Gallic acidGallic acidIUPAC name [hide]3,4,5-trihydroxybenzoic acidOther names[hide]Gaic acidGaate3,4,5-trihydroxybenzoateIdentifiersCA! n"mber#4$-$#-% , [5$$5-&'-&] ()onohydrate*P"bChem 3%+Chem!,ider 3'# U-II '3./0$+3!P 12GG C+#4.4 Ch23I C423I53+%%& Ch2)36 C42)36. 7mo-30 ima8es Ima8e #!)I62![sho9]InChI[sho9]Properties)oec"ar :orm"a C%4'O5)oar mass #%+;#. 8C, #++DPa*In:obox re:erencesGallic acid is a trihydroxybenzoic acid, a ty,e o: ,henoic acid, a ty,e o: or8anic acid, aso Dno9n as 3,4,5-trihydroxybenzoic acid, :o"nd in 8an"ts, s"mac, 9itch haze, tea eaBes, oaDbarD, and other ,ants;[#] Ehe chemica :orm"a is C'4.(O4*3COO4; Gaic acid is :o"nd both:ree and as ,art o: tannins;!ats and esters o: 8aic acid are termed F8aatesF; 0es,ite its name, it does not contain 8ai"m;Gaic acid is commony "sed in the ,harmace"tica ind"stry;[.] It is "sed as a standard :or determinin8 the ,heno content o: Bario"s anaytes by the ?oin-Ciocatea" assayG res"ts are re,orted in gallic acid equivalents;[3] Gaic acid can aso be "sed as a startin8 materia in the synthesis o: the ,sychedeic aDaoid mescaine;[4]Gaic acid seems to haBe anti-:"n8a and anti-Bira ,ro,erties; Gaic acid acts as an antioxidant and he,s to ,rotect h"man ces a8ainst oxidatiBe dama8e; Gaic acid 9as :o"nd to sho9 cytotoxicity a8ainst cancer ces, 9itho"t harmin8 heathy ces; Gaic acid is "sed asa remote astrin8ent in cases o: interna haemorrha8e; Gaic acid is aso "sed to treat ab"min"ria and diabetes; !ome ointments to treat ,soriasis and externa haemorrhoids contain 8aic acid;[5]Historical context and usesGaic acid is an im,ortant com,onent o: iron 8a inD, the standard 2"ro,ean 9ritin8 and dra9in8 inD :rom the #.th to #$th cent"ry 9ith a history extendin8 to the Aoman em,ire and the 0ead !ea !cros; Piny the 2der (.3-%$ A0* describes his ex,eriments 9ith it and 9ritesthat it 9as "sed to ,rod"ce dyes; Gas (aso Dno9n as oaD a,,es* :rom oaD trees 9ere cr"shed and mixed 9ith 9ater, ,rod"cin8 tannic acid (a macromoec"ar com,ex containin8 8aic acid*; It co"d then be mixed 9ith 8reen Bitrio (:erro"s s":ate* H obtained by ao9in8 s":ate-sat"rated 9ater :rom a s,rin8 or mine draina8e to eBa,orate H and 8"m arabic :rom acacia treesG this combination o: in8redients ,rod"ced the inD;[']Gaic acid 9as one o: the s"bstances "sed by An8eo )ai (#%&.I#&54*, amon8 other eary inBesti8ators o: ,aim,sests, to cear the to, ayer o: text o:: and reBea hidden man"scri,ts "nderneath; )ai 9as the :irst to em,oy it, b"t did so J9ith a heaBy handJ, o:ten renderin8 man"scri,ts too dama8ed :or s"bseK"ent st"dy by other researchers;[citation needed]Gaic acid 9as discoBered by ?rench chemist and ,harmacist 4enri 3raconnot (#%&+I#&55* in #&, and st"died by ?rench chemist EhLo,hie-7"es Peo"ze (#&+%I#&'%*;2ary ,hoto8ra,hers, inc"din8 7ose,h 3ancro:t Aeade (#&+#I#&%+* and =iiam ?ox Eabot (#&++I#&%%*, "sed 8aic acid :or deBeo,in8 atent ima8es in caoty,es; It has aso been "sedas a coatin8 a8ent in zinco8ra,hy;Geor8e =ashin8ton "sed 8aic acid to comm"nicate 9ith s,ies[clarification needed] d"rin8 the American AeBo"tionary =ar, accordin8 to the miniseries America: The Story of Us;[citation needed]Gaic acid is a com,onent o: some ,yrotechnic 9histe mixt"res;Natural occurrenceGaic acid is :o"nd in a n"mber o: and ,ants; It is aso :o"nd in the aK"atic ,ant Myriophyllum spicatum and sho9s an aeo,athic e::ect on the 8ro9th o: the b"e-8reen a8aMicrocystis aeruginosa;[%]List of plants that contain the chemical Gaic acid is :o"nd in oaDs s,ecies iDe the -orth American 9hite oaD (Quercus alba*and 2"ro,ean red oaD (Quercus robur*;[&] Caesalpinia mimosoides [$] rosera (s"nde9* !hodiola rosea (Goden root* Eri,haa (Ay"rBedic herba rasayana :orm"a* Toona sinensisAsam galat0ari =iDi,edia bahasa Indonesia, ensiDo,edia bebasBelum Diperiksa6an8s"n8 De5 naBi8asi, cari Asam GalatNama IPA! [semb"nyiDan]3,4,5-trihydroxybenzoic acid-ama ain[semb"nyiDan]Gaic acidGaate3,4,5-trihydroxybenzoateIdentifikasi-omor CA! [#4$-$#-%]P"bChem 3%+!)I62!Oc#cc(cc(O*c#O*C(O*MO"ifatA"m"s moeD" C%4'O5)assa moar #%+;#. 