Characterization of phenolic compounds,carotenoids, vitamins and antioxidant activities of selected Malaysian wild edible plants

This study was carried out to characterize phenolic compounds, carotenoids, vitamins and the antioxidant activity of selected wild edible plants. Plant extracts were purified, and phenolic compounds comprising 11 phenolic acids (hydroxybenzoic acid and hydrocinnamic acid) and 33 flavonoids (including catechin, glycosides and aglycones) were analysed using High Performance Liquid Chromatography - Diode Array Detector (HPLC-DAD). Furthermore, the contents of ascorbic acid and tocopherol ((α and γ tocopherol) and carotenoids (lutein and β-carotene) were also determined. The major phenolics identified consisted of glycosides of flavones (apigenin and luteolin) and flavonols (kaempferol and quercetin). Among the phenolic acids identified after hydrolysis, coumaric acid was the predominant phenolic acid in all the extracts of wild plants. Ascorbic acid [53.8 mg/100 g fresh weight (FW)] and β-carotene (656.5 mg/100 g FW) showed the highest content in the leaf of Heckeria umbellatum. In conclusion, the leaves of H. umbellatum, Aniseia martinicensis and Gonostegia hirta have excellent potential in the future to emerge as functional ingredients.     

Antioxidant capacity interactions and a chemical/structural model of phenolic compounds found in strawberries

The interactive antioxidant capacity of phenolic compounds from specific foods has not been well explored. The antioxidant capacity of a whole fruit exceeds the sum of the antioxidant capacities of individual antioxidants within that fruit, suggesting synergism among compounds. The interactions of seven phenolic compounds (p-coumaric acid, cyanidin, catechin, quercetin-3-glucoside, kaempferol, pelargonidin and ellagic acid) at relative concentrations found in strawberries were tested using the oxygen radical absorbance capacity assay. Statistically significant synergism was found for three combinations of two phenolic compounds, and among five combinations of three phenolic compounds. Statistically significant antagonism was observed among two combinations of two phenolic compounds and among one combination of three compounds. A chemical/structural model that best explained the results included reduction potentials, relative concentration, and the presence or absence of catechol (o-dihydroxy benzene) groups. This work demonstrates unique interactions that occur in a complex environment within the framework of strawberries. The synergism discovered at food-based antioxidant ratios could be applied to food preservation.     

Bioactivity and cell metabolism of in vitro digested sweet cherry (Prunus avium) phenolic compounds

In this study, the bioaccessibility of phenolic compounds after in vitro gastrointestinal digestion of two cherry cultivars was assessed. The phenolic profile was modified during in vitro digestion, with a considerable decrease of total and individual phenolic compounds. Hydroxycinnamic acids and especially coumaroylquinic acids showed the highest bioaccessibility. Isomerisation of caffeoylquinic and coumaroylquinic acids was observed after in vitro digestion. Modification of the phenolic profile after digestion resulted in an increased or decreased scavenging activity depending on the assay. In vitro digested phenolic-rich fractions also showed antiproliferative activity against SW480 but no effect against Caco-2 cell lines. Both Caco-2 and SW480 cell lines were able to metabolise cherry phenolic compounds with remarkable differences. An accumulation of glycosylated flavonols was observed in SW480 medium. In conclusion, phenolic compounds from cherries and especially hydroxycinnamic acids were efficiently released and remained bioaccessible after in vitro digestion, resulting in antioxidant and antiproliferative activities.     

Antioxidant activity and chemical difference in fruit of different Actinidia sp.

Abstract

The present research aimed at evaluating the vitamin C, total phenolic content (TPC), phenolic compounds, carotenoids, and chlorophyll contents, as well as antioxidant activity (AAC) of six Actinidia species fruit. Vitamin C, phenolic compounds, carotenoids and chlorophylls were measured using high-performance liquid chromatography. TPC was determined using the Folin–Ciocalteau reagent, and AAC using 2,2-diphenyl-1-picryl hydrazyl (DPPH) assay. The highest concentrations of vitamin C and TPC were found for Actinidia kolomikta fruit (1008.3 and 634.1 mg/100 g fresh weight [FW], respectively). Among phenolic compounds, seven phenolic acids and three flavonoids were identified. The 2,5-dihydroxybenzoic acid prevailed in A. kolomikta (425.54 mg/100 g FW), while tannic acid dominated in other species (4.63–100.43 mg/100 g FW). The largest amounts of chlorophylls and carotenoids were identified as Actinidia macrosperma (4.02 and 2.09 mg/100 g FW, respectively). The AAC of fruit extracts decreased in the order of A. kolomikta >?Actinidia purpurea >?Actinidia melanandra >?A. macrosperma >?Actinidia arguta >?Actinidia deliciosa according to the DPPH assay.     

