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Extraction of Antioxidant Compounds From Different Varieties of Mangifera Indica Leaves Using Green Technologies

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J. of Supercritical Fluids 72 (2012) 168–175 Contents lists available at SciVerse ScienceDirect The Journal of Supercritical Fluids j our nal homepage: www. el sevi er . com/ l ocat e/ supf l u Extraction of antioxidant compounds from different varieties of Mangifera indica leaves using green technologies M a Teresa Fernández-Ponce ∗ , Lourdes Casas, Casimiro Mantell, Miguel Rodríguez, Enrique Martínez de la Ossa Department of Chemical Engineering and Food Technology,
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   J.ofSupercriticalFluids 72 (2012) 168–175 ContentslistsavailableatSciVerseScienceDirect The    Journal   of    Supercritical   Fluids  journalhomepage:www.elsevier.com/locate/supflu Extraction   of    antioxidant   compounds   from   different   varieties   of    Mangifera   indica leaves   using   green   technologies M a Teresa   Fernández-Ponce ∗ ,   Lourdes   Casas,   Casimiro   Mantell,   Miguel   Rodríguez,Enrique   Martínez   de   la   Ossa DepartmentofChemicalEngineeringandFoodTechnology,ScienceFaculty,UniversityofCádizInternationalAgri-foodCampusofExcellence,ceiA3,P.O.   Box40,PuertoReal11510,Cádiz,Spain a   r   t   i   c   l   e   i   n   f   o  Articlehistory: Received15May   2012Receivedinrevisedform25July2012Accepted26July2012 Keywords: MangoleavesSupercriticalFluidExtractionSubcriticalWaterExtractionCo-solventsMangiferinQuercetinAntioxidantactivity a   b   s   t   r   a   c   t Supercritical   Fluid   Extraction   (SFE)   andSubcritical   Water   Extraction   (SWE)   from   mango   leaves   wereapplied   in   order   to   obtain   extracts   with   high   phenolic   content   and   potent   antioxidant   activity.   Theeffects   of    extraction   conditions   onsub-   and   supercritical   CO 2  extraction   were   analyzed:   temperature(35   and   55 ◦ C),   pressure   (10   and   40   MPa),   percentage   of    co-solvent   (0and   20%)   and   type   of    co-solvent(methanol/ethanol).   The   best   condition   (CO 2  +   20%   of    ethanol   at   10MPa,   55 ◦ C,   20   g/min   and   3h)was   com-pared   with   SWE   (4   MPa,   100 ◦ C,   10g/min,   and   3   h)   using   seven   mango   cultivars.   SWE   wasmore   efficientthan   subcritical   CO 2  +   ethanol.   The   antioxidant   activity   was   evaluated   byDPPH   assay,   and   the   quantifi-cation   of    the   main   polyphenols   of    mango   leaves   byHPLC   analysis.   SWE   showed   global   yields   up   to   35%for   Kent   variety,   and   extracts   with   antioxidant   activities   superior   to   (+)-  -tocopherol   related   with   theirhighcontent   on   the   polyphenols   mangiferin   and   quercetin. © 2012 Elsevier B.V. All rights reserved. 