8runet( 399%). 2ree radicals have been implicated in the etiolog" and pathogenesis of numerous disease states including cardiovascular disease( cancer and diabetes (!noue( Euzu4i( Ea4aguchi( ;i( Ta4eda( )gihara( aeuerle( 3991: ,oga( =oro( /a4amori( Fama4oshi( oso"ama( ,atao4a 8 Ariga( 3999( Terasa4a( Tamura( Ta4a"ama( ,ashimata( )htomo( =achino( 2u7isawa( Toguchi( ,anda( ,unii( ,usama( !shino( @atanabe( Eatoh( Ta4ano( Ta4ahama 8 Ea4agami( #'''). Antioxidant capacit" of gallate esters against h"drox"l( azide( and superoxide radicals has also been reported (=asa4i( Atsumi 8 Ea4urai( 3991: Eatoh( !da( Ea4agami( Tana4a 8 2u7isawa( 399%: >ors 8 =ichel( 3999: 6ulido( >ravo 8 Eaura0*alixto( #''': =etelitza( Gr"omin( Eviridov 8 ,am"shni4ov( #''3). GA is widespread in plant foods and beverages such as tea and wine and was proven to be oneof the anticarcinogenic pol"phenols present in green tea (o( *hen( Ehi( ?hang 8 Rosen( 399#: ,err" 8 Abbe"( 399$: Abu0Amsha *accetta( >ur4e( =ori( >eilin( 6udde" 8 *roft( #''3: ;andrault( 6oucheret( Ravel( Gasc( *ros 8 Teissedre( #''3). The consumption in 2rance of a diet high in saturated fat coupled with an apparentl" low incidence of coronar" heart disease (referred to as the Hfrench 6aradoxH) has been associated with the consumption of red wine (;andrault et al.( #''3). Antioxidants present in red wine have been shown to have a protective role against oxidation of ;D; in vitro (Arce( Rios 8 5olcarcel( 399%). GA is a strong chelating agent and forms complexes of high stabilit" with iron (!!!) (Ero4a( Rzad4ows4a0 >odals4a 8 =azol( 399.( ;i( >and"( Tsang 8Davison( #'''). !t has shown ph"totoxit" and antifungal activit" against Fusarium semitectum, F. fusiformis and Alternaria altternata (Dowd( Duvic4 8 Rood( 399$). GA is of great interest in arteriosclerosis prevention (Abella 8 *halas( 39$$)Fig. 1. Chemical structure of a) gallic acid; b) anion of gallic acidThe spectral properties of GA as reflected b" the absorption and fluorescence spectra received a little attention. !n view of the multiple roles pla"ed b" GA in medicine and food sciences its fluorescence could be a convenient tool to stud" the processes where GA is involved. )ur results show that GA fluorescence as measured b" its intensit"( emission and quantum "ield is p dependent.These results are further supported b" absorbance changes with p. !n biological milieu GA interacts in heterogeneous environment where its reaction rate( reactivit"( conformation and spectral properties ma" significantl" differ from those observed in aqueous( homogeneous solutions. @e thus investigated the fluorescence characteristics in nonpolar and micellar environments to enable us to mimic the changes that could ta4e place in GA fluorescence during its action in heterogeneous environment.!n this paper we have characterized the spectroscopic properties (absorption and fluorescence) and their modulation with the ionization state of GA molecules in aqueous and heterogeneous environment.MATERIALS AND MET0ODSMaterialsGallic acid( prop"l gallate and p"rogallol were from 2lu4a (2;I,A AG( German")( sodium dodec"l sulphate0(EDE)( tetradodec"ltrimeth"lammonium bromide0 (TTA>r)( J0c"clo0dextrin( gl"cerine and acr"lamide were purchased from Eigma *hemicals (E!G=A *o( /ew )rleans).)rganic solvents were from =erc4. (=GR*, *o.( IEA) The buffer used in the range of pfrom - to 9.. was sodium ammonium0acetate. The p value from # to - was ad7usted b"adding appropriate volumes of '.3 = *l to aqueous sample.All samples were prepared dail" and were measured directl" after mixing all components.MethodsThe absorption spectra from #'' nm were ta4en with ED 3''' spectrophotometer from Avantes (/etherlands) in 3 cm quartz cuvette. The fluorescence spectra were measured in 3cm path0length quartz cuvette with a Ehimadzu R2 1''3 6* spectrofluorimeter (Ehimadzu( r micelles calculated p,a3L ..