Microwave-assisted Extraction Research Articles

Eco-friendly technologies for obtaining antioxidant compounds and protein hydrolysates from edible insect Tenebrio molitor beetles

The functional properties of edible insects can be explored by a joint use of novel technologies. This work applied varied pre-treatments (ultra-sound-assisted extraction, UAE; microwave-assisted extraction, MAE; temperature-assisted extraction, TAE; CO2-assisted extraction) and solvents (water, ethanol, water:ethanol) in Tenebrio molitor beetles to enhance the extraction of phenolic compounds with antioxidant activity. An enzymatic hydrolysis (EH) was performed in wet and treated biomasses to determine the protein hydrolysis. Higher phenolic compounds and antioxidant activity was released after MAE using water as solvent compared to the other treatments and solvents. Treatments decreased 32 %, 19 % and 30 % the protein, chitin and lipids content. EH improved protein and amino acids hydrolysis in the MAE-treated insects, followed by UAE and TAE treatments. In conclusion, MAE was the most effective to release phenolics and antioxidant activity from T. molitor beetles, while using MAE followed by EH improved protein and amino acids hydrolysis, envisioning valuable applications for this insect biomass.

Topical formulations contained an extract from marine alga Cladophora glomerata

The Cladophora glomerata is a green alga abundant in fresh and seawater. The extraction of C. glomerata using glycol-based solvents, including butylene glycol (BG), polyethylene glycol 400 (PEG 400), and propylene glycol (PG), as the green solvents to obtain antioxidants and nutrients that can be further used in health care and pharmaceutical applications. The extraction of C. glomerata with glycol-base solvents using the microwave-assisted extraction (MAE) method was optimized. The liquid extraction using 60 % volume by volume of polyethylene glycol yielded the highest total phenolic content (4.00 ± 0.08 mg gallic acid equivalence per g dry weight) and antioxidant activity (IC50 0.14 ± 0.02 mg/mL). The algal extract was stable at pH 6 to 8 and a temperature lower than 25 °C. After incorporating the algal extract in topical formulations including serum and emulgel, we found that the preparations were stable and retained the extract's antioxidant activity. In addition, all algal extracts, extract-loaded serum, and emulgel did not show cytotoxicity effects in normal adult human dermal fibroblasts.

PH shift extraction technique for plant proteins: A promising technique for sustainable development

With the recognition of animal-derived foods as unhealthy and their association with climate change, researchers are increasingly focusing on plant-based protein as a sustainable alternative. Plant proteins offer versatile functional and dietary benefits, making them suitable for various food applications. This study investigates the influence of alkaline and acidic pH conditions on the extraction yield and the functional and nutritional properties of plant-based proteins. The primary sources of plant protein include cereals, legumes, and oilseeds, which can be used to address essential amino acid deficiencies through blending. Several methods have been employed for protein extraction from plant sources, such as salt extraction, microwave-assisted extraction, ultrasound-assisted extraction, and micellar precipitation. Among these techniques, the pH shift method stands out due to its non-thermal nature, sustainability, and cost-effectiveness. In this method, proteins are solubilized at alkaline pH and then precipitated at their isoelectric point, resulting in a collection of protein precipitate. It is crucial to optimize extraction techniques based on qualitative and quantitative analysis to enhance protein yield, characteristics, and nutritional value. Most conventional protein extraction methods require a large quantity of chemicals, which imposes the issue of safe disposal, compromising environmental sustainability. Traditional methods also produce protein with non-proteinaceous constituents, adding another purification step and resulting in increased overall cost. However, the pH shift method utilizes comparatively less harsh chemicals and has a high protein extraction yield, which makes it comparatively more environmentally and economically sustainable. The sustainable extraction of plant-based proteins addresses the health and environmental concerns associated with animal-derived foods and offers a promising solution to promote sustainability in the food industry.

