Extraction Of Antioxidant Phenolic Compounds Research Articles

Microwave and ultrasound extraction of antioxidant phenolic compounds from Lantana camara Linn. leaves: Optimization, comparative study, and FT-Orbitrap MS analysis.

The species Lantana camara is used in folk medicine. The biological activities of this medicinal plant are attributable to the presence of various derivatives of triterpenoids and phenolic compounds present in its preparations, indicating excellent economic potential. In this study, the operational conditions of ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were optimized using Box-Behnken design to improve the total phenolic content (TPC) recovered in hydroethanolic extracts of L. camara leaves. The TPC, total flavonoid content (TFC), and antioxidant activities of the hydroalcoholic extracts of L. camara, prepared by UAE and MAE under the optimized extraction conditions, were compared with those of the extracts obtained by conventional extraction methods. Under the optimal conditions, the extracts obtained by UAE (35% ethanol, 25 min, and a solvent-to-solid ratio of 60:1mL/g) and by MAE (53% ethanol, 15 min, and 300 W) provided high yields of 32.50% and 38.61% and TPC values of 102.89 and 109.83 mg GAE/g DW, respectively. The MAE extract showed the best results with respect to TPC, TFC, and antioxidant activities, followed by extracts obtained by UAE, Soxhlet extraction, decoction, maceration, and infusion, in that order. The results obtained indicate that L. camara may be used as an important source of antioxidant phenolic compounds to obtain products with high biological and economic potential, especially when the extraction process is performed under appropriate conditions using MAE and/or UAE, employing environmentally friendly solvents such as water and ethanol.

Exploring antioxidant potential and phenolic compound extraction from Vitis vinifera L. using ultrasound-assisted extraction

Abstract The research investigates the extraction of antioxidant phenolic compounds from grape pomace, a wine fermentation byproduct. Ultrasound-assisted extraction (UAE), varying parameters such as solute:solvent ratio, power, and time were utilized. UAE was specifically applied to Vitis vinifera L. using high-intensity ultrasound with ratios of 1:18 and 1:42 g:mL, 250 and 400 W power levels, and extraction times of 15 and 20 minutes. Total phenolic content was quantified via the Folin–Ciocalteau reagent, and total flavonoids were determined using quercetin as a standard. Antioxidant capacity was evaluated through ABTS, FRAP, and DPPH Radical Scavenging Assays, with Trolox equivalent antioxidant capacity (TEAC) for comparison. Results indicated a total phenolic content of 50 to 80 μmol GAE/g d.w., with no significant differences among treatments. Total flavonoid concentration ranged from 2.5 to 4 μmol QE/g d.w. Importantly, the solute:solvent ratio impacted antioxidant capacity, with higher ratios showing increased ABTS radical capacity. Treatment 1, with the highest flavonoid content, exhibited the greatest antioxidant capacity against DPPH radicals. This study underscores the intrinsic correlation between cumulative bioactive compound content and the inherent antioxidant capacity of grape pomace extracts. This highlights the potential application of these extracts as antioxidant reservoirs, poised for integration into functional foods and biomedical nutraceuticals.

Ohmic heating-based extraction of biocompounds from cocoa bean shell

Cocoa bean shell (CBS), a by-product of the chocolate industry, was employed as substrate for the sustainable recovery of bioactive compounds using ohmic heating (OH). Total phenolic content and antioxidant activity of the treated CBS were optimized by experimental design. Maximum extraction of antioxidant phenolic compounds (23 mg GAE/g CBS) was obtained at 67 °C, 50 min and 44% ethanol (v/v). The antioxidant activity of the extracts obtained under of the central point conditions was 284.5 μM Fe2+/g extract (FRAP) and 36.4 μM TE/g extract (DPPH). The use of OH increased the extraction of bioactive phenolic compounds when compared to the conventional process (CH) (approximately 40%). An increased on the chemical antioxidant activity was also observed, ranging from 4 to 20%. The metabolic activity of the extracts obtained by the two methods (OH and CH) was evaluated in non-tumoral (HEK293T and L929) and tumoral cell lines (Caco-2, HT-29, and HeLa). The CBS extracts presented low toxicity in non-tumoral cells and ROS preventive effects. These characteristics make them ideal to be used in food processing and formulation, as well as nutraceutical products due to their antioxidant protection. The use of OH results in an extract with higher phenolic content and higher antioxidant activity and low environmental impact.

