Sex-based and hormonal contraception effects on the metabolism of nicotine among adolescent tobacco-dependent smokers.

Variations in nicotine metabolism influence smoking patterns. Differences between sexes or related to sex hormones may affect nicotine metabolism. Because smoking initiation starts during adolescence, observations gathered from adolescent smokers might broaden our understanding of such sex-based differences. We tested the hypothesis that nicotine metabolism--as indexed primarily by the ratio of trans-3'-hydroxycotinine (3HC) to cotinine--is more rapid among adolescent girl smokers compared with boys and that regular use of hormonal contraceptives influences nicotine and cotinine metabolism. We also hypothesized that more rapid nicotine metabolism is associated with higher nicotine dependence as indexed by smoking frequency and morning urgency. Plasma samples of nicotine, cotinine, and 3HC concentrations were obtained from 120 adolescents (36 boys). Plasma nicotine and cotinine concentrations were similar in boys and girls. Median plasma 3HC concentrations were 44.45 ng/ml for girls versus 35.74 ng/ml for boys (p = .025), and median plasma 3HC-cotinine ratios were significantly higher in girls than in boys (0.317 vs. 0.253, p = .025). After stratifying girls into two groups based on use versus nonuse of hormonal contraception, plasma 3HC-cotinine ratios in girls using hormonal contraception (0.47) were substantially higher (p<.0001) than in boys (0.25) and were significantly higher than in girls not using hormonal contraception (0.28). Controlling for cigarettes smoked per day, ethnicity, and age did not modify these results. Although plasma nicotine, cotinine, or 3HC concentrations were significantly lower in less dependent adolescent smokers, nicotine and cotinine metabolite ratios were similar. This study showed that hormonal contraception in adolescent girls may accelerate cotinine metabolism, an effect likely related to induction of cytochrome P450 2A6 and independent of ethnicity and cigarette consumption. Prospective controlled studies are needed to further evaluate the role of hormonal contraception in patterns of adolescent smoking and nicotine metabolism.     

头发中烟碱和可替宁的超高效液相色谱测定

采用5%NaOH水溶液超声萃取-超高效液相色谱法同时测定了36个主动吸烟者头发样品和10个被动吸烟者头发样品中的烟碱和可替宁含量。结果表明:①烟碱和可替宁的RSD分别为3.52%和2.99%;回收率均为98.5%～101.6%;②主动吸烟者和被动吸烟者头发样品中均检测到烟碱,而可替宁只在主动吸烟者头发样品中检出;③主动吸烟者头发中的烟碱含量的高低主要是由其烟龄和日均吸烟支数决定的,而与其生理年龄关系较小;④主动吸烟者头发中的可替宁含量高低主要是由其烟龄决定的,而与其日均吸烟支数和生理年龄关系较小。该法操作简便,准确性高,重复性好,可用于批量头发样品中烟碱和可替宁含量的快速分析。     

Nicotine, cotinine, withdrawal, and craving patterns during smoking and nicotine nasal spray use: results from a pilot study with African American men.

Nicotine intake via smoking is highly variable. Individualized dosing of nicotine replacement therapy (NRT) may improve product efficacy, but a better understanding of the within-day and within-subject relationships between smoking, NRT use, nicotine and cotinine concentrations in blood, and cravings and withdrawal symptoms is needed to inform dosing algorithms. A pilot study was undertaken to collect data on these relationships and to assess the feasibility of the methods needed for this type of research, including a sophisticated statistical modeling technique (a two-part mixed-effects model with correlated random effects that accounts for clumping at zero). Because nicotine metabolism varies by gender and race, the sample was homogeneous with respect to these characteristics. In a within-subjects study, 27 African American adult male smokers carried a computerized cigarette dispenser for 1 week, capturing the time each cigarette was smoked. Subjects then entered an inpatient setting for 1 day of scheduled smoking (matched to data from the cigarette dispenser to create an ecologically valid schedule) and 4 days of ad libitum nicotine nasal spray use, while tobacco abstinent. Eight times per day, at 2-hour intervals, blood was drawn and ratings of cigarette cravings and withdrawal symptoms were obtained. On average, subjects used less than half of the manufacturer's recommended minimum daily dose of nicotine nasal spray. Large differences in nicotine and cotinine levels were observed between individuals. When predicting nicotine, cotinine, withdrawal, and cravings, we observed significant interactions between route of nicotine intake and a variety of independent variables.     

Smoke constituent exposure and smoking topography of adolescent daily cigarette smokers.

Adolescent smoking prevalence is a major health concern, with 24.4% reporting smoking in the past 30 days and 15.8% considered daily smokers. The purpose of this study was to characterize biobehavioral nicotine dependence, smoke constituent exposure and smoking topography in adolescent daily smokers. Relationships among biological markers of nicotine dependence (nicotine boost, carbon monoxide [CO] boost and cotinine levels) with existing self-report measures (modified Fagerstr?m Tolerance Questionnaire [mFTQ] and the motivations for smoking scale) were examined. Gender differences were characterized. Fifty adolescents 13-18 years old were recruited for the study, 50% female. CO, plasma nicotine levels pre- and postcigarette, cotinine, and smoking topography were measured during a smoking bout with participant's usual cigarette. Average CO boost, pre- to postcigarette was 7.2 + 3.6 ppm, baseline cotinine level averaged 224.0 +/- 169.6 ng/ml and nicotine boost averaged 23.4 +/- 21.7 ng/ml. Mean puffs per cigarette was 14.2 +/- 6.3. Males had significantly higher total puff volumes, but similar smoke constituent exposure to females, and higher handling of cigarettes as smoking motive. In regression analysis, 35% of variance in tobacco use, as indicated by baseline cotinine concentration, was explained by maximum puff duration, postcigarette CO level, and nicotine dependence, as measured by the mFTQ. Results indicated adolescents had considerable smoke constituent exposure and nicotine dependence suggesting the importance of appropriate smoking cessation treatment.     