Identification and quantification of a major anti-oxidant and anti-inflammatory phenolic compound found in basil,lemon thyme,mint, oregano,rosemary, sage,and thyme

Major phenolic compounds from basil, lemon thyme, mint, oregano, rosemary, sage, and thyme were investigated using a high-performance liquid chromatography (HPLC) profiling technique in combination with DPPH-radical scavenging, xanthine oxidase and cyclooxygenase assays. For the present study, 15 plant-derived phenolic compounds (gallic, protocatechuic, vanillic, syringic, chlorogenic, rosmarinic, caffeic, ferulic, and sinapic acids, protocatechualdehyde, vanillin, N-coumaroyltyramine, N-caffeoyltyramine, N-feruloyltyramine, and N-sinapoyltyramine) were selected and their DPPH-radical scavenging activities were first determined. Then, a standard HPLC profiling of these phenolics was constructed using an HPLC method to isolate anti-oxidant and anti-inflammatory phenolic compounds from MeOH extracts of the plants. Rosmarinic acid was identified as a major anti-oxidant compound (0.22–0.97%) in all seven herbs, confirmed by nuclear magnetic resonance. Rosmarinic acid from the plants quenched superoxide radicals from xanthine oxidase and inhibited cyclooxygenase I and II enzymes. In this study, the rosmarinic acid content of perilla was also determined and compared with those of the seven herbs.     

Efficacy of polymer coating of probiotic beads suspended in pressurized and pasteurized longan juices on the exposure to simulated gastrointestinal environment

Abstract

Alginate-coated Lactobacillus acidophilus LA5 or Lactobacillus casei 01 was recoated with either 0.1–0.5% (w/v) alginate or 0.05–0.15% (w/v) poly-L-lysine (PLL) plus 0.2% (w/v) alginate or 5–15% (w/v) gelatin, after which they were determined for survivability in gastric or bile longan juices. The morphology of encapsulated probiotic cells illustrated that recoated beads with 0.5% alginate showed a more compact surface and a greater protective effect than other recoating materials. The recoated beads with 0.5% alginate and 0.05–0.15% PLL plus 0.2% alginate of both strains showed the highest viability in gastric longan juice. In bile longan juice, only 0.5% alginate showed the best protection for both recoated beads. When considering the storage stability, encapsulated L. acidophilus LA5 exhibited a higher viable count than those of the free cells, whereas L. casei 01 showed equivalent viability of both free and double-coated cells. Based on the impact of pressurization or pasteurization, both processed juices gave rise to equivalent survivability of the probiotic cells during storage.     

Evolution of benzoate derivatives and their hydroxycinnamate analogues during ageing of white wines in oak barrels

Two white wines produced industrially, originating from the V. vinifera cultivars Asyrtiko and Chardonnay, were monitored with regard to the evolution of selected phenolic acids, during “on lees” ageing in oak casks for a period of 197 days. Four benzoic acid derivatives, namely p-hydroxybenzoic acid, protocatechuic acid, vanillic acid and syringic acid, and their corresponding hydroxycinnamate analogues p-coumaric acid, caffeic acid, ferulic acid and sinapic acid, were considered. The most abundant benzoate and hydroxycinnamate derivatives were protocatechuic acid and caffeic acid, with concentrations varying from 0.31 to 0.42 μg mL⁻¹ and 1.71 to 2.47 μg mL⁻¹, respectively, while the profile of both phenolic categories was essentially the same in both wines. The evolution pattern of benzoates showed that maximum concentration of protocatechuic acid was achieved after approximately 100 days (0.45–0.48 μg mL⁻¹) of ageing for both samples, whereas all other compounds exhibited an increasing trend towards the end of the examination period. The concentration of all hydroxycinnamates increased at the end of ageing, from 49.4% (caffeic acid) to 123% (p-coumaric acid), to the exception of sinapic acid which underwent practically no changes.     