Ultrasound-assisted extraction of antioxidant phenolic compounds from Lavandula angustifolia flowers using natural deep eutectic solvents: An experimental design approach

In this study, the green extraction of antioxidant phenolic compounds from Lavandula angustifolia was investigated using ultrasound-assisted extraction coupled with natural deep eutectic solvents (NADESs). One variable at a time, fractional factorial design, steepest ascent/descent method, and central composite design were used to optimize the extraction conditions. Eighteen NADESs based on choline chloride, organic acids, and sugars were tested by one variable at a time approach. The NADES composed of choline chloride and glycerol with a molar ratio of 1:2 showed higher extraction performance than other NADESs and benchmark solvents (70 % ethanol and 80 % methanol). After solvent selection, other extraction parameters including ultrasound amplitude (20–100 %), temperature (40–70 °C), time (5–30 min), liquid to solid ratio (10–50 mL/g), and water content in NADES (10–50 %) were screened using fractional factorial design. Subsequently, the steepest ascent/descent method was applied to approach the suitable level of the selected parameters. Finally, response surface methodology was used to determine the optimal extraction conditions. The optimum conditions were ultrasound amplitude of 60 %, temperature of 60 °C, time of 17.5 min, liquid to solid ratio of 31.7 mL/g, and water content in NADES of 33.5 % with the predicted phenolic content of 50.50 mg gallic acid equivalent/g, flavonoid content of 35.79 mg catechin equivalent/g, antioxidant capacity (AC)DPPH of 41.60 mg Trolox equivalent (TE)/g, ACABTS of 77.13 mg TE/g, and ACCUPRAC of 163.33 mg TE/g. Phenolics and volatiles were analyzed by HPLC and GC-MS, respectively. The results showed a sustainable, green, and effective extraction of antioxidant phenolic compounds from L. angustifolia.

Optimization of phenolic compound recovery and antioxidant activity from Fumaria officinalis L. using response surface methodology

The purpose of this study was to optimize the extraction of antioxidant phenolic compounds from Fumaria officinalis by two approaches, single-factor experiment and response surface methodology (RSM). After extraction optimization, the content of polyphenols, flavonoids, and tannins was performed. Antioxidant activities of optimal extract were evaluated by DPPH, ABTS, and iron chelating activities. Single-factor experiments showed that all extraction parameters had significant effects (p < 0.05) on total phenolic content and free radical scavenging activity. From the optimization process using response surface methodology through Box-Behnken design regarding the three selected significant parameters (solvent concentration, extraction time, and temperature), it was established that the best extraction conditions were 47% methanol, 54.40°C, and 168.02 min, respectively. Under these optimal conditions, the recorded values for TPC and DPPH scavenging activity were successively 1510.10 mg GAE/100g DW and 69.85%. These results were in accordance with model predictions indicating that the model was suitable for the extraction process. Furthermore, higher flavonoids and tannins contents and strong iron-chelating and ABTS scavenging activities were obtained.

Cellulase-assisted extraction of phenolic compounds from rice bran (Oryza sativa L.): process optimization and characterization

This study investigated the improvement in the extraction of antioxidant phenolic compounds from a by-product of the food industry, rice bran, using hydrolytic enzymes. To this purpose, the optimization process of obtaining these compounds was carried out, as well as chemical characterization of the rice bran extracts by high performance liquid chromatography (HPLC) and the determination of their antioxidant activity. First, the parameters that affect the extraction process, such as the type on enzyme, temperature and pH of the solution, the extraction time and the enzyme concentration used for obtaining phenolic compounds were studied. The influence of these factors was later examined by characterizing the compounds obtained by HPLC, and the antioxidant activity of the extracts. The optimum conditions were: temperature 35 °C, pH 3.0 solution, extraction time 4 hours and cellulase content of 1.0%. In these conditions, extraction yield ranged from 3.45 ± 0.9 mg ferulic acid/100 g rice bran (without cellulase) to 14.3 ± 2.2 mg ferulic acid/100 g rice bran (with 1 % cellulase). Finally, the increases in antioxidant activity are lighter than those produced in the concentration of phenolic compounds, so we concluded that the enhancement in bioactivity is more limited when cellulase enzyme-assisted extractions were carried out in rice bran.

Optimization of Extraction Conditions to Improve Phenolic Content and In Vitro Antioxidant Activity in Craft Brewers' Spent Grain Using Response Surface Methodology (RSM).

