Download - Research Article Influence of Hydroxypropyl- -Cyclodextrin ...downloads.hindawi.com/journals/ijp/2014/489873.pdf · Research Article Influence of Hydroxypropyl- -Cyclodextrin on the

Research ArticleInfluence of Hydroxypropyl-120573-Cyclodextrin onthe Photostability of Fungicide Pyrimethanil

Carlos Fernandes12 Igor Encarnaccedilatildeo12 Alexandra Gaspar12 Jorge Garrido12

Fernanda Borges2 and E Manuela Garrido12

1 Departamento de Engenharia Quımica Instituto Superior de Engenharia do Porto (ISEP)Instituto Politecnico do Porto 4200-072 Porto Portugal

2 CIQDepartamento de Quımica e Bioquımica Faculdade de Ciencias Universidade do Porto 4169-007 Porto Portugal

Correspondence should be addressed to Jorge Garrido jjgisepipppt

Received 2 December 2013 Revised 17 January 2014 Accepted 22 January 2014 Published 11 March 2014

Academic Editor Leonardo Palmisano

Copyright copy 2014 Carlos Fernandes 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

Pesticides continue to play an important role in pestmanagement However the intensive pesticide application has triggered severalenvironment negative effects that cannot be disregarded In this study the inclusion complex of pyrimethanil with HP-120573-CD hasbeen prepared and characterized by proton nuclearmagnetic resonance spectroscopyThe formation of the pyrimethanilHP-120573-CDinclusion complex increased the aqueous solubility of this fungicide aroundfive times To assess the influence ofmicroencapsulationon the environmental photostability of the fungicide the photochemical degradation of pyrimethanil and pyrimethanilHP-120573-CD inclusion complex has been investigated in different aqueous media such as ultrapure and river water under simulated solarirradiation The studies allow concluding that pyrimethanilHP-120573-CD inclusion complex increases significantly the photostabilityof the fungicide in aqueous solutions especially in natural water Actually the half-life of pyrimethanilHP-120573-CD inclusion complexwas increased approximately by a factor of four when compared to the free fungicideThe overall results point out that pyrimethanilcan be successfully encapsulated by HP-120573-CD a process that can improve its solubility and photostability properties

1 Introduction

Farmers use a wide range of chemical compounds to limitdamage losses in agriculture upcoming from pests In factnowadays a large percentage of crops are destroyed beforeharvest due to the presence of pests for instance of fungusorigin [1] In order to minimize the damage provoked bypests chemical compounds such as pesticides are widelyused in the agricultural production They can prevent orreduce losses and thus increase yield as well as the qualityof the product [2] Scientific research has been intense inpesticides area either with the goal of increasing the efficacyand reducing the nontarget effects or for reducing theirenvironmental risks [3ndash6]

The increase of pesticides consumption does not nec-essarily reflect the amount of pesticide that is actuallyapplied to pests partly because pesticide delivery systems

are inefficient [7] Some estimates concluded that less than1 of applied pesticides really reach the targets [8] Sunlightphotodegradation is one of the most destructive pathwaysfor pesticides after their release into the environment Infact photochemical reactions are one of the most frequentlydescribed transformations of pesticides in the environmentTherefore studies on the photodegradation processes canprovide a better knowledge on the transformations processesof pesticides in the environment and consequently on theiroxidationdegradation rate [9 10]

A class of pesticides which presents risks for environmentis the fungicides Actually the regular use of this type ofcompounds can potentially pose a risk to the environmentparticularly if their residues persist in the soil or migrateoff-site and enter waterways causing adverse impacts on thehealth of terrestrial and aquatic ecosystems However therisk to the environment posed by the use of fungicides in

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2014 Article ID 489873 8 pageshttpdxdoiorg1011552014489873

2 International Journal of Photoenergy

N

N

CH3

H3C NH

(a)

O

RO

RO

OOR

O

ORRO

O

OR O

OR

ORO

RO

O

OR

OR

ORO

O

OR

OR

O

RO

O

ROOR

O

RO

ORO

RO

O

OR

R = OCHndash2CH(CH3)OH or ndashH

HP-120573-CD

(b)

Figure 1 Schematic representation of (a) chemical structure of pyrimethanil and (b) 3D structure of (2-hydroxypropyl)-120573-cyclodextrin (HP-120573-CD)

horticultural production systems has received relatively littleattention when compared to other types of agrochemicalssuch as insecticides and herbicides [11]

Pyrimethanil N-(46-dimethylpyrimidin-2-yl)aniline(Figure 1(a)) is an anilino-pyrimidine fungicide particularlyactive against gray mold (Botrytis cinerea) and pear scab(Venturia spp) on fruits vegetables and ornamental plantsThe photodegradation by sunlight plays a significant role inpyrimethanil degradation due to its long half-life (approx 77days) in the environment [12] Although pyrimethanil hasno apparent mutagenic genotoxic or carcinogenic potentialthe concentration of pyrimethanil has been limited in foodcommodities by the European Commission [13 14] It is thusimportant to increase fungicide efficacy at reduced doses Inthis sense controlled release formulations of pesticides havebecome a very active research area in recent years Controlledrelease formulations of fungicides can allow extended periodsof activity while minimizing the environmental effects ofuse Concern over the contamination of soil and water hasled to the development of formulations that prevent entry

of the pesticides into the groundwater while maintainingeffective pest control In this context microencapsulationbecomes the most appellative industrial process for theproduction of controlled release agricultural formulations[15 16]

