Synthetic Antioxidant BHT Research Articles

Antioxidant Activity of Polyphenolic Compounds from Dalbergia odorifera T. Chen

2 Abstract: Seven compounds were isolated from Dalbergia odorifera T. Chen and their antioxidant activities were studied with Oil Stability Index (OSI) method, reducing power and radical scavenging methods. The compounds were identified by spectroscopic methods as (1) pinocembrin (2) biochanin A (3) sativanone (4) biochanin B (5) naringenin (6) 3´-hydroxymelanettin and (7) eriodictoyl. Results showed that compounds 6 and 7 exhibited stronger antioxidant activity than commonly used synthetic antioxidant BHT in the presented study.

In vitro antioxidant analysis of Achillea tenuifolia

Achillea tenuifolia (AT) is one of the most herbs are being used by people as a traditional medicinal remedy. Antioxidant activity of AT different extracts and total flavonoid and phenol levels in the extracts were investigated in this study. Plant extracts were prepared by maceration method using ethyl acetate, methanol and methanol-water (1:1). Folin Ciocalteu reagent in terms of gallic acid equivalent achieved the total phenol's content. AlCl3 was used as a reagent for flavonoid determination. Flavonoid content of the plant extracts obtained in terms of quercetin equivalent. DPPH radical scavenging effect of the extracts was determined by UV spectroscopy. Also in order to determine lipid peroxidation inhibition of the extracts of A. tenuifolia, ferric thiocyanate method with BHT, a synthetic reference standard, was carried out in this study. Phenol contents were 43.97 ± 0.034, 74.16 ± 0.55 and 106 ± 0.693 mg g-1 in the ethyl acetate, methanol and methanol-water extracts, respectively. Flavonoid amount obtained in the ethyl acetate, methanol and methanol-water extracts were 10.6 ± 1.85, 23.1 ± 0.5 and 190 ± 1.3 mg g-1, respectively. The percentage of DPPH radical scavenged by the most active extract (methanol-water) of A. tenuifolia was 92% at a concentration of 1 mgml-1 greater than 94% of BHT at 2 mgml-1. IC50 of methanol-water extract and BHT were 0.015 and 0.053 mgml-1, respectively. Lipid peroxidation inhibition was observed by the most polar extract of AT about 91.84%. Phenol and flavonoids content confirm the existence of more polar hydroxyl containing chemical structures in the plant. The potency of radical scavenging effect of methanol-water extract was about 3.5 times greater than synthetic antioxidant BHT. The inhibitory activity of the extracts on the lipid peroxidation of linoleic acid in ferric thiocyanate test was also significant (> 90%). In this study we concluded that there is a direct relation between phenol and flavonoid content of plant extracts and the antioxidant activity. So that the greater amount of phenolic compounds leads to more potent radical scavenging and lipid peroxidation inhibition activities as it was observed in A. tenuifolia polar extract in the present study.

Isolation of antioxidative secoiridoids from olive wood ( Olea europaea L.) guided by on-line HPLC–DAD–radical scavenging detection

The woody portion of olive tree pruning is a source of natural antioxidants of potential interest for the food industry. This work deals with the isolation and identification of further antioxidants present in an ethyl acetate extract of olive ( Olea europaea L.) wood. Thus, a new secoiridoid, oleuropein-3″-methyl ether ( 1), together with six known secoiridoids, 7″ S-hydroxyoleuropein ( 2), jaspolyanoside ( 3), ligustroside 3′- O-β- d-glucoside ( 4), jaspolyoside ( 5), isojaspolyoside A ( 6) and oleuropein 3′- O-β- d-glucoside ( 7) were isolated by combining HPLC with fast on-line post-column radical scavenging activity evaluation. The structures of these compounds were determined by spectroscopic methods. The antioxidant activity of the pure compounds was determined by measuring the radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH ). Compounds 2, 5 and 7 displayed a higher antioxidative effect than the synthetic antioxidant BHT and lower than rosmarinic acid, whereas compounds 3 and 4 showed weak DPPH scavenging activity.

