UV/VIS spectral properties of novel natural products from...

Vol. 07 INTERNATIONAL JOURNAL OF PHOTOENERGY 2005

UV/VIS spectral properties of novel natural productsfrom Turkish lichens

Yevgen Posokhov,1,2 Sule Erten,1,3 Ömer Koz,4 H. Anıl,4

Süheyla Kırmızıgül,4 and Sıddık Içli1

1 Solar Energy Institute, Ege University, Bornova, 35100 Izmir, Turkey2 Institute for Chemistry at Kharkov National University, 61077 Kharkov, Ukraine

3 Dokuz Eylul University, Faculty of Science Edu., Depatrment of Chemistry, Buca, Izmir, Turkey4 Ege University, Faculty of Science, Depatrment of Chemistry, Bornova, Izmir, Turkey

Abstract. UV/VIS spectral characteristics of three new biologically active natural products, isolated fromTurkish lichens, have been investigated in solvents of various polarity and proton donating ability. Theeffect of the solvent on spectral characteristics has been estimated. Quantum chemical calculations with theoptimization of molecular geometry were done with the full-valent semiempirical methods AM1 and PM3 forconformational analysis and in order to discuss the charge distributions and dipole moments in the groundand in the excited states.

1. INTRODUCTION

Lichens have in great variety metabolic products, someof which appear to occur naturally only in lichens andothers are also present in higher plants and fungi.Some known secondary metabolites of lichens are dep-sides, depsidones, benzoxazine, benzofurane, usnicacid and antraquinone derivatives [1–6]. Because oftheir metabolites, lichens are widely used as commer-cially in perfume dye and drug industry [7–11]: about60 lichen species are present in some different typesof commercial drugs such as antimicrobial, anticancer,antiallergen, immunugical and expectoral [12–15].

The practical usage in pharmaceutical industryarises the importance on studies of physico-chemicaland spectral properties of the isolated compoundsfrom lichens, e.g., the knowledge on the spectral prop-erties of isolated compounds could facilitate their bio-chemical analysis [16].

We already reported the molecular structure jus-tification of the three compounds (1, 2, 3) isolatedfrom Turkish lichens Pseudevernia furfuracea, Everniaprunastri, Letharia vulpina, respectively, [17].

In this report we wish to present the results of ourstudies on UV/VIS spectral properties of the above-mentioned compounds 1, 2, 3.

1

Me

MeO

Me OH

OH

O

HO

2

OMe

Me O

O

Cl Me

O

NH2

3

MeO

HO O

O

O

2. EXPERIMENTAL DETAILS

2.1. Materials. The separation, identification andpurification of compounds 1, 2, 3 were described earlier[17]. The organic solvents used were all of spectropho-tometric grade and were used as supplied from Fluka.

2.2. Spectroscopic measurements. The elec-tronic absorption spectra were measured using JascoV-530 UV/VIS spectrophotometer.

2.3. Theoretical calculations. Semi-empirical cal-culations were performed using the original AM1 [18],PM3 [19], ZINDO/S [20] parametrisations (included inHYPER Chem package). Restricted Hartree-Fock (RHF)formalism was used.

AM1 method is known to have better parameter-ization in comparison with PM3 for geometry opti-mization, though, intramolecular hydrogen-bonding is

28 Yevgen Posokhov et al. Vol. 07

better parameterized for PM3. ZINDO/S was usedfor calculations of the UV/VIS spectra because thismethod was specially parameterized for electronicspectroscopy.

The calculations were carried out with full groundstate geometry optimization without any assumptionof symmetry: Polak-Ribiere (conjugate gradient) geom-etry optimization algorithm was used with convergencecut-off criterion 0.1 kcal/mol.

Excited state calculations were conducted by meansof single point calculations (closed shell, singles) of thestructures with already optimized ground state geom-etry: CI matrix with 3 HOMO’s and 3 LUMO’s has beenused.

Mulliken charges [21] were used to discuss the dipo-lar moments.

3. RESULTS AND DISCUSSIONS

3.1. Absorption properties. In Tables 1, 2, 3 theabsorption wavelengths of the compounds 1, 2, 3 arepresented. Figures 1, 2, 3 show the absorption spectraof 1, 2, 3 in various solvents with different polarity andproton donating ability.

