Microwave-assisted Extraction Procedure Research Articles

Novel tributyl phosphate-based deep eutectic solvent: Application in microwave assisted extraction of carotenoids

A contribution to the use of deep eutectic solvents (DES) and microwave-assisted extraction (MAE) was made for bioactive compounds recovery, especially those with lipophilic character, from tomato and carrot samples rich in carotenoids. For the first time, a novel deep eutectic solvent was synthesized, comprising tributyl phosphate (TBP) as a hydrogen bond acceptor and acetic acid (AcOH) as a hydrogen bond donor. The total antioxidant capacity (TAC) of tomato and carrot extracts obtained by MAE, in which optimization of operational parameters and modeling were made with the use of Box-Behnken design of the response surface methodology (RSM), was evaluated using the Cupric Reducing Antioxidant Capacity (CUPRAC) method. For the highest TAC, operational parameters that best suit the MAE procedure were set at 80 °C, 35 min, and 25 mL/2.0 g. The TAC values of extracts obtained by MAE using TBP:AcOH, 1:2 (mol/mol) were examined against those of extracts acquired by classical solvent extraction using a mixture of hexane, ethanol and acetone (H:E:A, 2:1:1 (v/v/v)) mixture. TAC of extracts in DES varied between 5.10 and 0.71 lycopene equivalents (mmol LYC kg−1). The highest extraction yield comparable to conventional organic solvents was obtained with TBP:AcOH (1:2). It was observed that, in addition to lipophilic antioxidants, some hydrophilic antioxidant compounds were partially extracted with the proposed DES. Moreover, the extracted antioxidant compounds were identified and quantified by HPLC analysis. The proposed DES and MAE process will find potential application for hydrophobic antioxidant extraction from tomatoes and carrots on an industrial scale after further studies.

Green3: A green extraction of green additives for green plastics

PLA/PBAT bioplastic is a commercial biodegradable plastic employed for packaging and several food and agriculture applications. In this regard, properties such as the antioxidant ability to extend food shelf life and light resistance, are of great interest in the production of packaging and mulching films, respectively. These features are obtained by developing blends with pure chemicals and/or natural products as additives. In the present work blend formulations of PLA/PBAT with a walnut shell extract rich in antioxidants were developed and evaluated for their properties in comparison with classic PLA/PBAT. Specifically, natural additives, and most importantly the production process were purposely selected to i) be green and cost-effective; ii) confer antioxidant properties; and iii) improve material performance.To this aim, a walnut shell extract (EWS) with high antioxidant activity was obtained thanks to a novel green and cost-effective microwave-assisted extraction (MAE) procedure. A response surface methodology was utilized to explore how the total phenolic content (TPC) and antioxidant activity are influenced by varying aqueous ethanol concentration, extraction time, and microwave power. The highest predicted TPC and antioxidant activity were achieved when employing the ideal conditions for Microwave-Assisted Extraction (MAE): using a mixture of 30 % ethanol in water, an irradiation time of 120 s, and a microwave power of 670 W. The optimized EWS was characterized by HPLC-MS determining qualitative and quantitative data with the identification of flavonoids, fatty acids, and anacardic acids among the main components, responsible for antioxidant activity. The resulting EWS powder was melt-mixed at 140C° and 20 RPM with the bio-based PLA/PBAT bioplastic at two different concentrations (0.5 and 1.5 w/w) by forming film specimens. All EWS-based bioplastic films showed increased antioxidant features determined by the DPPH bleaching test, TEAC, and ORAC assays. The films keep the antioxidant capacity even after 7 days of UV-accelerated aging. Remarkably, adding 1.5 % EWS boosted the bioplastic UV light resistance, reducing the abatement of molecular masses by more than 60 % without affecting mechanical properties.

Standardization of microwave-assisted extraction procedures for characterizing non-labile metallic nanoparticles in environmental solid samples by means of single particle ICP-MS

Microwave-assisted extraction (MAE) treatments seem to be a promising sample preparation strategy to isolate nanomaterials (NMs) from environmental samples prior to single particle inductively coupled plasma mass (spICP-MS) determination.