1.Introduction Thechallengesofthiscenturybasedonasustainableandmorefriendlyenvironmentdevelopmenthaveturnedthevisionofchemicalproductiontowardanewindustryconceptofbiomassrefininginordertodecreaserapidconsumptionofnon-renewableresources(petroleum,naturalgas,coal,andminerals).Inthebegin-ning,atypicalbiorefineryconvertessentiallynaturalrenewablematterintobio-energyproducts.However,inthenextgenerationbiorefinery,thefeedstockwillbefractionatedfurtherintovaluablecomponentsbyextraction,fermentationandcontrolledpyrolysis,aswellasbymoretraditionalmethods.Oneofthefirststagesinthenewbiorefineryistheextractionofsecondarymetabolitesfromlowvaluebiomassconsideringthattheyareofgreatervalueincosmetic,nutraceuticalandpharmaceu-ticalindustries.Theuseofharmlessextractionmethodsisessentialtocomplywithandenvironmentalcompatibleandsustainablechemicalproduction[1–3].SupercriticalFluidExtraction(SFE)andSubcriticalWaterExtraction(SWE)areinterestingalternativessopresentsev-eraladvantagesincludingtheuseofgreensolvents,fasterandmoreselectiveprocesses,andthelowdegradationofchemical ∗ Correspondingauthor.Tel.:+34956016579;fax:+34956016411. E-mailaddress: teresafernandez.ponce@uca.es(M.T.Fernández-Ponce). compounds[4–8].Bothtechniqueshavebeenwidelyexploredin recentyearsinordertorecoverbioactivecompoundsfromdiverseplantsandagri-industrialby-products[4–22].Agriculturalby-productsofmango,particularlyleavesandbark,presentahighcontentonpotentphenoliccompounds,mainlymangiferinandquercetin,whosepharmaceuticalsandnutraceu-ticspropertieshavebeendemonstratedinseveralstudies[23–30].Mangoisoneofthemostimportanttropicalfruitworldwidewithaglobalproductionsuperiorto38milliontonesandanareaharvestedsuperiorto5millionhectaresin2010[31].Annu- allypruningactivitygeneratesconsiderablequantitiesofresidueswhichareusuallyburnedorusedforsoilamelioration.Thus,con-versionofpruningmangoresiduesintovaluablechemicalproductsbyefficientandlowimpactextractiontechniquesresultsclearlyattractivewithintheconceptofbiorefinery.Theextractionfrommangoby-productsusingSC-CO 2  orsub-criticalwaterhasnotbeenwidelystudied.Traditionalsolventextractiontechniquesarestillusuallyusedtorecoverbioactivecompoundsfrommango[23,25–30]despitethedrawbackspresent inthesetechniques[8,11–13,16,18].MangoleavesextractswithantioxidantactivityhavebeenobtainedbySC-CO 2  extraction[32],butpureCO 2 ,anonpolarsol-vent,providealowefficiencytoextracthighlyorslightlypolarcompounds.Thus,theadditionofCO 2  modifierssuchasalcoholco-solventsshouldincreasetheextractionofpolarpolyphenolsandalsoimprovetheantioxidantactivityofextracts,asdescribedby 0896-8446/$–seefrontmatter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.supflu.2012.07.016  M.T.Fernández-Ponceetal./J.ofSupercriticalFluids 72 (2012) 168–175 169 Fig.1. Schematicdiagramofthehighpressureequipment. otherauthorsusingdifferentnaturalmatters[7,8,10–15,18].   Ontheotherhand,althoughSWE   isefficienttoextractpolarcom-pounds,thistechniquehasnotbeenevaluatedbeforeusingthisrawmaterial.Therefore,inthisworkSub-andSupercriticalFluidExtrac-tionfrommangoleavesusingpureCO 2  andCO 2  plusco-solventsatdifferentconditionswasstudiedandcomparedwithSWE.Extractswereevaluatedconsideringtheglobalextractionyield,theantioxidantactivityandthephenoliccomposition.Inaddition,theperformanceofsevenvarietiesofmangoleaveswas   analyzedusingCO 2  plusco-solventsandSWE. 