- what indicates that the presence of cationic detergent changes the protonation equilibrium of GA forms.Fig. 3. The shifts of the position of emission maximum of the 5 10-6!"in buffered ammonium-acetate solutions and in $0 m TT"%r recorded atdifferent p'. +xcitation at 2,0 nm. The assignment of the cur)es is gi)en in the -egend.!n order to determine the nature of the observed interactions the absorption spectra of GA were ta4en inorganic solvents with different dielectric constant and different protic character. The spectral properties of GA in different solvents are collected in Table 3.The absorption maxima of the pea4s in organic solvents are red shifted compared to that in water. )nl" in '.3P D=E) solution the maximum is shifted to #1& nm. The positions of themaximum do not depend on the dielectric constant of the solvent and its permanent dipole moment. !n dioxane( the solvent with the lowest dielectric constant( #.#( the maximum is shifted to #&% nm compared to #&' nm in water( in alcohols to #$3 nm and to #&$ nm for acetonitrile( a nonprotic solvent with dielectric constant close to that of methanol. Euch results indicate that we observe specific interactions that in case of GA lead ver" probabl" to formation of efficient h"drogen bonding with solvent in protic solvents. Fluorescence spectra@hereas the apparent ionization process and h"drogen bonding formation detected b" absorption changes ma" reflect the behavior of GA onl" in ground state( the fluorescenceof GA will provide information of GA behavior in excited state.During our experiments the intrinsic fluorescence of GA acid was used to stud" its behavior in different conditions. 2igure - shows the change in GA fluorescence maximumposition with p in buffer and micellar solution. !n buffer solution the emission maximumof GA changes ver" fast from -&% nm at p # to -.& nm at p -.1 then remains stead" up to p 1. Eimultaneousl" the increase in intensit" is observed. The increase in fluorescence intensit" is not connected with absorbance changes observed for GA molecules at different p thus is mostl" due to higher quantum "ields of the ionized forms of GA compared to that of the neutral form which is ver" wea4l" fluorescent. *alculations show that the fluorescence quantum "ield of GA increases from '.''. at p #.1 to '.'3 at p $.The observed shift of the maximum above p & is accompanied b" a change in the shapeof spectrum( which results from the appearance of the new shoulder with maximum at .3. nm observedin the spectrum above p .. At higher p values( above %( in the presence of air( fast autooxidation of GA occurs what excludes an" further measurementsusing stationar" techniques. The presented above fluorescence data also confirm the existence of the two forms of GA. )ne( neutral form( (!a)( with emission maximum at -&% nm and another( anionic form( (!b)( with emission maximum at -.$ nm. Apparent p,a L #.. calculated from 2ig. - is much lower than that obtained from absorbance data.This indicates that in the lowest excited state GA molecule becomes more acidic then in ground state. These changes are related to the changes in charge distribution between the ground and excited states.Fig. 4. +mission spectra of 5 10-6!" obtained in buffer at p' 5.* #1) and $0 m TT"%r #2). +xcitation at 2,0 nm. Cur)e $ is the difference bet(een spectrum2 and spectrum 1. !n excited state of the GA molecule there should be a substantial decrease of electron densit" at carbox"lic h"drox" ox"gen atom leading to deprotonation at lower p than in buffer. The dielectric microenvironment experienced b" GA during its biological action would be significantl" lower than inthe bul4 aqueous phase thus we investigated the fluorescence properties of GA in environments of lower polarit" and different protic properties. >ecause above p -.