Anthocyanin Extraction from Roselle (Hibiscus sabdariffa L.) Calyces: A Microwave-Assisted Approach Using Box-Behnken Design

Roselle (Hibiscus sabdariffa L.) is a widely consumed edible flower, often utilized as a natural coloring agent. The bright red color of roselle is due to its anthocyanin content. Beyond their role as colorants, anthocyanins are known for their potent antioxidant properties, which have drawn significant interest for their potential health benefits. To fully harness the advantages of roselle's anthocyanins, developing a reliable extraction method is crucial. This study aimed to establish a fast, efficient, and environmentally friendly extraction technique using microwave-assisted extraction (MAE). Key factors, such as temperature (30, 65, and 100 °C), solvent concentration (30%, 50%, and 70% ethanol in water), and solvent-to-solid ratio (10:1, 25:1, 40:1), were optimized using the Box-Behnken design combined with response surface methodology. The extraction time (5-30 minutes) was also evaluated to maximize anthocyanin recovery. Two major anthocyanins, delphinidin-3-sambubioside and cyanidin-3-sambubioside, were identified using UHPLC-PDA-QToF-MS and quantified using a cyanidin-3-glucoside calibration curve. The optimal extraction conditions were found to be 72 °C, using 70% ethanol in water with a 40:1 solvent-to-solid ratio for 15 minutes. This method was validated with high accuracy (>98% recovery) and precision (CV <6%). It was successfully applied to quantify the anthocyanin content in both purple and red roselle varieties. This rapid and effective MAE method offers a more sustainable, energy-efficient, and time-saving alternative to conventional extraction methods, benefiting industries that rely on natural colorants and antioxidants.

From plant to nanomaterial: Green extraction of nanomucilage from Cordia dichotoma fruit and its multi-faceted biological and photocatalytic attributes

This study aimed to evaluate the extraction efficiency of mucilage from Cordia dichotoma fruits using various aqueous extraction methods, including microwave-assisted water extraction (MWE), hot-water extraction (HWE), and cold-water extraction (CWE). Different analytical techniques were employed to characterize the Cordia dichotoma mucilage (CDM). Additionally, the functional properties, anti-microbial, anti-inflammatory, and dye reduction potential of CDM were assessed. The results indicated a significantly (p < 0.05) higher yield of CDM (13.44 ± 0.94 %) using MWE compared to HWE (12.08 ± 0.82 %) and CWE (7.59 ± 0.73 %). The optimal extraction condition was utilized for the spray-drying process, yielding a spray-dried mucilage powder (SDMP) with a yield of 9.52 ± 1.27 %. The presence of galactose and arabinose as major sugar and functional groups such as OH, COOH, CH, and NH from proteins, uronic acids, and sugars were identified. CDM predominantly comprises galactose and arabinose as major sugars. CDM particles exhibited an irregular morphology and demonstrated thermal stability, with maximum weight loss occurring between 221.83 and 478.66 °C. The particle size of CDM was 681.16 ± 2.18 nm with a zeta potential of −21.46 ± 1.72 mV. Rheological analysis revealed that CDM exhibits shear-thinning behavior. Furthermore, CDM displayed inherent biological activities, including antimicrobial and anti-inflammatory properties. The dye reduction potential of CDM was evidenced by an 88.67 % degradation of indigo carmine dye. In summary, this study provides insights into the cost-effective extraction methods for CDM and its potential utilization as an eco-friendly material for dye reduction.

Isolation and Structural Characterization of Natural Deep Eutectic Solvent Lignin from Brewer's Spent Grains.

Brewer's spent grains (BSG) offer valuable opportunities for valorization beyond its conventional use as animal feed. Among its components, lignin-a natural polymer with inherent antioxidant properties-holds significant industrial potential. This work investigates the use of microwave-assisted extraction combined with acidic natural deep eutectic solvents (NaDESs) for efficient lignin recovery, evaluating three different NaDES formulations. The results indicate that choline chloride-lactic acid (ChCl-LA), a NaDES with superior thermal stability as confirmed via thermogravimetric analysis (TGA), is an ideal solvent for lignin extraction at 150 °C and 15 min, achieving a balance of high yield and quality. ChCl-LA also demonstrated good solubility and cell disruption capabilities, while microwaves significantly reduced processing time and severity. Under optimal conditions, i.e., 150 °C, 15 min, in the presence of ChCl-LA NaDES, the extracted lignin achieved a purity of up to 79% and demonstrated an IC50 (inhibitory concentration 50%) of approximately 0.022 mg/L, indicating a relatively strong antioxidant activity. Fourier transform infrared (FTIR) and 2D-HSQC NMR (heteronuclear single quantum coherence nuclear magnetic resonance) spectroscopy confirmed the successful isolation and preservation of its structural integrity. This study highlights the potential of BSG as a valuable lignocellulosic resource and underscores the effectiveness of acidic NaDESs combined with microwave extraction for lignin recovery.