Interactive effects of polyphenols, tocopherol and ascorbic acid on the Cu2+–mediated oxidative modification of human low density lipoproteins

Summary Background Only limited knowledge is available about any interactions between phenolic compounds and other antioxidants in inhibiting LDL oxidation. Many foods and beverages contain high levels of phenolic compounds; therefore, these compounds should not be considered in isolation from each other. Aim of the study The aim of this study was to examine the structure–antioxidant activity relationship of quercetin, caffeic acid, epicatechin, hesperetin and phloretin as well as α–tocopherol and ascorbic acid through their ability to interact with copper ions. Methods Isolated human LDL were incubated with single antioxidants or a combination of two and the kinetics of lipid peroxidation were assessed by measurement of conjugated diene formation (lag phase) via monitoring the absorbance at 234 nm after addition of copper ions. In addition, the degree of oxidation of the LDL protein moiety was followed by tryptophan fluorescence and carbonyl content measurements. Results α-Tocopherol and ascorbic acid showed a lower antioxidant activity in all test systems as compared to polyphenols at equimolar concentrations. Quercetin was the most effective compound in all three systems (p < 0.001 for lag phase and carbonyl content determination). A significant (p < 0.001) prolongation of the lag phase was found when combinations of ascorbic acid/quercetin, ascorbic acid/epicatechin, epicatechin/caffeic acid, and quercetin/epicatechin were tested as compared to the sum of the individual effects. Concerning the effects on LDL protein oxidation, the results from carbonyl content and the tryptophan fluorescence measurements showed that the combination of quercetin and caffeic acid revealed the strongest inhibitory effect (p < 0.001 carbonyl content; p ≤ 0.002 tryptohan fluorescence) on protein oxidation which was higher than the effect of the single compounds. Conclusions The results of the present study indicate that a combination of different antioxidants can be superior to the action of single antioxidants in protecting LDL lipid and protein moiety against oxidation. However, the substances may act by different antioxidative mechanisms, which are not necessarily complementary.     

Efficacy of phytol-derived diterpenoid immunoadjuvants over alum in shaping the murine host's immune response to Staphylococcus aureus

The ubiquitous gram-positive bacterium Staphylococcus aureus occupies a unique niche in humans for its ability to survive both as a commensal and a life-threatening pathogen. Its complex relationship with the host and its ability to engender a throng of virulence factors, have hindered the development of a successful vaccine against it. The use of immunoadjuvants to enhance host immunity and prevent the shift from commensalism to pathogenicity is a rational approach for containing infection. The objective of this study was to understand the mechanisms by which alum and two phytol-derived immunoadjuvants, phytanol (PHIS-01) ¹ and phytanyl chloride (PCl) ² shape the interaction between S. aureus and its murine host. We studied the effects of the phytol derivatives, relative to alum, on the induction of inflammatory cytokines and chemokines, recruitment of CD11b⁺ cells, generation of specific anti-S. aureus antibodies and in vitro clearance of S. aureus. Our results showed that both PHIS-01 and PCl were stronger inducers of protective cytokines IL-17 and IL-1β than alum, and far exceeded alum in enhancing anti-S. aureus antibody response. However, both alum and the phytol derivatives (particularly PCl) promoted efficient recruitment of CD11b⁺ cells. Furthermore, PHIS-01, alum and to a lesser extent, PCl were able to up-regulate the expression of key inflammation-related genes that were highly down-regulated by S. aureus alone. In vitro killing assays showed that both PHIS-01 and PCl were far more potent than alum in promoting S. aureus clearance; this indicated their efficiency in shaping an effective anti-S. aureus immune microenvironment. In summary, our study provides evidence for the better effectiveness of phytol-derived immunoadjuvants over alum in enhancing anti-S. aureus immunity.     

Antioxidant and antibacterial characteristics of phenolic extracts of locally produced honey in Saudi Arabia

The antibacterial and antioxidant properties of 30 selected honey samples produced in Saudi Arabia have been studied. The inhibitory action of the total phenolic content of the honey samples has been tested against Staphylococcus aureus, Micrococcus luteus and Escherichia coli. The MIC values of the ten selected honey samples against S. aureus, M. luteus and E. coli were in the range 0.5 ± 0.2 ? 3.6 ± 0.3; 0.45 ± 0.05 ? 5.0 ± 0.6 and 0.6 ± 0.2 ? 4.4 ± 0.4 mg mL^{? 1}. The antioxidant activities of the ethyl acetate extracts based on their anti-radical power using the 1,1-diphenyl-2-picrylhydrazyl scavenging assay and their ferric reducing antioxidant power were in the ranges 50.78 ± 1.4% to 99.52 ± 0.2% and 0.85 ± 0.13 to 1.167 ± 0.13 mg/ml, respectively. The total phenolic content was in the range 84.97 ± 0.57 to 317.39 ± 0.76 mg/100 g.     

