Heat Reflux Extraction Research Articles

Deep eutectic solvents as an efficient solvent system determination the volatile compounds with microextraction

In the present work, the Headspace-solid phase microextraction (HS-SDME) process was established utilizing a novel version of Deep-eutectic-solvents (DESs) for extracting and preconcentrating essential oils in plant followed by GC-FID determination. DESs seem to be a cost-effective and attractive alternative for the usage of ionic solvents in biotransformation. DESs are usually developed through gentle warming and stirring of two (low-cost and bio-based) salts. DESs have several superiority over ionic liquids such as their ease of preparation, low production cost and permits large scale applications. HS-SDMEwas made in the current research in order to extract volatile compounds by the use of deep eutectic solvents (DESs) serving as extraction solvents. HS-SDME was constructed as a solvent-minimized extraction method. However, there are a rare number of studies investigating the deep eutectic solvents (DESs) applications to the HS-SDME of bioactive compounds. Deep eutectic solvents, created by mixing choline chloride (ChCl) and p-Chlorophenol at varying ratios, were utilized for extracting essential oils from Echinophora platyloba DC via HS-SDME in the present study. Afterward, headspace single-drop micro-extraction (HS–SDME) was conducted, being connected to gas chromatography. HS-SDME is a quick and simple method in comparison with heat reflux extraction. In addition, it is possible to use DESs in HS-SDME for extracting various volatile compounds.

Optimization of usnic acid extraction conditions using fractional factorial design

AbstractUsnic acid is a unique lichen metabolite of industrial importance, widely studied to explore its pharmacological potential and valued especially as an antibacterial agent in cosmetics. Although a vast number of papers describe usnic acid extraction from various lichen species, none has so far provided an unequivocal indication of the best extraction procedure for this compound. Thus, the current study was focused on the direct comparison of three commonly used usnic acid extraction methods (heat reflux, shaking, ultrasound-assisted extractions), which were optimized using fractional factorial design. Heat reflux extraction, shaking extraction and ultrasound-assisted extraction were first optimized in a series of experiments using fractional factorial design, with respect to three parameters: the extraction time, the solvent used and the number of extraction repetitions. HPLC was employed for usnic acid quantitative analysis. The best scores for each extraction method were statistically compared and the optimal conditions were indicated. The optimal set of parameters for usnic acid was established to be a single, 60 min heat reflux extraction with acetone. This extraction scheme provided 4.25 ±0.08 mg g−1 d.w. of usnic acid, while for ultrasound-assisted and shaking extractions the amount was two- or even four times lower (2.33 ±0.17 and 0.97 ±0.08 mg g−1 d.w., respectively). The optimal procedure for usnic acid extraction described here may be suitable for effective acquisition of this compound for scientific research purposes, but also for applications in the pharmaceutical or cosmetic industries.

Comparison of Different Extraction Methods for the Recovery of Olive Leaves Polyphenols

In the present study, advanced extraction techniques, microwave (MAE), ultrasound (UAE), and high pressure (HPAE)-assisted extraction, were applied to improve extraction efficiency of olive (Olea europaea L.) leaves polyphenols. The effect of sample mass (1.5 and 3 g), MAE—time (2, 8.5, and 15 min) and temperature (45 and 80 °C), UAE—time (7, 14, and 21 min) and amplitude (50 and 100%) and HPAE—time (1, 5.5, and 10 min) and pressure (300 and 500 MPa) on the concentration of each analyzed polyphenol compound was examined. Identified polyphenols were oleuropein, hydroxytyrosol, chlorogenic acid, caffeic acid, verbascoside, and rutin. All three advanced extraction techniques yielded higher content of total polyphenols when compared to the conventional heat-reflux extraction (CE) along with a significant reduction of extraction time from 60 (CE) to 2, 21, and 5.5 min in MAE, UAE, and HPAE, respectively. The most intensive values of tested parameters in each technique were the ones that promoted cell wall disruption, e.g., temperature of 80 °C in MAE, 100% amplitude in UAE and 500 MPa in HPAE. MAE and UAE were more efficient in total polyphenols’ recovery than HPAE.