Absorption spectra of 1, 2, 3 in the region 200–450 nm consist of four bands of π -π∗ nature, the n-π∗

absorption bands are hidden by the more intense long-wavelength π -π∗ bands.

The absorption spectra of compound 1 couldbe considered as the spectra of substituted ortho-hydroxybenzoic acid. Such chromophoric fragmentscould be distinguished in 1: benzoic acid (λ1

max

227 nm, log ε 4.15; λ2max 267 nm, log ε 3.25), phenol

(λ1max 215 nm, log ε 4.0; λ2

max 273 nm, log ε 3.25),toluene (λmax 262 nm, log ε 2.48) [22]. The donor sub-stituents shifted the spectra of the above chromophoricfragments to long-wavelength region. Molecular extinc-tion coefficients for compound 1 (see inscription underTable 1) are much grater than those for the referencecompounds (benzoic acid, phenol), i.e., hyperchromiceffect is observed with the introduction of donor sub-stituents into phenyl ring of benzoic acid.

The absorption spectra of 2 are additive and shouldbe considered in the light of the spectra of the hydroxy-benzoic acids and their derivatives. Substituents clearlyexert bathochromic effects [22].

The absorption spectra of compound 3 origi-nated from the presence of the two chromophoricfragments: 1,4-diphenyl-trans-trans-butadiene-1, 3 andtrans, trans-muconic acid [22].

Intensive conformational search was conducted for1, 2, 3. We started the calculations from different start-ing geometries and, for each compound, the geometrysearch converged to one of the two most stable con-formers, designated as I and II (see Figures 4, 5, 6;Table 4). Other possible conformers were neglected,

because the rotation of the peripheral methyl groupscould not affect the absorption spectra considerably.

The conformers I have greater ground state dipolemoment values, calculated with AM1 and PM3 parame-ters, than corresponding values for conformers II (seeTable 4), calculated with the same parameters. Thus,with growth of solvent polarity, the conformers I willbe more favorable in comparison with the correspond-ing conformers II.

Quantum-chemical calculations of UV/VIS spectrafor compounds 1, 2, 3 in vacuum were made with theuse of AM1, PM3, ZINDO/S parameters. The results ofthe calculations are presented in Table 5.

In order to check the validity of 3× 3 CI matrix forexcited state calculations, a few calculations with CI ma-trix 5× 5 were made, but no considerable difference inresults of both calculations was noticed. For this rea-son, the majority of the excited state calculations wasperformed with the usage of 3× 3 CI matrix.

The comparison of the calculated spectra with theexperimental ones shows that the best coincidence ofthe experimental and calculated UV/VIS data is ob-served when ZINDO/S parameters are used in order tocalculate spectra of 1, when AM1 and PM3 parametersare used in order to calculate spectra of 2, and, whenAM1 and ZINDO/S parameters are used in order to cal-culate spectra of compound 3.

In general, the tendencies in calculated oscillatorstrength ratio’s for calculated absorption bands of 1,2, 3 (Table 5) qualitatively agree with the correspond-ing ratio’s of molar extinction coefficients for λ1, λ2,λ3 bands of 1, 2, 3 (see inscriptions under Tables 1, 2,3). The only exception is observed for long-wavelengthbands of compound 3: the calculated oscillator strengthratio for λ1 ∼ 370 nm and λ2 ∼ 286 nm is not in accor-dance with the corresponding ratio of molar extinctioncoefficients (see inscription under Table 3).

According to the calculations of UV/VIS spectra of1, 2, 3 in vacuum (Table 5), the long-wavelength absorp-tion bands of the conformers I are shifted to higherenergies in comparison with the corresponding absorp-tion bands of the conformer II.

By the growth of solvent polarity, short-wavelengthshifts in the absorption maxima are observed (up to5, 6, 10 nm for 1, 2, 3, respectively, see Tables 1, 2, 3and Figures 1, 2, 3). This fact could be caused by suchpossibilities: (a) probably, in polar solvents the ener-gies of the conformers I and II, calculated for 1, 2, 3 invacuum (Table 4), will change because of solvatation,and, perhaps, the energy difference between I and IIwill increase because of the greater solvent stabiliza-tion of the more polar conformers I, hence, conforma-tional equilibria between I and II will be shifted in thedirection of I for which, as shown by the calculations(AM1, PM3, ZINDO/S; see Table 5), the positions of thelong-wavelength maxima are slightly shifted to higherenergies; (b) the dipole moments of the some conform-

Vol. 07 UV/VIS spectral properties of novel natural products . . . 29

Table 1. UV/VIS spectroscopic data* of compound 1 in solvents with different polarities and hydrogen bonding abilities.