Effects of differing phenolic content in dietary olive oils on lipids and LDL oxidation

Summary.Background: Evidence from in vitro studies suggests that antioxidant olive oil phenolic compounds can prevent LDL oxidation. However, in vivo evidence in support of this hypothesis is sparse.Aim of the study: to establish the antioxidant effect of olive oils with differences in their phenolic compounds content in humansMethods: A controlled, double blind, cross-over, randomized, clinical trial using three similar olive oils with increasing phenolic concentration (from 0 to 150 mg/Kg) was conducted in 30 healthy volunteers. Olive oils were administered over three periods of 3 weeks preceded by two-week washout periods.Results: Urinary tyrosol and hydroxytyrosol increased (p < 0.020), in vivo plasma oxidized LDL decreased (p = 0.006), and ex vivo resistance of LDL to oxidation increased (p = 0.012) with the phenolic content of the olive oil administered. After virgin olive oil administration, an increase (p = 0.029) was observed in HDL cholesterol levels.Conclusions: Sustained consumption of virgin olive oil with the high phenolic content was more effective in protecting LDL from oxidation and in rising HDL cholesterol levels than that of other type of olive oils. Dose-dependent changes in oxidative stress markers, and phenolic compounds in urine, were observed with the phenolic content of the olive oil administered. Our results support the hypothesis that virgin olive oil consumption could provide benefits in the prevention of oxidative processes.* Participants of the SOLOS-Investigation are listed in the Appendix.     

Modulation of Fatty Acids and Interleukin-6 in Glioma Cells by South American Tea Extracts and their Phenolic Compounds

Dietary phenolic compounds are plant metabolites with beneficial effects on the central nervous system. Thus, our aim was to identify anti-inflammatory compounds from South American plants on glia, which regulates neuro-immune response. The compounds were extracted from Lantana grisebachii (LG), Aspidosperma quebracho-blanco (AQB), and Ilex paraguariensis (IP) teas and identified by HPLC-DAD-MS. Extracts (0–200 µg/ml) were tested on human T98-G and rat C6 glioma lines. Cellular viability (by the resazurin assay), fatty acid profile (by gas chromatography) and pro-inflammatory interleukin-6 release (IL-6 by ELISA) were determined. Data were analyzed by partial least-square regression to discriminate bioactive compounds. Twenty-one compounds were determined in LG, mainly iridoids, which were linked to ω-3 and ω-6 polyunsaturated fatty acids, but not to IL-6 release. Thirty-one compounds were found in AQB, mostly hydroxybenzoic derivatives, which were positively related to IL-6 release. Twenty-three compounds were identified in IP, including caffeoylquinic derivatives and mainly chlorogenic acid. They increased the ω-7 palmitoleic fatty acid, which was related to IL-6 decrease. These results enhances phytochemical knowledge of widely available plants, and suggest the lipid-related anti-inflammatory activity of IP phenolic compounds, which give nutritional relevance to the tea.     

Chemical constitution and effect of extracts of tomato plants byproducts on the enteric viral surrogates

Byproducts of tomato are known to include phenolic compounds but have not been studied in depth. In this study, the phenolic compositions of (stem, leaf, root, and whole plant) of two tomato cultivars, Pitenza and Floradade, were analyzed by HPLC-DAD. In parallel, the antiviral effects of crude extracts on viral surrogates, the bacteriophages MS2 and Av-05 were evaluated. The leaf extracts from the two varieties showed the highest concentration of phenolic compounds. The compounds identified were gallic acid, chlorogenic acid, ferulic acid, cafeic acid, rutin, and quercetin, and they represented 3174.3 and 1057.9?mg/100?g dried weight of the Pitenza and Floradade cultivars, respectively. MS2 and Av-05 titers at 5?mg/mL were reduced by 3.47 and 5.78 log₁₀ PFU/mL and 3.78 and 4.93 log₁₀ PFU/mL by Pitenza and Floradade cultivar leaf extract, respectively. These results show that tomato extracts are natural sources of bioactive substances with antiviral activity.     