# GA is a negativel" charged molecule we also chec4ed how it binds and partitions with positivel" charged micelles.!n neutral micelle TR!T)/ O03''( D=E) and anionic micelles( EDE( no changes in fluorescence spectraof GA compared to buffered solutions were noticed except that for the last one the inten sities are lower b" about #'P.!n J0c"clo dextrin small changes in position( 3 nm of red shift( and the emission intensit"( #P( were observed.!n the presence of cationic micelle TTA>r some significant changes in fluorescence spectra of GA are observed. The fluorescence intensitiesof GA in the presence of micelle are atleast two times higher compared to aqueous solutions. The positions of the fluorescence maxima are shifted with increasing p of the solution what is shown in 2igure -. !t shows that in all p range the maximum emission is blue shifted compared to the maximum observed in buffered solution. *alculated apparent p,a is about . compared to #.. found in buffered onl" solution. !n micellar environment the process of autooxidation is shifted toward higher p compared to buffered solution.Fig. 5. .luorescence intensit/ of 5 10-6!" in gl/cerin at its maximum recorded )ersus (ater content. +xcitation at 2,0 nm!t suggests that the presence of micelles protect( to a certain degree( GA molecules fromautooxidation.Above p . in the presence of TTA>r micelles the new pea4 at -9& nm appears. The emission spectrum in TTA>r is superposition of two pea4s.)ne pea4 is characteristic for the GA molecules in buffer with maximum at -.$ nm. The other pea4 located at -9$ nm( reflects the GA molecules interacting with the micellar environment. Gxamples of the emission spectra of GA in buffer and in TTA>r at p & are presented in 2ig. .. After subtraction the new spectrum with maximum at .'1 nm is revealed. !t seems obvious that this pea4 represents that part of GA anions( which interact with cationic micelle and this band will be used to determine the partition of GA molecules between phases.!n all organic solvents used different intensit" changes and different shifts of the fluorescence maximum compared to that in water are observed.The positions of the pea4s( fluorescence quantum "ields and Eto4es shifts are collected in Table 3. !n dioxane and in acetonitrile the emission maximum is located at --1 nm( in dieth"l ether at -#9 nm. !n methanol( ethanol and propanol the pea4 maxima are located around - nm and in water the maximum is located at --9 nm. The fact that the two solvents li4e methanol( protic( and acetonitrile( non0protic( with similar dielectric constants exhibit difference between positions of maxima and distinct intensities indicates that in protic and non0protic solvents two different t"pes of interaction mechanisms occur. Additionall"( in the investigated alcohols the spectral properties of GAare ver" similar( see Table 3. ;ower fluorescence intensities( red shift of the pea4 positions and similar positions of the maxima of GA observed in the presence of protic solvents( li4e alcohols( indicates on a ver" probable formation of h"drogen bonds between GA and solvent. The fact that GA in water exhibits spectral properties( except intensit"( which are closer to protic solvents( than to alcohols is an indication that GA molecule in aqueous solutions exists as h"drated molecule. !n dioxane GA shows maximum at --1 nm characteristic for non0protic solvents but it shows rather low quantum efficienc" comparable with the other protic solvents. !t ma" come from the factthat dioxane is able to form h"drogen bonds and despite its low dielectric constant behaves as a protic solvent (Echmit4e et al.( 399$). !n non0protic solvents the observed increasing quantum "ield(Table 3. Epectral and ph"sico0chemical properties of gallic acid (GA) in different solvents. Dielectric constant( dipole moment D( abosrbance and emission maxima nm( fluorescence quantum "ield and Eto4es shift cm03.Data for dielectric constants and dipole moments taken from P.W. Atkins, Physical Chemistry, ed. Freeman, New York,!"