Cyclodextrins (CDs) are a group of naturally occurringcyclic oligosaccharides derived from starch with six sevenor eight glucose residues linked by 120572 (1ndash4) glycosidic bonds ina cylinder-shaped structure (Figure 1(b))The CDs structuralcharacteristics a hydrophobic interior cavity and hydrophilicshell and their ability to alter the physical chemical andbiological properties of guest molecules have been regardedas a solution to improve pesticide formulations When apesticide is complexed with CD the interaction of the sidegroups on the guest pesticide molecule with the hydroxyl orsubstituted hydroxyl groups of the host can have an effect onthe reactivity of the guest molecule [17] Depending upon thegroup on the pesticide molecule this can result in catalysisof the reaction or stabilization of the guest molecule byprevention of chemical reactions [17] Studies of the catalytic

International Journal of Photoenergy 3

effects of CDs on the degradation of pesticides are thereforeimportant for an understanding of their persistence and fatein natural environments

This workwas aimed at studying the inclusion effect of (2-hydroxypropyl)-120573-cyclodextrin (HP-120573-CD) on the chemicaland photochemical properties of fungicide pyrimethanilUltraviolet spectroscopy and nuclear magnetic resonance(NMR) studies have been carried out to elucidate the strengthand binding mode of association of the complex The influ-ence of microencapsulation of pyrimethanil by HP-120573-CD onits rate of photodegradation was also assessed

2 Experimental

21 Reagents and Water Samples Pyrimethanil (2-hydroxypropyl)-120573-cyclodextrin (HP-120573-CD) and MeOD-D4(9996) were purchased from Sigma-Aldrich Quımica

(Sintra Portugal) Analytical grade reagents purchased fromSigma-Aldrich Quımica (Sintra Portugal) were used withoutadditional purification The water used was purified with aMillipore system (Milli-Q-50 18MΩ cm)

HPLC-grade acetonitrile and methanol were obtainedfrom Carlo Erba Prior to use the solvents were filteredthrough a 045 120583m filter

Environmental water used in the experiments was col-lected from Leca river basin located in the north of PortugalThe water samples were obtained from the top metre in25 L brown glass bottles Immediately after arrival in thelaboratory the samples were filtered through 1 120583m glass fibrefilters and 045120583m cellulose acetate filters sequentially toremove suspended particles and refrigerated at 4∘C prior touse

22 Apparatus The HPLC determinations [18] were per-formed using a HPLCDAD system consisting in a Shi-madzu instrument (pumps model LC-20AD Tokyo Japan)equipped with a commercially prepacked Nucleosil 100-5C18 analytical column (250mm times 46mm 5 120583m Macherey-Nagel Duren Germany) and UV detection (SPD-M20A)at the wavelength maximum determined by the analysis ofthe UV spectrum (268 nm) The mobile phase consisted ofmethanolwater (75 25 vv) It was delivered isocratically at1mLminminus1 at room temperature

The chromatographic data was processed in a Sam-sung computer fitted with LabSolutions software (ShimadzuJapan)1HNMR spectra were obtained at room temperature and

recorded on a Bruker Avance III operating at 400MHz TheNMR experiments were carried out in deuterated methanol(MeOD) Chemical shifts are expressed in 120575 (ppm) valuesrelative to tetramethylsilane (TMS) as internal referenceChemical shifts changes (Δ120575) were calculated according tothe formula Δ120575 = 120575

(complex) minus 120575(free)

23 Phase Solubility Studies Phase solubility studies werecarried out according to the procedure previously reported[5] Briefly an excess amount of pyrimethanil (20mg) wasadded to 25mL of aqueous solutions containing increasing

concentrations of HP-120573-CD (0ndash35mM) Then the suspen-sions were shaken on an incubator shaker (Ika KS 4000i)at 25 plusmn 2∘C for 2 days After the equilibrium was reachedsuspensions were filtered and properly diluted The con-centrations of pyrimethanil were determined spectrophoto-metrically (Shimadzu UV-Vis Spectrophotometer UV-1700PharmaSpec Japan) at 268 nm Each experiment was car-ried out in triplicate The apparent stability constant Kswas calculated from the phase solubility diagram with theassumption of 1 1 stoichiometry according to (1)

119870s = slope1198780(1 minus slope)

(1)