Solvent ε n λ1abs λ2

abs λ3abs λ4

abs

Tetrachloromethane 2.24 1.4574 307 266 – –

Benzene 2.28 1.5011 306 – – –

Toluene 2.38 1.4961 306 – – –

Chloroform 4.70 1.4459 305 266 – –

Ethyl acetate 6.02 1.3723 304 267 – –

Tetrahydrofuran 7.6 1.4076 304 266 237 214

Dichloromethane∗∗ 8.90 1.4242 303 265 227 –

Iso-propanol 18.3 1.3747 303 266 226 –

Methanol 32.63 1.3286 303 268 219 –

Acetonitrile∗∗∗ 36.2 1.3441 302 268 217 –

Dimethylformamide 36.7 1.4303 302 268 – –

∗Here ε and n-dielectric permeability and refractive index of the solvent; λ1–4abs—are the positions of the maxima in the absorption

spectra (nm).∗∗Molecular extinction coefficients were calculated to be: ε1(λ1

abs) = 9300; ε2(λ2abs) = 28500; ε3(λ3

abs) = 31700;∗∗∗Molecular extinction coefficients were calculated to be: ε1(λ1

abs) = 9500; ε2(λ2abs) = 30500; ε3(λ3

abs) = 104700.



abs λ3abs

Tetrachloromethane 2.24 1.4574 312 – –

Benzene 2.28 1.5011 312 – –

Toluene 2.38 1.4961 311 – –

Chloroform 4.70 1.4459 310 270 242

Ethyl acetate 6.02 1.3723 309 268 –

Tetrahydrofuran 7.6 1.4076 309 – –

Dichloromethane∗∗ 8.90 1.4242 309 270 237

Iso-propanol 18.3 1.3747 303 268 214

Methanol 32.63 1.3286 303 268 209

Acetonitrile∗∗∗ 36.2 1.3441 306 270 214

Dimethylformamide 36.7 1.4303 306 268 –



abs) = 15600; ε2(λ2abs) = 32400; ε3(λ3


abs) = 16700; ε2(λ2abs) = 29100; ε3(λ3

abs) = 230100.



abs λ3abs λ4

abs

Tetrachloromethane 2.24 1.4574 379 278 – –

Benzene 2.28 1.5011 379 – – –

Toluene 2.38 1.4961 378 – – –

Chloroform 4.70 1.4459 377 275 249 –

Ethyl acetate 6.02 1.3723 376 275 – –

Dichloromethane∗∗ 8.90 1.4242 374 275 237 –

Iso-propanol 18.3 1.3747 371 279 235 206

Methanol 32.63 1.3286 370 277 232 207

Acetonitrile∗∗∗ 36.2 1.3441 369 279 238 209



abs) = 21900; ε2(λ2abs) = 96120; ε3(λ3


abs) = 32100; ε2(λ2abs) = 34900; ε3(λ3

abs) = 36200;ε4(λ4

abs) = 38900.


0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

Ab

sorb

ance

200 225 250 275 300 325 350nm

A

B

C

Figure 1. Absorption spectra of compound 1: A- in

dichloromethane, B- in acetonitrile, C- in iso-propanol.

0.0

0.1

0.2

0.3

0.4

0.5

Ab

sorb

ance

250 300 350nm

A

B

C



ers of 1, 2, 3 in excited state is lower than the corre-sponding dipole moments in ground state. Increasingsolvent polarity stabilizes the ground state to a greaterdegree than the electronically excited state and, the ab-sorption spectrum tends to shift to shorter wavelengthwith the increasing solvent polarity [23].

In order to elucidate whether the latter possibilityoccurs, quantum-chemical calculations with AM1 [18]and with PM3 [19] parameters were used to estimatethe excited state dipole moments of comp. 1, 2, 3 (seeTable 4).