Kinetic Study on Solid-Liquid Extraction of Condensed Tannins from Rosa Canina Branches and Stems

The goal of this study was to point out the effect of parameters (solvent, solid to solvent ratio and extraction time) on the extraction of condensed tannins from Rosa canina feedstock, using conventional methods such as room temperature extraction (RTE) and heat reflux extraction (HRE). Moreover, the extraction kinetics behaviour for HRE has been extensively studied in order to foreshadow a scale up process. The second order rate model was applied to estimate the extraction kinetics of a conventional heat reflux extraction (HRE) at different solid to liquid ratios, concentrations of solvent extraction times. Results showed that the second order rate model was the rate-governing step of the extraction process, and the predicted and experimental data fits very well.

Enrichment in Antioxidant Flavonoids of Stamen Extracts from Nymphaea lotus L. Using Ultrasonic-Assisted Extraction and Macroporous Resin Adsorption.

Nymphaea lotus L. is the medicinal plant that has long been used for food, cosmetics and traditional medicines in Africa and Asia since ancient times. Its flavonoids and other interesting phytochemical compounds from rhizome, leaf and the whole flowers have been reported in the previous published research. However, stamens, which are essential for reproductive functions, may also represent new alternative sources of potential antioxidant flavonoids, as investigated in this study. The innovative green chemistry methods, i.e., ultrasound-assisted extraction (UAE) as well as a macroporous resin (MPR) purification procedure, were employed in this current research. Using a full factorial design coupled to three-dimensional (3D) surface plot methodology, the influence of three variables, namely aqEtOH concentration (ranging from 50 to 100% (v/v), US frequency (ranging from 0 (no US applied) to 45 kHz), and the extraction duration (ranging from 20 to 60 min), were evaluated. Five MPRs with different surface areas, average pore diameters, matrix types and polarities were also investigated for the purification of total flavonoids. The optimal UAE condition is 90% (v/v) aqEtOH with 34.65 khz ultrasonic frequency and 46 min of extraction duration. Compared with the conventional heat reflux extraction (HRE) method, a significant 1.35-fold increase in total flavonoids content was obtained using optimized UAE conditions (169.64 for HRE vs. 235.45 mg/g dry weight for UAE), causing a 2.80-fold increase when this UAE associated with MPR purification (475.42 mg/g dry weight). In vitro cell free antioxidant activity of N. lotus stamen extracts and in cellulo antioxidant investigation using yeast model showed the same trend, indicating that the best antioxidant flavonoid can be found in UAE coupled with MPR purification. Moreover, in the yeast model, the expression of key antioxidant genes such as SIR2 and SOD2 were expressed at the highest level in yeast cells treated with the extract from UAE together with MPR purification. Consequently, it can be seen that the UAE combined with MPR purification can help enhance the flavonoid antioxidant potential of the stamens extract from this medicinal species.

A novel microwave-assisted steam distillation approach for separation of essential oil from tree peony (Paeonia suffruticosa Andrews) petals: Optimization, kinetic, chemical composition and antioxidant activity

Microwave-assisted steam distillation (MSD) was developed as an efficient technique for the separation of essential oil (EO) from tree peony (Paeonia suffruticosa Andrews) petals, on the basis of ensuring the extraction of flavonoids. During MSD process, the raw material was separated from water to keep it in a relatively dry state, thus contributing to the subsequent extraction of flavonoids. In this work, the optimization of MSD process was conducted to obtain the optimum conditions (1.7 mL/g water ratio for soaking, 1 h soaking time, 540 W microwave irradiation power and 30 min microwave irradiation time) and high yield of EO (0.66 ± 0.03 mg/g). The MSD technique was compared with other reference methods in terms of kinetic model fitting, economic value, environmental impact, EO composition and antioxidant activity. The result pointed out that the MSD method could be reasonably fitted by first-order kinetic model, was environmentally friendly and economically sustainable, provided higher separation efficiency, required lower energy consumption, and had certain advantages in the separation of EO with higher proportion of oxygenated components and better antioxidant activity. Furthermore, microwave-assisted extraction (MAE) of flavonoids from the petal residues obtained after MSD showed better result than that obtained after microwave hydrodistillation, and the result was comparable with MAE and heat reflux extraction. Overall, MSD is a potential and powerful alternative to traditional methods for the efficient distillation of EO, on the premise of reducing the loss of flavonoids etc. non-volatile components.

