Antioxidant Activity of Lichen Cetraria Islandica

8/16/2019 Antioxidant Activity of Lichen Cetraria Islandica

1/5

Journal of Ethnopharmacology 79 (2002) 325–329

Determination of antioxidant activity of lichen Cetraria islandica(L) Ach

I lhami Gülçin a,*, Münir Oktay b, O . I rfan Küfrevioğlu a, Ali Aslan c

a Department of Chemistry, Faculty of Science and Arts, Atatürk Uni ersity, 25240 Erzurum, Turkeyb Department of Chemistry Education, Education Faculty, Atatürk Uni ersity, 25240 Erzurum, Turkey

c Department of Pharmacology, Medical Faculty, Atatürk Uni ersity, 25240 Erzurum, Turkey

Accepted 9 November 2001

Abstract

The study was aimed at evaluating the antioxidant activity of aqueous extract of C . islandica. The antioxidant activity, reducing

power, superoxide anion radical scavenging and free radical scavenging activities were studied. The antioxidant activity increased

with the increasing amount of extracts (from 50 to 500 g) added to linoleic acid emulsion. About 50, 100, 250, and 500 g of

aqueous extract of C . islandica showed higher antioxidant activity than 500 g of -tocopherol. The samples showed 96, 99, 100,

and 100% inhibition on peroxidation of linoleic acid, respectively. On the other hand, the 500 g of -tocopherol showed 77%

inhibition on peroxidation on linoleic acid emulsion. Like antioxidant activity, the reducing power, superoxide anion radical

scavenging and free radical scavenging activities of C . islandica depends on concentration and increasing with increased amount

of sample. The results obtained in the present study indicate that C . islandica is a potential source of natural antioxidant. © 2002

Elsevier Science Ireland Ltd. All rights reserved.

Keywords: Cetraria islandica (L) Ach.; Antioxidant activity; Lichen

www.elsevier.com/locate/ jethpharm

1. Introduction

Oxygen is present in the atmosphere as a stable

triplet biradical (3O2) in the ground state and a vital

component for the survival of the human. Once in-

haled, it undergoes a gradual reduction process and

ultimately gets metabolized into water. In this process,

a small amount of reactive intermediates, such as super-

oxide anion radicals (O2−), hydroxyl radicals (OH),

nonfree radical species (such as H2O2), and the singleoxygent (1O2) are formed (Sies, 1993). Those reactive

intermediates are collectively termed as reactive oxygen

species (ROS) (Halliwell, 1995; Sato et al., 1996;

Squadriato and Peyor, 1998; Yildirim et al., 2000).

These primary derivatives of oxygen play an important

role in mediating ROS-related effects (Halliwell and

Gutteridge, 1989). ROS can easily initiate the peroxida-

tion of the membrane lipids, leading to the accumula-

tion of lipid peroxides. The peroxidation products by

themselves and their secondary oxidation products,

such as malondialdehyde (MDA) and 4-hidroxinonenal

(4-HNE) are highly reactive; they react with biological

substrates, such as protein, amines, and deoxyribonu-

cleic acid (DNA) (Kehrer, 1993).

In living organisms various ROS can be formed by

different ways. In normal aerobic respiration, stimu-

lated polymorphonuclear leukocytes and macrophages,

and peroxisomes appear to be the main endogenous

sources of most of the oxidants produced by cells.Exogenous sources of free radicals include tobacco

smoke, ionizing radiation, certain pollutants, organic

solvents and pesticides. (Halliwell and Gutteridge, 1989;

Halliwell, 1994; Davies, 1994; Robinson et al., 1997;

Yildirim et al., 2000).

Most living species have an efficient defense systems

to protect themselves against the oxidative stress in-

duced by ROS (Sato et al., 1996). Recent investigations

have shown that the antioxidant properties of plants

could be correlated with oxidative stress defense and

different human diseases including cancer, atherosclero-

sis, and the aging processes (Stajner et al., 1998;

Sanchez-Moreno et al., 1999; Malencic et al., 2000).

* Corresponding author. Tel: +90-442-2311-936; fax: +90-442-2331-062.

E -mail address: [email protected] (I . Gülçin).

0378-8741/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved.