Extraction temperature, extraction time and liquid (water) to solid ratio were optimized in order to extract antioxidant phenolic compounds from brewers’ spent grain (BSG). The extracts were analysed for their total phenol content (TPC) and antioxidant activity was measured using three different methods: 2,2-diphenyl-2-picrylhydrazyl (DPPH) free radical, 2,2′-azino-bis(3-ethylbenothiazoline-6-sulphonic acid) (ABTS), and reducing power (RP) assays. All the parameters except extraction time promoted different efficiencies for the extraction of antioxidant phenolic compounds. TPC extraction was higher at lower temperatures and lower liquid/solid ratios up to a certain point. In this sense, a decrease in TPC with increasing liquid/solid ratios took place until a 16:1 ratio and a plateau was reached beyond that ratio. The highest DPPH activity was reported for 30–35 °C and 60–90 min extraction and 60–90 min extraction with a 25 mL/g ratio. ABTS values increased as the liquid to solid ratio decreased, being positively correlated with TPC (R = 0.788; p < 0.01). The highest RP was achieved at 30–33 °C extraction temperature and 10–14 mg/mL v/w ratio and at 116–120 min extraction and 16–17 mg/mL ratio. Gallic acid accounted for the majority of the phenolic compounds found, followed by hydroxyphenylacetic acid, epicatechin, and protocatechuic acid. Sinapic, 4-hydroxy benzoic, and syringic acids were also found in lower quantities. Coumaric, vanillic, ferulic, and caffeic acids were present in very small amounts. All the extracts contained phenolics and showed in vitro antioxidant activity, but the extracts obtained by using 30 °C, 121.9 min, and 10 mL/g liquid/solid ratio exhibited the highest content in TPC and antioxidant potential. The aqueous extraction of a potentially bioactive extract from BSG was demonstrated to be an efficient and simple method to recover these value-added compounds.

Evaluation of phenolic and antioxidant properties of strawberry as a function of extraction conditions

Abstract We studied the extraction of antioxidant phenolic compounds, anthocyanins and the evaluation of antioxidant activity of strawberries in different extraction conditions, varying the type of solvent (ethanol:water (50%) and acetone:water (60%), the extraction time (15 and 60 min) and the solvent volume to sample mass ratio (5 mL/g and 20 mL/g). In addition, we performed principal component analysis and cluster analysis. The results showed that, although the two solvents tested had similar influence on total phenolic compounds extraction and antioxidant activity, the 60 minutes of extraction and the use of the solvent volume/sample mass ratio of 20 mL/g were the best extraction conditions, both for the 1st and 2nd recovered extracts. However, the solvent had a marked effect on anthocyanins’ extraction, so that acetone/water extracted almost the double as compared to ethanol/water, for the same extraction conditions. Finally, factor analysis allowed identifying a grouping structure of two components, which was confirmed by the dendogram obtained from cluster analysis.

Mechanochemical extraction of antioxidant phenolic compounds from Mediterranean and medicinal Laurus nobilis: A comparative study with other traditional and green novel techniques

The main objective of this work was to carry out the extraction of antioxidant phenolic compounds from bay leaves (Laurus nobilis L.) through mechanochemical pretreatment (mechanochemical assisted extraction, MCAE). For this purpose, different solid reagents were screened (Na2CO3, BaCO3, Li2CO3, CoCO3, K2CO3 and CaCO3), and the results were compared with other extraction techniques: conventional Soxhlet, ultrasound (UAE) and microwave (MAE). The comparison was carried out based on total dissolved solids (TDS), total phenolic content (TPC) and antioxidant power (AOP). As-obtained extracts were analysed by gas chromatography and gas chromatography-mass spectrometry analysis (GC and GC–MS) to characterize their composition. In conventional Soxhlet extraction different solvents (water, ethanol and methanol) were tested. It was demonstrated that ethanol provided the best results. Mechanochemical processing resulted in comparable TPC (75.54 GAE g−1 extract) to Soxhlet. Therefore, MCAE is a step forward since, for the same TPC as conventional extraction, the total extraction time (mechanochemical pretreatment and extraction in ethanol) is reduced more than 10 times. The main phenolic compounds present in the extracts were identified as eugenol, methyleugenol and elemicin. Although the results obtained by means of UAE and MAE could be better than those of MCAE, the present study proposes the substitution of conventional extraction by mechanochemistry since the same yields were obtained.