2.Materialsandmethods  2.1.Materials Thesevenvarietiesof  Mangiferaindica L.leavesstudied(Kens-ington,Kent,Keitt,Tommy   Atkins,Osteen,AtaulfoandLangra)wereprovidedby“EstaciónExperimentalLaMayora”,SuperiorCentreof ScientificResearch(CSIC),Málaga,Spain.TheleaveswerecollectedinJune2010andFebruary2011.Allleavesweredriedatroomtem-peratureuntilconstantweightandkeptfrozenintheabsenceof light.Carbondioxide(99.995%)wasprovidedbyAbello-LindeS.A.(Barcelona,Spain).2,2-Diphenyl-1-picrylhydrazyl,freeradical(DPPH),mangiferin(1,3,6,7-tetrahydroxyxanthoneC2-  - d -glucoside),quercetin3-  - d -glucoside,purity ≥ 90%HPLCgrade(3,3  ,4  ,5,7-pentahydroxyflavone3-  - d -glucoside),and(+)-  -tocopherolwereprovidedbySigma–Aldrich(Steinheim,Germany).Theorganicsolventsethanol,methanolandaceticacid,allHPLCgradientgrade,wereprovidedbyPanreac(Barcelona,Spain).Thewaterusedinallexperimentswasdouble-distilledmilliQgrade.  2.2.Extractionprocedurewithsolventsathighpressures ExtractiontestswerecarriedoutinahighpressureapparatussuppliedbyTharTechnology(Pittsburgh,PA,USA,modelSF100).AschematicdiagramoftheequipmentusedinthisworkisshowninFig.1.Thisset-upincludedanextractionvessel(capacityof100mL)withathermostaticjackettocontroltheextractiontemperature,twopumpswithamaximumflowrateof50g/min(oneforcar-bondioxideandtheotherforco-solvent),abackpressurevalveregulatortocontrolthesystempressure,andacyclonicseparatortoallowperiodicdischargeoftheextractedmaterialduringtheextractionprocess.Forallteststheextractionvesselwasloadedwithapproximately15gofsample.Extractswererecoveredinacyclonicseparatorandthencollectedinglassbottlesandstoredintheextractionsolventindarknessat − 20 ◦ Cpriortoassay.Theglobalyield(  X  0 )forallextractionmethodwascalculatedconsider-ingtheratiobetweenmassofextractandmassofdryrawmaterial.ApreliminarystudywasconductedinordertoimprovetheyieldandantioxidantactivityoftheextractsobtainedusingCO 2  andCO 2 plusco-solvents.Theeffectsofdifferentvariablesontheextrac-tionprocesswereanalyzedbyconsideringthefollowingoperatingconditions:pressuresof10and40MPa,temperaturesof35and55 ◦ C,co-solventpercentagesof0and20%andtypeofco-solvent,methanolandethanol.AlltestswerecarriedoutwithaCO 2  flowrateof20g/minandanextractiontimeof3h.ResultswerecomparedwithSWE.Thistechniqueislessdepend-entonpressureandhighlydependentontemperature[19,20].However,itisimportanttoconsiderthatthetemperaturesabove100 ◦ Ccouldgenerateunwantedoxidativeprocesses[22],thusSWE testswerecarriedoutat100 ◦ C,4MPa,aflowrateof10g/minand3h.ForthispreliminarystudymangoleavesofthevarietyOsteenwereusedasrawmaterialsoitisthevarietywidelycultivatedintheregionofMálaga,Spain.  