PII: S 0 3 7 8 - 8 7 4 1 ( 0 1 ) 0 0 3 9 6 - 8

mailto:[email protected]


2/5

I . Gü lc ¸in et al . / Journal of Ethnopharmacology 79 (2002) 325 – 329 326

Antioxidants can interfere with the oxidation process

by reacting with free radicals, chelating free catalytic

metals and also by acting as oxygen scavengers. Pheno-

lic antioxidants functions are free radical terminators

and sometimes also metal chelators (Shahidi and

Wanasundara, 1992; Sanchez-Moreno et al., 1999).

Thus, antioxidant defense systems have co-evolved with

aerobic metabolism to counteract oxidative damage

from ROS.The antioxidants may be used to preserve food qual-

ity from oxidative deterioration of lipid. Therefore,

antioxidants play a very important role in the food

industry. Synthetic antioxidants, such as butylated hy-

droxyanisole (BHA), butylated hydroxytoluene (BHT),

and tert-butylhydroquinone (TBHQ) are widely used in

the food industry, but BHA and BHT have suspected

of being responsible for liver damage and carcinogene-

sis (Grice, 1986; Wichi, 1988). Therefore, the develop-

ment and utilization of more effective antioxidants of

natural origin are desired.

Lichens have been used for medicinal purposesthroughout the ages and some, such as C . islandica,

Lobaria pulmonaria and Cladonia speres were reputed

to be effective in the treatment of pulmonary tuberculo-

sis (Vartia, 1973). Lichen species are very common in

Turkey. Especially, C . islandica is one of the most

common lichen species, which grows in west regions of

Turkey (Dülger et al., 1998). Some lichen species are

used as stomachic and antidiabetic drug in Turkish folk

medicine (Baytop, 1999). C . islandica is well known in

Turkish folk medicine and used for treatment of dis-

eases such as hemorrhoids, bronchitis, dysentery andtuberculosis (Dülger et al., 1998). In addition, this

lichen species has been used as hemostatic drug (Bay-

top, 1999).

Many scientists have investigated the chemical com-

position of the lichen C . islandica beginning from the

XIX century till today. However, so far the nature of

the lichen has not been elucidated exactly (Stepanenko

et al., 1997). In addition to this, there are some phar-

maceutical studies about composition of this lichen

species. Protolichesterinic acid isolated from C . is-

landica has in-vitro inhibitory effects on arachidonate

5-lipoxygenase. Protolichesterinic acid, -methylene--lactone, fumarprotocetric acid and -orcinol depsidone

are considered to be the major biologically active sec-

ondary metabolites in the lichen C . islandica (Og-

mundsdottir et al., 1998). Several lichen metabolities of

C . islandica exhibited highest antimiyobacterial activity

(Ingolfsdottir et al., 1998). Aliphatic -methylene--lac-

tone isolated from the lichen C . islandica were found to

be potent inhibitors of the DNA polymerase activity of

human immunodeficiency virus-1 reverse transcriptase

(HIV-1 RT) (Pengsuparp et al., 1995). However, there

is no information about antioxidant activity of aqueous

extract of lichen C . islandica. In our investigation, we

wanted to describe the antioxidant effects of C . is-

landica and to compare their antioxidant effects with

those commonly used as food antioxidants, such as

BHT, BHA, and -tocopherol. In addition to this, the

components responsible for the antioxidative ability of

C . islandica are currently unclear. Hence, it is suggested

that further work could be performed on the isolation

and identification of the antioxidative components in C .

islandica.The aim of the present study was to investigate the

antioxidant properties of C . islandica in order to evalu-

ate its medicinal value and to point to an easily accessi-

ble source of natural antioxidants that could be used as

a possible food supplement or in the pharmaceutical

industry.

2. Materials and methods

2 .1. Chemicals

Ammonium thiocyanate was purchased from E.

Merck. Ferrous chloride, polyoxyethylenesorbitan

monolaurate (Tween-20), -tocopherol, 1,1-diphenyl-2-

picryl-hydrazyl (DPPH.), nicotinamide adenine dinucle-

otide (NADH), butylated hydroxyanisole (BHA),

butylated hydroxytoluene (BHT), quercetin and trichlo-

racetic acid (TCA) were purchased from Sigma Chemi-

cal Co. All other unlabeled chemicals and reagents were

analytical grade.

2 .2 . Lichen material

The lichen C . islandica was collected in Oltu, Erzu-

rum regions of Turkey and authenticated by Dr Ali

Aslan, Medical Faculty, Atatürk University.