Optimization of the extraction of antioxidant phenolic compounds from grape pomace using response surface methodology

The extraction of phenolic compounds with antioxidant activity (AA) of winemaking by-products using response surface methodology and fractional factorial design was investigated. The effects of grape pomace from wine (GWP) and juice production (GJP), temperature, solvent type and time on the extraction of total phenolic compounds (TPC) and AA were evaluated. The TPC and AA varied from 17.91 to 35.10 mg (GAE) g−1 (gallic acid equivalent) and from 65.12 to 149.27 µmol Trolox g−1 of pomace, respectively. For both by-products the optimization suggest that solvent acetone at 60 °C was the best condition. However, the best time for GJP and GWP were 15 min and 45 min, respectively. Gallic acid was the major phenolic compound identified by liquid chromatography in the GJP, followed by coumaric acid, ferulic acid, trans-resveratrol and caffeic acid. The content of anthocyanins for GWP and GJP varied from 640 to 780 mg cyanidin g−1. The responses of the factorial design showed that the GJP had the highest content of TPC and AA when compared to the GWP. Despite superiority of the GJP, these finding supporting the utilization of both grape pomace in food industry due to their high amount of bioactive compounds.

Increasing the Sustainability of the Coffee Agro-Industry: Spent Coffee Grounds as a Source of New Beverages

This work describes a new process for the production of beverages from spent coffee grounds (SCG), as well as the chemical and sensory profiles. The process consisted of the extraction of antioxidant phenolic compounds of SCG, followed by the fermentation of this extract supplemented with sucrose and fermented broth distillation. Thus, two fermented (10.4% and 10.0% of ethanol, by volume) and two distillated (38.1% and 40.2% of ethanol, by volume) beverages were obtained. A total of 45 and 59 volatile compounds (alcohols, esters, aldehydes, terpenes, lactones, pyrazines, norisoprenoids, volatile phenols and acids) identified and quantified by GC-MS characterized the aroma and flavor of the fermented and distilled beverages, respectively. Twenty sensory descriptors define the sensory profile of the two beverages which corroborated the pleasant smell and taste of coffee in the distillate beverage. Therefore, this work demonstrates that the fermented and distilled beverages obtained from spent coffee grounds have acceptable organoleptic qualities that make them suitable for human consumption.

Extraction of Antioxidant Phenolic Compounds from Brewer's Spent Grain: Optimization and Kinetics Modeling.

The kinetics of polyphenol extraction from brewer’s spent grain (BSG), using a batch system, ultrasound assistance, and microwave assistance and the evolution of antioxidant capacity of these extracts over time, were studied. The main parameters of extraction employed in the batch system were evaluated, and, by applying response surface analysis, the following optimal conditions were obtained: Liquid/solid ratio of 30:1 mL/g at 80 °C, using 72% (v/v) ethanol:water as the solvent system. Under these optimized conditions, ultrasound assistance demonstrated the highest extraction rate and equilibrium yield, as well as shortest extraction times, followed by microwave assistance. Among the mathematical models used, Patricelli’s model proved the most suitable for describing the extraction kinetics for each method tested, and is therefore able to predict the response values and estimate the extraction rates and potential maximum yields in each case.

Green Ultrasound-Assisted Extraction of Antioxidant Phenolic Compounds Determined by High Performance Liquid Chromatography from Bilberry (Vaccinium Myrtillus L.) Juice By-products

In this paper, the effect of ultrasound assisted extraction (UAE) combined with stirring and conventional technique of maceration of wild bilberry juice by-products has been studied. Juice by-products were subjected to conventional maceration by stirring, and ultrasound probe using four different ultrasonic intensities (4.4, 9.4, 13.4 and 16.7 W cm− 2). The anthocyanins and flavonol profile of the obtained extracts were studied by HPLC-DAD. UAE resulted in a decrease of monomeric anthocyanins. However, the total phenolic compounds was higher when ultrasound was used and the extracts obtained with this “green” technology were more antioxidants than the extracts obtained by conventional maceration. Lab parameters and absorbances at 420 and 520 nm showed greater recovery of yellow and red compounds when the ultrasonic intensity was higher.