Lentil Waste Extracts for Inflammatory Bowel Disease (IBD) Symptoms Control: Anti-Inflammatory and Spasmolytic Effects

Background/Objectives: In the contest of agro-industrial waste valorization, we focused our attention on lentil seed coats as a source of health-promoting phytochemicals possibly useful in managing inflammatory bowel diseases (IBDs), usually characterized by inflammation and altered intestinal motility. Methods: Both traditional (maceration) and innovative microwave-assisted extractions were performed using green solvents, and the anti-inflammatory and spasmolytic activities of the so-obtained extracts were determined through in vitro and ex vivo assays, respectively. Results: The extract obtained through the microwave-assisted procedure using ethyl acetate as the extraction solvent (BEVa) proved to be the most useful in inflammation and intestinal motility management. In LPS-activated Caco-2 cells, BEVa down-regulated TLR4 expression, reduced iNOS expression and the pro-inflammatory cytokine IL-1 production, and upregulated the anti-inflammatory cytokine IL-10 production, thus positively affecting cell inflammatory responses. Moreover, a significant decrease in the longitudinal and circular tones of the guinea pig ileum, with a reduction of transit speed and pain at the ileum level, together with reduced transit speed, pain, and muscular tone at the colon level, was observed with BEVa. HPLC separation combined with an Orbitrap-based high-resolution mass spectrometry (HRMS) technique indicated that 7% of all the identified metabolites were endowed with proven anti-inflammatory and antispasmodic activities, among which niacinamide, apocynin, and p-coumaric acid were the most abundant. Conclusions: Our results suggest that lentil hull extract consumption could contribute to overall intestinal health maintenance, with BEVa possibly representing a dietary supplementation and a promising approach to treating intestinal barrier dysfunction.

Optimization and Bioactive Evaluation of Bifurcaria bifurcata Antioxidant-Rich Extracts for Functional Food and Pharmaceutical Applications.

In recent years, consumers have been increasingly interested in natural, healthier, functional foods, with a focus on sea-based products such as algae. Bifurcaria bifurcata (BB) is a macroalga that belongs to the Phaeophyceae class. These brown algae are recognized as the source of bioactive molecules of great interest to the pharmaceutical and nutraceutical industries. The present work applied response surface methodology to optimize the microwave-assisted extraction of the poorly studied algae. The optimization variables were time, pressure, and solvent composition (ethanol/water) and the response parameters selected were yield, total phenolic and flavonoid content, and the antioxidant profile by evaluating DPPH•+, ABTS•+ scavenging activity, and β-carotene discoloration capacity. The results obtained reveal remarkable bioactivity of the crude extract of BB with positive results as an antioxidant and antimicrobial agent. Furthermore, the BB extract's capacity to inhibit enzymes related to neurodegenerative diseases and its anti-inflammatory and anti-proliferation activity open the possibility of future food or pharmaceutical applications.

