Benzophenone Suppression of Quercetin Antioxidant Activity towards Lipids under UV-B Irradiation...

Hindawi Publishing CorporationJournal of ChemistryVolume 2013 Article ID 761675 9 pageshttpdxdoiorg1011552013761675

Research ArticleBenzophenone Suppression of Quercetin AntioxidantActivity towards Lipids under UV-B Irradiation RegimeDetection by HPLC Chromatography

Jelena S StanojeviT Dejan Z MarkoviT and Jelena B ZvezdanoviT

Faculty of Technology University of Nis 124 Bulevar Oslobodjenja 16000 Leskovac Serbia

Correspondence should be addressed to Dejan Z Markovic dejan markovic57yahoocom

Received 4 June 2013 Revised 8 August 2013 Accepted 26 August 2013

Academic Editor Wieslaw Wiczkowski

Copyright copy 2013 Jelena S Stanojevic et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Quercetin a well-known flavonoid antioxidant has been employed to control benzophenone-sensitized peroxidation of the lipidmixture in methanol solution induced by continuous UV-B irradiation Surprisingly the detected quercetin antioxidant activitywas almost negligible The presented data suggests that the reason is not in its own UV-B-induced degradation but rather inits interrelationship with benzophenone during UV-B stress On the other side of this relationship benzophenone anticipatedsensitizing role towards lipids that is the initiation of lipid peroxidation has been affected as well These results obtained byHPLC chromatography partly confirm but partly relativize to some extent recent results obtained with the same system byspectrophotometric method

1 Introduction

It has already been widely recognized that UV-B radiationthe most damaging part of total natural sunlight spectrum(280ndash320 nm) induces events which affect some crucialbiologically important processes of global importance suchas DNA replication [1 2] or photosynthesis [3 4] It hasalso been especially recognized as one of the major agents toinitiate a lot of harmful free radicals-mediated processes suchas lipid peroxidation (LP) Lipid peroxidation is a free radicalchain reaction (Type I) or it occurs through a nonradicalpathway (Type II) by direct reaction with singlet oxygencreated in the presence of a photosensitizer [5ndash9]

In a form of chain reaction lipid peroxidation consists ofan initiation step (leading to formation of lipid radicalsmdashL∙)a propagation step (where lipid radicals react with oxygento form lipid peroxy radicalsmdashLOO∙) and a terminationstep (formation of dienes type lipid hydroperoxidesmdashLOOH)[8 10] Lipid peroxidation initiators belong to reactive oxygenspecies (ROS) like hydroxy radicals (OH∙) or peroxy radicals(ROO∙) They can be created through different pathwaysincluding variety of external stresses [8] implying very

commonly an external radiation [10ndash12] in case of UV-irradiation LPmay include a special type of LP initiators pho-tosensitizers such as benzophenone (BZP) in very differentmedia [13ndash15]

Photochemical reactions of benzophenone (BZPmdashFigure 1) including H-abstraction by its long-lived tripletstate [13ndash15] have been relatively long-known in organicphotochemistry The related mechanisms are very complexand depend on particular solvent [16ndash18] or on particularBZP interactive compound in the given solvent [19 20]Upon the absorption of UV-light benzophenone may reachits long-lived triplet state (3BZP) very reactive toward itssurroundings (eg phospholipids mixture and quercetin)including a direct reaction with lipids this interaction resultsin the production of lipid radicals (L∙) (1) which is theinitiation step of lipid peroxidation (LP) chain reaction [21]as follows

3BZP+ LH 997888rarr BZPH + L∙ (1)

(3BZPmdashtriplet state of benzophenone BZPHmdashBZP-ketyl radical LHmdashunsaturated lipid L∙mdashlipid radical)

2 Journal of Chemistry

OH

OH

OH

OH

O O

OHO

Figure 1 Structures of quercetin (left) and benzophenone (right)

On the other hand lipid peroxidation is mostly con-trolled by antioxidants action in vivo Many biomolecules(and classes of biomolecules) serve as antioxidants includ-ing flavonoids [22 23] and quercetin (QC) among them(Figure 1)Theupdated studies connect high flavonols antiox-idant activity with the presence of OH-group in C-ring 3-position in combination with catechol B-ring structure [2224ndash27]

Quercetin and its glycosides have been reportedly syn-thesized in plants as a part of its total response toward UV-radiation to prevent an extended induced damage [28 29]Quercetin absorbs UV radiation with absorbance maxima inthe UV-A (120582max = 365 nm 120576 = 28400molminus1 dm3 cmminus1) andUV-C range (120582max = 256 nm 120576 = 28300molminus1 dm3 cmminus1)However flavonoids can also act as free-radical scavengersto prevent oxidative skin damage [30ndash34] and their topicalapplication has met considerable interest [35ndash38] generallythey are of significant interest for medicinal chemistry [3940]

So quercetin may act as a protector against UV radiationthrough (i) either absorption (preventive inhibition mode)or (ii) scavenging activities (ldquochain-breakingrdquo antioxidantmode) In the former case the absorbed UV energy may bedissipated as heat [41] or converted into quercetin decompo-sition products in vitro as in vivo [27 42 43] in the lattercase-quercetin scavenges already-created free radicals (suchas lipid peroxy radicals LOO∙) mostly by hydrogen atomtransfer mechanism shown in (2) [44 45] as follows

Fl-OH + L∙ 997888rarr Fl-O∙ + LH (2)

Theoxidized Fl-O∙ radical (which can be stabilized by oneintramolecular H-bonding in the B-ring ndashO∙ sdot sdot sdot HndashOndash) [45]may react with a second radical (L∙) acquiring a quite stablequinone structure [23]

In our former paper we have tested QC antioxidantability toward lipids in the presence of sensitizing BZP (asLP initiator) in methanol solution under continuous UV-B irradiation by spectrophotometric method [46] We havegot somewhat surprising conclusions on QC activity inthe presence of BZP (under UV-B stress) which led us toreexamine the same system (BZP + QC + lipids in MeOH)by HPLC chromatography to confirm or at least relativizethese conclusions HPLC separation should provide ldquocleanerrdquopicture since providing satisfying separation of the involvingspecies eliminates partial overlapping of the absorption spec-tra and potentially doubtful related interpretations