#higher energ" of emission and lower Eto4es shift indicate that excited energ" is dissipated to surrounding less efficient then in polar solvents.The lac4 of an" additional band in non0protic solvent in absorbance spectra excludes the formation of ground state complex. !n excited state the formation of new entit"( li4e excimer or dimer and GA molecule ma" occur. Gspeciall"( that GA molecule is prone to form such dimer because of the presence of carbox"lic moiet" in its structure.That carbox"lic moiet" is bearing donor function of ) group and acceptor function of *L) group.Therefore the" ma" form ver" stable h"drogen bonded dimers( especiall" in nonprotic solvents.owever( the data presented in Table 3( li4e blue shift and higher quantum "ield compared to protic solvents( indicates that emission occur from monomeric forms of GA molecules. This indicates on the van der @aals interactions between excited GA molecules and solvent molecules.The absorption and emission spectra of GA in gl"cerin and gl"cerin0water mixtures were ta4en in order to explore the influence of viscosit" on the observed phenomena. The plotof fluorescence intensit" at its maximum versus water content is given in 2ig. 1. The sudden drop of the fluorescence intensit" when water is added to the s"stem is observed. This confirms again that h"drogen bond formation is the main phenomenon in protic solvents( which is responsible for the spectroscopic properties of GA.The observed intensit" increase( spectral shift and newl" formed pea4 indicates that in the presence of cationic detergent occur some interactions which lead to partition of GA forms between aqueous and micellar phases. >ecause the h"drophilic character of GA molecule prevents it from entering micellar interior( the main force responsible for the observed spectrum is an electrostatic interaction between charged micelle and GA anion.Fluorescence quenching and partition studies!n order to estimate how GA molecules are distributed between micellar and aqueous phase we used the spectra( which characterize GA in aqueous solutions( pea4 at -.$ nm(and micellar solutions( pea4 at .'1 nm. The method was described in the =ethods section. *alculated area under that band divided b" the area of the whole spectrum recorded in micellar phase gave the partition coefficient.)btained that wa" values indicate that at p ..# about $'P of GA molecules interact with micellar environment. This partition is slowl" decreasing with p and starting from p 1.. it remains constant at 1'P up to p $. Ta4ing into account the fact that the micelle concentration at given condition is two orders of magnitude higher than concentration of GA molecules( this behavior ma" reflect the process connected with concentration equilibrium between excited GA anions and available cationic micelles..ig. 6. +mission intensit/ of 5 10-6!" obser)ed at *05 nm )ersus TT"%r micelle concentration at p' 5.*. +xcitation at 2,0 nm. To explain this problem we observedthe behavior of GA emission recorded at .'1 nm with increasing concentration of TTA>r micelle. The results are presented in 2ig. &. At low concentration of TTA>r( bellow 3.1 m=( the GA fluorescence is quenched. Above 3.1 m= the emission intensit" shows sharp increase what arises from the interactions between single molecule of TTA>r and GA. Above $ m= TTA>r(close to critical micelle concentration (cmc) literature value for that detergent (@omac4( ,endall 8 =acDonald( 39%-)( the emission increases much slower compared to the premicellar concentrations of the detergent. This comes from the fact that in micelles the existence of so called Etern la"er( where up to $'P of counterions reside( ma" repulse part of the anionic GA molecules.Quenching studies were carried out to determine the localization of GA molecules and determine how GA molecules interact with micelles. The results are presented as the Etern05olmer plot in 2ig. $. !t shows the data for GA in solution at p & in the presence of detergent and without. The fluorescence intensities are monitored at -.$ nm and .'1 nm( which describe the GA molecules in aqueous and micellar phase respectivel". !n buffer solutions and in the presence of detergent( the plots are straight lines with larger slope in micellar environment. The calculated quenching constant var" from $%& L 3&.