Antibacterial Activity of Ethanol Extract of Red Spinach Leaves (Amaranthus tricolor L.) Extracted Using Microwave-Assisted Extraction Against Pseudomonas aeruginosa and Streptococcus pyogenes

Background: Humans are among the most susceptible living beings to bacterial infections. Infectious wounds on the skin surface are easily colonized by various kinds of bacteria such as Pseudomonas aeruginosa and Streptococcus pyogenes. Red spinach (Amaranthus tricolor L.) contains flavonoids with antimicrobial properties. Objective: The aim of this study was to determine the antibacterial activity of ethanol extract of red spinach leaves (Amaranthus tricolor L.) against Pseudomonas aeruginosa and Streptococcus pyogenes. Methods: This research includes the preparation, characterization, phytochemical screening of dried powder and extract. Extraction was performed by microwave-assisted extraction (MAE) method using 70% and 96% ethanol variations and then antibacterial activity of ethanol extract of red spinach leaves against Pseudomonas aeruginosa and Streptococcus pyogenes bacteria was carried out by paper disc diffusion method (Kirby-Bauer test) to obtain the diameter of inhibition. Results: The 70% ethanol extract of red spinach leaves has the lowest concentrations of 0.78 mg/ml and 25 mg/ml against Pseudomonas aeruginosa and Streptococcus pyogenes bacteria with diameters of 7.23 mm, and 7.90 mm respectively. While the 96% ethanol extract of red spinach leaves has the lowest concentration of 0.78 mg/ml against Pseudomonas aeruginosa and Streptococcus pyogenes bacteria with a same diameter of 7.43 mm. Conclusion: Ethanol extract of red spinach leaves has antibacterial activity against Pseudomonas aeruginosa and Streptococcus pyogenes.

From Waste to New Ways: Feasibility of Microwave-Assisted Extraction of Chitin from Green Mussels (Perna Viridis) for Development of TEA-Functionalized CO2 Capture Adsorbent

As the world progresses, environmental problems emerge, such as the rise in global greenhouse gas emissions, specifically carbon dioxide (CO2) and improper waste management. To address these issues, this study aims to extract a natural polymer, chitin, from waste green mussel shells using a novel microwave-assisted extraction method. The extracted chitin was used as a support material for the functionalization of the adsorbent for potential CO2 capture. The process involves demineralization and deproteinization for mussel shells under the influence of a microwave unit. Results show that microwave power level 2 has produced the highest chitin yield (6.40%) among all the power levels. To enhance its CO₂ adsorption capacity, the extracted chitin underwent a sol-gel pre-treatment followed by functionalization with triethanolamine (TEA). Scanning electron microscopy (SEM) revealed a "brick wall-like" or flaky crystal structure with an increased surface roughness, suggesting successful TEA incorporation. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirmed the presence of amine groups and enhanced thermal stability of the functionalized chitin. These characteristics are essential for CO₂ capture applications. This research demonstrates that waste green mussel shells coupled with microwave-assisted extraction can be a promising route in extracting chitin and its potential application to CO2 capture. Future work will focus on improving the pre-treatment process to produce a more suitable chitin support and optimizing the adsorbent's CO₂ capture capacity.

Optimizing the microwave-assisted extraction and ultrasonic-assisted processes to acquire flavonoid and phenolic compounds from watermelon rinds using natural deep eutectic solvents

ABSTRACTS This study extracted flavonoids and phenolics from watermelon fruit by microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) combined with a natural deep eutectic solvent (NADES). The effectiveness of NADES combined with UAE and MAE was evaluated for extracting these compounds from watermelon rinds. The study chose a 2:1 molar ratio of hydrogen bond donors (HBDs) to hydrogen bond acceptors (HBAs). Among the tested combinations, 1,2-propanediol-lactic acid showed the highest solubility for flavonoids and phenolics within the extraction system. Experiments with a single factor were used to examine the effects of different parameters on total phenolic content (TPC) and total flavonoid content (TFC). The Box-Behnken design (BBD) model optimized the NADES-based UAE and MAE processes based on TPC and TFC responses. The results of the experiment and the predicted values from the BBD agreed well. Optimal conditions for recovering phenolics and flavonoids from watermelon rinds with NADES-based UAE were determined as 1/60 g/ml for SLR, 300 W, 20% water content, and 15 min, while NADES-based MAE: 1/50 g/ml for SLR, 400 W, and 3 min. This study presents an efficient approach for extracting biologically active compounds from watermelon.