1198780is the solubility of pyrimethanil in the absence of HP-120573-

CD

24 Preparation of the PyrimethanilHP-120573-CD Inclusion Com-plex The pyrimethanilHP-120573-CD complex was prepared bykneading procedure Equimolar amounts of pyrimethaniland HP-120573-CD were accurately weighed and mixed togetherusing a mortar The mixture was then triturated and anappropriate amount of ethanol was added till a homogenouspaste was formedThe paste was then kneaded for 45min anddried at 50∘C in an oven under vacuum The dried productwas gently ground into a fine powder

25 Irradiation Experiments Photodegradation rates ofpyrimethanil were determined in natural water (Leca river)and in ultrapure water under simulated solar radiationPhotodegradation studies were carried out using a FitoclimaS600PL thermostatic chamber (Aralab Portugal) equippedwith eight Repti Glo (20 W) UV-Vis lamps to simulate solarradiations (UVB 280ndash315 nm (10) UVA 320ndash370 nm (33)and 400ndash640 nm (57)) Considering the emission spectraof the lamps (280ndash640 nm) all tests were performed usingcapped pyrex (275 nm cut off) flasks Aqueous solutions ofpyrimethanil (25mL 005mmolL) weremaintained at roomtemperature and exposed (in a 60-degree angle positionrelative to the radiation source) to UV-Vis irradiation for 42days at a fixed distance of 30 cm At this distance the irradia-tion intensity reaching the sample surface was approximately12mWsdotcmminus2 Similar experiments were performed in thepresence of HP-120573-CD at a concentration of 300mM Controlexperiments in the dark (blank experiments) under the sameconditions and initial concentrations of pyrimethanil sampleswere carried out in parallel for comparison At selectedtime intervals samples were collected and quantitativelyanalyzed after proper dilution by high performance liquidchromatography (HPLC)The amount of pyrimethanil in thesolution after irradiation was calculated based on externalcalibration All experiments were carried out in triplicate at25 plusmn 1∘C

26 Analysis of Data Thedisappearance rate of pyrimethanilfollows first-order kinetics given by the equation

119862119905= 1198620119890minus119896119905 (2)


00 50 100 150 200 250 300 350 40002

04

06

08

10

12

14

16

18

20

[Pyr

imet

hani

l] (m

M)

[HP-120573-CD] (mM)

Figure 2 Phase solubility diagram obtained for fungicidepyrimethanil and increasing concentrations of HP-120573-CD in waterat 25∘C Each point represents the mean of three determinations

where 1198620and 119862

119905are the concentrations at times 0 and 119905 119905 is

the irradiation time and 119896 is the first-order rate constantThe half-life (119905

12) of pyrimethanil time required for its

concentration to decrease to half its initial value is related tothe rate constant by the equation 119905

12= ln 2119896

Results are expressed as mean plusmn standard error (3independent samples) Statistically significant difference wasdetermined using the Studentrsquos t-test and analysis of variance(Anova) with 119875 = 005 as a minimal level of significance

3 Results and Discussion

31 Phase Solubility Studies The stoichiometric ratio andstability constant of the inclusion complex were derivedfrom the changes in the solubility of pyrimethanil in thepresence of increasing amounts of HP-120573-CD measured byUV spectrophotometry Figure 2 presents the phase solubilityplot obtained for pyrimethanil and increasing concentrationsof HP-120573-CD in water at 25∘C

As can be seen it shows119860119871-type solubility diagram as the

pyrimethanil solubility increases with increasing HP-120573-CDconcentrations according to the classification established byHiguchi and Connors [19] The linear host-guest correlation(1199032 = 09994) and the slope of 00402 suggest the formationof a 1 1 complex with respect to HP-120573-CD concentration[19] The apparent stability constant Ks obtained from thestraight-line portion of the phase solubility diagram was100 plusmn 10Mminus1 (see (1)) Results evidenced that pyrimethanilsolubility is enhanced by the HP-120573-CD inclusion complex-ation Actually the formation of the inclusion complex hasincreased the solubility of pyrimethanil in water around 5times when compared with the free fungicide

32 Nuclear Magnetic Resonance Analysis Nuclear magneticresonance (NMR) spectroscopy is a powerful and versa-tile method for structure elucidation Thus it has beenwidely used for studying inclusion complexes formed by

cyclodextrins [17] NMR spectroscopy provides a superiormethod to study complexation phenomena because guestand hostmolecules are simultaneously observed at the atomiclevel Therefore evidences were acquired by proton nuclearmagnetic resonance (1H NMR) to confirm the inclusion ofpyrimethanil inside of cavity of HP-120573-CD as the formationof inclusion complex will cause a modification on protonchemical shifts in the 1H NMR spectra The variation of thechemical shift displacements (Δ120575) defined as the differencein chemical shift in the presence and absence of the hostwill reflect the degree of the intermolecular proximity of theprotons directly involved in the encapsulation process Theobserved changes are intrinsically related to the position ofthe molecule into the CD cavity1H-NMR spectra of pyrimethanil HP-120573-CD and

pyrimethanilHP-120573-CD synthesized by kneading procedure(see Subsection 24) are shown in Figure 3 Due to the lowaqueous solubility of pyrimethanil the NMR measurementshave been carried out in methanol-119889