$ =B3 in buffer to $%& L 39.#=B3 (at -.$ nm in micelle) and .% =B3 (at .'1 nm) in TTA>r. Those results indicate thatquencher has equal access to GA molecules in bul4 phase in both environments. !n micellar environment more efficient quenching occurs. This indicates that GA molecule definitel" is not embedded into micellar interior and quenching is the result of the electrostatic interactions between charged GA anion( cationic micelle TTA>r and a quencher. The higher quenching constant of GA in micelle ma" come from the fact that electrostatic interaction between quencher ion with cationic micelle changes the concentration homogeneit" of quencher molecules around micelle. This causes that morefluorophores are ad7acent to a quencher at the moment of excitation and the deactivation process is more efficient.Quantum-mechanical calculationsFig. 7. 0tern-1olmer plots of 5 1026!" emission &uenched b/ acr/lamide in buffered solution at p' 5.* and (ith added $0 m detergent TT"%r. +xcitation at 2,0 nm. 3ata are ta4en at $65 nm in buffer and *05 nm in TT"%r. The assignment of the cur)es is gi)en in the -egend.Ising 6=- semi0empirical method we calculated the distribution of electron densit" for ground and few lowest excited states for neutral and ionic forms of GA. Those calculations show that electron densit" distribution in ground state are mainl" located on the aromatic ring and ox"gen ) atoms of h"drox"l groups attached to the aromatic ring.!n the lowest excited states the electron densit" is still mainl" located on aromatic ring however some of electronic charge is shifted to the carbox"lic moiet". The calculation also have shown that GA molecule in neutral and anionic form in the ground state ma" form five to eight h"drogen bonds with water molecules. Distribution of electron densit" on the flexible groups( especiall"when connected through h"drogen bonds to surrounding environment( forms man" paths to deexcite GA molecule and ma" explain observed low fluorescence quantum "ield in protic solvents.These calculations confirm our conclusions based on the experimental results that in protic solvent GA molecule exists as a highl" h"drated molecule.DISCUSSIONThe presented results show that GA absorbance and fluorescence (intensit"( emission maximum and shape) depend on the p of the solvent. The apparent p,a values of GA obtained from our experiments are close to p,a3L-.3- and p,a#L%..1 as reported b" >"4ova et al. (39$'). An examination of chemical structure of GA shows that there are two ionizable moieties in the GA molecule+ the carbox"lic group and three phenolic h"drox"l groups. The first p,a value for that molecule is connected with ionization at carbox"lic group. At basic p( above p %.1( the observed maximum at #91 nm is ver" probabl" associated with ionization of the proton of %0h"drox" group because 10) group has ver" high p,a due to efficient intramolecularbonding. Euch coincidence found for the p,a values clearl" indicates that observed changes are not due to solel" excited0state processes but rather are connected with ionization state of the GA moleculewhere neutral and anionic forms are present. The effect of micelles on the protonation equilibrium of GA can be explained on the basis of the pseudophase ion exchange model (Romsted 8 ?anette( 39%%). !n terms of this model( the shifts in p,a values( compared to buffer solution( is caused b" transfer of GA monoanion into cationic surface of TTA>r. This leads to new the neutral0monoanion equilibrium at higher p.!n the lowest excited state GA molecule undergoes dissociation at lower p( #.