Phycocyanin-Loaded Alginate-Based Hydrogel Synthesis and Characterization.

Phycocyanin was extracted from Spirulina platensis using conventional extraction (CE), direct ultrasonic-assisted extraction (direct UAE), indirect ultrasonic-assisted extraction (indirect UAE), and microwave-assisted extraction (MAE) methods at different temperatures, extraction intervals, stirring rate, and power intensities while maintaining the same algae to solvent ratio (1:15 w/v). The optimization of the extraction parameters indicated that the direct UAE yielded the highest phycocyanin concentration (29.31 ± 0.33 mg/mL) and antioxidant activity (23.6 ± 0.56 mg TE/g algae), while MAE achieved the highest purity (Rp = 0.5 ± 0.002). Based on the RP value, phycocyanin extract obtained by MAE (1:15 w/v algae to solvent ratio, 40 min, 40 °C, and 900 rpm) was selected as active compound in an alginate-based hydrogel formulation designed as potential wound dressings. Phycocyanin extracts and loaded hydrogels were characterized by FT-IR analysis. SEM analysis confirmed a porous structure for both blank and phycocyanin loaded hydrogels, while the mechanical properties remained approximately unchanged in the presence of phycocyanin. Phycocyanin release kinetics was investigated at two pH values using Zero-order, First-order, Higuchi, and Korsmeyer-Peppas kinetics models. The Higuchi model best fitted the experimental results. The R2 value at higher pH was nearly 1, indicating a superior fit compared with lower pH values.

Biosynthesis and Extraction of Chlorophyll, Carotenoids, Anthocyanins, and Betalaine In Vivo and In Vitro.

As natural bioactive compounds, plant pigments play crucial roles not only in plant phenotype, growth, development, and adaptation to stress but also hold unique value in biotechnology, healthcare, and industrial applications. There is growing interest in the biosynthesis and acquisition of plant pigments. Thus, this paper explores emerging extraction methods of natural pigments and elucidates the biosynthesis pathways of four key plant pigments, chlorophylls, carotenoids, anthocyanins, and betalaine in vivo and in vitro. We comprehensively discuss the application of solvent, supercritical fluid [extraction], ultrasonic, and microwave-assisted extraction techniques, as well as introducing key enzymes, precursors, and synthetic pathways involved in pigment synthesis. δ-Aminolevulinic acid represents a pivotal initiating enzyme for chlorophyll synthesis, whereas isopentenylpyrophosphate, (IPP) and dimethylallyl pyrophosphate, (DMAPP) are closely associated with carotenoid biosynthesis. Phenylalanine and tyrosine are critical substances for anthocyanin and betalaine synthesis, respectively. Hence, crucial genes such as chlI, crtB, PGT8, CYP76AD1, and BvDODA can be employed for heterologous biosynthesis in vitro to meet the demand for increased plant pigment amount. As a pivotal determinant of plant coloration, an in-depth exploration into the high-quality acquisition of plant pigments can provide a basis for developing superior pigments and offer new insights into increasing pigment yield.

Simultaneous and sequential combination of techniques for the sustainable and extensive extraction of proteins and polyphenols from malt rootlets

The emergence of tecnhiques such as microwave-assisted extraction (MAE), enzyme-assisted extraction (EAE), ultrasounds-assisted extraction (UAE), and pressurized liquid extraction (PLE) has brough many benefits but their single use does not guarantee the hollistic extraction of target compounds from complex samples. Taking into account their different principles and that one technique may favour the extraction of certain compounds over others, this work proposes the combination of these techniques for improving extraction yields in the recovery of proteins, as example of large molecule, and phenolic compounds, as example of small molecule, from a recalcitrant sample. No single extraction technique recovered all proteins or phenolic compounds, even after a proper optimization. Among them, PLE was the most advantageous, enabling the extraction of 67 % proteins and 1.20 g gallic acid equivalent (GAE)/100 g sample. Analysis of samples by scanning electron microscopy (SEM) and separation of extracts by reversed-phase high performance liquid chromatography (RP-HPLC) and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that PLE showed the most distinct efficiency among EAE, MAE, and UAE, whereas the latter three exhibited more similar results. Based in these results, ten different combinations (sequential and/or simultaneous) of these techniques were proposed. PLE in combination with another technique showed a great potential for the extraction of both large and small molecules. Particularly, the combination of EAE and PLE recovered 100 % of proteins and more than three times the phenolic compounds extracted by other methods reported in the literature, even revealing significant synergistic effects.