As could be seen from the Table 4, the values ofthe excited state dipole moment µe for conformer II ofcompound 1 (as calculated with PM3), for conformerI of compound 2 (as calculated with AM1 and PM3)and for conformer II of compound 3 (as calculatedwith PM3), are greater than the corresponding valuesof ground state dipole moment µg , calculated with the

200 250 300 350 400 450

1.0

0.8

0.6

0.4

0.2

0.0

C

B

A

Ab

sorb

ance

nm



use of the same parameters. In general, the changes ofthe dipole moments on excitation are not considerable.

In contrast to solvent polarity, which affects theposition of the long-wavelenth absorption band of 1,according to the data presented in Table 1, solventH-bond donating and H-bond accepting ability havepractically no influence on the position of the long-wavelength maximum in absorption spectra of comp. 1.

The blue (short-wavelength) shifts of long-wavelength absorption maxima are observed inproton-donating solvents, such as iso-propanol ormethanol, for compound 2 (see Table 2). Accordingto the quantum chemical calculations (see Figure 5)electronic density redistributes from amino groupto carbonyl group on excitation. Taking into accountthis fact, one could explain that the blue shifts oflong-wavelength absorption maxima of compound 2 inproton donating solvents caused by the interaction ofhydrogen-bond donor solvents with unshared valenceelectron pairs of the amino group. The latter is chargedonor in the excited state. This interaction preventsthe charge transfer from the amino group to carbonylgroup in an excited state, and, consequently destabi-lizes the charge-transfer excited state relative to theground state, so that the absorption spectra tend toshift to higher energies with increasing hydrogen-bonddonor capacity of the solvent [23].

According to the quantum chemical calculationsfor compound 3 (see Figure 6), electronic density re-distributes to lactone carbonyl group on excitation.Taking into account this fact, one could expect long-wavelength shift of absorption maxima of compound 3in proton donating iso-propanol and methanol causedby the interaction of hydrogen-bond donor solventswith unshared valence electron pairs of the lactone car-bonyl group, which is charge acceptor in the excitedstate.


O

H

O −0.411O−0.307

H

−0.255HH

H −

+ H

H

HH

O−0.200H

H

H

I

H

−0.409OO−0.304

H

O −0.258

HH

H

H

−

+H

HHO−0.223

H

HH

II(a) Ground State

H

−0.314O

−0.438O

H

O −0.262HH

H

H

H

H

−

+H

O−0.177HH

H

I

H

O −0.456O−0.315

H

O −0.231

HH

H

H

−

+

HH

HO−0.205H

HH

II(b) Excited State

Figure 4. Calculated by AM1 method charge distribution and dipole moment directions in S0 (a) and in S1 (b) electronic

state of the most stable conformers (I and II) of compound 1 in vacuum.

Nevertheless, no spectral shifts of the long-wavelength band of compound 3 are observed in polarproton-donating iso-propanol and methanol in compar-ison with polar aprotic acetonitrile (see Table 3).

Probably, the expected long-wavelength shift iscompensated by the short-wavelength shift of absorp-tion maxima, the latter is caused by the interaction ofhydrogen-bond donor solvents with unshared valenceelectron pairs of methoxy group, which is charge donorin the excited state.

It should be noted that absorption spectrum ofcomp. 3 in dichloromethane solution differs from theabsorption spectra of the same compound in the othersolvents used: i.e., the ratio of intensities of the bandsλ1 and λ2 (see Figure 3, Table 3) is different from thecorresponding ratios for the other solvents used. Suchanomalous behavior of comp. 3 in dichloromethane so-lution will be the subject for the future study.

Fluorescence is known to be a powerful tool forpharmaco-chemical analysis, provided that analyte isfluorescent [23].

Unfortunately, all the studied compounds are non-fluorescent in all the solvents used (the roughly esti-mated quantum yields are very low ∼ 10−3).

For comp. 1, provided that the presence of methylsubstituents in phenyl ring do not suppress the hy-droxy group acidity on excitation, the fluorescencequenching could be linked with the excited state in-tramolecular proton transfer (ESIPT) of the 2-hydroxyproton to the carbonyl oxygen followed by radiation-less decay and fast back proton transfer [24].