2 Materials and Methods

Phospholipids (Phospholipon 90) were gifted byPHOSPHOLIPID GmbH Koln Germany Accordingto the accompanied declaration the mixture content isPhospholipon 90 (PL90)mdashphosphatidylcholine 98 lyso-phosphatidylcholine 21 fatty acid composition palmiticacid 12 plusmn 2 stearic acid 3 plusmn 1 oleic acid 10 plusmn 3linoleic acid 66 plusmn 5 linolenic acid 5 plusmn 2 peroxide valuemax 13 The phospholipids mixtures were kept in dark toprevent at least the photooxidation process Benzophenone(BZP) was obtained from Sigma Chemical Co (St LouisUSA) Standard of quercetin was purchased from Merck(Darmstadt Germany)

21 The Samples The (studied system) componentsrsquo finalconcentrations in methanol solution were phospholipids13sdot10minus3 mol dmminus3 quercetin 1sdot10minus4 mol dm minus3 BZP 11sdot10minus4mol dm minus3 The pH was 76 and the experiments were doneat room temperature

22 UV-Irradiation Continuous irradiations of samples inmethanol were performed in cylindrical photochemical reac-tor ldquoRayonnetrdquo with 10 symmetrically placed lamps withemission maxima at 300 nm (UV-B) The samples wereirradiated in quartz closed cuvettes (1 times 1 times 45 cm) placedon rotating circular holder The total measured energy fluxwas 150Wmminus2 for 300 nm at 10 cm distance from the lampsThemethanol solutions of BZP only and phospholipids (withor without BZP) as a kind of blank were irradiated andanalyzed simultaneously with the phospholipidsquercetinand phospholipidsquercetinBZP mixtures

23 HPLC The irradiated samples were immediately anal-ysed with Agilent 1100 Series system (Waldbron Germany)on Zorbax Eclipse XDB-C18 column 46 times 250mm 5 120583mwith DAD detector The samples volume was 20 120583L Theisocratic regime with 100 methanol was applied underflow of 10mLmin The column temperature was 25∘C Thechromatograms were recorded at 210 nm (unoxidized lipids)234 nm (peroxides-[47 48]) 250 nm (BZP) 295 nm (possiblequercetin decomposition products) and 371 nm (quercetin)

Most of the experiments (UV-irrad followed by HPLCanalysis) were repeated at least oncemore some of themweretriplicated

3 Results and Discussion

Structures of benzophenone and quercetin are shown inFigure 1

The changes in the samples recorded chromatograms asa result of increased UV-B irradiation periods are shown inFigures 2(a)ndash4(a) Figure 2(a) shows degradation of quercetin(recorded at 371 nm) and Figure 3(a) shows degradation ofBZP (recorded at 250 nm) while Figure 4(a) documentsa proliferation of LP process that is a rise in peroxidesproduction (recorded at 234 nm)

Journal of Chemistry 3

0 5 10 15 20

0

50

100

150

200

250

Retention time (min)

12

34

56Ab

sorb

ance

at371

nm (m

AU)

1 QC-BZP-PL90 not irradiated2 QC-BZP-PL90 UV-B 15min3 QC-BZP-PL90 UV-B 30min4 QC-BZP-PL90 UV-B 45min5 QC-BZP-PL90 UV-B 60min6 QC-BZP-PL90 UV-B 75min

(a)

300 400 5000

50

100

150

200

250

300

Abso

rban

ce (m

AU)

QC 1

2

3456

tret = 26min

120582 (nm)

1 QC not irradiated2 QC UV-B 15min3 QC UV-B 30min4 QC UV-B 45min5 QC UV-B 60min6 QC UV-B 75min

(b)

kQCdegrad = minus003432 plusmn 000562minminus1

05

00

minus05

minus10

minus15

minus20

minus25

minus10 0 10 20 30 40 50 60 70 80

UV-B

tirr (min)

QCtret = 26min

lnP371n

m

(c)

Figure 2 Degradation (bleaching) of quercetin from theUV-B-irradiated sample that is quercetinBZPphospholipidsmixture inmethanol(a)The recorded samples chromatograms recorded at 371 nm (quercetin retention time 119905ret of 26min) (b) Changes in quercetin absorptionspectra taken from the upper (a) chromatogram (quercetin peak at 119905ret = 26min) as a result of the increasing UV-B irradiation periods(119905irr) (c) Kinetics of UV-B irradiation-induced bleaching followed through a decrease of quercetin peak (119905ret = 26min) integrated areas asa result of the increased UV-B irradiation periods ln119875

371 nm = 119891(119905irr) The corresponding bleaching rate constant and the related error barsare shown in the plot

The corresponding changes in the absorption spectraof quercetin BZP and the two peroxides (taken for thecorresponding peaks of the recorded HPLC chromatograms)are shown in Figures 2(b) 3(b) 4(b) and 4(c) respectivelyThe difference in the absorption spectra of the two detectedperoxidesmdashthe absence and the presence of the ldquoright shoul-derrdquo with 119860max around 280 nm (Figures 4(b) and 4(c)resp)mdashsuggests they have somewhat different structures stillthe basic peroxide diene chromophore responsible for 119860maxat 234 nm is obviously present in both cases

The related kinetic plots referring to the degradation ofquercetin BZP and production of the two peroxides are givenin Figures 2(c) 3(c) 4(d) and 4(e) respectively

The slopes calculated from kinetic ln-plots shown inFigures 2(c) 3(c) 4(d) and 4(e) representing the ratesof quercetin degradation BZP degradation and the twoperoxides production in the UV-B irradiated samples areshown in Tables 1(a) and 1(b) respectively

In our recent publication [49] we have compared stabilityof two flavonoid components quercetin and rutin in solution


0 5 10 15 20

0

100

200

300

400

500


12

34

56

Abso

rban

ce at

250

nm (m

AU)


(a)

0

100

200

300

40012345

300 400 500

BZPtret = 33min

120582 (nm)

1 BZP not irradiated2 BZP UV-B 15min3 BZP UV-B 30min4 BZP UV-B 45min5 BZP UV-B 60min

Abso

rban

ce (m

AU)

(b)

0 10 20 30 40 50 60

UV-B

tirr (min)

BZPtret = 33min

kBZPdegard = minus000281plusmn 000039minminus1

092

088

084

080

076

072

lnP250n

m

(c)