2.3.AntioxidantactivityassaywithDPPH  Antioxidantactivityofextractsandstandardcompounds((+)-  -tocopherol,mangiferinandquercetin3-  - d -glucoside)wasdeterminedby2,2-diphenyl-1-picrylhydrazylradical(DPPH)assay.Themethodemployedwas   designedhavinginaccountthemeth-odsdescribedbyBrand-WilliamsandSchererandGodoy[33,34].About0.1mL    aliquotsofmethanolicsolutionsofthesamplesorstandardsatdifferentconcentrationswereeachaddedto3.9mL ofa6 × 10 − 5 mol/LDPPHmethanolicsolution.Theabsorbanceof DPPHwasmonitoredspectrophotometricallyat515nmat0minandevery2minuntilthereactionreachedthesteadystate.TheDPPHconcentration( C  DPPH )inthereactionmediumwas   calculatedfromacalibrationcurvedeterminedbylinearregressionwithEq.(1):Abs = 12 ,   709 · C  DPPH + 0 . 002(1)ThepercentageofDPPHremainingwas   calculatedasdescribedinEq.(2)%DPPH   remaining = C  DPPH t  C  DPPH 0 × 100(2)TheEC 50  (efficientconcentrationproviding50%inhibition)wascalculatedgraphicallyusinganon-linearfittingcurvebyplottingthesampleconcentrationvs.the%DPPHremainingonsteadystate.TheantioxidantactivitywasexpressedastheAntioxidantActivityIndex(AAI)whichwas   calculatedconsideringthefinalconcentra-tionofDPPHandtheEC 50  ofthetestedcompoundinthereactionasfollows(Eq.(3)):AAI = finalconcentrationofDPPH (  g/mL)EC 50  (  g/mL) (3)ThefinalconcentrationofDPPHwascalculatedrespecttotheconcentrationofDPPHinthereactionmedium.PlantextractsshowedpoorantioxidantactivitywhenAAI<0.5,moderateantiox-idantactivitywhenAAIisbetween0.5and1.0,strongantioxidantactivitywhenAAIisbetween1.0and2.0,andverystrongwhenAAI>2.0[34].Theassayswerecarriedoutintriplicate.Results werecomparedwithstandardsof(+)-  -tocopherol,mangiferinandquercetin3-  - d -glucoside.  2.4.IdentificationandquantificationofphenoliccompoundsbyHPLC  SeparationofphenoliccompoundswasperformedusinganAgi-lentHPLCseries1100system(Agilent,Germany)equippedwitha  170  M.T.Fernández-Ponceetal./J.ofSupercriticalFluids 72 (2012) 168–175 quaternarypump,anautosampler,a250mm   × 4.6mmi.d.,5  m,C18reversed-phasecolumn(ThermoElectronCorporation)andaUV/visdetector,connectedtoaHPChemStation ® software.ThemethodusedisamodificationofthemethoddescribedbyBarretoetal.[23].Thesolventsthatconstitutedthemobilephase wereA(aceticacid–water,2:98,v/v)andB(methanol).Theelutionconditionsappliedwere:0–2min,5%Bisocratic;2–7min,lineargradient5–25%B;7–11min,25%Bisocratic;11–19min,lineargradient25–32%B;19–27min,32%Bisocratic;27–28min,lineargradient32–40%B;28–38min,40%Bisocraticandfinally,washingandreconditioningstepsofthecolumnwereincluded(38–50min,lineargradient40–100%B;50–60min,100%Bisocratic;60–70min,lineargradient100–5%B;and5min,5%Bisocratic).Theflow-ratewas0.9ml/minandtheinjectionvolumewas50  L.Thesystemwasoperatedatroomtemperature.Phenoliccompoundsweredetectedat340nmbyitsretentiontimesandquantifiedusingacalibrationcurveofthecorre-spondingstandardcompounds.Thecalibrationcurveofthemainpolyphenolsofmangoleaves,mangiferin(Eq.(4))   andquercetin3-  - d -glucoside(Eq.(5)),wasasfollows:  A = 54 ,   252 · C  − 100 . 12(4)  A = 87 ,   077 · C  − 130 . 11(5)where  A istheareaexpressedinmAu   and C  istheconcentrationexpressedin  g/ml.Thecorrelationcoefficient( R 2 )was0.9999forbothcalibrationcurves.Theexperimentsoneachextractionwerecarriedoutintriplicateinordertoevaluatethevariabilityofthemeasurements.HPLCchromatogramsoftheextractsobtainedfortwovarietiesstudiedareshowninFig.5.  