Otherwise, if the presence of methyl substituentsin phenyl ring of 1 suppress the hydroxy group acidityon excitation, and, the ESIPT does not occur, efficientintersystem crossing (with the participation of singletor triplet states of nπ∗ nature, introduced into the sys-tem by the presence of the carbonyl group) could beconsidered as the possible cause of the fluorescencequenching of 1.

Few cases of the ESIPT with amino group as proton-odonor are reported in literature [24, 25], though, oneof such cases is the ESIPT in 2-amino-3-naphtoic acid


HO

−0.243

H

H

H

H

H

O−0.194

H

HH

+−0.226

−OO

−0.308

H

Cl

H

H

N−0.341

H

O−0.309

HH

H

I

−0.244

OH

H

H

H H

H

O−0.206

H

H

H

−0.322O

O−0.216

+

−

H

Cl

H

H

N −0.342

H

O −0.304HH

H

II(a) Ground State

HO

−0.244

H

H

HH

OH −0.193

H

HH

+

−0.211

−OO

−0.308

H

Cl

H

H

N−0.220

H

O−0.308

HH

H

I

−0.244

OH

H

H

H H

H

O−0.206

H

H

H

−0.317O

O−0.198

H +

−

H

Cl

H

N−0.215

H

O−0.309HH

H

II

(b) Excited State



(a) Ground State

I II

H

H

HO

−0.207

H

H

H

H

O−0.348O

−0.320

H

+

−O

−0.199

O−0.254

H H H

HH

H HH

H

H O−0.208

H

H

H

H

O−0.300 O −0.381H +

−O

−0.200

O−0.250

H

H H

H H

H

O−0.313

O−0.369+

−

(b) Excited State

I II

H

HH

O−0.188

H

H

H H H H

HH O−0.201

−0.278 O H H

H

H

HO−0.190

H

H

H

H

+

−

H

O−0.318O −0.380

O−0.201

O−0.278

H H H

H H

H




Table 4. Relative heats of formation* (Hf , kcal/mol), total energy** (ET , kcal/mol) and dipole moments (µ, Debye) for S0

and S1 states of the most stable conformers of 1, 2, 3 in vacuum calculated with AM1 and PM3 parameters.

Comp. Conformer

AM1 PM3

S0 S1 S0 S1

Hf ET µg Hf µe Hf ET µg Hf µe

1I 0 −62909.0 3.68 83.0 3.91 4.94 −58689.3 3.43 87.69 3.80

II 2.76 −62906.2 1.80 85.28 2.36 0 −58694.3 2.42 82.45 2.11

2I 0 −105593.3 4.25 94.87 3.70 0 −97033.1 4.31 102.0 3.77

II 1.52 −105591.7 0.85 94.06 1.13 3.57 −97029.5 0.55 96.58 1.75

3I 0 −97438.3 3.21 81.02 3.19 0 −90705.2 2.83 87.32 3.01

II 0.31 −97438.0 2.91 80.91 3.86 0.15 −90705.1 2.80 91.69 2.54∗Here, heat of formation for the most stable conformer for each compound was taken as zero.∗∗Presented only for S0 states of the conformers I and II.

and its methyl ester [25]. Taking into account this fact,one could suggest that fluorescence quenching of 2 iscaused by the excited state proton transfer of 2-aminoproton to the carbonyl group followed by efficient non-radiative deactivation in phototautomer form.

On the other hand, another cause of the observedfluorescence quenching of 2 could be efficient intersys-tem crossing.

In compound 3 there is no possibility for the ESIPT,but another two possibilities of fluorescence quenchingoccur: (i) intersystem crossing; (ii) fast rotation arounddouble bond to a perpendicular minimum of the S1

state followed by surface crossing to S0 surface. Thesecond possibility seems less probable: fast rotationaround double bond is usually linked with ethylene-like cis-trans photoisomerisation [26], but, accordingto experimental results for compound 3, no spectralchanges were noticed after a long-time irradiation withthe use of UV/VIS lamp (the light source of Jasco spec-trophotometer).

Thus, the possibility of the effective quenching pro-cesses with the participation of singlet or triplet statesof n-π∗ nature, introduced into the molecules 1, 2, 3by the presence of the carbonyl groups, could exist forall the studied compounds.