Protective Effect on Human Lymphocytes of Some Flavonoids Isolated from Two Achillea Species

This study was conducted to elucidate the in vitro protective effect of five flavonoids [apigenin (1), apigenin-7-O-glucoside (2), centaureidin (3), jaceidin (4) and quercetin (5)] against chromosomal damage in mitogen-induced human lymphocytes. Using the Cytochalasin-B blocked micronucleus (CBMN) assay, in which the biomarker of chromosome breakage and/or chromosome loss is the elevated frequency of micronucleus (MN) in binucleated (BN) cells, the presence of flavonoid 2 in minimal concentration (3 microg/mL) gave a 35.5% decrease in the frequency of MN when compared with control human lymphocytes. The same concentration of flavonoids 1, 3 and 4, reduced the MN frequency by 24.4%, 28.0% and 28.0%, respectively. Higher concentrations (6 microg/mL and 10 microg/mL) seemed less effective. Flavonoid 5 (3 microg/mL) induced a slight decrease in MN frequency (5%), while higher doses (6 microg/mL and 10 microg/mL) provoked an increase of DNA damage. The comparable values for the cytokinesis-block proliferation index (CBPI) of the tested flavonoids and positive control suggested an inhibitory effect on lymphocyte proliferation. In the DPPH scavenging assay, flavonoids 1-4 demonstrated modest activity, in a dose-dependent manner, compared with the synthetic antioxidants BHT and Trolox, while 5 exhibited comparably high antioxidative activity.

Six Edible Wild Fruits as Potential Antioxidant Additives or Nutritional Supplements

Total antioxidant activity of six non-cultivated but traditionally collected fruits from the south of Europe was assessed by measuring their ability to reduce the hydroxyl radical (OH) and hydrogen peroxide (H(2)O(2)), and their Trolox equivalent antioxidant capacity (TEAC). This antioxidant activity was compared with that shown by the synthetic antioxidants BHA (E-320), BHT (E-321) and propyl gallate (E-310). Total phenolics, ascorbic acid and the carotenoid content of the fruits were also analyzed. All fruits showed a high ability to scavenge the OH radical, ranging from 60.61% to 81.04% inhibition for Rosa canina and Crataegus monogyna, respectively. The H(2)O(2) scavenging capacity and the TEAC value varied widely, ranging between 3.63% and 87.26% inhibition of H(2)O(2) and between 0.47 and 416.64 mM trolox g(-1) FW for Sorbus domestica and Rosa canina, respectively. The antioxidant activity of fruits was higher than that of the synthetic additives analyzed, except in the TEAC assay. The phenolic and carotenoid content of R. canina was much higher than that of the other fruits analyzed and its ascorbic acid concentration was also high, reflecting its higher efficacy towards ABTS⁻ (TEAC assay) and H(2)O(2) species(.) In spite of these associations, the correlation coefficients between total antioxidant activity and the antioxidant compounds analyzed were not very significant; only phenolics and carotenoids showed a marginal correlation with the TEAC assay. The results support the possible use of R. canina as natural antioxidant to replace the synthetic additives, as well as their use in the production of functional foods with a high antioxidant activity.

Free Radical Scavenging Activity and Total Phenolic Content of Methanolic Extracts from Male Inflorescence of Salix aegyptiaca Grown in Iran.

This study was designed to examine the in vitro antioxidant activities and total phenolic contents of the methanolic extracts from male inflorescence of Salix aegyptiaca L. grown in Iran. The methanolic extract (ME) and its three fractions including water (WF), butanol (BF) and chloroform (CF) were prepared and then their antioxidant activities, as well as total phenolic contents, were evaluated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and the Folin-Ciocalteu method, respectively. Among the different fractions of methanol extract, BF indicated the most antioxidant activity with an IC50 value of 27.7 μg/mL and total phenols of 313.8 ppm, which is comparable with the synthetic antioxidant BHT (IC50 = 26.5μg/mL). The antioxidant activities of the other fractions decreased in the order of ME >WF > CF. The potent antioxidant activity of S. aegyptiaca supported its possible use as a natural antioxidant in food industries and other pharmaceutical preparations.