Retraction Statement: Multiple Response Analysis and Optimization of Microwave-Assisted Extraction of Antioxidant Phenolic Compounds of Waste Mangifera indica L Peel

Journal of Food Processing and PreservationVolume 40, Issue 2 p. 348-348 RetractionFree Access Retraction Statement: Multiple Response Analysis and Optimization of Microwave-Assisted Extraction of Antioxidant Phenolic Compounds of Waste Mangifera indica L Peel This article retracts the following: Retracted: Multiple Response Analysis and Optimization of Microwave-Assisted Extraction of Antioxidant Phenolic Compounds of Waste Mangifera indica L Peel J. Prakash Maran, K. Swathi, P. Jeevitha, J. Jayalakshmi, G. Ashvini, Volume 39Issue 6Journal of Food Processing and Preservation pages: 2276-2285 First Published online: March 25, 2015 First published: 29 March 2016 https://doi.org/10.1111/jfpp.12900AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract “MULTIPLE RESPONSE ANALYSIS AND OPTIMIZATION OF MICROWAVE-ASSISTED EXTRACTION OF ANTIOXIDANT PHENOLIC COMPOUNDS OF WASTE MANGIFERA INDICA L PEEL” by PRAKASH MARAN, J., SWATHI, K., JEEVITHA, P., JAYALAKSHMI, J. and ASHVINI, G. doi: 10.1111/jfpp.12473 The above article, published online on 25 March 2015 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editors in Chief, Charles Brennan and Brijesh K. Tiwari, and Wiley Periodicals, Inc. The retraction has been agreed due to evidence indicating that the peer review of this paper was compromised. It is believed that the paper was accepted based on recommendations from reviewers not suitably qualified. Reference Prakash Maran, J., Swathi, K., Jeevitha, P., Jayalakshmi, J. and Ashvini, G. 2015. Multiple response analysis and optimization of microwave-assisted extraction of antioxidant phenolic compounds of waste Mangifera indica L peel. J. Food Process. Preserv. 39, 2276– 2285. doi: 10.1111/jfpp.12473. Volume40, Issue2April 2016Pages 348-348 RelatedInformation

Optimized extraction of polyphenolic antioxidant compounds from Brazil nut (Bertholletia excelsa) cake and evaluation of the polyphenol profile by HPLC.

The solid residue (cake) of pressed Brazil nut oil has high energy value and contains high levels of nutrients and bioactive compounds, such as polyphenols. However, little is known about these components in this by-product. Extraction is the first step in investigating the phenolic compounds in Brazil nut cake because extraction conditions might impact the yields of phenolic compounds and antioxidant capacity. The aim of this study was to select the best phenolic compound extraction conditions for Brazil nut cake by using factorial experimental design and to characterize the phenolic compounds in the extract. The optimal extraction of antioxidant phenolic compounds from Brazil nut cake was achieved under the following conditions: ethanol-water (40:60; v/v); 2.5 min homogenization; and 1 h extraction at 60 °C. The phenolic compound profile of the Brazil nut cake extract using the optimized extraction was determined by high-performance liquid chromatography with photodiode array detection. Six phenolic acids (gallic acid, protocatechuic acid, 2,4-dihydroxybenzoic acid, p-hydroxybenzoic acid, p-coumaric acid and sinapic acid) and one flavonoid ((+)-catechin) were identified, and the contents of the phenolic compounds varied from 70.0 to 421 mg kg(-1) . Knowledge of the potential bioactivity of Brazil nut cake identified in the present study might promote its use in the food industry. © 2015 Society of Chemical Industry.

Retracted: Multiple Response Analysis and Optimization of Microwave-Assisted Extraction of Antioxidant Phenolic Compounds of Waste M angifera indica L Peel

The above article, published online on 25 March 2015 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editors in Chief, Charles Brennan and Brijesh K. Tiwari, and Wiley Periodicals, Inc. The retraction has been agreed due to evidence indicating that the peer review of this paper was compromised. It is believed that the paper was accepted based on recommendations from reviewers not suitably qualified. Reference Prakash Maran, J., Swathi, K., Jeevitha, P., Jayalakshmi, J. and Ashvini, G. 2015. Multiple response analysis and optimization of microwave-assisted extraction of antioxidant phenolic compounds of waste Mangifera indica L peel. J. Food Process. Preserv. 39, 2276– 2285. doi: 10.1111/jfpp.12473.

Subcritical water extraction of antioxidant phenolic compounds from XiLan olive fruit dreg.