$( what indicates on the charge decrease on the ox"gen atom in ) group in carbox"lic moiet". !n micelle in the excited state the new neutral0monoanion equilibrium at p,a L . is established which is close to that in ground state( ..1. This indicates that interaction between micelle and GA molecules is independent on protic properties of solvent and thisdriving force is an electrostatic interaction.Absorption spectrum of p"rogallol( a compound that has structure similar to GA except isdevoid of carbox"lic group( do not exhibit an" shift in water and organic solvents and its absorbance maximum positions are similar to that observed for GA. 2or prop"l gallate( derivative of GA with carbox"l group replaced b" prop"l group( the absorption maximum in water is shifted to #&9 nm. This data suggest that h"drogen bonding interactions is the main interaction in protic solvents and that absorption spectrum is sub7ect to change when significant changes in the electronic distribution in the GA molecule occurs( i.e. li4ea new( more h"drophobic prop"l moiet" is attached.The variation of fluorescence quantum "ield of GA with p can be further interpreted b" use of the rotamer model based on the quantummechanical calculation. According to thismodel this process ma" be rationalized in terms of electrostatic repulsion between deprotonated ox"gen from carbox"lic group and R0electrons from aromatic ring. !n case of neutral form( at pSp,a3( such interactions are much wea4er and whole group ma" rotate freel" then dissipation of excitation energ" is ver" efficient and "ield of fluorescence is ver" low. At pTp,a3 but lower than p,a# GA will exist predominantl" asanion. This is due to stabilization gained from the energeticall" favorable electrostatic interactions between negativel" charged h"drox"l ox"gen from carbox"lic group and R0electrons from aromatic ring. Thus the molecule becomes more rigid and fluorescence quantum "ield increases. This model calculated for the molecule in vacuum is probabl" correct for neutral form of GA( where quantum "ield is indeed ver" low. !n protic solventswhere efficient h"dration of GA molecule occurs the steric hindrance is canceled b" the attached solvents molecules what efficientl" dissipate excitation energ" and even for anionic form the fluorescence quantum "ield is low.!ncubation of GA acid with D)DA> membranes( data not shown( J0c"clodextrin and micelles did not result in appreciable partitioning or binding( as evidenced b" a lac4 of change of fluorescence maximum( quantum "ield and quenching.The inabilit" of GA to bind to the membrane and micelles could be attributed to its insufficient h"drophobicit".!n ph"siological conditions interactions between molecules occur in the dielectric microenvironment which is different then aqueous and additionall" depend on the h"drophobic nature of the molecule. The obtained results indicate that the binding of GA to involves some t"pe of specific polar interactions. The fact that neutral GA molecule does not interact with cationic micelle whereas anionic GA molecules interact with cationic micelle easil" indicates on electrostatic forces as a main mechanism responsible for that phenomenon.The results of spectroscopic studies reported here indicate that GA molecule ma" exert its biological role b" combining its electrostatic and h"drogen bonding properties according to actual microenvironment.AcknowledgmenThis wor4 was supported b" grant DE 1'%U%#0# from the Agricultural Iniversit" of 6oznaV( 6oland. The authors wish to than4 to =r 6iotr Rolews4i for a great technical assistance during measurements.GALLIC ACIDMSDS Number: G0806 --- Effective Date: 10/29/011. Prou!" Ie#"i$i!%"io#"#non#ms( 3,4,5-Erihydroxybenzoic acid, monohydrateG 8aic acid, monohydrate!A" No)( #4$-$#-% (Anhydro"s* 5$$5-&'-& ()onohydrate**olecular +eight( #&&;#4!hemical ,ormula( C'4.(O4*3COO4;4.OProduct !odes( 7;E; 3aDer5 )'&5)aincDrodt5 3##.&. Com'o(i"io#)I#$orm%"io# o# I#greie#"(IngredientCAS No Percent Hazardous--------------------------------------- ------------ ------------ ---------Gallic Acid149-91-7100% Yes3. *%+%r( Ie#"i$i!