A Quick, Green and Simple Ultrasound-Assisted Extraction for the Valorization of Antioxidant Phenolic Acids from Moroccan Almond Cold-Pressed Oil Residues

Almond (Prunus dulcis (Mill.) D.A. Webb) is one of the most important nut crops both in terms of area and production. Over the last few decades, an important part of the beneficial actions for health associated with their consumption was attributed to the phenolic compounds, mainly accumulated in almond skin. Interestingly, after cold-pressed oil extraction, most of these antioxidant phenolic compounds are retained in a skin-enriched by-product, a so-called almond cold-pressed oil residue. In Morocco, the fifth highest ranking producer in the world, this production generates an important part of this valuable byproduct. In the present study, using a multivariate Box–Behnken design, an ultrasound-assisted extraction method of phenolic compounds from Moroccan almond cold-pressed oil residue was developed and validated. Response surface methodology resulted in the optimal extraction conditions: the use of aqueous ethanol 53.0% (v/v) as a green solvent, applying an ultrasound frequency of 27.0 kHz for an extraction duration of 29.4 min. The present ultrasound-assisted extraction allowed substantial gains in terms of extraction efficiency compared to conventional heat reflux extraction. Applied to three different local Beldi genotypes growing at three different experimental sites, the optimal conditions for ultrasound-assisted extraction led to a total phenolic content of 13.86 mg/g dry weight. HPLC analysis revealed that the main phenolic compounds from this valuable byproduct were: chlorogenic acid followed by protocatechuic acid, p-hydroxybenzoic acid, and p-coumaric acid. The accumulation of these phenolic compounds appeared to be more dependent on the genetic background than on the environmental impact here represented by the three experimental culture sites. Both in vitro cell free and cellular antioxidant assays were performed, and revealed the great potential of these extracts. In particular, correlation analysis provided evidence of the prominent roles of chlorogenic acid, protocatechuic acid, and p-hydroxybenzoic acid. To summarize, the validated ultrasound-assisted extraction method presented here is a quick, green, simple and efficient for the possible valorization of antioxidant phenolic compounds from Moroccan almond cold-pressed oil residues, making it possible to generate extracts with attractive antioxidant activities for future nutraceutical and/or cosmetic applications.

Development and validation of an ultrasound-assisted supercritical carbon-dioxide procedure for the production of essential oils from Perilla frutescens

Four different isolation techniques, the ultrasound-assisted supercritical CO2 (UscCO2) extraction, traditional supercritical CO2 (TscCO2) extraction, steam distillation (STD) and heat-reflux extraction (HRE), were utilized to isolate volatile oils from the purple leaves of P. frutescens. The highest yield of volatile oils obtained by the UscCO2 procedure was 1.62% (weight of extracted oil/dry weight of plant material), which was 13.7, 30.2 and 72.2% higher than the oil yields obtained by TscCO2 extraction, STD and HRE, respectively. In addition, the content of perillaldehyde (49.76%, w/w) obtained by the UscCO2 process was approximately 1.09, 1.43 and 1.23 times higher than the contents obtained by STD, HRE and TscCO2 extraction, respectively. Moreover, the theoretical solubility of volatile oils in supercritical solvent was evaluated with the dynamic extraction method and then correlated with the Chrastil, Bartle and Kumar and Johnston models, with average absolute relative deviations (AARDs) of 0.71%, 0.74% and 3.56%, respectively.