Chemical composition and characteristic profiles of seed oils from three Tunisian Acacia species

In this paper, physicochemical properties, fatty acid and phenolic compositions of Acacia cyclops, Acacia cyanophylla and Acacia mollissima oils were studied. These oils were compared in terms of physicochemical properties and fatty acid composition to soybean oil. The oil content of Acacia seeds is 8.85%,11.13% and 7.16%, respectively. A small difference was observed in the acid and saponification value. However, no differences were observed for refractive index, iodine value and fatty acid composition. This latter was essentially dominated by linoleic acid (56.66–60.52%), oleic acid (19.45–22.74%) and palmitic acid (9.36–12.25%). This study compares also the phenolic composition in Acacia seed oils. Syringic and ferulic acids were the dominant phenolic compounds observed in the studied oils. Minor amounts of phenolic acids as o-coumaric, p-coumaric and protocatechuic are also detected. The results of this preliminary study showed that Acacia samples are promising oilseed crops and the high level of unsaturated fatty acids makes them desirable in terms of nutrition and could be used as a potential oil in the human diet.     

Wild Leafy Vegetables Consumed in Buhera District of Zimbabwe and Their Phenolic Compounds Content

A questionnaire was used to gather information on the wild leafy vegetables consumed. The phenolic concentrations were determined by the vanillin, butanol, and tannin binding assays. Seventy-nine traditional vegetables were mentioned by the respondents and 20 of these were classified according to their species. The contents of flavonoids varied from 1.2 mg/g for Cleome gynandra to 8.0 mg/g for Bidens pilosa. The levels of proanthocyanidins ranged from 1.9 mg/g for lettuce to 11.2 mg/g for Bidens pilosa. The tannin contents of the vegetables ranged from 5.7 mg/g for Cleome gynandra to 8.3 mg/g for Bidens pilosa. The present study showed that these vegetables are valuable sources of phenolic compounds as compared to some exotic species.     

Phenolic acids inhibit the formation of advanced glycation end products in food simulation systems depending on their reducing powers and structures

The concentration of advanced glycation end products (AGEs) in foods, which are formed by Maillard reaction, has demonstrated as risk factors associated with many chronic diseases. The AGEs inhibitory activities of five common phenolic acids (protocatechuic acid, dihydroferulic acid, p-coumaric acid, p-hydroxybenzoic acid and salicylic acid) with different chemical properties had been investigated in two food simulation systems (glucose-bovine serum albumin (BSA) and oleic acid-BSA). The results substantiated that the AGEs inhibitory abilities of phenolic acids in the oleic acid BSA system were much better than the glucose-BSA system for their strong reducing powers and structures. Among them, dihydrogenferulic acid showed strong inhibition of AGEs formation in oleic acid-BSA system at 0.01?mg/mL compared to nonsignificant AGEs inhibitory effect in oleic acid-BSA system at 10-fold higher concentration (0.1?mg/mL). This study suggests that edible plants rich in phenolic acids may be used as AGEs inhibitor during high-fat cooking.     

Acute toxicity of some chlorinated phenolic compounds toSelenastrum capricornutum and phytoplankton

Acute toxicity of several chlorinated phenolic compounds detected in waste waters of bleached pulp was determined forSelenastrum capricornutum and indigenous phytoplankton using bioassays. Five of the phenolic compounds were chlorocatechols, four were chloroguaiacols and one was chlorosyringol. The response ofSelenastrum capricornutum to chemicals was measured by cell counting and phytoplankton¹⁴C-uptake. Chlorinated catechols inhibited the growth ofSelenastrum cultures in lower concentrations than chlorinated guaiacols. The increasing number of chlorine substituents on the phenolic ring increased the toxicity of both chlorinated catechols and guaiacols. The EC₅₀-values (0-96 hr) of the compounds ranged from 3.2 × 10^–4 mM to 1.6 × 10^–2 mM, with tetrachlorocatechol being the most toxic toSelenastrum capricornutum. The response of indigenous phytoplankton to chemicals was less sensitive than that ofSelenastrum capricornutum in nutrient solution; the weaker response may be caused by different physico-chemical properties in lake water.     