Phytochemical Bioactivides from Mentha spicata Essential Oil for Health Promotion

The antibacterial effect of Mentha spicata revealed the sensitivity order of Escherichia coli > Staphylococcus aureus > Klebsiella pneumoniae > Enterococcus faecalis Decimal reduction time (D-value) for E. coli, S. aureus, E. faecalis and K. pneumoniae 4.28, 17.14, 6.42 and 6.42 minutes respecticvely. The oils concentrations required for 50 %free radical scavenging (IC50) was 17.40 μg/ml with total phenol content of 80.43 μg GAE/mg and 30.52 % DPPH scavenging capacity. Lipid peroxidation inhibitions were comparable to the synthetic antioxidant BHT and BHA. Ferric-reducing antioxidant power (FRAP) in the blood sera of the rats gavaged with a daily dose of 100 μl oil showed 36.51 %hike. Lipid peroxidation inhibition by M. spicata oil was statistically (P>0.05) at the same level of the synthetic antioxidant BHT and lower (P<0.001) than BHA. Therapeutic effects were noted as a result of essential oil feeding of rats. The volatile oil displayed excellent cytotoxic actions towards the human tumor cell line (HeLa cells) with the IC50 of 1.1 μg/ml. Although all in vitro experiments hold limitations with regards to possible in vivo efficacy, M. spicata essential oil maybe exploited as a natural source of bioactive phytopchemicals bearing antimicrobial, antioxidant and possible anti-neoplastic chemotherapy potentials.

Antioxidant Efficacy of Mulberry (Morus Indica L.) Leaves Extract and Powder in Edible Oil

The antioxidant activity of mulberry (Morus Indica L.) leaves was evaluated in rice bran oil (RBO). The oil was subjected to accelerated oxidation at 100° C for 5 days and heat treatment at 180°C for 1 h. In order to examine its potential antioxidant activity, the oxidative stability of the oils was evaluated by employing peroxide value (PV), radical scavenging activity (RSA), thiobarbituric acid reactive substances assay (TBARS), and percent free fatty acids (FFA). Mulberry in two forms viz: the methanolic extract and powder were applied to RBO at 200 ppm and 0.05%, respectively, and results were compared with RBO treated with a synthetic antioxidant-BHT. The PV, RSA, TBARS, and FFA values indicated that both mulberry extract and powder were effective in inhibiting lipid oxidation when compared to synthetic antioxidant BHT. Thus, mulberry leaves may serve as a new source of natural antioxidant for use in food systems.

Antioxidant Activity of the Essential Oil and Metanolic Extract of Eucalyptus largiflorens and Eucalyptus intertexta from Central Iran

This study was designed to examine the in vitro antioxidant activities of the essential oil and the subfractions of methanol extract from leaves of Eucalyptus largiflorens and Eucalyptus intertexta by using 2,2-diphenyl-l-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. According to the result of DPPH assay, IC50 of polar subfractions of the methanol extract was lower than that of non polar one, while in the case of the linoleic acid system; oxidation of the linoleic acid was effectively inhibited by the non polar subfraction of the methanol extract (92 - 94.5 %), that is close to the synthetic antioxidant BHT. It is interesting to point out that in both systems the oils were less effective. The amounts of total phenolics in the polar subfractions of each extracts were determined. Particularly, a positive correlation was observed between the total phenolic content and the antioxidant activity of the extracts.

Antioxidant properties and polyphenol contents of trembling aspen bark extracts

Trembling aspen (Populus tremuloides Michx) bark was extracted with water and the crude extract fractionated with tert-butyl-methyl ether (TBME), ethyl acetate (EtOAc) and n-butanol (BuOH) to obtain four different fractions. The antioxidant properties of the bark hot water extracts and its fractions were determined by three in vitro experiments: DPPH assay, phosphomolybdenum assay and canola oil thermoxidation assay by DSC analysis. Most of the results of the reported tests showed that the crude hot water extract and its fractions exhibited a strong antioxidant activity, higher than the synthetic antioxidant BHT. The results of this study confirm that antioxidant activity is a property that strongly depends on the oxidation conditions used in the particular oxidation test. Among the fractions separated from the aqueous extracts of bark, BuOH, TBME and EtOAc soluble fractions exhibited the best antioxidant efficiency, in phosphomolybdenum assay, DPPH assay and canola oil thermoxidation, respectively. Total phenol, flavonoid and flavanol contents were also evaluated and the results confirmed that the polyphenols contained in the hot water extract of this bark are mainly composed of non-flavonoid compounds.