Box–Behnken Design to Optimize Standardized Mangiferin-Rich Mango Peel Extract from Agro-Industrial Waste Product

The light mango or “Ma-Muang Bao” (Mangifere indica L. var.) is a native mango species originating from Malaysia and southern Thailand. The whole Ma-Muang Bao fruit, except peels, is popular as both a raw and ripe fruit for consumption, as well as being used in various processed food products. This study aims to transform the peel of a specific mango variety, which is a byproduct of the agro-industrial sweet, pickled mangoes industry, into a valuable bioactive ingredient for healthcare products. This is achieved through the establishment of a standardized mangiferin-rich mango peel extract (SMPE). Employing the Box–Behnken design (BBD) within the framework of response surface methodology (RSM), an optimal microwave-assisted extraction procedure was developed. A total of 27 experiments, each with four independent variables, including solvent ratio, extraction power, extraction time, and ethanol (EtOH) ratio, were conducted to optimize the extraction method in terms of mangiferin content and extraction yield. The optimized extraction conditions encompassed a solvent ratio of 120 mL EtOH/100 g sample, an extraction power of 450 W, an extraction time of approximately 4.3 min, and an EtOH ratio of 69.44% (EtOH in water). Small-scale extractions were carried out using the following specified parameters: solvent ratio of 120 mL, extraction power of 450 W, extraction time of 4 min, and EtOH ratio of 70% EtOH. These extractions yielded an extract with a mangiferin content of 27.24 ± 2.05 mg/g and an extraction yield of 3.71 ± 0.17% w/w. Notably, these outcomes were better from the mangiferin content of 19.62 mg/g and a yield of fresh peel of 5.61% estimated through BBD analysis. Furthermore, a pilot-scale extraction was performed using 7 kg of fresh mango peel and 70% EtOH (8.4 L) for 4 min, resulting in an extract with a mangiferin content of 51.85 ± 0.35 mg/g and a fresh peel yield of 4.35% w/w. This method emerges as the most suitable for mango peel extraction and forms the basis of the SMPE. The results from biological activities highlight the potential use of SMPE as the active ingredient for cosmeceutical or healthcare products for wound-healing and skin-brightening agents. Additionally, the knowledge from this study presents an alternative approach to various plant sources and sustainable extraction methods for the herbal extract industry.

Simulation and experimentation on parameters influencing microwave-assisted extraction of bioactive compounds from Punica granatum waste and its preliminary analysis

Nowadays, the revalorization of high-value components of waste is the business goal for the development of food supplements in personalized nutrition, pharmaceuticals, and cosmetics. The objective of this study was to simulate and upgrade the extract quality of the medicinal plant Punica granatum L. peel powder by using microwave-assisted extraction (MAE). The central composite design was implemented for optimized parameters ethanol concentration of (50%), solvent: solid ratio (25:1 mL/g), extraction time (4 min), microwave power (450 W), on yield of 47.3%, total phenolic content of 432.05 mg GAE/g, DPPH reduction of 87.34%, was observed. The extract obtained after MAE of phenolic compounds contained 279.2 mg TAE/g DM of the highest total ellagitannin content and 25 mg QE/g DM of the flavonoid content of pomegranate peel powder. The structural characterization of bioactive compounds before and after MAE was performed using FTIR, SEM, and XRD. FT-IR technique was used to identify the functional groups in the pomegranate peel extract. The highest antioxidant active rich pomegranate peel extract proved that it can be utilized for the preparation of functional foods. This ‘green technology’ can be applied to various by-product processing and can be useful for upgrade studies for the value-addition of food products using an extraction approach. Practical applicationsThis study aims to establish a sustainable prototype for agro-industrial wastage management using an approach to process pomegranate peel that can deliver better economic and environmental outcomes. In this case, the application of the pomegranate peel extract is presented as an alternative to synthetic preservatives due to its highest antioxidant capacity. The advantage of the MAE procedure was the higher yield of up to 50% of extract per gram of peel powder. Our study demonstrates that statistically designed experiments allow for significant enhancement of the extraction process, which application could aid better use of natural resources and deliver more potent extracts than those obtained by currently recommended procedures.