4 The proton chemical

shifts (120575) data found for pyrimethanil HP-120573-CD andpyrimethanilHP-120573-CD complex are shown in Table 1

HP-120573-CD cyclodextrin consists of seven identicalmonomers that assume a cone-shaped structure Inconsequence protons H110158401015840 H210158401015840 and H410158401015840 are orientedtowards the outside of the cavity whereas the H310158401015840 and H510158401015840protons are facing the interior of the CD cavity and H610158401015840protons are located in the narrower end of CD rim (Figures 1and 3) [20 21] The numbering of the hydrogen atoms facedinside and outside of the CD cavities has been ascribed inaccordance with the literature [20 21] Owing to their innerlocalization H310158401015840 and H510158401015840 are frequently the most affectedprotons upon complexation which results in a variation oftheir shifts

The chemical shift displacements found in the spectraof pyrimethanilHP-120573-CD when compared with free fungi-cide (guest) point out the occurrence of a complexationprocess that can be attributed to the influence of the guest(pyrimethanil) included in CD cavity In the presence ofHP-120573-CD pyrimethanil protons exhibit noticeable downfieldshifts (Δ120575 gt 0) evidencing the occurrence of host-guestinteractionsAs the higherΔ120575 values are related to the protonsof methyl groups and H5 it is reasonable to speculate thatthe pyrimidine ring (Table 1) is included in the lipophiliccore of HP-120573-CD The smooth variation in chemical shiftsand the absence of new peaks that could be assigned tothe complex suggest the occurrence of a dynamic processwith a fast exchange between free pyrimethanil and includedforms The low shifts deviations observed in the spectrafor the H310158401015840 and H510158401015840 signals of HP-120573-CD in the inclusioncomplex can be related to the cyclodextrin nature Actuallythe HP-120573-CD protons especially H310158401015840 and H510158401015840 are difficultto assign as the cyclodextrin contains between 10 and 45of hydroxypropoxy groups randomly distributed a realitythat is translated in the appearance of broad and overlappedresonance signals in the spectra [21]

In summary the mentioned displacements are indicativeof the presence of host-guest interactions and the forma-tion of the inclusion complex The stoichiometry of the


Pyrimethanil

HP-120573-CD

PyrimethanilHP-120573-CD

8 6 4 2 0

76 74 72 70 68 66 26 24 22 20

Figure 3 1H NMR spectra of pyrimethanil HP-120573-CD and pyrimethanilHP-120573-CD inclusion complex

Table 1 1H NMR chemical shift (120575) data of pyrimethanil HP-120573-CD and pyrimethanilHP-120573-CD inclusion complex

N

N

CH3

H3C

H

NH

H

H H

H

H

1

23

4

56

Pyrimethanil

1998400

2998400

3998400

4998400

5998400

6998400

O

H

O

H

RO

H

HORH

O

OR

7

HP-120573-CD

R = H or CH2CHOCH3

1998400998400

2998400998400

3998400998400

4998400998400

5998400998400

6998400998400

middot

H assignment 120575 pyrimethanil(CH3OD)

120575HP-120573-CD(CH3OD)

120575 pyrimethanilHP-120573-CD(CH3OD)

Δ120575

2 times (CH3) 2315 (s) mdash 2338 0023H5 6538 (s) mdash 6581 0043H41015840 6954 (m) mdash 6967 0013H31015840H51015840 7257 (dd) mdash 7271 0014H21015840H61015840 7669 (dd) mdash 7671 0002H110158401015840 mdash 5048 (m) 5046 minus0002H310158401015840 mdash 3967 (s) 3950 minus0017H610158401015840 mdash 3831 (s) 3828 minus0003H510158401015840 mdash 3727 (s) 3731 0004H210158401015840 mdash 3528 (m) 3529 0001H410158401015840 mdash 3413 (m) 3417 0004


0 10 20 30 4020

30

40

50

60

70

80

90

100

110

Dark control river waterRiver waterDark control ultrapure waterUltrapure water

Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)

Irradiation time (days)

Figure 4 Photodegradation of pyrimethanil in (open red circlesolid red circle) ultrapure and (open blue square solid blue square)river water under simulated solar irradiation

complex was calculated by integration of the 1HNMR signalsat 6538 and 5048 ppm related to the protons of H5 ofpyrimethanil and H110158401015840 of HP-120573-CD respectively The ratio ofpyrimethanilHP-120573-CD inclusion complex was 1 1

33 Photodegradation Studies Previous studies on the degra-dation of pyrimethanil were carried out mainly in a wastewater treatment context and focused on the photocatalyticdegradation using various salts as catalysts [22ndash24] Recentlythe identification and elucidation of the structures of UV-visible phototransformation products of pyrimethanil inwater have been accomplished [12]