Antioxidant activities of herbs, fruit and medicinal mushroom Ganoderma lucidum extracts produced by microfiltration process

This paper presents kinds of extraction and cross-flow filtration of composition of 46 healthful and aromatic herbs, 8 fruits and fungi Ganoderma lucidum. Those extracts are part of Bitter 55, which have significant antioxidant capacity. Antioxidative activities of plant extracts have been determined by DPPH test using method of Blois. Bitter 55 which was kept at the green bottle in the dark has EC50 = 141.07 ?l/ml and it was stable during 150 days. Synthetic anti-oxidants BHT (ditertbutilhydroxytoluen, EC50 = 6.2 ?gml-1), trolox (vitamin E analog soluble in water, EC50 = 6.8 ?gml-1) were used for comparison. EC50 values were calculated as concentration of the extract necessary to decrease DPPH radical concentration for 50 %. Bitter 55 contents 35% vol of alcohol (wheat origin), 88.22 g/l total extract and slice of medicinal mushroom Ganoderma lucidum (1 % w/v) which was extracted 30 days before analyses. The main problem in practical applications of MF is the reduction of permeate flux with time, caused by the accumulation of feed components in the pores. During microfiltration bitter herbal liquor, the function of filtrate flux is decreased with VCR. Dependence of decreasing flux with VCR can be separated in three periods. For the first, starting period, rapid decrease of filtrate flux is characteristic. Second period is defined with much smaller decrease of the flux than in the first phase. Third period has as characteristic minor decrease of flux and can be defined as steady state. Steady state emerges after ?s = 80 min.

Physico-chemical characterization and bioactive compounds of blackberry fruits (Rubus sp.) grown in Brazil

Five blackberry cultivars (Rubus sp.) were evaluated for antioxidant capacity, bioactive compounds and composition. Ascorbic acid levels, consisting of dehydro-ascorbic acid, ranged from 9.8 to 21.4 mg.100 g-1 fresh weight. Cyanidin (66 to 80% of total flavonoids), epicatechin, quercetin and traces of kaempferol were the main flavonoids found in all cultivars. The five cultivars presented high antioxidant capacity in the β-carotene/linoleic acid system, with inhibition similar to the synthetic antioxidant BHT, at a 50 µM concentration. Caingangue cultivar presented high vitamin C and total phenolics content, while Guarani had the highest cyanidin, total anthocyanin and total flavonoids levels and also the highest antioxidant capacity. These cultivars also presented good TSS/TA ratios. From the data, at a quantitative level, blackberry can be considered a good source of bioactive compounds, as well as potentially beneficial to human health.

Use of an in Vitro Digestion Model To Study the Bioaccessibility of 4-Hydroxy-2-nonenal and Related Aldehydes Present in Oxidized Oils Rich in Omega-6 Acyl Groups

Mixtures of either sunflower oil or thermodegraded sunflower oil and a standard meal were submitted to an in vitro digestion model. The same experiment was carried out with fluid deep-frying fat and thermodegraded fluid deep-frying fat. The thermodegradation of the oil and fat was provoked by submitting them to 190 degrees C with aeration in a convection oven, and the presence in the headspace of the thermodegraded oil and fat of oxygenated alpha,beta-unsaturated aldehydes (OalphabetaUAs), such as 4-hydroxy-2-nonenal (HNE), 4-oxo-2-nonenal (ONE), and 4,5-epoxy-2-decenal (EDE), was monitored by solid phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). The digestion products were separated by centrifugation in a lipidic phase, an aqueous phase, and a pellet phase. The headspace of these three phases was also studied by SPME/GC-MS to check if the toxic and very reactive OalphabetaUAs above-mentioned remained unaltered after the in vitro digestion process or if they had reacted with the various compounds present in the digestion products, so disappearing from the samples. With the same aim the extract in ethyl acetate of the aqueous and pellet phases, and of the lipidic phase after dilution, were studied by GC-MS. All results obtained showed that a certain proportion of the toxic OalphabetaUAs remains unaltered after digestion, dispersed in the three phases above-mentioned, and thus are bioaccessible in the gastrointestinal tract and so could reach the systemic circulation. Compounds that may originate in Maillard type reactions (2-pentylpyridine) are found among digestion products, proving that these reactions are possible in this process if adequate substrates are present. In addition, it has been shown that toxic metabolites from the synthetic antioxidant BHT, present in fat before digestion, remain unaltered after this process and could reach the systemic circulation.