Figure 3 Degradation (bleaching) of benzophenone from the UV-B-irradiated sample that is quercetinBZPphospholipids mixture inmethanol (a)The recorded samples chromatograms recorded at 250 nm (BZP retention time 119905ret of 33min) (b) Changes in BZP absorptionspectra taken from the upper (a) chromatogram (BZP peak at 119905ret = 33min) as a result of the increasing UV-B irradiation periods (119905irr) (c)Kinetics of UV-B irradiation-induced bleaching followed through a decrease of BZP peak (119905ret = 33min) integrated areas as a result of theincreased UV-B irradiation periods ln119875

250 nm = 119891(119905irr) The corresponding bleaching rate constant and the related error bars are shown inthe plot

toward UV-irradiation (from the three subranges UV-A UV-BUV-C) aswell as their antioxidant activities in the presenceof lipoidal mixture (ie lecithin) as the ldquoprotection targetrdquodespite the lower QC stability against UV-irradiation itsantioxidant ability to protect lipid mixture from peroxidationwas found to be higher compared to rutin In addition wehave recently observed that UV continuous irradiation ofquercetin and rutin in solution led to creation of productswhich absorb in spectral regions between 250 and 350 nm[50] And in the most recent report [46] we have addedbenzophenone inQCphospholipidsmixtureThe purpose of

BZP involvement in the systemwas to producemore radicalsfor example lipid radicals since it is not only very efficientbut very selective sensitizer [5 13 14] Therefore the newsystem (BZP + QC + lipids in MeOH) contributed to someextent to better understanding of both quercetin protectiveactions during prolonged continuous UV-irradiation thepreventive one (studied through UV-induced degradation)as well as the antioxidant one (studied by tracing expansionof UV-induced LP process expressed through creation of LPperoxides dienes structures in the presence and in the absenceof benzophenone) While quercetin suppression effect on LP


0 5 10 15 200

50

100

150

200


12

34

56

Abso

rban

ce at

234

nm (m

AU)


(a)

12

3

4

6

510

8

6

4

2

0

300 400 500

Per1tret = 55min

120582 (nm)

Abso

rban

ce (m

AU)

1 Per1 not irradiated2 Per1 UV-B 15min3 Per1 UV-B 30min

4 Per1 UV-B 45min5 Per1 UV-B 60min6 Per1 UV-B 75min

(b)

12

3

4

65

6

4

2

0

300 400 500

Per2tret = 65min

120582 (nm)

Abso

rban

ce (m

AU)



(c)

0 10 20 30 40 50 60 70 80

minus12

minus14

minus16

minus18

minus20

minus22

minus24

minus26

minus10

kprodPer1 = 001414 plusmn 000070minminus1

UV-B

tirr (min)

Per1tret = 55min

lnP234n

m

(d)

0 10 20 30 40 50 60 70 80minus10

UV-B

tirr (min)

Per2tret = 65min

minus16

minus18

minus20

minus22

minus24

minus26

minus28

minus30


lnP234n

m

(e)

Figure 4 Formation of lipid peroxides in the UV-B-irradiated sample that is quercetinBZPphospholipids mixture in methanol (a) Therecorded samples chromatograms recorded at 234 nm (peroxides retention times 119905ret of 55 and 65min) ((b) and (c)) changes in the twoperoxides absorption spectra taken from the upper (a) chromatogram (Per1 119905ret = 55min Per2 119905ret = 65min) as a result of the increasingUV-B irradiation periods (119905irr) ((d) and (e)) Kinetics of rise of the two peroxides peaks (Per1 119905ret = 55min Per2 119905ret = 65min) integratedareas as a result of the increased UV-B irradiation periods ln 119875

234 nm = 119891(119905irr) The corresponding rate constants and the related error barsare shown in the plots


Table 1 (a) Rate constants for degradation of quercetin (QC) and benzophenone (BZP) (minminus1) obtained from the slopes of the 1st order linearplots ln 119875371250 nm = 119891 (119905irr) representing proportional decrease of QC and BZP concentrations as a result of the increasing UV-B irradiationperiods 119875371250 nm presents integrated areas of QC and BZP peaks from the HPLC chromatograms (shown in Figures 2(a) and 3(a)) recordedat 371 and 250 nm respectively (b) Rate constants for the two peroxides formation obtained from the slopes of the 1st order linear plot ln119875234 nm =119891 (119905irr) representing proportional increase of the two peroxides concentrations as a result of the increasingUV-B irradiation periods119875234 nm presents integrated areas of the peroxides peaks (Per1 119905ret = 55min Per2 119905ret = 65min) from the HPLC chromatograms (shown inFigure 4(a)) recorded at 234 nm

(a) 119896degrad minminus1

QC+PL90 +BZP QC+PL90 BZP+PL90QC119905ret = 26min minus003432 minus000332

BZP119905ret = 33min minus000281 minus001288

(b) Peroxides production 119896prod Per minminus1

QC+PL90 +BZP QC+PL90 BZP+PL90Per1119905ret = 55min 001414 minus000009 001734

Per2119905ret = 65min 001756 001473

process has been proven it was found that the suppressioneffect is less effective when BZP was present [46] evidentlyquercetin degradation was more favored in the presence ofBZP However the deeper conclusions could not be offeredpartly because of the obvious limitations of the appliedspectrophotometric method based on a clear overlapping ofthe involved species (BZP quercetin peroxides) absorptionspectra (120582max = 250 nm for BZP 234 nm for peroxides 260and 370 nm for quercetin)This report is one step ahead sincethe method has been changed now the same system hasbeen analysed by HPLC chromatography providing a kineticanalysis of the clearly separated involved species As in thecited two reports [46 49] due to the complexity of the studiedsystem the mixture of BZP and lipids has been irradiated asa blank in order to evaluate in the next step LP control byquercetin during UV-B irradiation (290ndash320 nm)

The chromatograms recorded at the involved speciesabsorption maxima (Figures 2(a) 3(a) and 4(a)) deal withthe separated compounds the kinetic plots (Figures 2(c) 3(c)4(d) and 4(e)) have been obtained from the correspondingpeaks integrated areas and the calculated rate constantsfor quercetin and BZP degradation as well as for the twoperoxides (Per1 amp Per2) formation represent much ldquopurebehaviorrdquo compared to at least partly ldquomixed behaviorrdquoreported in the former paper [46]