Comparison of different extraction techniques and optimization of the microwave-assisted extraction of saponins from Aralia elata (Miq.) Seem fruits and rachises

The total saponins from Aralia elata (Miq.) Seem fruits and rachises were isolated by microwave-assisted extraction (MAE), ultrasonic extraction, heat reflux extraction, and soxhlet extraction. These techniques were compared from four perspectives: extraction kinetics, saponin yield, disintegration to the raw materials, and antioxidant activity. MAE had the highest extraction efficiency, shortest time, and greatest disintegration to the raw materials. The extracts obtained with MAE had the highest antioxidant activities, as the DPPH free radical scavenging abilities of the fruit and rachis extracts were 70.86 ± 1.33 and 50.85 ± 1.68 mg VC g−1md, respectively. The MAE parameters were optimized by the response surface methodology. The optimum conditions (92% and 91% ethanol, solid-to-liquid ratios of 1:30 and 1:22, microwave powers of 530 W and 400 W, microwave times of 40 s and 54 s) provided extraction yields of 2.98 ± 0.037 mg g−1 and 0.94 ± 0.026 mg g−1 from the fruits and rachises, respectively.

A green approach for the extraction and characterization of oridonin and ursolic and oleanolic acids from Rabdosia rubescens and its kinetic behavior

An ultrasound-assisted supercritical carbon dioxide (USC-CO2) procedure was developed for the extraction of ursolic acid, oleanolic acid and oridonin from Rabdosia rubescens, with yields that were 9.84–10.46 and 15.43–21.10% higher than those of the conventional SC-CO2 and heat-reflux extractions, respectively. USC-CO2 uses a shorter extraction time (1.83–2.09 times) and less organic solvent (3.39–173.25 times) to operate at a lower extraction temperature (5–16 °C). The dominant component in the extract was oridonin, which may indicate that the kinetic behavior in the extraction system is predominated by that of oridonin. Furthermore, the USC-CO2 and conventional SC-CO2 dynamic extraction kinetics of oridonin from R. rubescens were well described by the second-order rate and Fick’s second law models. The extraction rate constant, energy of activation for diffusion, Biot number and thermodynamic parameters were deduced from the data obtained. These results provide valuable insights into the USC-CO2 and conventional SC-CO2 procedures.

Determination of Flavonoids in Magnolia officinalis Leaves Based on Response Surface Optimization of Infrared Assisted Extraction Followed by High-Performance Liquid Chromatography (HPLC)

A simple and economical method for the rapid extraction and measurement of rutin, isoquercitrin, and quercitrin in Magnolia officinalis leaves was developed using response surface methodology with determination by high performance liquid chromatography (HPLC). By the use of Box-Behnken response surface optimization of infrared-assisted extraction (IRAE), the optimized conditions of flavonoids were as follows: extraction time of 11 min, ethanol concentration of 53% (v/v), liquid–solid ratio of 40:1, and extraction power of 60 W. The yields of flavonoids by the IRAE protocol were higher by 7.12 and 10.59% than using heating reflux extraction (HRE) and ultrasound-assisted extraction (UAE), respectively. In addition, the extraction period of flavonoids by the IRAE method was approximately 1/3 and 1/9 of the time intervals required employing HRE and UAE, respectively. IRAE method was verified by HPLC and successfully applied for analysis of ten samples collected from different geographical areas. The relative standard deviation values of the precision and accuracy were favorable for analytical applications, with values from 0.21 to 2.33% and 0.50 to 1.96%, respectively. The recovery results were achieved at a 95% confidence level. The study shows that the IRAE method coupled with HPLC is a simple, cost-effective and reliable tool for the routine determination of flavonoids in M. officinalis leaves for quality control applications.

Optimization in continuous phase-transition extraction of crude flavonoids from finger citron fruit and evaluation on their antiaging activities.

