as high costs, scale barriers, and industrial feasibility still exist. Overall, green extraction techniques are promising for valorizing VFW antioxidants and facilitating circular economic practices. Future studies should focus on developing improved green extraction techniques, increasing cost savings, and exploring prospects at the industrial level to promote the sustainable utilization of VFW.

Organic ultraviolet filters in the blubber of two free-ranging deep-diving cetacean species.

From berries to health and beauty: Studies and applications of antioxidant components: A review.