In order to comprehend the photodegradation process ofthe fungicide and to evaluate the effect of its microencapsu-lation by HP-120573-CD on its environmental impact the rate ofphotodegradation of pyrimethanil and pyrimethanilHP-120573-CD complex was assessed in ultrapure and in natural water

The degradation of pyrimethanil was followed by HPLCmeasurements of the remaining concentration of the fungi-cide or its HP-120573-CD complex in aqueous solution undersimulated solar radiation

The percentage of free and HP-120573-CD-complexedpyrimethanil concentrations (obtained by HPLC analysis)was plotted as a function of time as shown in Figures4 and 5 The photodegradation kinetics of pyrimethanildisappearance was of first-order in all cases (ultrapureand river water) In fact pyrimethanil photodegradationprofile followed an exponential decay showing that it isaffected by photoirradiation in solution On the contrary nodisappearance of pyrimethanil has been detected in the darkexperiments (Figure 4) demonstrating that the disappearanceof this fungicide was only due to photodegradationpermitting the exclusion of other phenomena such as

0 10 20 30 40 5070

75

80

85

90

95

100


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)


Figure 5 Photodegradation of pyrimethanilHP-120573-CD inclusioncomplex in (open red circle solid red circle) ultrapure and (openblue square solid blue square) river water under simulated solarirradiation

microbial degradation The photodegradation rate ofpyrimethanil was much higher in river water than inultrapure water showing that there is a relation betweenthe degradation of the fungicide and the constitution ofthe irradiated media After 42 days of irradiation thecontent of pyrimethanil remaining in ultrapure and inriver water was 905 and 294 respectively Actually thephototransformation of a pollutant in surface water mayresult from the light absorption by the compound or may bephotoinduced by natural organic or inorganic substancessuch as organic matter or nitrate ions present in the water[25 26]

Table 2 lists the values of the rate constant (119896) and half-life(11990512) for the kinetics of the photodegradation of pyrimethanil

for simulated solar irradiationThe irradiation of pyrimethanil in aqueous solution in the

presence of HP-120573-CD (30mM) showed a significant decreasein the degradation of fungicide throughout the course ofirradiation more noticeable in the case of river waterdemonstrating the photoprotective effect of the cyclodextrin(Figure 5) Actually cyclodextrin-encapsulated pyrimethanilwas more slowly photodegraded in all the waters studiedproducing first-order rate constants of 212 versus 208 forultrapure water and 292 versus 72 for river water respec-tively (Table 2) In river water the half-lives were increasedapproximately by a factor of four After 42 days of irradiationthe content of HP-120573-CD-complexed pyrimethanil remain-ing in ultrapure and in river water was 978 and 759respectively The microencapsulation in HP-120573-CD seems toact as a physical barrier through which the encapsulatedpyrimethanil is protected against the action of light andornatural photocatalysts present in the water This may explainwhy the residual concentrations of pyrimethanil in river


Table 2 Kinetic parameters of pyrimethanil photodegradation in different aqueous media

Fungicide Concentration HP-120573-CD (mM) Water type 119896 (10minus3 sdot daysminus1) 11990512

(days)

Pyrimethanil0 Ultrapure 212 plusmn 01 327 plusmn 25

River 292 plusmn 06 24 plusmn 05

30 Ultrapure 208 plusmn 01 333 plusmn 29


water are much higher in the irradiated samples whenfungicide is encapsulated in HP-120573-CD than in the free formafter 42 days (Figures 4 and 5)

The initiation of the degradation process correspondsas suggested in literature to two major routes which con-tinue with a sequence of reactions resulting in a complexand interconnected pathway [22] One route involves theattack of hydroxyl radicals to the benzene andor pyrimidinerings with subsequent rings opening and the other onecorresponds to a photoinduced hydrolysis of pyrimethanilmolecule by the amine bond [22] The demonstrated effec-tiveness of HP-120573-CD complexation in improving the pho-tostability of pyrimethanil can therefore be ascribed to theinclusion of the main photoactive centers (as revealed inNMR analysis) of the fungicide in the CD cavity enabling adeceleration effect of the degradation process being the reac-tion rate dependent on the free pyrimethanil concentrationarising from dissociation of the complex

4 Conclusion

The ability of cyclodextrins to alter the physical chemicaland biological properties of guest molecules has been used toimprove the performance of pesticide formulationsThemostquoted benefits of CD applications in agriculture includeamong others alterations of the solubility of the pesticidestabilization against the effects of light or (bio)chemicaldegradation and a reduction of volatility

Owing to the growing interest in cyclodextrins and theirability to improve the stability of drug pesticides the inclu-sion complex of pyrimethanil with HP-120573-CD has been pre-pared and characterizedThe formation of the inclusion com-plex increased the solubility of pyrimethanil in water aroundfive times when compared with the free fungicide Moreoverthe formation of pyrimethanilHP-120573-CD inclusion complexincreased significantly the photostability of this fungicide inaqueous solutions presenting a special significance in naturalwater Cyclodextrin-encapsulated pyrimethanil was moreslowly photodegraded in all the waters studied producingfirst-order rate constants of 212 versus 208 for ultrapurewater and 292 versus 72 for river water respectively In riverwater the fungicide half-lives were increased approximatelyby a factor of four