If the lowest-lying transitions of organic substanceare of π -π∗ type such a substance usually have rel-atively high fluorescence quantum yield. When a het-eroatom is involved in the π -system an n-π∗ transitionmay be the lowest-lying transition. This opens the pos-sibility for radiotionless deactivations of the lowest sin-glet excited state via the efficient intersystem crossing(ISC) of S(nπ∗)-T(ππ∗) or S(ππ∗)-T(nπ∗) type. Accord-ing to El-Sayed rule [27], the rate of ISC between the sin-glet and triplet states of the different orbital nature ex-ceeds that for the states of the identical orbital natureup to several orders of magnitude. Owing to this cir-cumstance, the ISC between nπ∗ and ππ∗ states suc-cessfully compete with the radiative depopulation ofS1∗ energetic level.

This explains the low fluorescence quantum yieldsof many molecules in which the lowest excited stateis nπ∗ in nature. This is the case for most of the azocompounds and some compounds containing carbonylgroups and nitrogen heterocycles (with pyridine-typenitrogens) [28].

Many aromatic aldehydes and ketones (e.g., ben-zophenone. anthrone. 1- and 2-naphthaldehyde) havea low-lying nπ∗ excited state and thus exhibit lowfluorescence quantum yields, as explained above. Thedominant de-excitation pathway is intersystem cross-ing (whose efficiency has been found to be close to 1for benzophenone) [29].

According to the absorption spectra of 1, 2, 3 (seeFigures 1, 2, 3 and Tables 1, 2, 3), the S(nπ∗) levelsof 1, 2, 3 are found to be higher in energy then corre-sponding S(ππ∗) levels (nπ∗ absorption bands of 1, 2,3 are hidden by the more intense long-wavelength ππ∗

bands). Thus, probably, the quenching of the fluores-cence for 1, 2, 3 is caused by S(ππ∗)-T(nπ∗) intersys-tem crossing. Though, to prove this, additional futurestudy appears to be necessary.

As it was mentioned above, in cases where the low-est excited states of carbonyl-containing compoundsare of the nπ∗ type (usually, such cases are ob-served in non-polar/ non-hydrogen bonding solvents),no fluorescence takes place. However, if ππ∗ statesof carbonyl-containing compounds lies only slightlyhigher than nπ∗ states, the increase of solvent polarityor hydrogen-bonding ability could change the arrange-ment of the nπ∗ and ππ∗ levels and, hence, rather in-tense fluorescence can be observed in polar or in proticsolvents.

The solvent may not only change the arrangementof the singlet nπ∗ and ππ∗ levels, but also promotesthe vibrational spin-orbital interaction between the low-est S(ππ∗) and the higher S(nπ∗) level with subsequenttransition to the triplet level. This vibrational interac-tion is more probable in hydrocarbon solvents. In po-lar solvents, such interaction is insignificant, and, as


Tab

le5

.Sin

gle

t-st

ate

tra

nsi

tion

exci

tati

onen

ergie

s(λ

,n

m)

an

dco

rres

pon

din

gos

cilla

tor

stre

ngth

valu

es(f

)ca

lcu

late

dfo

rco

nfo

rmer

sI

an

dII

ofco

mp

oun

ds

1,2

,3in

vacu

um

.

Com

p.