2 .3 . Extraction

For water extraction, 20 g sample was mixed with

400 ml distillated and boiling water by magnetic stirrer

for 15 min. Then the extract was filtered over Whatman

No. 1 paper. The filtrates were frozen and lyophilized

in lyophilizator (Labconco, Freezone IL).

2 .4 . Antioxidant acti ity determination

The antioxidant activity of C . islandica was deter-

mined according to the thiocyanate method (Mitsuda et

al., 1996). About 10 mg of C . islandica was dissolved in

10 ml water. Then, 1.0 mg of C . islandica in 1 ml of

water was added to linoleic acid in potassium phos-

phate buffer (2.5 ml, 0.04 M, pH 7.0). The mixed

solution was incubated at 37 °C in a glass flask. The

peroxide value was determined by reading the ab-

sorbance at 500 nm, after reaction with FeCl2 and


3/5


thiocyanate at several intervals during incubation. The

solutions without added extracts were used as blank

samples. All data are the average of duplicate analyses.

2 .5 . Reducing power

The reducing power of C . islandica was determined

according to the method of Oyaizu (Oyaizu, 1986). Ten

mg of C . islandica extract in 1 ml of distilled water wasmixed with phosphate buffer (2.5 ml, 0.2 M, pH 6.6)

and potassium ferricyanide [K3Fe(CN)6] (2.5 ml, 1%).

The mixture was incubated at 50 °C for 20 min. A

portion (2.5 ml) of trichloroacetic acid (10%) was added

to the mixture, which was then centrifuged at 3000 rpm

(MSE Mistral 2000, UK) for 10 min. The upper layer

of the solution (2.5 ml) was mixed with distilled water

(2.5 ml) and FeCl3 (0.5 ml, 0.1%), and the absorbance

was measured at 700 nm. Increased absorbance of the

reaction mixture indicated increased reducing power.

2 .6 . Superoxide anion scaenging acti ity

Measurement of superoxide anion scavenging activity

of C . islandica was done based on the method described

by Nishimiki (Nishimiki et al., 1972) and slightly

modified. About 1 ml of nitroblue tetrazolium (NBT)

solution (156 M NBT in 100 mM phosphate buffer,

pH 7.4) 1 ml NADH solution (468 M in 100 mM

phosphate buffer, pH 7.4) and 0.1 ml of sample solu-

tion of C . islandica in water were mixed. The reaction

started by adding 100 l of phenazine methosulphate(PMS) solution (60 M PMS in 100 mM phosphate

buffer, pH 7.4) to the mixture. The reaction mixture

was incubated at 25 °C for 5 min, and the absorbance

at 560 nm was measured against blank samples. De-

creased absorbance of the reaction mixture indicated

increased superoxide anion scavenging activity.

2 .7 . Free radical scaenging acti ity

The free radical scavenging activity of C . islandica

was measured by 1,1-diphenyl-2-picryl-hydrazil(DPPH.) using the method of Blois (Blois, 1958).

Briefly, 0.1 mM solution of DPPH. in ethanol was

prepared and 1 ml of this solution was added 3 ml of C .

islandica solution in water at different concentrations

(50 – 250 g). After 30 min, absorbance was measured at

517 nm. Lower absorbance of the reaction mixture

indicated higher free radical scavenging activity. The

DPPH concentration in the reaction medium was cal-

culated from the following calibration curve, deter-

mined by linear regression:

Absorbance=2.4928× [DPPH]+0.0392

2 .8 . Determination of total phenolic compounds

Total soluble phenolics in the aqueous extract of C .

islandica were determined with Folin – Ciocalteu reagent

according to the method of Slinkard and Singleton

(Slinkard and Singleton, 1977) using pyrocatechol as a

standard. Briefly, 0.1 ml of extract solution (contains

1000 g extracts) in a volumetric flask diluted distilled

water (46 ml). About 1 ml of Folin – Ciocalteu reagentwas added and the contents of the flask mixed thor-

oughly. After 3 min, 3 ml of Na2CO3 (2%) was added,

then the mixture was allowed to stand for 2 h with

intermittent shaking. The absorbance was measured at

760 nm. The concentration of total phenolic com-

pounds in the C . islandica determined as microgram of

pyrocatechol equivalent by using an equation that was

obtained from standard pyrocatechol graph. The equa-

tion is given below:

Absorbance=0.001×Pyrocatechol (g)+0.0033

2 .9 . Statistical analysis

Experimental results were meanS.D. of five paral-

lel measurements. P-values 0.05 were regarded as

significant and P-values 0.01 very significant.