Bioactivity and application potential of O/W emulsions derived from carboxylic acid-based NADES-extracted total saponins from Polygonatum cyrtonema Hua

This study focuses on evaluating new methods for the green extraction of saponin compounds from Polygonatum cyrtonema Hua (PCH). This study utilized a combination of carboxylic acid-based natural deep eutectic solvents (NADES) and various extraction techniques including conventional heat reflux-, ultrasound-, and microwave-assisted extraction. The primary objectives were to assess total saponin yield, antioxidant capacity, and enzyme inhibition efficiency. Additionally, the solvents and extracts were evaluated for their antibacterial activity. Oil-in-water (O/W) emulsions of NADES extracts were also characterized and analyzed for stability. Results indicated that three NADES systems were effective in extracting saponins, with choline chloride and lactic acid (ChCl-LA) system being the most efficient. The ChCl:LA extract exhibited antimicrobial and antioxidant activities superior to conventional organic solvent extracts. Additionally, it demonstrated maximum inhibitory activity (IC50 values: 0.98 ± 0.03 and 1.46 ± 0.07 mg/mL, respectively) against α-glucosidase and α-amylase. The NADES extract as an aqueous phase significantly improved the stationarity of the O/W emulsion. Collectively, the study highlights the antimicrobial and technological advantages of NADES as a potential solvent for extracting saponin compounds from PCH.

Characterization and Encapsulation Methods for Pomegranate Seed (P. Granatum) Oils, Review

The use of bioactive components in herbal products across different industries is growing.As a result, ecologically friendly techniques such simple mixing, pressure-assisted extraction, enzymatic extraction, ultrasound-assisted extraction, pulsed electric fields, high hydrostatic pressure, ohmic heating, and microwave-assisted extraction are being investigated. These methods enhance the equipment design, extraction efficiency and extraction method of bioactive constituents with organic solvents. Consequently, encapsulation techniques preserve oil quality and other pomegranate seed components. Encapsulation enables the safe delivery, preservation and regulation of the targeted release of bioactive constituents in food systems. This study provides information on encapsulation techniques that protect sensitive compounds and their benefits. Increasing problems related to food quality, safety and reliability cause undesirable effects on product quality. Capsulation and ecological methods are expected to achieve food safety and reliability goals in the future effectively.

Phytochemical characterization and biological evaluation of lemongrass (Cymbopogon citratus) extracts: A systematic experimental study

Lemongrass () is widely used in traditional medicine, with growing interest in its pharmacological properties. This study aims to systematically investigate the phytochemical composition and biological activities of lemongrass extracts, focusing on optimizing extraction methods and evaluating their therapeutic potential.Various extraction techniques were employed, including solvent-based methods (ethanol, methanol, and water) and green extraction approaches (ultrasound-assisted and microwave-assisted extraction). Phytochemical profiling was conducted using qualitative and quantitative techniques, including gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The biological activities of the extracts were assessed through in vitro assays for antioxidant (DPPH, ABTS), antimicrobial (agar diffusion), anti-inflammatory (COX inhibition), and cytotoxicity activities (on HeLa, MCF-7, and HEK-293 cell lines). Ethanol extracts showed the highest yield of bioactive compounds, including flavonoids, terpenoids, and phenolic acids. These extracts also exhibited significant antioxidant activity with DPPH and ABTS assays. The antimicrobial tests revealed strong activity against Staphylococcus aureus and Candida albicans, while the COX inhibition assay indicated notable anti-inflammatory effects. Cytotoxicity studies demonstrated selective toxicity toward cancer cell lines (HeLa, MCF-7) with minimal effects on normal cells (HEK-293). Lemongrass extracts, particularly those obtained via ethanol extraction, exhibit promising antioxidant, antimicrobial, anti-inflammatory, and anticancer properties. These findings highlight its potential for pharmaceutical and therapeutic applications, warranting further investigation in vivo and in clinical trials.