Prolonged continuous irradiation of quercetin inmethanol (in the presence of lipid mixture and BZP) causesa gradual decrease of the corresponding integrated peak(119905ret = 26min) areas during increasing irradiation periods(Figure 2(a)) the corresponding kinetic plot (Figure 2(c))and the changes in the corresponding absorption spectrashown in Figure 2(b) confirm this degradation pattern Thisdegradation pattern (of QC in MeOH) has been alreadynoted in our two previous reports where QC decompositioninto ring C-opening products has been recorded by HPLC

techniques [50] or by spectrophotometric method (in thelast case in the presence of BZP [46]) confirming theprevious work (with BZP and QC in MeOH) and theproposed mechanism of Fahlman and Krol [51] (it should beadded at this place that the oxidation pattern of quercetin ishighly dependent on the applied initiating mechanism butthe related details are out of scope of this paper [52 53])However the real issue in QC degradation kinetics is therole of BZP If one compares the QC degradation rateconstants from Table 1(a) (119896QCdegrad) in the presence and inthe absence of BZP (the last one obtained under absolutelythe same chromatographic conditions not shown) 003432versus 000332minminus1 it is evident that BZP presencedramatically speeds up QC degradation The same fact wasseen in the previous report [46] when the same (BZP +QC + lipids) mixture was irradiated under the same UVirradiation regime though the (degradation constants inthe presence and in the absence of BZP) relationship is notthat huge as in this study (roughly 3 versus 10) Still havingin mind objective limits of spectrophotometric method theHPLC data from Table 1(a) looks not only confirming butalso more accurate It is also important to note that thereported quercetin degradation rate constant in the presenceof lipids but in the absence of BZP (000332minminus1) is in alogical agreement with the one obtained for QC degradationunder the same (UV-B) conditions and in the same solventmethanol in the absence of all other species (000183minminus1)[50] the latter one is obviously smaller confirming quercetinantioxidant activity toward lipids before introduction of BZP

However it appears that not only BZP largely affectsquercetin degradation (and so its antioxidant ability) but alsoits own main anticipated activity towards lipids [5 13 14]BZP-sensitizing (H-abstraction) activity becomes almost 5times slower in the presence of quercetin rate constants forBZP degradation (119896BZPdegrad) of 001288 and 000281minminus1


respectively (Table 1a calculated from the kinetic plot shownin Figure 3(c))

That clearly suggests that the cause has to be somehowrelated to BZP (ie 3BZP)-QC mutual interaction no otherinteraction can match an explosive 3BZP attack to doublebonds in the used lipoidal mixture and the abstraction ofallylic and double-allylicH-atoms [5 13 14] especially havingin mind high percentage of present linoleic acid (morethan 50) with its two double bonds in each of the twohydrophobic branches

As reported-quercetin has two absorption maximums inUV-A (120582max = 372 nm) and UV-C (120582max = 260 nm) spectralranges [49] which partly overlap with the applied UV-Birradiation range used in this work In recently publishedpaper Fahlman et al [51] studiedUV-A andUV-B irradiationof quercetin in BZP-containing methanol solution yieldingan irreversible degradation followed by formation of severalC-ring-opened photoproducts they noticed BZP impact onboth QC degradation as well as on photoproducts formation[51] this confirms that BZP-QC connection is found in thiswork and in the previous report [46]

The other side of the anticipated BZP-QC interactionsis a question of QC antioxidant activity against lipids howmuch has it been affected by this interaction To be ableto evaluate the possible change a blank experiment hasbeen done with QC and the lipids (without BZP) from thecorresponding slope (Figure Add-1 in Supplementary Mate-rials available online at httpdxdoiorg1011552013761675)for the peroxides production a rate constant has beencalculated (119896prodPer = minus000009minminus1 Table 1) The lineardecrease in the peroxides production represents an obviousQC-governing effect However when BZP is brought inthe system the situation dramatically changes First of allthe sign of peroxides production has been changed thatis reversed from minus (minus) in BZP absence to plus (+)in its presence (Figures 4(d) and 4(e)) In addition theperoxides production rate constants for the two detectedand separated peroxides species 119896prodPer 1 and 119896prodPer 2 arealmost 200 times bigger And the most important it is hardto see almost any QC antioxidant activity on BZP-inducedlipid peroxidation (more expressed than in the former [46]ldquospectrophotometricrdquo report) the two peroxides productionrate constants for the two peroxides peaks Per1 119905ret = 55minand Per2 119905ret = 65min obtained from kinetic plots shown inFigures 4(d) and 4(e) in the presence and in the absence ofquercetin are almost the same (001414 versus 001734minminus1and 001756 versus 001473minminus1 Table 1)

4 Conclusion

To conclude it appears that while a QC general control effecton LP process is not ultimately denied the suppression isdefinitely not only less effective but practically absent whenBZP is present HPLC results obtained in this paper notonly support spectrophotometric data obtained for the samesystem in the last report [46] (concerning this fact) but alsostrengthen it The very newly found fact that is the noveltyof this study (compared to [46]) is that suppression has

the other side a slower BZP sensitizing activity (against lipidsas the target) This emphasizes a necessity of further effortsto determine more precisely BZP-QC relationship in thepresence of lipids under conditions of external continuousUV-B irradiation stress

Acknowledgments

This work was supported by the Project on Developmentof Technology no TR-34012 as well as under the BasicInvestigations Project no OI-172044 by the Ministry ofEducation and Science of the Republic of Serbia

References

[1] M Ichihashi M Ueda A Budiyanto et al ldquoUV-induced skindamagerdquo Toxicology vol 189 no 1-2 pp 21ndash39 2003

[2] G P Pfeifer Y You and A Besaratinia ldquoMutations induced byultraviolet lightrdquoMutation Research vol 571 no 1-2 pp 19ndash312005

[3] A Teramura and L Ziska Photosynthesis and the EnvironmentKluwer Academic Dodrecht The Netherlands 1996

[4] A Strid W S Chow and J M Anderson ldquoEffects of sup-plementary ultraviolet-B radiation on photosynthesis in PisumsativumrdquoBiochimica et BiophysicaActa vol 1020 no 3 pp 260ndash268 1990