Optimization of a Green Microwave-Assisted Extraction Method to Obtain Multifunctional Extracts of Mentha sp.

A microwave-assisted extraction (MAE) procedure has been optimized to simultaneously provide multifunctional extracts of Mentha sp. leaves with improved antioxidant properties and, for the first time, with optimal antimicrobial activity. Among the solvents evaluated, water was selected as the extractant in order to develop a green procedure and also for its improved bioactive properties (higher TPC and Staphylococcus aureus inhibition halo). MAE operating conditions were optimized by means of a 3-level factorial experimental design (100 °C, 14.7 min, 1 g of dry leaves/12 mL of water and 1 extraction cycle), and further applied to the extraction of bioactives from 6 different Mentha species. A comparative LC-Q MS and LC-QToF MS analysis of these MAE extracts was carried out for the first time in a single study, allowing the characterization of up to 40 phenolics and the quantitation of the most abundant. Antioxidant, antimicrobial (Staphylococcus aureus, Escherichia coli and Salmonella typhimurium) and antifungal (Candida albicans) activities of MAE extracts depended on the Mentha species considered. In conclusion, the new MAE method developed here is shown as a green and efficient approach to provide multifunctional Mentha sp. extracts with an added value as natural food preservatives.

Chemical Profile and Skin-Beneficial Activities of the Petal Extracts of Paeonia tenuifolia L. from Serbia.

Without being aware of its chemical makeup, many ancient societies have used Steppe peony in their traditional medicine. Given that modern phytopreparation intended for use on human skin requires, above all, knowledge of its chemical composition, the goal of this study was to make a screening of the composition of aqueous and methanolic extracts of the petals of P. tenuifolia L. and to examine them for various skin-beneficial properties. The extracts were prepared by maceration, ultrasound-assisted, and microwave-assisted extraction procedures. The chemical profiling was conducted by the use of UHPLC-LTQ-OrbiTrap MS and UHPLC/MS, and spectrophotometric methods for the determination of total polyphenol and total flavonoid contents. The biological activities entailed antioxidant ABTS, DPPH, CUPRAC (Cupric Ion Reducing Antioxidant Capacity), and FRAP (Ferric Reducing Antioxidant Power) assays, antimicrobial (antibacterial and antifungal) and antibiofilm activities, cytotoxicity, wound healing potential, as well as the adhesion and invasion of Staphylococcus lugdunensis. The results showed that the petals are rich in phenolic acids and flavonoids, which are commonly associated with numerous biological activities. The aqueous extracts were more efficient in the majority of the bioactivity assays then the methanolic ones, whereas the optimal extraction method varied between the assays. This study is the first step towards the safe use of the aqueous extracts of P. tenuifolia petals for therapeutic skin treatments.

Extraction and Characterization of Antioxidant Compounds in Almond (Prunus amygdalus) Shell Residues for Food Packaging Applications.

This work proposes the revalorization of almond shell (AS) wastes as an active additive for food packaging applications. A new microwave-assisted extraction (MAE) method to obtain extracts rich in polyphenolic compounds with high antioxidant capacity was optimized. An experimental design to optimize the MAE procedure through response surface methodology (RSM) using a Box–Behnken design was proposed. The effects of extraction temperature, irradiation time, ethanol:water concentration, and solvent pH at three levels were evaluated in terms of total phenolic content (TPC) and antioxidant activity (DPPH (2,2-diphenyl-1-picrylhydrazyl) and ferric reducing antioxidant power (FRAP) assays). The optimal conditions found were 57 min, 80 °C, pH 8, and 70% (v/v) ethanol. Optimized MAE extracts showed low soluble protein content (0.43 mg BSA g−1) and were rich in TPC (5.64 mg GAE g−1), flavonoids (1.42 mg CE g−1), and polysaccharides (1.59 mg glucose g−1), with good antioxidant capacity (2.82 mg AAE acid g−1). These results suggest the potential application of these extracts in the food industry as active additives. This strategy opens new pathways to valorize almond shell residues, contributing to the circular economy.