3. Results and discussion

C . islandica (L) Ach. demonstrated effective antioxi-

dant activity at all concentrations (Fig. 1). The antioxi-

dant activity of C . islandica was determined by the

thiocyanate method. The effects of various amounts of

aqueous extract of C . islandica (from 50 to 500 g) on

peroxidation of linoleic acid emulsion are shown in Fig.

1. All concentrations of aqueous extract of C . islandica

showed higher antioxidant activities than that 500 g of

-tocopherol and had 96, 99, 100 and 100% inhibition

on lipid peroxidation of linoleic acid system, respec-

Fig. 1. Inhibition (%) of lipid peroxidation of -tocopherol and

different doses of aqueous extract of C . islandica (CI) in the linoleicacid emulsion. Toc, -tocopherol.


4/5


Fig. 2. Reducing power of aqueous extract of C . islandica (CI ) doses

and BHT. Results are meanS.D. of five parallel measurements.

P0.01 when compared with control. Spectrophotometric dedection

of the Fe+3 – Fe+2 transformation; BHT, butylated hydroxytoluene.

Fig. 3. Superoxide anion scavenging activity of 100 g of aqueous

extract of C . islandica (CI ), and same dose of quercetin, BHA, and

BHT by the PMS/NADH-NBT method. Results are meanS.D. of

five parallel measurements. P0.05 when compared with control.

BHT, Butylated hydroxytoluene; BHA, butylated hydroxyanisole.

tively, and greater than that 500 g of -tocopherol

(77%) (Fig. 1). The inhibition of lipid peroxidation in

percent was calculated by the following equation:

% Inhibition=A0−A1A0

100where A0 is the absorbance of the control reaction and

A1 is the absorbance in the presence of the sample of

aqueous extract of C . islandica (Burits and Bucar,

2000).

Fig. 2 shows the reductive capabilities of samples of

C . islandica compared with BHT. For the measure-

ments of the reductive ability, we investigated the Fe3+

– Fe2+ transformation in the presence of the aqueous

extract samples of C . islandica using the method of Oyaizu (Oyaizu, 1986). The reducing capacity of a

compound may serve as a significant indicator of its

potential antioxidant activity (Meir et al., 1995). How-

ever, the antioxidant activity of putative antioxidants

have been attributed to various mechanisms, among

which are prevention of chain initiation, binding of

transition metal ion catalysts, decomposition of perox-

ides, prevention of continued hydrogen abstraction,

and radical scavenging (Diplock, 1997; Yildirim et al.,

2001). Like the antioxidant activity, the reducing power

of C . islandica increased with increasing amount of

sample. All of the amounts of C . islandica showedhigher activities than control and these differences were

statistically very significant (P0.01).

In the PMS/NADH-NBT system, superoxide anion

derived from dissolved oxygen by PMS/NADH cou-

pling reaction reduces NBT. The decrease of ab-

sorbance at 560 nm with antioxidants thus indicates the

consumption of superoxide anion in the reaction mix-

ture. Fig. 3 shows the superoxide radical scavenging

activity of 100 g of aqueous extract of C . islandica in

comparison with same doses of BHA, BHT, and

quercetin. C . islandica had strong superoxide radical

scavenging activity and exhibited higher superoxide

radical scavenging activity than quercetin and BHT.

The results were found statistically significant (P

0.05). Superoxide radical scavenging activity of those

samples followed the order: BHAaqueous extract of

C . islandicaBHTquercetin.

Fig. 4 illustrates a significant (P0.05) decrease the

concentration of DPPH radical due to the scavenging

ability of soluble solids in the aqueous extract of C .

islandica and standards. We used BHA and quercetin as

standards.

Phenols are very important plant constituents be-

cause of their scavenging ability due to their hydroxyl

groups (Hatano et al., 1989). In the aqueous extract of

C . islandica (1 mg), 0.0387 g pyrocatechol equivalent

of phenols was detected. The phenolic compounds may

contribute directly to antioxidative action (Duh et al.,

1999). It is suggested that polyphenolic compounds

have inhibitory effects on mutagenesis and carcinogene-

sis in humans, when up to 1.0 g daily ingested from a

diet rich in fruits and vegetables (Tanaka et al., 1998).