ZIN

DO

/S

AM

1PM

3m

ole

cula

rgeo

mer

try

op

tim

ized

by

AM

1PM

3

III

III

III

III

λf

λf

λf

λf

λf

λf

λf

λf

1

35

2.5

0.0

43

35

3.6

0.0

68

34

9.6

0.0

37

35

2.8

0.0

91

––

––

––

––

32

6.3

0.0

49

32

2.8

0.0

22

31

5.0

0.0

49

31

0.5

b0

.00

43

30

.90

.12

33

31

.90

.12

53

30

.90

.12

33

33

.10

.12

4

23

5.9

1.0

47

23

4.8

1.1

14

25

2.1

b0

.00

42

32

.70

.78

32

96

.8b

0.0

01

29

1.0

b0

.00

22

96

.8b

0.0

01

29

7.0

b0

.00

1

23

0.8

0.5

58

22

7.0

0.4

07

23

6.6

0.9

30

22

6.2

0.6

25

26

4.7

0.3

51

25

9.9

0.3

57

26

4.7

0.3

51

25

6.6

0.3

39

21

1.8

b0

.03

27

21

5.7

b0

.00

04

23

0.1

0.7

33

21

4.1

0.0

20

23

1.8

0.3

24

22

9.1

0.2

13

23

1.8

0.3

24

22

8.1

0.0

90

19

9.6

0.3

72

20

5.4

0.5

82

20

7.0

0.2

04

20

8.3

0.6

69

21

3.4

0.5

97

21

3.5

0.6

78

21

3.4

0.5

97

21

5.1

0.7

85

2

30

9.8

0.2

62

31

5.4

0.2

62

87

.21

.23

53

05

.80

.27

7

29

0.3

1.2

34

28

8.8

1.2

82

26

8.1

0.0

51

28

7.9

1.1

76

26

7.6

0.1

94

26

5.9

0.2

23

25

4.8

0.1

98

26

4.4

0.1

13

–a

25

3.3

0.2

97

25

2.7

0.2

31

25

0.8

0.4

70

25

1.2

0.3

61

20

5.3

b0

.00

61

96

.3b

0.0

08

19

6.4

b0

.00

21

93

.5b

0.0

03

3

37

8.1

1.4

16

38

0.4

1.2

68

34

5.4

1.3

56

32

6.1

1.1

63

37

0.8

1.3

42

37

2.5

1.1

94

33

0.8

1.3

85

32

3.1

1.1

40

28

7.5

0.1

64

29

5.2

0.2

20

27

6.2

0.1

95

28

2.7

0.2

26

28

6.0

0.2

00

30

0.0

0.1

89

27

2.8

0.2

02

28

5.3

0.3

21

25

8.5

0.0

80

26

2.8

0.0

78

25

4.8

0.1

03

25

0.0

0.0

63

26

4.0

0.0

84

27

0.8

0.1

05

25

6.8

0.1

35

24

7.2

0.0

59

23

9.9

0.3

46

23

8.7

0.3

64

24

1.5

0.3

18

22

2.8

0.2

86

25

9.8

0.1

67

24

7.3

0.2

65

25

3.2

0.2

18

24

5.3

0.0

27

23

4.0

0.0

93

23

1.3

0.1

01

23

0.2

0.0

95

21

7.1

0.0

39

23

2.2

0.1

63

22

8.3

0.3

24

22

7.9

0.0

48

22

4.7

0.3

35

17

5.6

0.2

45

17

7.1

0.2

85

18

3.8

0.2

99

18

7.7

0.2

28

19

8.2

0.1

87

19

9.0

0.1

27

20

2.6

0.1

39

21

4.3

0.1

49

15

5.4

b0

.02

81

58

.30

.02

81

67

.5b

0.0

34

17

3.7

0.0

56

17

9.5

0.1

34

19

4.8

0.2

30

18

9.9

0.3

52

19

6.8

0.1

74

15

3.3

0.1

06

15

3.3

0.1

11

15

6.2

0.1

02

16

6.5

0.0

22

17

5.4

0.0

96

17

8.8

0.0

77

16

9.3

0.1

28

17

6.7

b0

.02

6

––

13

1.6

b0

.00

04

––

15

1.9

b0

.01

51

47

.4b

0.0

02

14

9.3

b0

.00

04

15

9.6

b0

.02

21

56

.00

.02

9aca

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a result—the fluorescence intensity is higher [30]. Thisfact is considered as the another reason for the increaseof fluorescence quantum yield of the compounds, con-taining nπ∗-levels, with increase of solvent polarity[30].

Nevertheless, unfortunately, in case of compounds1, 2, 3 the fluorescence emission remains very low evenin polar solvents (dichloromethane, acetonitrile).

4. CONCLUSION

The UV/VIS spectral properties of the compounds 1,2, 3, isolated from Turkish lichens Pseudevernia fur-furacea, Evernia prunastri, Letharia vulpina, respec-tively, have been conducted. It has been found that theabsorption spectra of all the three compounds shifthypsochromically with the growth of the solvent po-larity.

UV/VIS spectral results can be enlightening formonitoring of the above compounds at pharmaco-chemical analysis.