2.5.Experimentaldesign Amultilevelfactorialdesignwascarriedoutinordertodeterminetheeffectoftemperatureandpressure(experimentalvariables)ontheyieldoftheprocesswhenCO 2 +20%ofethanolisusedassolventsystem,accordinglyethanolwasselectedasthebestCO 2 modifier.Therangesforthefactorialdesignwere35–55 ◦ Cfortemperature,and10–40MPa   forpressure.Then,theextrac-tionprocesswasanalyzedthroughafactorialexperimentaldesignusing2 2 +2centralpointswheretemperatureandpressurewereadjusted.Onthebasisofthisdesignatotalof6experimentswerecarriedoutinasingleblock.Theresponsevariablewastheextrac-tionyieldexpressedasg/100gofdrymatter.TheexperimentaldatawereanalyzedbyStatgraphicsPlus5.1 ® (1994–2001,Statisti-calGraphicsCorp.).Empiricalcorrelationsweredevelopedinordertopredicttheinfluenceofextractionconditionsontheextractionyieldoftheprocessstudied.  2.6.Evaluationofdifferentmangoleavescultivars MangoisanIndiannativefruitthatoccupiesthethirdpositioninworldwideproductionandimportationoftropicalfruits.Thecul-tivarsusedinthepresentworkwereselectedaccordingtotheirimportanceworldwide.TheFloridacultivarsTommyAtkins,KentandKeittarethemainlycurrentcommercialvarietiesproducedandexportedbymostcountries,includingleadingexportersasMexico,Pakistan,Brazil,PeruandEcuador.Ataulfoisotherimportantcul-tivarofMexico,whichistooappreciatedinNorthAmerica.OsteenistheessentialcultivarofSpainproduction.LangraisanimportantcommercialmangovarietyofnorthIndiawithgoodqualityfruits.Finally,KensingtonisthedominantvarietygrowninAustraliawellreceivedinoverseasmarkets[35,36].Theperformanceofthe M.   indica L.varietiesabovementioned(Kensington,Kent,Keitt,Tommy   Atkins,Osteen,AtaulfoandLan-gra)wasevaluatedusingthebestconditionsobtainedinthe Fig.2. Globalyield(A)andantioxidantactivity(B)ofmangoleavesextractsofthevarietyOsteenobtainedusingSC-CO 2 ,CO 2  +20%methanolandCO 2  +20%ethanol. preliminarystudywithOsteenvariety:CO 2 +20%(w/w)   ofethanolat10MPa,55 ◦ C,20g/minand3h,andalsousingsubcriticalwaterat100 ◦ C,4MPa,aflowrateof10g/min,andanextractiontimeof 3h.Cultivarswereevaluatedaccordinglytotheglobalextractionyield,antioxidantactivityandphenolicprofile. 3.Resultsanddiscussion  3.1.SupercriticalFluidExtractionwithpureCO  2 OneoftheadvantagesofSFEisCO 2  solvatingpowercanbemanipulatedbychangingpressure( P  )and/ortemperature( T  );therefore,knowingtheinfluenceofextractionconditionsontheprocessisnecessarytoobtainhighextractionyields.SC-CO 2 extrac-tionyieldsobtainedatdifferentconditionsof  P  and/or T  frommangoleavesofthevarietyOsteenareshowninFig.2A.Globalyields obtainedwithpureCO 2  wereunsatisfactoryandevenchangesintheextractionconditionsledtonegligibleimprovements.Thehigh-estyieldwas   1.22 ± 0.13%obtainedat40MPa   and55 ◦ C.TheeffectofpressureonSC-CO 2  extractionfrommangoleaveswaspositiveforbothtemperaturesstudied.ThisbehaviorcanbeexplainedbytheincreaseindensitywithpressureresultingingreatersolvatingpowerofCO 2  [16,17].Moreover,highpressurescausedisruptionsinplantcellsandallowcompoundstobemoreavailable,therebyfavoringtheextractionyield[37].Abouttheeffectoftemperature,itismorecomplexbecauseitdependsontwo   