The effectiveness of HP-120573-CD complexation in improv-ing the photostability of pyrimethanil was ascribed to theinclusion of the main photoactive centers of the fungicideinto the CD cavity Therefore it is predictable that theformation of inclusion complexes with CDs may improve

the properties of pyrimethanil formulations increasing theherbicide effectiveness for future applications

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

Financial support from Fundacao para a Ciencia e Tecnolo-gia FCTMCTES project PTDCAGRAAM1050442008National Funds PIDDAC also cofinanced by the EuropeanCommunity Fund FEDER through COMPETE-ProgramaOperacional Factores de Competitividade (POFC) is grate-fully acknowledged

References

[1] E A Martin B Reineking B Seo and I Steffan-DewenterldquoNatural enemy interactions constrain pest control in complexagricultural landscapesrdquo Proceedings of the National Academy ofSciences vol 110 no 14 pp 5534ndash5539 2013

[2] P Fantke and R Juraske ldquoVariability of pesticide dissipationhalf-lives in plantsrdquo Environmental Science and Technology vol47 no 8 pp 3548ndash3562 2013

[3] A Gogos K Knauer and T D Bucheli ldquoNanomaterials in plantprotection and fertilization current state foreseen applicationsand research prioritiesrdquo Journal of Agricultural and Food Chem-istry vol 60 no 39 pp 9781ndash9792 2012

[4] A Perez-de-Luque andM C Hermosın ldquoNanotechnology andits use in agriculturerdquo in Bio-Nanotechnology A Revolution inFood Biomedical and Health Sciences D Bagchi M Bagchi HMoriyama and F Shahidi Eds pp 383ndash398 Wiley-BlackwellWest Sussex UK 2013

[5] E M Garrido M Santos P Silva F Cagide J Garrido and FBorges ldquoHost-guest complexes of phenoxy alkyl acid herbicidesand cyclodextrins MCPA and 120573-cyclodextrinrdquo Journal of Envi-ronmental Science and Health B Pesticides Food Contaminantsand Agricultural Wastes vol 47 no 9 pp 869ndash875 2012

[6] S Benfeito T Rodrigues J Garrido F Borges and E M Gar-rido ldquoHost-guest interaction between herbicide oxadiargyl andhydroxypropyl-120573-cyclodextrinrdquo The Scientific World Journalvol 2013 Article ID 825206 6 pages 2013

[7] M Yudelman A Ratta and D Nygaard Pest Managementand Food Production Looking to the Future International FoodPolicy Research Institute Washington DC USA 1998

[8] D Pimentel and L Levitan ldquoPesticides amounts applied andamounts reaching pests Often less than 01 of pesticidesapplied to crops reaches target pestsrdquo BioScience vol 36 no 2pp 86ndash91 1986


[9] M Franko M Sarakha A Cibej A Boskin M Bavcon andP Trebse ldquoPhotodegradation of pesticides and application ofbioanalytical methods for their detectionrdquo Pure and AppliedChemistry vol 77 no 10 pp 1727ndash1736 2005

[10] C Costa S Maia P Silva J Garrido F Borges and E MGarrido ldquoPhotostabilization of phenoxyacetic acid herbicidesMCPA andmecoprop by hydroxypropyl-120573-cyclodextrinrdquo Inter-national Journal of Photoenergy vol 2013 Article ID 542783 8pages 2013

[11] A Wightwick R Walters G Allinson S Reichman and NMenzies ldquoEnvironmental risks of fungicides used in horticul-tural production systemsrdquo in Fungicides O Carisse Ed InTechRijeka Croatia 2010

[12] A Kinani A Rifai S Bourcier F Jaber and S BouchonnetldquoStructural characterization of photoproducts of pyrimethanilrdquoJournal of Mass Spectrometry vol 48 no 8 pp 983ndash987 2013

[13] ldquoCommission Regulation (EU)No 9782011 amending AnnexesII and III to Regulation (EC) No 3962005 of the European Par-liament and of the Council as regards maximum residue levelsfor acetamiprid biphenyl captan chlorantraniliprole cyflufe-namid cymoxanil dichlorprop-P difenoconazole dimetho-morph dithiocarbamates epoxiconazole ethephon flutri-afol fluxapyroxad isopyrazam propamocarb pyraclostrobinpyrimethanil and spirotetramat in or on certain productsrdquoOfficial Journal of the European Union L 25812 2011

[14] P V Shah and V Dellarco ldquoPyrimethanilrdquo in Pesticide Residuesin Foodmdash2007 Toxicological Evaluations World Health Orga-nization Geneva Switzerland 2009

[15] A Markus ldquoAdvances in the technology of controlled-releasepesticide formulationsrdquo in Microencapsulation Methods andIndustrial Applications S Benita Ed pp 73ndash91Marcel DekkerNew York NY USA 1996