Antioxidant activity of ovine casein hydrolysates: identification of active peptides by HPLC–MS/MS

This paper shows the potential role of different ovine casein fractions and their hydrolysates to exert antioxidant activity. ABTS·+ decolorization assay was used to evaluate the antioxidant activity of the casein fractions (β-, κ- and αs-caseins) before and after their hydrolysis by pepsin, trypsin and chymotrypsin. Although the antioxidant activity increased in all the fractions after hydrolysis, the effect was particularly remarkable in the κ-casein fraction, which increased its antioxidant activity almost threefold. Further assays in a linoleic acid oxidation system showed that κ-casein hydrolysate inhibited lipid peroxidation. Analysis of the ovine κ-casein hydrolysate by RP-HPLC–MS/MS allowed the identification of 12 peptide sequences with potential antioxidant properties. One of the most abundant peptides, the fragment HPHPHLSF [f(98–105)] was chemically synthesized. Results showed that this κ-casein-derived peptide was a potent inhibitor of linoleic acid oxidation with an activity similar to that obtained with the synthetic antioxidant BHT. Although other peptides might also contribute, HPHPHLSF was the one most likely to be responsible for the activity found in the κ-casein hydrolysate.

Evaluation of antioxidant capacity of Allium ursinum L. volatile oil and its effect on membrane fluidity

A total of 20 components were identified in Allium ursinum volatile oil (AUVO) by GC–MS, and 10 of them are found for the first time in this plant species. The antioxidant capacity of AUVO was examined by β-carotene–linoleic acid bleaching, lipid peroxidation by Fenton reaction, EPR spin-probing assay using stable nitroxide radicals, DPPH , and ABTS + scavenging assays. Reaction mechanism of the volatile oil components with nitroxide radicals, based on IR spectra analysis, is proposed. AUVO demonstrated poor scavenging ability against DPPH and ABTS + comparing to synthetic antioxidants BHT and trolox, while in β-carotene–linoleic acid system AUVO showed an effect comparable to those for BHT. AUVO was also capable to scavenge stable nitroxide radicals such as water-soluble Tempone, and 7-DS and 12-DS, incorporated into the liposome membrane. Finally, AUVO increased membrane fluidity, which could be an important feature for further in vivo investigation of some disorders, such as hypertension and atherosclerosis.

Screening of Antioxidative Properties and Total Phenolic Compounds of Various Extracts of Three Different Seed of Grape Varieties (Vitis vinifera L.) From Turkish Flora

This study was designed to examine the in vitro antioxidant activities and total phenolic contents of various extracts prepared by using solvents of varying polarity from three different seed of grape varieties (Vitis vinifera L.) of which local names are Siyah gemre, Adana Karasi and Tilki kuyrugu in Turkish folk medicine, respectively. The extracts were screened for their possible antioxidant activity by two complementary test systems namely DPPH free radical scavenging and beta-carotene/linoleic acid. In the first case, polar fractions of the methanol extracts of grape seeds exerted excellent activity patterns than those of non-polar fractions, while hexane and dichloromethane extracts did not exhibited activity. Among the polar ones, the most active extract was Adana karasi (5.90 +/- 0.20 microg mL(-1), followed by Tilki kuyrugu and Siyah gemre (6.40 +/- 0.50 microg mL(-1) and 6.90 +/- 0.40 microg mL(-1), respectively). In DPPH system, grape seeds exerted two-fold greater antioxidant activity than that of synthetic antioxidant BHT. In beta-carotene/linoleic acid test system, inhibition of linoleic acid oxidation was effectively achieved by polar and non-polar extracts of Siyah gemre. In this system, polar extracts exhibited greater antioxidant activity than those of non-polar ones, whereas hexane and dichloromethane extracts had no activity. The amount of total phenolics was highest in polar and non-polar extracts of grape seeds. Especially, a positive correlation was observed between total phenolic content and antioxidant activity of polar extracts. As estimated from the results given above, amount of phenolic compounds were less in hexane and dichloromethane extracts than the others. In conclusion, antioxidant potentials of polar and nonpolar methanol extracts could be attributed to their high phenolic content.