The development of antiaging functional products is a hot topic in the field of functional foods. However, the efficient extraction of functional ingredients is the limiting step for the functional food industry. Continuous phase‐transition extraction (CPE) is a new extraction technique that combines the advantages of Soxhlet extraction and supercritical extraction, which may have a distinct advantage over traditional methods in the extraction of flavonoids. In our study, the Box–Behnken design combined with response surface methodology was used to optimize CPE of crude flavonoids from finger citron fruit. The antiaging activities of finger citron crude flavonoids (FCCF) were evaluated by Caenorhabditis elegans (C. elegans) model. The optimal extraction conditions for CPE were as follows: ethanol concentration 85%, temperature 90°C, time 120 min, and pressure 0.2 MPa. Compared with the heat reflux extraction, the extraction rate and content of FCCF extracted by CPE increased by 24.28% and 33.22% (p < .05), respectively. FCCF extended the lifespan of C. elegans by 14.94% without causing adverse effects on their reproduction and locomotion ability. A further analysis suggested that FCCF prolonged the lifespan of nematodes under normal and oxidative stress by increasing the activity of major enzymes in endogenous antioxidant defense system and reducing the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA). The results confirmed the effectiveness of CPE in extracting crude flavonoids from finger citron fruit, and the extracted FCCF exhibited strong antiaging activities.

Conventional and nonconventional extraction techniques for optimal extraction processes of rosmarinic acid from six Lamiaceae plants as determined by HPLC-DAD measurement

The goal of this study was to improve the extraction efficiency of rosmarinic acid (RA) from Lamiaceae herbs (lemon balm, peppermint, oregano, rosemary, sage, and thyme) using various extraction techniques (maceration with stirring, MACS; heat reflux, HRE; and microwave-assisted extraction, MAE) and extraction conditions (solvent acidity, solvent type, extraction time and temperature). The RA content was measured by high-performance liquid chromatography with diode-array detection (HPLC-DAD) under test conditions. Our results showed that extraction with acidified aqueous ethanol (EtOH-H2O-HCl, 70:29:1, v/v/v) was the best choice for the recovery of RA compared to other solvent systems. Further study suggested the following optimal extraction times for the different techniques: 120 min at 25 °C with MACS, 15 min at boiling point with HRE, and 5 min at 50 °C and 80 °C with MAE. Based on our results, we demonstrated that by careful adjustment of the extraction conditions, it is possible to set up a single extraction protocol to extract RA from different plants.

Comparative antioxidant, anticancer and antimicrobial activities of essential oils from Semen Platycladi by different extraction methods

Semen Platycladi is a highly valued seed tonic from the Cupressaceae Platycladus orientalis (L.) Franco, which contains abundant essential oils exhibiting antioxidant, antimicrobial, sedative and hypnotic potency. The study was formulated to estimate the potential antioxidant, anticancer and antibacterial activities of its essential oils as well as its correlation with chemical constituents. The comparison of three isolation methods including steam distillation extraction, heating reflux extraction, and Soxhlet extraction of ethanol was carried out to isolate essential oils whose chemical composition were identified and evaluated by Gas Chromatography-Mass Spectrometer. It turned out that the yield of essential oils obtained through heating reflux extraction and Soxhlet extraction was almost 40 % higher than those extracted by steam distillation extraction in nearly one-quarter of a time used by the steam distillation extraction. A total of 76 compounds were identified, including ten alkanes, 14 alkenes, 13 alcohols, one aldehyde ketone, three ethers, one acid, 17 esters, five aromatic compounds, and 12 others. The essential oils extracted by steam distillation extraction were proved to have the best antioxidant and antimicrobial activity although with the lowest yield. Scanning electron microscopic observation displayed that the of S. aureus revealed serious disruption of cell membranes resulting in the loss of cell viability. Therefore, it’s vital to adopt a proper method to obtain the target ingredients recommended as nutraceuticals and/or phytomedicines.

Concurrent Extraction and Purification of Gentiopicroside from Gentiana scabra Bunge Using Microwave-Assisted Ethanol-Salt Aqueous Two-Phase Systems.