Microwave assisted extraction, characterization of a polysaccharide from Salvia miltiorrhiza Bunge and its antioxidant effects via ferroptosis-mediated activation of the Nrf2/HO-1 pathway

A microwave-assisted extraction procedure for the crude Salvia miltiorrhiza polysaccharides (SMPs) obtained from Salvia miltiorrhiza Bunge was optimized. Four independent variables were studied: microwave power, extraction time, solvent-to-solid ratio, and concentration of ethanol, with optimal settings of 1200 W, 12 min, 38, and 86 %, respectively. The SMPs were successively purified by DEAE Sepharose Fast Flow and Sephadex G-100 chromatography to produce a novel polysaccharide termed SMP1. The SMP1 was composed of glucose, galactose, and fructose in a molar ratio of 1:1.67:1.12 with an average molecular weight of 6087 Da. Pharmacological studies showed that SMP1 protected from OGD/R-induced ferroptosis and lipid peroxidation by activating Nrf2/HO-1 pathway in PC12 cells. Our research systematically indicated that polysaccharide could inhibit ferroptosis to alleviate oxidative stress injury, which laid the foundation for the future clinical application of Salvia miltiorrhiza polysaccharide.

Effect of Extraction Techniques and Evaluation of Antimicrobial Activity of Argemone mexicana L. Leaves and Roots Extracts in Different Solvents

Aim: The main objective of the study is to estimate the effect of extraction techniques and antimicrobial activity of different solvent extract of A. mexicana leaves and roots.
 Study Design: The research is experimental in nature.
 Place and Duration of Study: Department of Chemistry and Microbiology at CCSHAU, Hisar, between late 2020 and January 2022.
 Methodology: The leaves and roots of A. mexicana were harvested for this study. Shade dried roots and leaves were cut into small pieces of 2-3 inches and processed into powder using a mixer grinder. Soxhlet extraction and microwave-assisted extraction procedures were used to extract leaves and roots in solvents such as acetone, methanol, and water. The antimicrobial activity of the roots and leaves extracts were evaluated against Gram +ve bacteria (Xanthomonas campesteris, Bacillus cereus, Staphylococcus aureus) and fungal species (Fusarium oxysporum, Macrophomina phaseolina and Candida albicans) and their zones of inhibition in mm are measured by Agar well diffusion method.
 Results: Soxhlet extraction technique gave better extract yield 12.19 g /100 g and 8.54 g / 100 g while microwave-assisted extraction gave 8.88 g / 100 g and 6.94 g / 100 g for leaves and roots respectively. The methanoilc root and leaves extracts exhibited higher antimicrobial activity followed by acetone and water extracts.
 Conclusion: The result of the investigation showed that extraction techniques considerably affected extraction yield and antimicrobial activity. Soxhlet extraction is better one extraction method among these two and methanolic extract of leaves was found to be good antimicrobial followed by acetone and aqueous.

Microwave-assisted extraction of antioxidant compounds from by-products of Turkish hazelnut (Corylus avellana L.) using natural deep eutectic solvents: Modeling, optimization and phenolic characterization

An environmentally friendly method using natural deep eutectic solvents (NADES) and microwave-assisted extraction (MAE) for the recovery of bioactive compounds from hazelnut pomace (a hazelnut oil process by-product) was developed to contribute to their sustainable valorization. Eight different NADES were prepared for the extraction of antioxidant constituents from hazelnut pomace, and choline chloride:1,2-propylene glycol (CC-PG) was determined as the most suitable NADES, considering their extraction efficiency and physicochemical properties. After selecting suitable NADES, operational parameters for the MAE process of antioxidants from hazelnut pomace were optimized and modeled using response surface methodology. For the highest recovery of antioxidants, the operational parameters of the MAE process were found to be 24% water, 38 min, 92 °C and 18 mL/0.1 g-DS. Under optimized conditions, extracts of both pomace as a by-product and unprocessed hazelnut flours of three different hazelnut samples (Tombul, Çakıldak, and Palaz) were prepared, and their antioxidant capacities were evaluated by spectrophotometric methods. Antioxidant capacities of CC-PG extracts of all hazelnut samples were 2–3 times higher than those of ethanolic extracts. In addition, phenolic characterization of the prepared extracts was carried out using the UPLC-PDA-ESI-MS/MS system. The results of this study suggest that hazelnut by-products can potentially be considered an important and readily available source of natural antioxidants. Furthermore, the modeled MAE procedure has the potential to create an effective and sustainable alternative for pharmaceutical and food industries.