[5] D Markovic and L Patterson ldquoBenzophenone-sensitized lipidperoxidation in linoleate micellesrdquo Photochemistry and Photo-biology vol 58 no 3 pp 329ndash334 1993

[6] N Paillous and S Fery-Forgues ldquoInterest of photochemicalmethods for induction of lipid peroxidationrdquo Biochimie vol 76no 5 pp 355ndash368 1994

[7] R Wheatley ldquoSome recent trends in the analytical chemistry oflipid peroxidationrdquo TrAC Trends in Analytical Chemistry vol19 no 10 pp 617ndash628 2000

[8] A Girotti ldquoPhotosensitized oxidation of membrane lipidsreaction pathways cytotoxic effects and cytoprotective mech-anismsrdquo Journal of Photochemistry and Photobiology B vol 63pp 103ndash113 2001

[9] E Niki Y Yoshida Y Saito and N Noguchi ldquoLipid peroxida-tion mechanisms inhibition and biological effectsrdquo Biochemi-cal and Biophysical Research Communications vol 338 no 1 pp668ndash676 2005

[10] J Aikens and T A Dix ldquoHydrodioxyl (perhydroxyl) per-oxyl and hydroxyl radical-initiated lipid peroxidation of largeunilamellar vesicles (liposomes) comparative and mechanisticstudiesrdquo Archives of Biochemistry and Biophysics vol 305 no 2pp 516ndash525 1993

[11] L R C Barclay and M R Vinqvist ldquoMembrane peroxidationinhibiting effects of watersoluble antioxidants on phospholipidsof different charge typesrdquoFree Radical Biology andMedicine vol16 no 6 pp 779ndash788 1994

[12] Q-T Li M H Yeo and B K Tan ldquoLipid peroxidation insmall and large phospholipid unilamellar vesicles induced bywater-soluble free radical sourcesrdquo Biochemical and BiophysicalResearch Communications vol 273 no 1 pp 72ndash76 2000

[13] D Markovic and L Patterson ldquoRadical processes in lipidsSelectivity of hydrogen abstraction from lipids by benzophe-none tripletrdquo Photochemistry and Photobiology vol 49 no 5pp 531ndash535 1989


[14] D Markovic T Durand and L Patterson ldquoHydrogen abstrac-tion from lipids by triplet states of derivatized benzophenonephotosensitizersrdquo Photochemistry and Photobiology vol 51 pp389ndash394 1990

[15] D Markovic ldquoBenzophenone-sensitized peroxidation in com-pressed lipid monolayers at air-water interfacerdquo Collection ofCzechoslovak Chemical Communications vol 66 pp 1603ndash16142001

[16] C Viltres Costa M A Grela andM S Chorio ldquoOn the yield ofintermediates formed in the photoreduction of benzophenonerdquoJournal of Photochemistry and Photobiology A vol 99 pp 51ndash561996

[17] M von Raumer P Suppan and P Jacques ldquoPhotoinducedcharge transfer processes of triplet benzophenone in acetoni-trilerdquo Journal of Photochemistry and Photobiology A vol 105 no1 pp 21ndash28 1997

[18] P McGarry C Heitner J Schmidt et al ldquoA dramatic sol-vent effect on high-yield pulp yellowing inhibition for abenzophenone-based ultraviolet absorberrdquo Journal of Photo-chemistry and Photobiology A vol 151 pp 145ndash155 2002

[19] M Dossot X Allonas and P Jacques ldquoComparative time-resolved photoconductivity and absorption spectroscopy stud-ies on dark secondary reactions following the photoreductionof benzophenone by triethylaminerdquo Journal of Photochemistryand Photobiology A vol 128 pp 47ndash55 1999

[20] Q Q Zhu and W Schnabel ldquoInteraction of triplet-excitedbenzophenone with hindered amines and amino ethers alaser flash photolysis study employing photoconductivity andlight emission measurementsrdquo Journal of Photochemistry andPhotobiology A vol 130 no 2-3 pp 119ndash125 2000

[21] D Cvetkovic and D Markovic ldquoBeta-carotene suppression ofbenzophenone-sensitized lipid peroxidation in hexane throughadditional chain-breaking activitiesrdquo Radiation Physics andChemistry vol 80 no 1 pp 76ndash84 2011

[22] K E Heim A R Tagliaferro and D J Bobilya ldquoFlavonoidantioxidants chemistry metabolism and structure-activityrelationshipsrdquo Journal of Nutritional Biochemistry vol 13 no10 pp 572ndash584 2002

[23] P G Pietta ldquoFlavonoids as antioxidantsrdquo Journal of NaturalProducts vol 63 no 7 pp 1035ndash1042 2000

[24] D Amic D Davidovic-Amic D Beslo and N Trina-jstic ldquoStructure-radical scavenging activity relationships offlavonoidsrdquo Croatica Chemica Acta vol 76 pp 55ndash61 2003

[25] D P Makris and J T Rossiter ldquoAn investigation on structuralaspects influencing product formation in enzymic and chemicaloxidation of quercetin and related flavonolsrdquo Food Chemistryvol 77 no 2 pp 177ndash185 2002

[26] S Erkoc F Erkoc and N Keskin ldquoTheoretical investigationof quercetin and its radical isomersrdquo Journal of MolecularStructure vol 631 pp 141ndash146 2003

[27] G J Smith S J Thomsen K R Markham C Andaryand D Cardon ldquoThe photostabilities of naturally occurring5-hydroxyflavones flavonols their glycosides and their alu-minium complexesrdquo Journal of Photochemistry and Photobiol-ogy A vol 136 no 1-2 pp 87ndash91 2000

[28] A Strid andR J Porra ldquoAlterations in pigment content in leavesof pisum sativum after exposure to supplementary UV-Brdquo Plantand Cell Physiology vol 33 no 7 pp 1015ndash1023 1992

[29] A Strid W S Chow and J M Anderson ldquoUV-B damageand protection at the molecular level in plantsrdquo PhotosynthesisResearch vol 39 no 3 pp 475ndash489 1994

[30] J H Schoemaker M T Schoemaker H Zijlstra and F A vander Horst ldquoTreatment of erythropoietic protoporphyria withhydroxyethylrutosidesrdquo Dermatology vol 191 no 1 pp 36ndash381995