A potential method called microwave-assisted aqueous two-phase extraction (MA-ATPE) was developed for concurrent extraction and purification of gentiopicroside from Gentiana scabra Bunge. Formation characteristics of aqueous two-phase system (ATPS) composed of ethanol and 25 kinds of salts were investigated; K2HPO4 (w/w, 21.71%) and ethanol (w/w, 40.72%) were determined to be the optimal compositions of ATPS. Response surface methodology based on Box-Behnken design was used to investigate the extraction conditions, the optimal parameters were summarized as follows: 80°C of extraction temperature, 31s of extraction time, 11:1 (mL/g) of liquid-to-solid ratio, 100 meshes of particle size and 806W of microwave power. Under these conditions, the extraction yield of gentiopicroside was 65.32±0.24mg/g with a recovery of 96.51%. Compared with other four methods, the purity of gentiopicroside in the crude extracts reached 17.16±0.25%, which was significantly higher than that of smashing tissue extraction, microwave assisted-extraction, ultrasonic-assisted extraction and heat reflux extraction, respectively. In addition, the phase-forming salt can be recyclable. Therefore, MA-ATPE was an excellent and alternative technique to the conventional extraction approaches of gentiopicroside.

Enhanced Extraction of Bioactive Components of 3,29–Dibenzoylkarounidiol and Polysaccharides from Semen richonsanthis Using Subcritical Water Technology

AbstractThe efficient and green extraction of oil– and water–soluble essences from natural products is a key step in producing bioactive compounds and value–added chemicals. Herein, two components with different polarities from Semen richonsanthis were extracted using static subcritical water extraction technology at different temperatures (80–160°C), extraction times (5.0–30.0 min), and water loadings (2.0–6.0 mL). The oil–soluble and water–soluble components were measured by HPLC and phenol–sulfuric acid method, respectively. The optimum conditions of 3,29–dibenzoylkarounidiol (0.102±0.004%) and polysaccharides (0.462 ±0.021%) were obtained at 130°C, 10 min and 4.0 mL water loading. Compared with ultrasonic and heating reflux extraction, the three extracts were assessed by antioxidant activity against 2,2–diphenyl–1–picrylhydrazyl and the cytotoxicity towards HeLa cells. Overall results showed that the activities of subcritical water extracts are more promising than the other extracts and can be safely applied to pharmaceutical and nutraceutical products. Lastly, the morphological changes were evaluated by SEM which indicated subcritical water have a destructive effect on the cell wall.

Comparison study for the recovery of bioactive compounds from Tribulus terrestris, Panax ginseng, Gingko biloba, Lepidium meyenii, Turnera diffusa and Withania somnifera by using microwave-assisted, ultrasound-assisted and conventional extraction methods

Heat reflux (CONV), Soxhlet (SOX), microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction methods, using ethanol, water and their mixtures, were studied for the recovery of bioactive compounds from Tribulus terrestris, Panax ginseng, Gingko biloba, Lepidium meyenii, Turnera diffusa and Withania somnifera. The study revealed that SOX method achieved extracts with the highest yieldTPC in terms of the total phenolic content (TPC) (66.65 ± 1.50%); MAE and UAE resulted also in extracts with high TPC and shorter treatment times compared to SOX. More specifically, the TPC values for MAE and UAE were 91.783 ± 0.026 mg GA/g dw and 81.113 ± 0.103 mg GA/g dw, respectively, the antioxidant activity (DPPH) was 63.577 ± 0.057 mg Trolox/g dw and 64.923 mg Trolox/g dw, and the yieldTPC was 60.82% and 61.89%, respectively. All were higher compared to those obtained by the CONV method. The use of pure ethanol as the extraction solvent, provided maximum TPC and similar results for DPPH and yieldTPC (%). Moreover, maximum TPC (183.70 mg GA/g dw) and DPPH (377.21 mg Trolox/g dw) values were achieved for T. diffusa. The HPLC analysis of T. terrestris, P. ginseng and G. biloba extracts showed that G. biloba contained its characteristic bioactive compound in the highest concentration (13.512 mg gingkolide/g herb).