Methicillin-resistant Staphylococcus aureus (MRSA) isolated in clinics and hospitals in the Fukuoka city area

Bacteriological and clinical studies were carried out on 280 strains of Staphylococcus aureus isolated in clinics and hospitals in the Fukuoka city area from September 1990 to March 1991. The percentage of methicillin-resistant S. aureus (MRSA) strains studied was 41·4% (116 of 280). Of 116 MRSA strains, 48 (41·3%) produced coagulase VII and 21 (18·1%) produced coagulase II. The mean age of the patients who harboured MRSA, 70·5 ± 16·9 years, was significantly higher than that of patients with methicillin-sensitive S. aureus (MSSA), 44·2 ± 29·3 years (P < 0·001). MRSA was detected more frequently than MSSA in sputum (P < 0 · 01), while MSSA was detected more frequently than MRSA in pus (P < 0 · 01). Ninety (89 · 1%) of 101 strains of MRSA were isolated from inpatients and 98 (71 · 0%) of 130 strains of MSSA were isolated from outpatients. Similar number of MRSA strains were recovered in a variety of hospitals, indicating that there was no relationship between hospital size (number of beds) and the incidence of MRSA. As for drug susceptibility, coagulase VII-producing MRSA strains were more sensitive to clindamycin (P < 0 · 01) and more resistant to mino-cycline (P < 0 · 01) than were other MRSA strains.     

Phenolic compounds,melissopalynological, physicochemical analysis and antioxidant activity of jandaíra (Melipona subnitida) honey

Profile of phenolic compounds, melissopalynological, physicochemical analysis and antioxidant activity of Melipona subnitida honeys from Brazil are presented. The constituents in the EtOAc fraction were identified by HPLC-DAD. The melissopalynological analysis showed 19 pollen types from 9 families. Mimosa caesalpiniifolia was the predominant pollen type in 8 of the 9 honey samples. The physicochemical analysis revealed that the samples showed a similar profile. All jandaíra honey samples had similar characteristic profile of phenolic compounds, strong antioxidant activity accompanied by high total polyphenol contents. The flavonoids naringenin, quercetin, and isorhamnetin along with gallic, vanillic, 3,4-dihydroxybenzoic, and cumaric acids are common to eight samples and were adequately quantified. The two isomers of abscisic acid (trans–trans and cis–trans) present in major quantity in the sample 9 were isolated and quantified in all samples. The antioxidant activity of the honey samples strongly correlated with their phenolic content.     

Urinary excretion of phenols as an indicator of occupational exposure in the coke-plant industry

Objective: In the present study the relationship between the level of exposure to o-cresol and of 2,4- +2,5-, 3,4-, and 3,5-xylenols and the urinary excretion of their metabolites was examined. The mixed exposure to phenolic derivatives of exposed workers during their work shift was monitored by personal air sampling of the breathing-zone air and by measurements of phenol, o-cresol, and xylenol isomer concentrations in shift-end urine. Methods: The study subjects were 76 men working at a coke plant who were 22–58 years old and 34 nonexposed subjects. Concentrations of phenolic compounds were determined in the breathing-zone air during the work shift, whereas concentrations of phenol, cresol, and xylenol isomers were measured in urine collected after the work shift. Concentrations of phenols in air and urine were determined by gas chromatography with flame-ionization detection. Urine samples were extracted after acid hydrolysis of glucuronides and sulfates by solid-phase extraction. The gas chromatography-mass spectrometry method was applied to identify metabolites in urine samples. Results: The time-weighted average concentrations of phenol, cresol, and xylenol isomers detected in breathing-zone air showed that the exposure level of the workers was relatively low. The geometric mean values were as follows: 0.26 mg/m³ for phenol, 0.09 mg/m³ for o-cresol, 0.13 mg/m³ for p- and m-cresol, and 0.02–0.04 mg/m³ for xylenols at the tar-distillation process. Corresponding urinary concentrations were 10.39, 0.53, and 0.25–0.88 mg/g creatinine for phenol, o-cresol, and xylenol isomers, respectively. The correlation coefficients between the o-cresol and 2,4-, 2,5-, 3,4-, and 3,5-xylenol concentrations measured in urine and in the breathing-zone air were statistically significant, varying in the range of 0.54–0.74 for xylenol isomers and being 0.69 for o-cresol. Conclusion: We have found that the presence of o-cresol and xylenol isomers in urine can be used as a biomarker for phenol exposure. Analysis performed on workers at the tar-distillation process showed that they were exposed to relatively low concentrations of phenolic compounds. Received: 15 October 1996 / Accepted: 5 May 1997