[31] P S Mortimer ldquoTherapy approaches for lymphedemardquo Angiol-ogy vol 48 no 1 pp 87ndash91 1997

[32] B Choquenet C Couteau E Paparis and L J M CoiffardldquoQuercetin and rutin as potential sunscreen agents determi-nation of efficacy by an in vitro methodrdquo Journal of NaturalProducts vol 71 no 6 pp 1117ndash1118 2008

[33] R Casagrande S R Georgetti W A Verri Jr D J Dorta AC dos Santos and M J V Fonseca ldquoProtective effect of top-ical formulations containing quercetin against UVB-inducedoxidative stress in hairless micerdquo Journal of Photochemistry andPhotobiology B vol 84 no 1 pp 21ndash27 2006

[34] R Hirano W Sasamoto A Matsumoto H Itakura O Igrashiand K Kondo ldquoAntioxidant ability of various flavonoids againstDPPH radicals and LDL oxidationrdquo Journal of NutritionalScience and Vitaminology vol 47 no 5 pp 357ndash362 2001

[35] V Cody E Middleton Jr and J B Harborne Plant Flavonoidsin Biology and Medicine Biochemical Pharmacological andStructure-Activity Relationships Alan R Liss New York NYUSA 1985

[36] B Li and D F Birt ldquoIn vivo and in vitro percutaneousabsorption of cancer preventive flavonoid apigenin in differentvehicles in mouse skinrdquo Pharmaceutical Research vol 13 no 11pp 1710ndash1715 1996

[37] A Saija A Tomaino D TrombettaM Giacchi A De Pasqualeand F Bonina ldquoInfluence of different penetration enhancers onin vitro skin permeation and in vivo photoprotective effect offlavonoidsrdquo International Journal of Pharmaceutics vol 175 no1 pp 85ndash94 1998

[38] A Svobodova J Psotova and D Walterova ldquoNatural phenolicsin the prevention of UV-induced skin damage A reviewrdquoBiomedical Papers vol 147 no 2 pp 137ndash145 2003

[39] M Duenas F Surco-Laos S Gonzalez-Manzano A MGonzalez-Paramas and C Santos-Buelga ldquoAntioxidant proper-ties of major metabolites of quercetinrdquo European Food Researchand Technology vol 232 no 1 pp 103ndash111 2011

[40] H Pool D Quintanar J de Dios Figueroa J E H Bechara D JMcClements and S Mendoza ldquoPolymeric nanoparticles as oraldelivery systems for encapsulation and release of polyphenoliccompounds impact on quercetin antioxidant activity amp bioac-cessibilityrdquo Food Biophysics vol 7 no 3 pp 276ndash288 2012

[41] E Falkovskaia P K Sengupta and M Kasha ldquoPhotophysicalinduction of dual fluorescence of quercetin and related hydrox-yflavones upon intermolecular H-bonding to solvent matrixrdquoChemical Physics Letters vol 297 no 1-2 pp 109ndash114 1998

[42] B M Fahlman and E S Krol ldquoInhibition of UVA and UVBradiation-induced lipid oxidation by quercetinrdquo Journal ofAgricultural and Food Chemistry vol 57 no 12 pp 5301ndash53052009

[43] E S B Ferreira A Quye H McNab and A N Hulme ldquoPhoto-oxidation products of quercetin and morin as markers for thecharacterisation of natural flavonoid yellow dyes in ancienttextilesrdquo Dyes in History and Archaeology vol 18 pp 63ndash722002

[44] S G Chiodo M Leopoldini N Russo and M Toscano ldquoTheinactivation of lipid peroxide radical by quercetin A theoreticalinsightrdquo Physical Chemistry Chemical Physics vol 12 no 27 pp7662ndash7670 2010


[45] P Pedrielli G F Pedulli and L H Skibsted ldquoAntioxidantmech-anism of flavonoids Solvent effect on rate constant for chain-breaking reaction of quercetin and epicatechin in autoxidationof methyl linoleaterdquo Journal of Agricultural and Food Chemistryvol 49 no 6 pp 3034ndash3040 2001

[46] J B Zvezdanovic D Z Markovic D J Cvetkovic and JS Stanojevic ldquoUV-induced change in quercetin antioxidantactivity toward benzophenone initiated lipid peroxidationrdquoJournal of the Serbian Chemical Society vol 77 no 11 pp 1571ndash1588 2012

[47] R O Recknagel and E A Glende Jr ldquoSpectrophotometricdetection of lipid conjugated dienesrdquo Methods in Enzymologyvol 105 pp 331ndash337 1984

[48] A Subagio and N Morita ldquoProoxidant activity of lutein and itsdimyristate esters in corn triacylglyceriderdquo Food Chemistry vol81 no 1 pp 97ndash102 2003

[49] D Cvetkovic D Markovic D Cvetkovic and B RadovanovicldquoEffects of continuous UV-irradiation on the antioxidant activi-ties of quercetin and rutin in solution in the presence of lecithinas the protective targetrdquo Journal of the Serbian Chemical Societyvol 76 pp 973ndash985 2011

[50] J B Zvezdanovic J S Stanojevic D Z Markovic and DJ Cvetkovic ldquoIrreversible UV-induced quercetin and rutindegradation in solution studied by UV-spectrophotometryand HPLC chromatographyrdquo Journal of the Serbian ChemicalSociety vol 77 no 3 pp 297ndash312 2012

[51] B M Fahlman and E S Krol ldquoUVA and UVB radiation-induced oxidation products of quercetinrdquo Journal of Photo-chemistry and Photobiology B vol 97 pp 123ndash131 2009

[52] V Krishnamachari L H Levine and P W Pare ldquoFlavonoidoxidation by the radical generator AIBN a unified mechanismfor quercetin radical scavengingrdquo Journal of Agricultural andFood Chemistry vol 50 pp 4357ndash4363 2002

[53] V Krishnamachari L H Levine C Zhou and P W Pare ldquoInvitro flavon-3-ol oxidation mediated by a B ring hydroxylationpatternrdquo Chemical Research in Toxicology vol 17 pp 795ndash8042004