Ionic liquid-immobilized NaY zeolite-based matrix solid phase dispersion for the extraction of active constituents in Rheum palmatum L.

The ionic liquid-immobilized NaY zeolite was prepared by means of impregnation approach and used as the dispersant of matrix solid phase dispersion for the extraction of aloe-emodin, emodin, chrysophanol and physcion in Rheum palmatum L.. High performance liquid chromatography coupled with diode-array detection was used for the separation and determination of target analytes. The ionic liquid-immobilized NaY zeolite was further characterized by SEM, FT-IR, TG, XRD and BET. The experimental parameters, such as type and content of ionic liquid, mass ratio of sample to dispersant, type of washing solvent, and type and volume of elution solvent, were optimized. The results revealed that the prepared ionic liquid-immobilized NaY zeolite presents suitable properties and can be used as the dispersant of matrix solid phase dispersion for the extraction of anthraquinones. Good linearities (r > 0.9995) were obtained in the range of analyte concentration investigated. The recoveries were 73–98% with the relative standard deviations lower than 6%. Compared with ultrasound-assisted extraction and heat reflux extraction, the present method requires less sample, organic solvent and extraction time. The present method can be applied to the determination of anthraquinones from medicinal plant.

A Design of Experiments Strategy to Enhance the Recovery of Polyphenolic Compounds from Vitis vinifera By-Products through Heat Reflux Extraction.

The aim of the present study was to establish the best experimental conditions that lead to the extracts richest in polyphenolic compounds obtained from pomace and canes of Vitis vinifera. In this regard, a D-Optimal design of experiments (DoE) method was applied to investigate the extraction process parameters from each of three materials: red pomace (RP), white pomace (WP) and canes (C). The input variables were the extraction temperature and the ethanol ratio and as response, the total polyphenols content (TPC) was determined. A design space was generated for each of the plant materials and the most concentrated polyphenol extracts were obtained using 50% ethanol at a temperature of 80 °C. Further, the phenolic profiles of the concentrated extracts were detected by LC/MS/MS and the results showed that WP extract was richer in polyphenolic compounds, both flavonoid and phenolic acids, followed by the RP and C extracts. The antioxidant assays revealed that WP and RP extracts exhibited a higher antioxidant activity which correlated to the high content of polyphenols. These findings revealed that RP, WP and C, currently considered agricultural wastes from winery, may be valorized as an important source of natural antioxidants.

Ultrasound-Assisted Extraction of Total Flavonoids from Pteris cretica L.: Process Optimization, HPLC Analysis, and Evaluation of Antioxidant Activity.

In the present work, the ultrasonic-assisted extraction (UAE) of total flavonoids (TF) from Pteris cretica L. was optimized by response surface methodology (RSM) on the basis of a single-factor experiment. The optimized UAE parameters were as follows: Ethanol concentration 56.74%, extraction time 45.94 min, extraction temperature 74.27 °C, and liquid/solid ratio 33.69 mL/g. Under the optimized conditions, the total flavonoids yield (TFY) was 4.71 ± 0.04%, which was higher than that obtained by heat reflux extraction (HRE). The extracts were further analyzed by HPLC, and five major flavonoids, including rutin, quercitrin, luteolin, apigenin, and luteolin-7-O-glucoside, were identified and quantified. Furthermore, the results of the antioxidant test showed that the TF extract obtained under optimized UAE conditions exhibited good 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS+•), nitric oxide radical (NO•) scavenging activities, and ferrous ion (Fe2+) chelating capacity, with IC50 values of 74.49, 82.92, 89.12, and 713.41 µg/mL, respectively. Results indicated that the UAE technique developed in this work was an efficient, rapid, and simple approach for the extraction of flavonoids with antioxidant activity from P. cretica.