Cinnamomum camphora leaves as a source of proanthocyanidins separated using microwave-assisted extraction method and evaluation of their antioxidant activity in vitro

Cinnamomum camphora is a notable tree species of great significance to human beings. Proanthocyanidins (PCs) were separated from C. camphora leaves using microwave assisted extraction (MAE) method. Four variables of the MAE procedure were studied using the Box-Behnken design of response surface method. The results demonstrated that the optimal extraction conditions were: ethanol concentration of 77%; liquid/solid ratio of 20 mL/g, microwave time of 18 min, and microwave power of 530 W to achieve an actual yield of 81.56 ± 2.03 mg/g for C. camphora PCs. Extraction kinetic study results indicated that MAE is the most efficient method for C. camphora leaf PCs extraction under the obtained conditions in comparison to the reference methods (heat reflux extraction, ultrasound extraction, and Soxhlet extraction), by which the highest yield of PCs and the volumetric mass transfer coefficient were obtained in the shortest extraction time. Antioxidant activity study revealed that C. camphora leaf PCs could be used as a natural alternative to the synthetic commercial antioxidants.

A Design of Experiment (DoE) Approach to Model the Yield and Chemical Composition of Ajowan (Trachyspermum ammi L.) Essential Oil Obtained by Microwave-Assisted Extraction.

Ajowan (Trachyspermum ammi L.) is a spice traditionally used in Middle Eastern medicine and contains a valuable essential oil (EO) exploited in different fields, such as pharmaceutics, agrochemicals and food additives. This EO is mostly characterized by the thymol to which most of its biological properties are related. Given the economic value of ajowan and its increasing demand across the globe, the extraction method used for its EO is of paramount importance in terms of quality and quantity of the final product. In the present study, we used the design of experiment (DoE) approach to study and optimize the extraction of the ajowan EO using the microwave-assisted extraction (MAE), a novel extraction technique with high efficiency, low energy consumption, short process length and low environmental impact. A two-step DoE (screening followed by surface response methodology) was used to reduce the number of experiments and to improve the cost/benefit ratio. Reliable mathematical models, relating the more relevant EO features with the extraction conditions, were obtained and used to identify the best experimental conditions able to maximize the yield and thymol concentration. The optimized MAE procedure assures an EO with a higher yield and thymol amount compared with the standard hydrodistillation procedure.

Characterization of Bioactive and Antioxidant Composition of Mountain Tea (Sideritis montana ssp. montana): Microwave-Assisted Technology

The use of synthetic antioxidants has been restricted and even prohibited in some countries due to their toxic effects. This study aims to perform the biochemical assays representing the bioactive compounds in Sideritis montana L. ssp. montana L. known as mountain tea. The study specifically investigates the potential application of mountain tea in the food industry as a natural antioxidant. Different extraction procedures using various solvents are carried out to obtain phenolic compounds and antioxidant activities in plant matrices. In this study, the maceration method was used for the extraction procedure. Furthermore, the microwave-assisted extraction method was applied to shorten the extraction time and decrease the solvent quantity. Methanol was used as a solvent in both conventional and microwave-assisted extraction procedures. The samples were evaluated in terms of the total phenolic compounds, total flavonoids, antioxidant activities, and metal chelating capacity. The obtained results for classical extraction and microwave-assisted extraction methods were found to be 51 and 55 mg/g for TPC, 16.3 and 22 mg/g for TFC, 93 and 103 mg/g for FRAP, and 284 and 282 mg/g for MCC, respectively. The microwave-assisted extraction method produced higher concentrations of bioactive molecules as compared to the classical method. Microwave-assisted extraction was found to be superior to the conventional method in terms of effectiveness, extraction time, and solvent quantity. Besides, Sideritis montana ssp. montana is suggested in the food industry as a natural antioxidant instead of synthetic ones to prevent health-damaging effects.