Submit your manuscripts athttpwwwhindawicom

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2013


Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom


Analytical ChemistryVolume 2013

ISRN Chromatography


Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawi Publishing Corporation httpwwwhindawicom Volume 2013

The Scientific World Journal

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2013


CatalystsJournal of

ISRN Analytical Chemistry


ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013


Advances in

Physical Chemistry

ISRN Physical Chemistry


SpectroscopyInternational Journal of


ISRN Inorganic Chemistry



Journal of

Chemistry


Inorganic ChemistryInternational Journal of


International Journal ofPhotoenergy


Analytical Methods in Chemistry

Journal of

Volume 2013

ISRN Organic Chemistry



Journal of

Spectroscopy


OH

OH

OH

OH

O O

OHO

Figure 1 Structures of quercetin (left) and benzophenone (right)

On the other hand lipid peroxidation is mostly con-trolled by antioxidants action in vivo Many biomolecules(and classes of biomolecules) serve as antioxidants includ-ing flavonoids [22 23] and quercetin (QC) among them(Figure 1)Theupdated studies connect high flavonols antiox-idant activity with the presence of OH-group in C-ring 3-position in combination with catechol B-ring structure [2224ndash27]

Quercetin and its glycosides have been reportedly syn-thesized in plants as a part of its total response toward UV-radiation to prevent an extended induced damage [28 29]Quercetin absorbs UV radiation with absorbance maxima inthe UV-A (120582max = 365 nm 120576 = 28400molminus1 dm3 cmminus1) andUV-C range (120582max = 256 nm 120576 = 28300molminus1 dm3 cmminus1)However flavonoids can also act as free-radical scavengersto prevent oxidative skin damage [30ndash34] and their topicalapplication has met considerable interest [35ndash38] generallythey are of significant interest for medicinal chemistry [3940]

So quercetin may act as a protector against UV radiationthrough (i) either absorption (preventive inhibition mode)or (ii) scavenging activities (ldquochain-breakingrdquo antioxidantmode) In the former case the absorbed UV energy may bedissipated as heat [41] or converted into quercetin decompo-sition products in vitro as in vivo [27 42 43] in the lattercase-quercetin scavenges already-created free radicals (suchas lipid peroxy radicals LOO∙) mostly by hydrogen atomtransfer mechanism shown in (2) [44 45] as follows

Fl-OH + L∙ 997888rarr Fl-O∙ + LH (2)

Theoxidized Fl-O∙ radical (which can be stabilized by oneintramolecular H-bonding in the B-ring ndashO∙ sdot sdot sdot HndashOndash) [45]may react with a second radical (L∙) acquiring a quite stablequinone structure [23]

In our former paper we have tested QC antioxidantability toward lipids in the presence of sensitizing BZP (asLP initiator) in methanol solution under continuous UV-B irradiation by spectrophotometric method [46] We havegot somewhat surprising conclusions on QC activity inthe presence of BZP (under UV-B stress) which led us toreexamine the same system (BZP + QC + lipids in MeOH)by HPLC chromatography to confirm or at least relativizethese conclusions HPLC separation should provide ldquocleanerrdquopicture since providing satisfying separation of the involvingspecies eliminates partial overlapping of the absorption spec-tra and potentially doubtful related interpretations

2 Materials and Methods

Phospholipids (Phospholipon 90) were gifted byPHOSPHOLIPID GmbH Koln Germany Accordingto the accompanied declaration the mixture content isPhospholipon 90 (PL90)mdashphosphatidylcholine 98 lyso-phosphatidylcholine 21 fatty acid composition palmiticacid 12 plusmn 2 stearic acid 3 plusmn 1 oleic acid 10 plusmn 3linoleic acid 66 plusmn 5 linolenic acid 5 plusmn 2 peroxide valuemax 13 The phospholipids mixtures were kept in dark toprevent at least the photooxidation process Benzophenone(BZP) was obtained from Sigma Chemical Co (St LouisUSA) Standard of quercetin was purchased from Merck(Darmstadt Germany)

21 The Samples The (studied system) componentsrsquo finalconcentrations in methanol solution were phospholipids13sdot10minus3 mol dmminus3 quercetin 1sdot10minus4 mol dm minus3 BZP 11sdot10minus4mol dm minus3 The pH was 76 and the experiments were doneat room temperature

22 UV-Irradiation Continuous irradiations of samples inmethanol were performed in cylindrical photochemical reac-tor ldquoRayonnetrdquo with 10 symmetrically placed lamps withemission maxima at 300 nm (UV-B) The samples wereirradiated in quartz closed cuvettes (1 times 1 times 45 cm) placedon rotating circular holder The total measured energy fluxwas 150Wmminus2 for 300 nm at 10 cm distance from the lampsThemethanol solutions of BZP only and phospholipids (withor without BZP) as a kind of blank were irradiated andanalyzed simultaneously with the phospholipidsquercetinand phospholipidsquercetinBZP mixtures

23 HPLC The irradiated samples were immediately anal-ysed with Agilent 1100 Series system (Waldbron Germany)on Zorbax Eclipse XDB-C18 column 46 times 250mm 5 120583mwith DAD detector The samples volume was 20 120583L Theisocratic regime with 100 methanol was applied underflow of 10mLmin The column temperature was 25∘C Thechromatograms were recorded at 210 nm (unoxidized lipids)234 nm (peroxides-[47 48]) 250 nm (BZP) 295 nm (possiblequercetin decomposition products) and 371 nm (quercetin)

Most of the experiments (UV-irrad followed by HPLCanalysis) were repeated at least oncemore some of themweretriplicated

3 Results and Discussion

Structures of benzophenone and quercetin are shown inFigure 1

The changes in the samples recorded chromatograms asa result of increased UV-B irradiation periods are shown inFigures 2(a)ndash4(a) Figure 2(a) shows degradation of quercetin(recorded at 371 nm) and Figure 3(a) shows degradation ofBZP (recorded at 250 nm) while Figure 4(a) documentsa proliferation of LP process that is a rise in peroxidesproduction (recorded at 234 nm)


0 5 10 15 20

0

50

100

150

200

250


12

34

56Ab

sorb

ance

at371

nm (m

AU)


(a)

300 400 5000

50

100

150

200

250

300

Abso

rban

ce (m

AU)

QC 1

2

3456

tret = 26min

120582 (nm)


(b)