Fig. 4. Free radical scavenging activity of aqueous extract of C .

islandica (CI ), BHA and quercetin by 1,1-diphenyl-2-picrylhydrazyl

radicals. Results are meanS.D. of five parallel measurements.

P0.01 when compared with control. BHA, butylated hydroxyan-isole.


5/5


4. Conclusion

Aqueous extract of C . islandica showed strong an-

tioxidant activity, reducing power, DPPH radical and

superoxide anion scavenging activities when compared

with different standards such as -tocopherol, BHA,

BHT, and quercetin. The results of this study show that

aqueous extract of C . islandica can be of use as an

easily accessible source of natural antioxidants and as apossible food supplement or in pharmaceutical indus-

try. However, the components responsible for the an-

tioxidative activity of aqueous extract of C . islandica

are currently unclear. Therefore, it is suggested that

further work could be done on the isolation and iden-

tification of the antioxidative components in C .

islandica.

References

Baytop, T., 1999. Therapy with Medicinal Plants in Turkey (Past andPresent). Istanbul University, Istanbul, p. 233.

Blois, M.S., 1958. Antioxidant determinations by the use of a stable

free radical. Nature 26, 1199 – 1200.

Burits, M., Bucar, F., 2000. Antioxidant activity of Nigella sati a

essential oil. Phytotherapy Research 14, 323 – 328.

Davies, K.J.A., 1994. Oxidative stress: the paradox of aerobic life.

Biochemistry Society Symphosium 61, 1 – 34.

Diplock, A.T., 1997. Will the ‘good fairies’ please proves to us that

vitamin E lessens human degenerative of disease? Free Radical

Research 27, 511 – 532.

Duh, P.D., Tu, Y.Y., Yen, G.C., 1999. Antioxidant activity of

aqueous extract of harn jyur (Chyrsanthemum morifolium Ramat).

Lebensmittel-Wissenschaft und Technologie 32, 269 – 277.

Dülger, B., Gücin, F., Aslan, A., 1998. Cetraria islandica (L) Ach.Likeninin Antimikrobiyal Aktivitesi. Turkish Journal of Biology

22, 11 – 118.

Grice, H.C., 1986. Safety evaluation of butylated hydroxytoluene

(BHT) in the liver, lung and gastrointestinal tract. Food and

Chemical Toxicology 24, 1127 – 1130.

Halliwell, B., 1994. Free radicals, antioxidants and human disease:

curiosity, cause or consequence. Lancet 67, 85 – 91.

Halliwell, B., 1995. How to characterize an antioxidant: an update?

Biochemistry Society Symphosium 61, 73 – 101.

Halliwell, B., Gutteridge, J.M., 1989. Free Radical in Biology and

Medicine. Clarendon Press, Oxford, p. 23.

Hatano, T., Edamatsu, R., Mori, A., Fujita, Y., Yasuhara, E., 1989.

Effect of interaction of tannins with co-existing substances. VI.

Effects of tannins and related polyphenols on superoxide anion

radical and on DPPH radical. Chemical and Pharmaceutical

Bulletin 37, 2016 – 2021.

Ingolfsdottir, K., chung, G.A.C., Skulason, V.G., Gissurarson, S.R.,

Vilhemsdottir, M., 1998. Antimiyobacteriyal of lichen metabolites

in vitro. European Journal of Pharmaceutical Sciences 6, 141 –

144.

Kehrer, J.P., 1993. Free radicals as mediators of tissue injury and

disease. CRC Critical Reviews in Toxicology 23, 21 – 48.

Malencic, Dj., Gasiç, O., Popovic, M., Boza, P., 2000. Screening for

antioxidant properties of Sal ia reflexa hornem. Phytotherapy

Research 14, 546 – 548.

Meir, S., Kanner, J., Akiri, B., Hadas, S.P., 1995. Determination and

involvement of aqueous reducing compounds in oxidative defense

systems of various senescing leaves. Journal of Agricultural and

Food Chemistry 43, 1813 – 1817.

Mitsuda, H., Yuasumoto, K., Iwami, K., 1996. Antioxidation action

of indole compounds during the autoxidation of linoleic acid.

Eiyo to Shokuryo 19, 210 – 214.