Microwave-assisted extraction of phenolic compounds from Commiphora gileadensis leaf and their characterization

Commiphora gileadensis (C. gileadensis) is a plant traditionally used in many parts of the world for medicinal purposes. However, the benefits of this plant are yet to be uncovered due to the use of conventional extraction methods during its extraction. Hence, there is a need for more efficient and environment-friendly extraction methods for optimum recovery of the bioactive components of C. gileadensis. This study aims to evaluate the impact of microwave-assisted extraction (MAE) process parameters (individually and in combination) on the recovery of phenolic compounds from C. gileadensis leaf. One-Factor-At-a-Time (OFAT) optimization method was used in this work to study the impact of varying the MAE process parameters (sample: solvent ratio, microwave power, ethanol concentration, and extraction temperature) on the optimum yield of phenolic compounds. The obtained phenolic compounds were characterized using Gas chromatography-mass spectrometry (GC–MS) for tentative identification of the component phytochemicals of the extract. The results showed that the optimal process condition of microwave power at 300 W, solvent/sample ratio of 1:10 g/mL, solvent concentration of 40 % v/v, and extraction temperature of 40 °C gave the maximum extraction yield of 33.20 ± 0.42 % w/w, total phenolic content (TPC) of 114.65 ± 3.14 mg GAE/g d.w., and total flavonoids content (TFC) of 37.56 mg QE/g d.w.). Furthermore, the GC-MS analysis identified 25 phenolic compounds with good antioxidant activities from the extracts. Therefore, MAE is considered a non-conventional green method for improved extraction of phenolic compounds from C. gileadensis leaf compared to the existing conventional extraction methods.

Characterization of carbon dots from fructus gardeniae (Zhi-zi) and gardenia charcoal (black Zhi-zi) via microwave-assisted extraction

Characterization of carbon dots from fructus gardeniae (Zhi-zi) and gardenia charcoal (black Zhi-zi) via microwave-assisted extraction

Green biorefinery of walnut husk: Phenolic extraction and ethanol production

Microwave and ultrasound techniques were utilized on walnut green husk (WGH) to extract valuable phenolic compounds and enhance the residual biomass's susceptibility to hydrolysis for subsequent ethanol production. The aim was to optimize process variables in order to achieve an integrated biorefinery with the zero-waste-base standpoint. For microwave-assisted extraction (MAE), four-time levels (0.5, 1.0, 2.0, and 5 min) and power settings (300, 450, 600, and 800 W) were tested. Ultrasound-assisted extraction (UAE) was conducted at a frequency of 28 kHz and power of 100 W over varying time intervals (2, 6, 10, 14, 18, and 22 min). Generally, higher power settings and longer extraction times produced higher contents. Specifically, the maximum total phenolic content (TPC) (220.13 mg GAE/g-DW), total flavonoid content (TFC) (63.21 mg catechin/g-DW), and DPPH scavenging activity (86.13 %) were achieved using the highest power and longest extraction time for MAE. Similarly, the longest UAE time resulted in the highest TPC (214.32 mg GAE/g-DW), highest TFC (58.44 mg catechin/g-DW), and DPPH scavenging activity (76.15 %). Moreover, increased microwave power and longer extraction times favored glucose and ethanol yields, with maximum yields of 55.30 % and 36.67 %, respectively, obtained at 800 W for 5 min. For UAE, the highest glucose and ethanol yields (52.33 % and 34.16 %, respectively) were obtained at 22 min. Conversely, lower extraction times and power settings for microwave, as well as shorter ultrasound times, were beneficial for lignin removal. The application of MAE and UAE in the WGH biorefinery process enhanced the extraction of phenolics and improved biomass hydrolysis, leading to more efficient, sustainable, and economically viable production of biofuels and bioproducts.