Direct steam injection pretreatment improves microwave-assisted extraction yield for total flavonoids and myricetin from Hovenia dulcis Thunb.

A direct steam injection pretreatment was added before the microwave-assisted extraction procedure for the extraction of flavonoids from seeds of Hovenia dulcis Thunb, and the antioxidant activity of flavonoid extracts was determined. Based on the experimental results, the addition of direct steam injection simultaneously increased the extraction yield of total flavonoids compared with direct microwave-assisted extraction, and antioxidant activity of flavonoid extracts obtained by adopting the steam injection pretreatment was higher than that by direct microwave extraction alone. Myricetin was isolated from the flavonoid extracts, and the structure was identified by infrared spectroscopy (IR), electrospray ionization mass spectrometry (ESI-MS), and 1H nuclear magnetic resonance (1H-NMR). Recovery yield of total flavonoids was increased by 11.63% when the direct steam injection pretreatment was added to direct microwave extraction.

Performance Parameters of Inductively Coupled Plasma Optical Emission Spectrometry and Graphite Furnace Atomic Absorption Spectrometry Techniques for Pd and Pt Determination in Automotive Catalysts.

Palladium (Pd) and platinum (Pt) are extensively used as catalysts in the petrochemical and automotive industries, and due to high demand for them on the market, their recycling from spent supported catalysts is clearly needed. To assess the content of Pd and Pt in catalysts in order to establish their commercial value or to evaluate the recovery efficiency of technologies used for recycling, reliable analytical methods for determination of these elements are required. Spectrometric methods, such as inductively coupled plasma optical emission spectrometry (ICP-OES) and graphite furnace atomic absorption spectrometry (GFAAS) are powerful tools that can be employed for the determination of Pd and Pt in various sample matrices. However, these methods allow only the injection of liquid samples. In this regard, the digestion of solid sample by microwave-assisted acid extraction procedures at high pressures and temperatures is often used. In this study, a microwave acid digestion method was optimized for the extraction of Pd and Pt from spent catalysts, using a four-step program, at a maximum 200 °C. The resulting solutions were analyzed using ICP-OES, at two different wavelengths for each metal (Pd at 340.458 and 363.470 nm, and Pt at 265.945 and 214.423 nm, respectively) and using GFAAS (Pd at 247.64 nm, Pt at 265.94 nm). Five types of spent catalyst were analyzed and the standard deviations of repeatability for five parallel samples were less than predicted relative standard deviations (PRSD%) calculated using Horvitz’s equation for all the analyzed samples.

A cost effective method for immobilization of Cu and Ni polluted river sediment with nZVI synthesized from leaf extract

This study investigates the performance of oak (OL) and mulberry (ML) leaves for synthesized of nanoscale zero-valent iron (nZVI), in immobilizing Cu and Ni in contaminated sediment. Characterization of synthesized Fe nanoparticles from oak and mulberry leaf extracts demonstrated that they are nontoxic and stabile nanomaterials for application in the sediment remediation. Effectiveness of stabilization process was performed by microwave-assisted sequential extraction procedure (MWSE) and single-step leaching tests which have been applied to evaluate the metal extraction potential. This research showed that OL-nZVI and ML-nZVI were effective in transforming available Cu and Ni to stable fraction. The maximum residual percentage of Cu increased by 76% and 73%, and for Ni 81% and 80%, respectively, with addition of 5% OL-nZVI and 5% ML-nZVI. Used single-step leaching tests (Toxicity Characteristic Leaching Procedure–TCLP and German standard test- DIN) indicated that all stabilized samples can be considered as non-hazardous waste, as all leached metal concentrations met the appropriate set criteria. Cost analysis showed that the operating cost for contaminated sediment treatment with green synthesized nZVI are 50.37 €/m3/per year. This work provides a new insight into the immobilization mechanism and environmental impact of Cu and Ni in contaminated sediment and potential way of treatment with OL-nZVI and ML-nZVI. Generally, nZVI can be an effective and versatile tool for stabilization of sediment polluted with toxic metals.