factors.ThedensityofCO 2  decreaseswithtem-perature,reducingthesolvatingpower,whilethesolutevaporpressureincreasesfavoringthesolubilityonSC-CO 2 .Thus,depend-ingontheoperatingconditions,onefactorisdominantovertheother[16,17].Inthisway,atlowpressures(10MPa)theeffect onthedensitywas   predominant,sohighextractionyieldswereobtainedonreducingtemperature.But,athighpressures(40MPa)  M.T.Fernández-Ponceetal./J.ofSupercriticalFluids 72 (2012) 168–175 171  Table   1 ExtractionyieldsofphenoliccompoundsobtainedfrommangoleavesofthevarietyOsteen,expressedasmg/100gdryleaves.ExtractionmethodConditionsYieldofphenoliccompounds a (mg/100gdryleaves)Mangiferin R t  =20.9minQuercetin3-  - d -glucoside R t  =34.4minSC-CO 2  100–400bar35–55 ◦ C n.d. b n.d.CO 2  +20%methanol100bar35 ◦ C7.8 ± 0.16.1 ± 0.155 ◦ C93.9 ± 0.188.7 ± 1.0400bar35 ◦ C7.8 ± 0.66.4 ± 0.155 ◦ C12.9 ± 0.315.3 ± 0.1CO 2  +20%ethanol100bar35 ◦ C191.8 ± 0.3140.9 ± 1.255 ◦ C184.5 ± 0.4 231.4 ± 3.3400   bar 35 ◦ C62.6 ± 0.2 55.4 ± 0.155 ◦ C40.6 ± 0.049.7 ± 0.4Subcriticalwater 40bar100 ◦ C1365.9 ± 1.2409.5 ± 6.7 a Yieldofphenoliccompoundsexpressedasmg/100gdrymatterwas   representedasthemeanvalue ± standarddeviations. b n.d.:compoundnotdetected. theeffectofvaporpressurewasdominantandthehighvolatilityofthesolutesresultedinanoverallincreaseintheextractionyield.Inspiteoftheincreaseontheglobalyieldathighpressureandhightemperature,SC-CO 2  wasnotefficientenoughtoobtainhighyieldsfrommangoleaves.Thiscanbeattributingtothehighcontentonpolarphenoliccompoundsofmangoleaves[23,24],poorlysolubleinSC-CO 2 ,anonpolarsolvent[10–14,38].   Themainpolyphenolsofmangoleavesaremangiferinandquercetin3-  - d -glucosideknownbytheirpotentantioxidantproperties[24,26–30].Table1showstheextractionyieldsofbothcompoundsobtainedbyHPLCforthedifferentextractiontechniquesexplored,andFig.2BshowstheantioxidantactivityofextractsobtainedwithSC-CO 2 .Mangiferinandquercetin3-  - d -glucosidewerenotdetectedbyHPLConSC-CO 2  extracts.Bothpolyphenolsareslightlypolarcom-poundshenceSC-CO 2  isnotefficienttoextractthem[38].Asa result,theantioxidantactivityofSC-CO 2  extractswas   poortoo.AnyantioxidantactivitywasobservedfortheextractsobtainedwithSC-CO 2  atlowpressures(10MPa),andraisingthepressureto40MPadidnotleadtoanincreaseinthisactivity.Consequently,pureCO 2 resultedinappropriatetoobtainextractsfrommangoleaves.  3.2.SubcriticalFluidExtractionwithCO  2  plusco-solvents GiventhelowcapacityofSC-CO 2  toextractantioxidantcom-poundsfrommangoleaves,theadditionofco-solventswasnecessarytoimprovethequalityofextracts.Thesolubilityof polarsubstances,suchaspolyphenols,inSC-CO 2  isverylow[10–14,38–40],howevertheuseoforganicco-solventsincreasesthesolventpowerofCO 2  andtheextractionyield[7,18,38–40].Amongallthemodifiersincludingmethanol,ethanol,acetoni-trile,acetone,water,ethyletheranddichloromethane,methanolandethanolaremostfrequentlyusedforSFEofpolyphenols.Alco-holco-solventsinducedipole/dipoleinteractionsandhydrogenbondingwithpolarfunctionalgroups,andalsotheycanbreakpolarinteractionssolute–matrixincreasingthesolubilityofpolarsolutes[18,40].Methanoliscommonlyusedasco-solventbecauseitismisci-bleupto20%withCO 