Olive fruit dreg (OFD), waste from olive softdrink processing, has caused disposal problems. Nevertheless, OFD is a good source of functional ingredients, such as phenolic compounds. This study investigated the extraction conditions of phenolic compounds from OFD by using subcritical water (SCW) extraction method, antioxidant activity of SCW extracts, and components of phenolic compounds by LC-MS. SCW extraction experiments were performed in a batch stainless steel reactor at temperatures ranging from 100 to 180°C at residence time of 5 to 60min, and at solid-to-liquid ratio of 1:20 to 1:60. Higher recoveries of phenolic compounds [37.52 ± 0.87mg gallic acid equivalents (GAE)/g, dry weight (DW)] were obtained at 160°C, solid-to-liquid ratio of 1:50, and extract time of 30min than at 2h extraction with methanol (1.21 ± 0.16mg GAE/g DW), ethanol (0.24 ± 0.07mg GAE/g DW), and acetone (0.34 ± 0.01mg GAE/g DW). The antioxidant activities of the SCW extracts were significantly stronger than those in methanol extracts at the same concentration of total phenolic contents. LC-MS analysis results indicated that SCW extracts contained higher amounts of phenolic compounds, such as chlorogenic acid, homovanillic acid, gallic acid, hydroxytyrosol, quercetin, and syringic acid. SCW at 160°C, 30min, and solid-to-liquid ratio of 1:50 may be a good substitute of organic solvents, such as methanol, ethanol, and acetone to recover phenolic compounds from OFD.

Assessment of (poly)phenols in grape (Vitis vinifera L.) stems by using food/pharma industry compatible solvents and Response Surface Methodology

A Box–Behnken design of Response Surface Methodology (RSM) was conducted to analyse the effect of time (10–30min), temperature (25–95°C), and solvents concentration (5–90%) on the extraction of total phenolics, flavonoids, ortho-diphenols, and anthocyanins as well as to assess the ABTS+ scavenging capacity, which were considered as response variables. Values coefficients of determination (R2), ranging from 0.903 to 0.996, fitted for describing efficient extraction of bioactive (poly)phenols and antioxidant activity. The recorded data allowed to establish the optimal extraction conditions at 23.0min, 95.0°C, and 57.9% of food-quality ethanol/water for Vitis vinifera L. var. ‘Viosinho’ (white variety), and 23.4min, 84.2°C, and 63.8% for var. ‘Touriga Nacional’ (red variety). The achievement of optimal extraction conditions of phenolics from grape stems using solvents compatible with further uses in food/pharma industries demonstrated that RSM constitutes a powerful tool for deriving optimal conditions for extraction of antioxidant phenolic compounds from grape stems.

MICROWAVE-ASSISTED EXTRACTION OF PHENOLIC ANTIOXIDANTS FROM SEMIARID PLANTS

Microwave-Assisted Extraction (MAE) kinetic in three temperatures was investigated for extraction of antioxidant phenolic compounds from Jatropha dioica , Flourensia cernua , Eucalyptus camaldulensis and Turnera diffusa which are plants of semiarid regions of Mexico. The two-site kinetic model and saturation simple equation were used to describe the experimental data. The fit of the data demonstrated that sat uration simple equation was better and could explain the da ta with a slight loss of goodness of fit. The resul ts showed that MAE optimum conditions were extraction temperature of 60°C and extraction time in the rang e from 1 to 6 min. The MAE was more efficient than the conventional Heat Reflux Extraction (HRE). Maximal antioxidant potential was observed in E. camaldulensis extracts. Interestingly differences in phenolic composition and antioxidant activity were observed in the extracts obtained by MAE and HRE for all plants used. Quercetin and catechin were found to be the predominant phenolic compounds. The MAE procedure resulted in suitable alternative to obtai n bioactive phenolic compounds from semiarid plants due to this technology is higher efficient than convent ional methods increasing yield in shorter times.

Selection of the Solvent and Extraction Conditions for Maximum Recovery of Antioxidant Phenolic Compounds from Coffee Silverskin

The extraction of antioxidant phenolic compounds from coffee silverskin (CS) was studied. Firstly, the effect of different solvents (methanol, ethanol, acetone, and distilled water) on the production of antioxidant extracts was evaluated. All the extracts showed antioxidant activity (FRAP and DPPH assays), but those obtained with methanol and ethanol had significantly higher (p < 0.05) DPPH inhibition than the remaining ones. Due to the lower toxicity, ethanol was selected as extraction solvent, and further experiments were performed in order to define the solvent concentration, solvent/solid ratio, and time to maximize the extraction results. The best condition to produce an extract with high content of phenolic compounds (13 mg gallic acid equivalents/g CS) and antioxidant activity [DPPH = 18.24 μmol Trolox equivalents/g CS and FRAP = 0.83 mmol Fe(II)/g CS] was achieved when using 60 % ethanol in a ratio of 35 ml/g CS, during 30 min at 60–65 °C.