[16] F Sopena C Maqueda and E Morillo ldquoControlled releaseformulations of herbicides based on micro-encapsulationrdquoCiencia e Investigacion Agraria vol 36 no 1 pp 27ndash42 2009

[17] H Dodziuk Cyclodextrins and Their Complexes ChemistryAnalytical Methods Applications JohnWiley amp Sons HobokenNJ USA 2006

[18] J Cheng Y Xia Y Zhou F Guo and G Chen ldquoApplicationof an ultrasound-assisted surfactant-enhanced emulsificationmicroextraction method for the analysis of diethofencarb andpyrimethanil fungicides in water and fruit juice samplesrdquoAnalytica Chimica Acta vol 701 no 1 pp 86ndash91 2011

[19] T Higuchi and K A Connors ldquoPhase-solubility techniquesrdquoAdvances in Analytical Chemistry and Instrumentation vol 4pp 117ndash212 1965

[20] B Yang J Lin Y Chen andY Liu ldquoArtemetherhydroxypropyl-120573-cyclodextrin host-guest system characterization phase-solubility and inclusionmoderdquoBioorganic andMedicinal Chem-istry vol 17 no 17 pp 6311ndash6317 2009

[21] F J B Veiga C M Fernandes R A Carvalho and C F G CGeraldes ldquoMolecular modelling and 1H-NMR ultimate toolsfor the investigation of tolbutamide 120573-cyclodextrin and tolbu-tamide hydroxypropyl-120573-cyclodextrin complexesrdquo Chemicaland Pharmaceutical Bulletin vol 49 no 10 pp 1251ndash1256 2001

[22] A Aguera E Almansa A Tejedor and A Fernandez-AlbaldquoPhotocatalytic pilot scale degradation study of pyrimethaniland its main degradation products in waters by means of solid-phase extraction followed by gas and liquid chromatographywith mass spectrometry detectionrdquo Environmental Science andTechnology vol 34 no 8 pp 1563ndash1571 2000

[23] A Vanni and F Fontana ldquoPhotodegradation of pyrimethanilinduced by iron(III) in aqueous solutionsrdquo Journal of Environ-mental Monitoring vol 5 no 4 pp 635ndash639 2003

[24] S Navarro J Fenoll N Vela E Ruiz and G Navarro ldquoPhoto-catalytic degradation of eight pesticides in leaching water by useof ZnO under natural sunlightrdquo Journal of HazardousMaterialsvol 172 no 2-3 pp 1303ndash1310 2009

[25] J J Guerard P L Miller T D Trouts and Y P Chin ldquoThe roleof fulvic acid composition in the photosensitized degradation ofaquatic contaminantsrdquo Aquatic Sciences vol 71 no 2 pp 160ndash169 2009

[26] L Mao C Meng C Zeng Y Ji X Yang and S Gao ldquoTheeffect of nitrate bicarbonate and natural organic matter onthe degradation of sunscreen agent p-aminobenzoic acid bysimulated solar irradiationrdquo Science of the Total Environmentvol 409 no 24 pp 5376ndash5381 2011

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


N

N

CH3

H3C NH

(a)

O

RO

RO

OOR

O

ORRO

O

OR O

OR

ORO

RO

O

OR

OR

ORO

O

OR

OR

O

RO

O

ROOR

O

RO

ORO

RO

O

OR

R = OCHndash2CH(CH3)OH or ndashH

HP-120573-CD

(b)

Figure 1 Schematic representation of (a) chemical structure of pyrimethanil and (b) 3D structure of (2-hydroxypropyl)-120573-cyclodextrin (HP-120573-CD)

horticultural production systems has received relatively littleattention when compared to other types of agrochemicalssuch as insecticides and herbicides [11]

Pyrimethanil N-(46-dimethylpyrimidin-2-yl)aniline(Figure 1(a)) is an anilino-pyrimidine fungicide particularlyactive against gray mold (Botrytis cinerea) and pear scab(Venturia spp) on fruits vegetables and ornamental plantsThe photodegradation by sunlight plays a significant role inpyrimethanil degradation due to its long half-life (approx 77days) in the environment [12] Although pyrimethanil hasno apparent mutagenic genotoxic or carcinogenic potentialthe concentration of pyrimethanil has been limited in foodcommodities by the European Commission [13 14] It is thusimportant to increase fungicide efficacy at reduced doses Inthis sense controlled release formulations of pesticides havebecome a very active research area in recent years Controlledrelease formulations of fungicides can allow extended periodsof activity while minimizing the environmental effects ofuse Concern over the contamination of soil and water hasled to the development of formulations that prevent entry

of the pesticides into the groundwater while maintainingeffective pest control In this context microencapsulationbecomes the most appellative industrial process for theproduction of controlled release agricultural formulations[15 16]