ACKNOWLEDGMENTS

Ph.D. student Özgül Hakli is acknowledged for the mea-surements of fluorescence spectra. The authors expresstheir gratitude to Alexander von Humboldt Foundationof Germany, Ege University Research Funds Office andTUBITAK-Scientific and Technical Research Council ofTurkey for their support.

REFERENCES

[1] Y. Asahina and S. Shibata, Chemistry of LichenSubstances, Asher, A, Co. Ltd. Vaals - Amsterdam,1971.

[2] C. F. Culberson, Chemical and Botanical Guide toLichen Products, The University of North CarolinaPress, Chabel Hill, 1969.

[3] C. F. Culberson and J. A. Elix, Lichen Substances:Methods in Plant Biochemistry (P. M. Dey and J. B.Harborne, eds.), vol. 1, Academic Press, London,1989.

[4] J. A. Elix and D. A. Venables, Mycotaxon 47 (1993),275.

[5] S. Huneck and I. Yoshimura, Identification of LichenSubstances, Springer, 1966.

[6] U. Zeybek, H. T. Lumbsch, G. B. Feige, J. A. Elix, andV. John, Crypt. Bot. 3 (1993), 263.

[7] I. K. Bergwein, Dragoca Rep. 3 (1972), 48.[8] K. Karamanoglu, Türk Biol. Der. 2 (1966), 114.[9] T. H. Moxham, Dragoco Rep. 2 (1981), 31.

[10] T. H. Moxham, The Commercial Exploitation ofLichens for Perfume Industry, in Progress in Essen-tial Oil Research (W. D. Gruyter, ed.), Berlin, 1986.

[11] F. Speta, Flechten als Nutzpflanzen, Flechtenbedrohte Wunder der Natur (W. Seipel, ed.), 1975.

[12] E. B. Bergter, Chemical Structure Immunologyand Application of polysaccharides of Fungi andLichens, Studies in Natural products Chemistry,Structure Elucidation Part B (A. Rahma, ed.), vol.5, Elsevier, London, 1987.

[13] V. M. Dembitsky, T. Rezanka, I. A. Bychek, and M. V.Shustov, Phytochem. 31 (1992), 841.

[14] Y. Nishikawa, K. Ohki, K. Takahashi, G. Kurono, F.Fukuoka, and M. Emori, Chem. Pharm. Bull. 22 11(1974), 2692.

[15] K. O. Vartia, Ann. Med. Ex. 27 (1950), 46.[16] R. A. Norton, Biochemical Spectroscopy, vol. 2,

Adams-Hilger, Bristol, 1975.[17] S. Kırmızıgül, Ö. Koz, H. Anıl, S. Içli, and U. Zeybek,

Türk Journ. Chem., in press.[18] M. J. S. Dewar, E. G. Zoebisch, E. F. Healy, and J. J. P.

Stewart, J. Am. Chem. Soc. 107 (1985), 3902.[19] J. P. Stewart, J. Comput. Chem. 10 (1989), 209.[20] A. D. Bacon and M. C. Zerner, Theo. Chim. Acta. 53

(1979), 21.[21] R. S. Mulliken, J. Chem. Phys. 23 (1995), 1833.[22] H. Ebel (ed.), UV/VIS Atlas of Organic Compounds,

VCH, 1992.[23] A. Sharma and S. G. Schulman, Introduction to Flu-

orescence Spectroscopy, John Willey & Sons, NewYork, 1999.

[24] D. L. Gourrierec, S. M. Ormson, and R. G. Brown,Progr. React. Kinetics 19 (1994), 211.

[25] S. Srivastava and S. K. Dogra, J. Photochem. Photo-biol. A: Chem. 46 (1989), 329.

[26] T. Arai, Ethylenic Bonds, Present Status of the Pho-toisomerization Abut, in Advances in Photochem-istry, vol. 20, Wiley & Sons, New York, 1995.

[27] M. A. El-Sayed, J. Phys. Chem. 38 (1963), 2834.[28] B. Valeur, Molecular fluorescence, Wiley-VCH,

Weinheim (FRG), 2002.[29] N. J. Turro, Molecular Photochemistry, Benjamin,

London, 1965.[30] L. A. Lee and R. A. Robb, J. Quantum Electronics

QE-16 (1980), 777.

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