Maltol determination in food by microwave assisted extraction and electrochemical detection

An electrochemical method is proposed for the determination of maltol in food. Microwave-assisted extraction procedures were developed to assist sample pre-treating steps. Experiments carried out in cyclic voltammetry showed an irreversible and adsorption controlled reduction of maltol. A cathodic peak was observed at -1.0 V for a Hanging Mercury Drop Electrode versus an AgCl/Ag (in saturated KCl), and the peak potential was pH independent. Square wave voltammetric procedures were selected to plot calibration curves. These procedures were carried out with the optimum conditions: pH 6.5; frequency 50 Hz; deposition potential 0.6 V; and deposition time 10 s. A linear behaviour was observed within 5.0×10^(-8) and 3.5×10^(-7) M. The proposed method was applied to the analysis of cakes, and results were compared with those obtained by an independent method. The voltammetric procedure was proven suitable for the analysis of cakes and provided environmental and economical advantages, including reduced toxicity and volume of effluents and decreased consumption of reagents.

Effects of different extraction methods on yield, purity, composition, antioxidant and antimicrobial activities of phenolics from peony flowers

In the present study, microwave-assisted extraction (MAE), ultrasound-microwave synergistic extraction (UMSE) and conventional liquid–solid extraction (CLSE) methods were performed to extract the phenolics from ground peony flowers. For MAE and UMSE, the effect of extraction conditions (microwave power, extraction time, solid/solvent ratio, ethanol concentration) on the yield of phenolics was evaluated. Optimum conditions were determined in experiments where a single factor was varied. Under optimal conditions, yield, purity, composition, antioxidant and antimicrobial activities of the phenolics from the different extracts were analyzed. The antioxidant activities were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and reducing power assays. Thus, the half-maximal inhibitory concentration (IC50) was defined for the different extraction procedures in both DPPH and ABTS assays. The antimicrobial activities of the extracts were determined using an agar well diffusion assay. Although CLSE extracts exhibited the strongest free radical scavenging activities for both ABTS (IC50 = 11.35 ± 0.36 μg/mL) and DPPH (IC50 = 18.07 ± 0.21 μg/mL), and displayed the greatest reducing power, they also had the weakest inhibitory activities for all tested bacteria. Conversely, MAE extracts exhibited the largest zone of inhibition for Escherichia coli (E. coli) (14.00 ± 1.00 mm), Streptococcus mutans (S. mutan) (13.75 ± 0.50 mm), and Streptococcus agalactiae (S. agalactiae) (12.00 ± 0.10 mm), indicating that MAE extracts exerted the best antimicrobial activities. Therefore, the CLSE method should be selected for producing the strongest antioxidant activities and the MAE procedure for generating the strongest antimicrobial activities.

Liquid Phase and Microwave-Assisted Extractions for Multicomponent Phenolic Pattern Determination of Five Romanian Galium Species Coupled with Bioassays.

Background: Galium is a plant rich in iridoid glycosides, flavonoids, anthraquinones, and small amounts of essential oils and vitamin C. Recent works showed the antibacterial, antifungal, antiparasitic, and antioxidant activity of this plant genus. Methods: For the determination of the multicomponent phenolic pattern, liquid phase microextraction procedures were applied, combined with HPLC-PDA instrument configuration in five Galium species aerial parts (G. verum, G. album, G. rivale, G. pseudoaristatum, and G. purpureum). Dispersive Liquid–Liquid MicroExtraction (DLLME) with NaCl and NAtural Deep Eutectic Solvent (NADES) medium and Ultrasound-Assisted (UA)-DLLME with β-cyclodextrin medium were optimized. Results: The optimal DLLME conditions were found to be: 10 mg of the sample, 10% NaCl, 15% NADES or 1% β-cyclodextrin as extraction solvent—400 μL of ethyl acetate as dispersive solvent—300 μL of ethanol, vortex time—30 s, extraction time—1 min, centrifugation at 12000× g for 5 min. Conclusions: These results were compared with microwave-assisted extraction procedures. G. purpureum and G. verum extracts showed the highest total phenolic and flavonoid content, respectively. The most potent extract in terms of antioxidant capacity was obtained from G. purpureum, whereas the extract obtained from G. album exhibited the strongest inhibitory effect against tyrosinase.