%"io#-mergenc# ./er/ie$--------------------------!A0I.N1 *A2 !A"- IRRI0A0I.N 0. "3IN4 -2-"4 AND R-"PIRA0.R2 0RA!0)5)0) Baker "A,606DA0A&tm' Aatin8s (ProBided here :or yo"r conBenience*-----------------------------------------------------------------------------------------------------------4eath Aatin85 # - !i8ht?ammabiity Aatin85 # - !i8htAeactiBity Aatin85 + - -oneContact Aatin85 # - !i8ht6ab ProtectiBe 2K"i,5 GOGG62!G 6A3 COAE!tora8e Coor Code5 Oran8e (Genera !tora8e*-----------------------------------------------------------------------------------------------------------Potential Health -ffects----------------------------------Ehere is ins"::icient data in the ,"bished iterat"re to ,er:orm a com,ete hazard eBa"ation :or this ,rod"ct;!,ecia ,reca"tions m"st be "sed in stora8e, "se and handin8; ProtectiBe eK"i,ment sho"d be chosen "sin8 ,ro:essiona O"d8ment;Inhalation()ay ca"se irritation to res,iratory tract res"tin8 in co"8hin8 and sneezin8;Ingestion(6o9 systemic toxicity; 6ar8e amo"nts may ca"se some 8astrointestina discom:ort, na"sea or diarrhea;"kin !ontact()ay ca"se irritation to the sDin 9ith redness or minor in:ammation on moist sDin;-#e !ontact()ay ca"se eye irritation d"e to ,ossibe tem,orary abrasiBeness; Can ca"se redness, tearin8 and ,ossiby some ,ain;!hronic -xposure(-o in:ormation :o"nd;Aggra/ation of Pre6existing !onditions(-o adBerse heath e::ects ex,ected;4. Fir(" Ai Me%(ure(Inhalation(AemoBe to :resh air; Get medica attention :or any breathin8 di::ic"ty;Ingestion(GiBe seBera 8asses o: 9ater to drinD to di"te; I: ar8e amo"nts 9ere s9ao9ed, 8et medicaadBice;"kin !ontact(=ash ex,osed area 9ith soa, and 9ater; Get medica adBice i: irritation deBeo,s;-#e !ontact(=ash eyes 9ith ,enty o: 9ater :or at east #5 min"tes; Ca a ,hysician;5. Fire Fig,"i#g Me%(ure(,ire(As 9ith most or8anic soids, :ire is ,ossibe at eeBated tem,erat"res or by contact 9ith an i8nition so"rce;-xplosion(-ot considered to be an ex,osion hazard;,ire -xtinguishing *edia(=ater s,ray, dry chemica, acoho :oam, or carbon dioxide;"pecial Information(In the eBent o: a :ire, 9ear :" ,rotectiBe cothin8 and -IO!4-a,,roBed se:-contained breathin8 a,,arat"s 9ith :" :ace,iece o,erated in the ,ress"re demand or other ,ositiBe ,ress"re mode;6. A!!ie#"%- .e-e%(e Me%(ure(AemoBe a so"rces o: i8nition; Pentiate area o: eaD or s,i; =ear a,,ro,riate ,ersona ,rotectiBe eK"i,ment as s,eci:ied in !ection &; !,is5 !9ee, ", and containerize :or recamation or dis,osa; Pac""min8 or 9et s9ee,in8 may be "sed to aBoid d"st dis,ersa;7. *%#-i#g %# S"or%ge1ee, in a ti8hty cosed container, stored in a coo, dry, Bentiated area; Protect a8ainst ,hysica dama8e; Protect :rom i8ht; Containers o: this materia may be hazardo"s 9hen em,ty since they retain ,rod"ct resid"es (d"st, soids*G obserBe a 9arnin8s and ,reca"tions isted :or the ,rod"ct;8. /0'o(ure Co#"ro-()Per(o#%- Pro"e!"io#Air7orne -xposure Limits(-one estabished;8entilation "#stem(A system o: oca andur4e 5.( =ori T.A.( >eilin ;.lagodats4ava ?.G. (39$'). Relative acidit" of phenol and its derivatives in a medium of nonaqueous solvents. -h. ./shch. $him.( 34( ##910-'''.Dowd 6.2.( Duvic4 odals4a .8 =azol !. (399.). Antioxidative effect of extracts from Grodium cicutarium ;. - Naturforsch 7C8( 3:( %%30%%..Terasa4a .( Tamura A.( Ta4a"ama 2.( ,ashimata =.( )htomo ,.( =achino =.( 2u7isawa E.( Toguchi =.( ,anda F.( ,unii E.( ,usama ,.( !shino A.( @atanabe E.( Eatoh ,.( Ta4ano .( Ta4ahama =.8 Ea4agami . (#'''). !nduction of apoptosis b" dopamine in human oral tumor cell lines. Anticancer 'es( 54( #.-0#1'.@omac4 =.D.( ,endall D.A.8 =acDonald R.*. (39%-). Detergent effects on enz"me activit" and solubilization of lipid bila"er membranes. (iochim (iophys Acta( 722( #3'0#31.?heng @. 8 @ang E.F. (#''3). Antioxidant Activit" and 6henolic *ompounds in Eelected erbs. * A+ric Food Chem( 3:( 13&1013$'.http://taninos.tripod.com/acidogalico.htm"u7stance(Gallic acid *ain !hem"pider page )oec"ar :orm"a5 C%4'O5 )oar mass5 #%+;#.+ CA! Ae8istry -"mber5 -ot aBaiabe A,,earance5 3,4,5-Erihydroxybenzoic acid, anhydro"s, $$TG 3,4,5-Erihydroxybenzoic acid, anhydro"s, $$TG 9hite ,o9der )etin8 ,oint5 .5# 3oiin8 ,oint5 .%3 to .%4 !o"biity5 =ater, #;#$eU++4 m8