05

00

minus05

minus10

minus15

minus20

minus25

minus10 0 10 20 30 40 50 60 70 80

UV-B

tirr (min)

QCtret = 26min

lnP371n

m

(c)








0 5 10 15 20

0

100

200

300

400

500


12

34

56

Abso

rban

ce at

250

nm (m

AU)


(a)

0

100

200

300

40012345

300 400 500

BZPtret = 33min

120582 (nm)


Abso

rban

ce (m

AU)

(b)

0 10 20 30 40 50 60

UV-B

tirr (min)

BZPtret = 33min


092

088

084

080

076

072

lnP250n

m

(c)






0 5 10 15 200

50

100

150

200


12

34

56

Abso

rban

ce at

234

nm (m

AU)


(a)

12

3

4

6

510

8

6

4

2

0

300 400 500

Per1tret = 55min

120582 (nm)

Abso

rban

ce (m

AU)



(b)

12

3

4

65

6

4

2

0

300 400 500

Per2tret = 65min

120582 (nm)

Abso

rban

ce (m

AU)



(c)

0 10 20 30 40 50 60 70 80

minus12

minus14

minus16

minus18

minus20

minus22

minus24

minus26

minus10


UV-B

tirr (min)

Per1tret = 55min

lnP234n

m

(d)

0 10 20 30 40 50 60 70 80minus10

UV-B

tirr (min)

Per2tret = 65min

minus16

minus18

minus20

minus22

minus24

minus26

minus28

minus30


lnP234n

m

(e)










Per2119905ret = 65min 001756 001473











4 Conclusion



Acknowledgments


References

































































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy


0 5 10 15 20

0

50

100

150

200

250


12

34

56Ab

sorb

ance

at371

nm (m

AU)


(a)

300 400 5000

50

100

150

200

250

300

Abso

rban

ce (m

AU)

QC 1

2

3456

tret = 26min

120582 (nm)


(b)


05

00

minus05

minus10

minus15

minus20

minus25

minus10 0 10 20 30 40 50 60 70 80

UV-B

tirr (min)

QCtret = 26min

lnP371n

m

(c)








0 5 10 15 20

0

100

200

300

400

500


12

34

56

Abso

rban

ce at

250

nm (m

AU)


(a)

0

100

200

300

40012345

300 400 500

BZPtret = 33min

120582 (nm)


Abso

rban

ce (m

AU)

(b)

0 10 20 30 40 50 60

UV-B

tirr (min)

BZPtret = 33min


092

088

084

080

076

072

lnP250n

m

(c)






0 5 10 15 200

50

100

150

200


12

34

56

Abso

rban

ce at

234

nm (m

AU)


(a)

12

3

4

6

510

8

6

4

2

0

300 400 500

Per1tret = 55min

120582 (nm)

Abso

rban

ce (m

AU)



(b)

12

3

4

65

6

4

2

0

300 400 500

Per2tret = 65min

120582 (nm)

Abso

rban

ce (m

AU)



(c)

0 10 20 30 40 50 60 70 80

minus12

minus14

minus16

minus18

minus20

minus22

minus24

minus26

minus10


UV-B

tirr (min)

Per1tret = 55min

lnP234n

m

(d)

0 10 20 30 40 50 60 70 80minus10

UV-B

tirr (min)

Per2tret = 65min

minus16

minus18

minus20

minus22

minus24

minus26

minus28

minus30


lnP234n

m

(e)










Per2119905ret = 65min 001756 001473











4 Conclusion



Acknowledgments


References

































































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy


0 5 10 15 20

0

100

200

300

400

500


12

34

56

Abso

rban

ce at

250

nm (m

AU)


(a)

0

100

200

300

40012345

300 400 500

BZPtret = 33min

120582 (nm)


Abso

rban

ce (m

AU)

(b)

0 10 20 30 40 50 60

UV-B

tirr (min)

BZPtret = 33min


092

088

084

080

076

072

lnP250n

m

(c)






0 5 10 15 200

50

100

150

200


12

34

56

Abso

rban

ce at

234

nm (m

AU)


(a)

12

3

4

6

510

8

6

4

2

0

300 400 500

Per1tret = 55min

120582 (nm)

Abso

rban

ce (m

AU)



(b)

12

3

4

65

6

4

2

0

300 400 500

Per2tret = 65min

120582 (nm)

Abso

rban

ce (m

AU)



(c)

0 10 20 30 40 50 60 70 80

minus12

minus14

minus16

minus18

minus20

minus22

minus24

minus26

minus10


UV-B

tirr (min)

Per1tret = 55min

lnP234n

m

(d)

0 10 20 30 40 50 60 70 80minus10

UV-B

tirr (min)

Per2tret = 65min

minus16

minus18

minus20

minus22

minus24

minus26

minus28

minus30


lnP234n

m

(e)










Per2119905ret = 65min 001756 001473











4 Conclusion



Acknowledgments


References

































































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy


0 5 10 15 200

50

100

150

200


12

34

56

Abso

rban

ce at

234

nm (m

AU)


(a)

12

3

4

6

510

8

6

4

2

0

300 400 500

Per1tret = 55min

120582 (nm)

Abso

rban

ce (m

AU)



(b)

12

3

4

65

6

4

2

0

300 400 500

Per2tret = 65min

120582 (nm)

Abso

rban

ce (m

AU)



(c)

0 10 20 30 40 50 60 70 80

minus12

minus14

minus16

minus18

minus20

minus22

minus24

minus26

minus10


UV-B

tirr (min)

Per1tret = 55min

lnP234n

m

(d)

0 10 20 30 40 50 60 70 80minus10

UV-B

tirr (min)

Per2tret = 65min

minus16

minus18

minus20

minus22

minus24

minus26

minus28

minus30


lnP234n

m

(e)










Per2119905ret = 65min 001756 001473











4 Conclusion



Acknowledgments


References

































































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy








Per2119905ret = 65min 001756 001473











4 Conclusion



Acknowledgments


References

































































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy






4 Conclusion



Acknowledgments


References

































































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy




















































ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy

Benzophenone Suppression of Quercetin Antioxidant Activity towards Lipids under UV-B Irradiation...

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Transcript of Benzophenone Suppression of Quercetin Antioxidant Activity towards Lipids under UV-B Irradiation...