Cyclodextrins (CDs) are a group of naturally occurringcyclic oligosaccharides derived from starch with six sevenor eight glucose residues linked by 120572 (1ndash4) glycosidic bonds ina cylinder-shaped structure (Figure 1(b))The CDs structuralcharacteristics a hydrophobic interior cavity and hydrophilicshell and their ability to alter the physical chemical andbiological properties of guest molecules have been regardedas a solution to improve pesticide formulations When apesticide is complexed with CD the interaction of the sidegroups on the guest pesticide molecule with the hydroxyl orsubstituted hydroxyl groups of the host can have an effect onthe reactivity of the guest molecule [17] Depending upon thegroup on the pesticide molecule this can result in catalysisof the reaction or stabilization of the guest molecule byprevention of chemical reactions [17] Studies of the catalytic




2 Experimental












(1)


CD




119862119905= 1198620119890minus119896119905 (2)


00 50 100 150 200 250 300 350 40002

04

06

08

10

12

14

16

18

20

[Pyr

imet

hani

l] (m

M)

[HP-120573-CD] (mM)


where 1198620and 119862





12= ln 2119896















Pyrimethanil

HP-120573-CD


8 6 4 2 0

76 74 72 70 68 66 26 24 22 20



N

N

CH3

H3C

H

NH

H

H H

H

H

1

23

4

56

Pyrimethanil

1998400

2998400

3998400

4998400

5998400

6998400

O

H

O

H

RO

H

HORH

O

OR

7

HP-120573-CD

R = H or CH2CHOCH3

1998400998400

2998400998400

3998400998400

4998400998400

5998400998400

6998400998400

middot


120575HP-120573-CD(CH3OD)


Δ120575



0 10 20 30 4020

30

40

50

60

70

80

90

100

110


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)








0 10 20 30 40 5070

75

80

85

90

95

100


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)










(days)







4 Conclusion







Acknowledgments


References





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




2 Experimental












(1)


CD




119862119905= 1198620119890minus119896119905 (2)


00 50 100 150 200 250 300 350 40002

04

06

08

10

12

14

16

18

20

[Pyr

imet

hani

l] (m

M)

[HP-120573-CD] (mM)


where 1198620and 119862





12= ln 2119896















Pyrimethanil

HP-120573-CD


8 6 4 2 0

76 74 72 70 68 66 26 24 22 20



N

N

CH3

H3C

H

NH

H

H H

H

H

1

23

4

56

Pyrimethanil

1998400

2998400

3998400

4998400

5998400

6998400

O

H

O

H

RO

H

HORH

O

OR

7

HP-120573-CD

R = H or CH2CHOCH3

1998400998400

2998400998400

3998400998400

4998400998400

5998400998400

6998400998400

middot


120575HP-120573-CD(CH3OD)


Δ120575



0 10 20 30 4020

30

40

50

60

70

80

90

100

110


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)








0 10 20 30 40 5070

75

80

85

90

95

100


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)










(days)







4 Conclusion







Acknowledgments


References





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


00 50 100 150 200 250 300 350 40002

04

06

08

10

12

14

16

18

20

[Pyr

imet

hani

l] (m

M)

[HP-120573-CD] (mM)


where 1198620and 119862





12= ln 2119896















Pyrimethanil

HP-120573-CD


8 6 4 2 0

76 74 72 70 68 66 26 24 22 20



N

N

CH3

H3C

H

NH

H

H H

H

H

1

23

4

56

Pyrimethanil

1998400

2998400

3998400

4998400

5998400

6998400

O

H

O

H

RO

H

HORH

O

OR

7

HP-120573-CD

R = H or CH2CHOCH3

1998400998400

2998400998400

3998400998400

4998400998400

5998400998400

6998400998400

middot


120575HP-120573-CD(CH3OD)


Δ120575



0 10 20 30 4020

30

40

50

60

70

80

90

100

110


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)








0 10 20 30 40 5070

75

80

85

90

95

100


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)










(days)







4 Conclusion







Acknowledgments


References





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Pyrimethanil

HP-120573-CD


8 6 4 2 0

76 74 72 70 68 66 26 24 22 20



N

N

CH3

H3C

H

NH

H

H H

H

H

1

23

4

56

Pyrimethanil

1998400

2998400

3998400

4998400

5998400

6998400

O

H

O

H

RO

H

HORH

O

OR

7

HP-120573-CD

R = H or CH2CHOCH3

1998400998400

2998400998400

3998400998400

4998400998400

5998400998400

6998400998400

middot


120575HP-120573-CD(CH3OD)


Δ120575



0 10 20 30 4020

30

40

50

60

70

80

90

100

110


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)








0 10 20 30 40 5070

75

80

85

90

95

100


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)










(days)







4 Conclusion







Acknowledgments


References





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 10 20 30 4020

30

40

50

60

70

80

90

100

110


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)








0 10 20 30 40 5070

75

80

85

90

95

100


Pyrim

etha

nil r

emai

ning

in so

lutio

n (

)










(days)







4 Conclusion







Acknowledgments


References





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




(days)







4 Conclusion







Acknowledgments


References





































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of