Phenolics as radical scavengers in Plantago species

The genus Plantago L. (Plantaginaceae) comprises about 275 species found all over the world. Ancient use of plantains as herbal remedies is a consequence of their adstringent, anti-toxic, antimicrobial, anti-inflammatory, expectorant and diuretic properties. Although studies concerning the antioxidant activity of some plantains are available [1, 2], there are no reports on the antioxidant activity of some other Plantago species. The aim of this study was to examine antioxidative properties of methanolic extracts from four Plantago species (P. maior L., P. media L., P. lanceolata L. and P. holosteum Scop.) collected from three different locations in Serbia. The extracts were investigated regarding their composition by different colorimetric techniques, such as the content of total phenolic compounds by the Folin-Ciocalteu assay [3] and flavonoids by AlCl3 reagent [4]. Their radical scavenger capacity (RSC) was evaluated measuring spectrophotometrically the decrease of DPPH* (diphenylpicrylhydrazyl radical) [5]. The content of total phenolic compounds (expressed as g chlorogenic acid equivalents/g of dry extract) varied from 0.1281 (P. maior location N. Sad) to 0.2774 (P. media-Mt. Kopaonik). Flavonoid content was the highest in P. holosteum, followed by P. media, P. lanceolata and P. maior (from 19.76 to 7.77mg quercetine equiv/g of dry extract, respectively). The most potent extracts of P. media (Mt. Kopaonik) and P. holosteum (Mt. Stara Planina) inhibited the DPPH* by 50% (IC50) at 4.25 and 4.28µg/ml respectively indicating higher activity than the synthetic antioxidant BHT (IC50 4.62µg/ml). The extracts of P. maior and P. lanceolata also showed significant scavenging capacity. Beside estimated correlation between the scavenging potency and the total phenolic content of the extracts, this study presented P. media and P. holosteum as a possible new source of natural antioxidants.

On the extraction and antioxidant activity of phenolic compounds from winery wastes

Winery waste (from red winemaking, variety Agiorgitiko) was extracted under various conditions using different solvents. The minimum time required for ensuring maximum extraction of phenols was 180 min at a solvent to sample ratio 9:1 v/w and at pH 1.5. The antioxidant activity of solvent extracts was investigated by DPPH radical scavenging method, by determination of peroxide value on virgin olive oil and by the Rancimat method on sunflower oil. Ethanol extract exhibited the highest antioxidant activity compared to the other solvent extracts, to synthetic food antioxidants BHT, ascorbyl palmitate and to the natural food antioxidant, vitamin E. No correlation was found between antioxidant activity and total phenol content. HPLC analysis of the extracts showed that gallic acid, catechin and epicatechin were the major phenolic compounds in winery waste. Hydroxytyrosol, tyrosol, cyanidin glycosides and various phenolic acids such as caffeic, syringic, vanillic, p-coumaric and o-coumaric acids were also identified.

Isolation and identification of radical scavengers in olive tree ( Olea europaea) wood

Several extracts of Olea europaea wood (Picual olive cultivar) were obtained with solvents of different polarity and their antioxidant activities determined. The active compounds were detected in fractions of an ethyl acetate extract using HPLC with on-line radical scavenging detection. After applying different separation techniques, hydroxytyrosol, tyrosol, cycloolivil, 7-deoxyloganic acid, oleuropein and ligustroside were isolated and characterized. Hydroxytyrosol showed a higher activity than the natural antioxidant rosmarinic acid in scavenging the DPPH model radical. Cycloolivil and oleuropein showed stronger activities than the synthetic antioxidant BHT against the same radical. Ligustroside, tyrosol and 7-deoxyloganic acid showed little activity. The latter compound has not been previously identified in the genus Olea.

Screening of antioxidative properties of the methanolic extracts of Pelargonium endlicherianum Fenzl., Verbascum wiedemannianum Fisch. & Mey., Sideritis libanotica Labill. subsp. linearis (Bentham) Borm., Centaurea mucronifera DC. and Hieracium cappadocicum Freyn from Turkish flora

Five extracts from five plants, of which four are endemic to Turkish flora, were screened for their possible in vitro antioxidant activities by two complementary test systems, namely DPPH free radical-scavenging and β-carotene/linoleic acid. In the first case, Pelargonium endlicherianum extract exerted greater antioxidant activity than those of other plant extracts studied with an IC 50 value of 7.43 ± 0.47 μg/ml, followed by Hieracium cappadocicum (30.0 ± 0.14 μg/ml). When compared to the synthetic antioxidant BHT (18.0 ± 0.40 μg/ml), the methanolic extract of P. endlicherianum exhibited more than two fold greater antioxidant activity. In the β-carotene/linoleic acid test system, the most active plant was P. endlicherianum with 72.6% ± 2.96 inhibition rate, followed by H. cappadocicum (55.1% ± 2.33) and Verbascum wiedemannianum (52.5% ± 3.11). Antioxidant activities of curcumin and ascorbic acid were also determined as positive controls in parallel experiments.