2  andsomepublicationshaveshownthatthisismoreefficientthanethanoltoremovepolyphenols[40,41],butthetemperaturenecessarytoreachthesupercriticalstateishigherandcouldbenotsuitablefornaturalproducts[18].About ethanol,itsignificantlyenhancedtheextractionofflavonoids[18]andmay   beabetterchoiceconsideringitasnon-toxicandcanbeusedinnutraceuticalorcosmeticapplications[39].Withthisin mind,ethanolandmethanolwereusedasCO 2  modifiersinthiswork.Theextractionswithco-solventswerecarriedoutusing20%ofmethanol/ethanol.Attheconditionsofpressureandtempera-turetested,themixturesofCO 2 +co-solventarebelowtheircriticalpointbecausehighconcentrationsofCO 2  modifiersincreasethecriticalpointofthemixture[7,39].Thesesystemscalledenhancedfluidityliquidshaveresultedmoreefficienttoextractpolarcompoundsthanmixtureswithlowerconcentrationsofco-solvents.Forexample,otherauthorsreportedthat20%ofco-solventsduplicatetheextractionyieldsofanthocyaninsfromredgrapepomaceinsteadusingonly5%of co-solvents[7].   Adiletal.[39]showedthattheoptimumethanol concentrationsforCO 2  extractionofpolyphenolsfromappleandpeachpomacewerefoundtobe20%.ThereasonforthisisbasedonthefactthatthesolvatingpowerofCO 2  andthesolubilityofpolarcompoundsinCO 2  increasewithincreasingtheamountofco-solventconcentrationfrom5to30%,duetoaugmentedphenol–alcoholinteractionsthatfacilitatetheextractionofthesolute[7,38,39].TheglobalextractionyieldsandantioxidantactivityofextractsobtainedwithbothsolventsystemsareshowninFig.2.Comparing theyieldobtainedusingSC-CO 2  andthemixturesofCO 2 +20%of co-solvents(Fig.2A),itisclearthattheadditionofmethanolor ethanolallowedhigherextractionyieldsthanthoseobtainedwithpureCO 2  atallconditionstested.Theinfluenceof  P  and/or T  ontheextractionprocessusingsub-criticalmixturesofCO 2  plusco-solventsresulteddifferentthanthatobservedwithpureCO 2 .Abouttemperature,theglobalyieldsincreasewithtemperaturewhenextractionswerecarriedoutat10MPa.Thispositiveeffectoftemperatureisrelatedwiththeincreaseinthediffusivityanddecreaseintheviscosityofthesolventimprovingthemasstransferpropertiesalongwiththeintensificationofsolutevolatilityfavoringtheextraction.However,at40MPa   theeffectoftemperatureontheextractionprocessfrommangoleaveswasnotrelevantusingco-solvents.Inrelationtothepressure,atlowtemperatures(35 ◦ C),pres-surehadapositiveeffectontheextractionyieldsusingbothco-solvents.Bycontrast,athightemperatures(55 ◦ C)amarkedincreaseintheextractionyieldwasobservedwhenpressurewasdecreasedfrom40to10MPa,showinganegativeeffect.Lowpressuresenhancedtheextractionofpolyphenolsresultinginextractswithhighercontentonmangiferinandquercetinandthusbetterantioxidantcapacity.Thehigherextractionyieldsforbothco-solvents(methanolandethanol)wereobtainedat10MPa   and55 ◦ C(6.53 ± 0.83and6.37 ± 0.13%,respectively).ThenegativeeffectofpressureontheextractionprocessusingCO 2 +20%ofco-solventwas   alsoobservedforthephenolic

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Jul 29, 2017
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