Nishimiki, M., Rao, N.A., Yagi, K., 1972. The occurrence of super-

oxide anion in the reaction of reduced phenazine methosulfate

and molecular oxygen. Biochemical and Biophysical Research

Communication 46, 849 – 853.

Ogmundsdottir, H.M., Zoega, G.M., Gissurarson, S.R., Ingolfsdottir,

K., 1998. Anti-proliferative effects of lichen-derived inhibitors of 5-lipoxygenase on malignant cell-lines and mitogen-stimulated

lymphocytes. Journal of Pharmacy and Pharmacology 50, 107 –

115.

Oyaizu, M., 1986. Studies on product of browning reaction prepared

from glucose amine. Japanese Journal of Nutrition 44, 307 – 315.

Pengsuparp, T., Cai, L., Constant, H., Fong, H.H.S., Lin, L.Z.,

Kinghorn, A.D., Pezzuto, J.M., Cordell, G.A., Ingolfsdottir, K.,

Wagner, H., Hughes, S.H., 1995. Mechanistic evaluation of new

plant-derived compounds that inhibit HIV-1 reverse transcriptase.

Journal of Natural Products (Lloydia) 58, 1024 – 1031.

Robinson, F.E., Maxwell, S.R.J., Thorpe, G.H.G., 1997. An investi-

gation of the antioxidant activity of black tea using enhanced

chemiluminescence. Free Radical Research 26, 291 – 302.

Sanchez-Moreno, C., Larrauri, J.A., Saura-Calixto, F., 1999. Freeradical scavenging capacity an inhibition of lipid oxidation of

wines, grape juices and related polyphenolic constituents. Food

Research International 32, 407 – 412.

Sato, M., Ramarathnam, N., Suzuki, Y., Ohkubo, T., Takeuchi, M.,

Ochi, H., 1996. Varietal differences in the phenolic content and

superoxide radical scavenging potential of wines from different

sources. Journal of Agricultural and Food Chemistry 44, 37 – 41.

Shahidi, F., Wanasundara, P.K.J.P.D., 1992. Phenolic antioxidants.

Critica Reviews in Food Science and Nutrition 32, 67 – 103.

Sies, H., 1993. Strategies of antioxidant defense. Europan Journal of

Biochemistry 215, 213 – 219.

Slinkard, K., Singleton, V.L., 1977. Total phenol analyses: automa-

tion and comparison with manual methods. American Journal of

Enol. Vitic. 28, 49 – 55.Squadriato, G.L., Peyor, W.A., 1998. Oxidative chemistry of nitric

oxide: the role of superoxide, peroxynitrite and carbon dioxide.

Free Radical Biology and Medicine 25, 392 – 403.

Stajner, D., Miliç, N., Mimica-Dukic, N., Lazic, B., Igic, R., 1998.

Antioxidant abilities of cultivated and wild species of garlic.

Phytotherapy Research 12, 513 – 514.

Stepanenko, L.S., Krivoshchekova, O.E., Dimitrenok, P.S., Maxi-

mov, O.B., 1997. Quinones of Cetraria islandica. Phytochemistry

, 565 46, 568.

Tanaka, M., Kuei, C.W., Nagashima, Y., Taguchi, T., 1998. Applica-

tion of antioxidative maillrad reaction products from histidine

and glucose to sardine products. Nippon Suisan Gakkaishi 54,

1409 – 1414.

Vartia, K.O., 1973. Antibiotics in lichens. In: Ahmadjian, V., Hale,

M.E. (Eds.), The lichens. Academic Press, New York, p. 547.

Wichi, H.P., 1988. Enhanced tumor development by butylated hy-

droxyanisole (BHA) from the prospective of effect on forestom-

ach and oesophageal squamous epithelium. Food and Chemical

Toxicology 26, 717 – 723.

Yildirim, A., Mavi, A., Oktay, M., Kara, A.A., Algur, O .F., Bi-

laloglu, V., 2000. Comparision of antioxidant and antimicrobial

activities of Tilia (Tilia argenta Desf Ex DC), Sage (Sal ia Triloba

L.) and Black tea (Camellia Sinensis) Extracts. Journal of Agricul-

tural and Food Chemistry 48, 5030 – 5034.

Yildirim, A., Oktay, M., Bilaloglu, V., 2001. The antioxidant activity

of the leaves of Cydonia ulgaris. Turkish Journal of Medical

Science 31, 23 – 27.

Documents

Antioxidant Activity of Lichen Cetraria Islandica