In vitro and in vivo metabolism of the soy isoflavone glycitein

Glycitein (GLY) is a major isoflavone of soy germ which is used as a functional ingredient to enrich foods with isoflavones as well as a component of soy supplements. Since data on the metabolism of GLY are incomplete, the in vitro phase I metabolism of GLY using rat liver microsomes, human liver microsomes (HLM), as well as human fecal flora was investigated. Furthermore, the in vivo metabolism has been studied after administration of GLY to Sprague-Dawley rats. The identification of the formed metabolites has been elucidated using HPLC/DAD, HPLC/API-ES MS, GC/MS, as well as reference compounds. With respect to the phase I metabolism, GLY has been converted to ten metabolites by liver microsomes of Aroclor-induced Wistar rats with 8-hydroxy(OH)-GLY as the main metabolite. HLM converted GLY to six metabolites with 8-OH-GLY and 6-OH-daidzein (DAI) being the major products. No sex-related differences were observed in each system. Intestinal metabolism of GLY led to four metabolites with 6-OH-DAI as the main product. The in vivo metabolism in rat urine after single-dose administration of GLY resulted in the identification of three oxidative and two bacterial metabolites as well as the demethylation product 6-OH-DAI as the main metabolite.     

Distributions of pharmaceuticals in an urban estuary during both dry- and wet-weather conditions

Pharmaceuticals and selected major human metabolites are ubiquitous in Jamaica Bay, a wastewater-impacted estuary at concentrations in the low ng/L to low/microg/L range. Concentrations throughout the bay are often consistent with conservative behavior during dry-weather conditions, as evidenced by nearly linear concentration-salinity relationships. Deviation from conservative behavior is noted for some pharmaceuticals and attributed to microbial degradation. Caffeine, cotinine, nicotine, and paraxanthine were detected with the greatest analytical signal, although evidence is presented for in situ removal, especially for nicotine and caffeine. There is little evidence for significant removal of carbamazepine and sulfamethoxazole, suggesting they are more conservative and useful wastewater tracers. Immediately following heavy precipitation, which induced a combined sewer overflow (CSO) event, the concentrations of all compounds but acetaminophen and nicotine decreased or disappeared. This observation is consistent with a simple model illustrating the effect of precipitation has on pharmaceutical concentration in the wastewater stream, given the balance between dilution from rain and the bypass of treatment.     

The contribution of dietary nicotine and dietary cotinine to salivary cotinine levels as a nicotine biomarker

Dietary nicotine, as a source of nicotine biomarkers such as salivary cotinine, has been a controversial topic, mainly because of limited published data on nicotine in foods. Recently, a sample preparation method for nicotine in foods and an analytical method, based on gas chromatography with mass spectrometric detection, were developed and validated in our laboratory. Nicotine was determined in fresh, cooked and processed foods of the Solanaceae family. In this study we have furthered this work to investigate the presence of cotinine in these vegetables, using GC–MS and HPLC–MS as independent alternative analytical techniques. A large number of samples was investigated, but cotinine was not detected in any of the samples, although very high sensitivity could be achieved. Based on the results, we report a Monte Carlo simulation of salivary cotinine levels obtained utilising dietary nicotine, food consumption data, and the variance in these parameters. In this estimate, a mean salivary cotinine concentration of 0.022 ng ml⁻¹ is predicted from dietary sources. This level is below the limit of detection for traditional analytical methods, but perhaps not for newly-developed methods.     

Nicotine derivatives in wastewater and surface waters: application as chemical markers for domestic wastewater

Nicotine is extensively metabolized in the human body to a number of compounds, which may enter natural waters via discharge of domestic wastewater. However, little is known on exposure of and potential effects on the aquatic environment. In this study, two major urinary metabolites, cotinine and 3'-hydroxycotinine, as well as a further tobacco alkaloid, N-formylnornicotine, were measured in wastewater and water from Swiss lakes using an analytical procedure based on SPE and LC-MS/MS SRM with cotinine-d3 as internal standard (LOQs, 1.0-1.5 ng/L). Typical concentrations of cotinine and 3'-hydroxycotinine were approximately 1-10 microg/L in untreated wastewater, but clearly less in treated wastewater (approximately 0.01-0.6 microg/L), corresponding to elimination efficiencies of 90-99%. N-Formylnornicotine, however,was found at similar concentrations in untreated and treated wastewater (0.02-0.15 microg/L). Its apparent persistence during wastewater treatment was further confirmed by incubation experiments with activated sludge. In lakes, cotinine, 3'-hydroxycotinine, and N-formylnornicotine were detected at concentrations up to 15, 80, and 6 ng/L, respectively. Concentrations in lakes correlated with the expected anthropogenic burden by domestic wastewater (ratio population per water throughflow), demonstrating the suitability of these nicotine derivatives as hydrophilic, anthropogenic markers. In small receiving waters with significant wastewater discharges, concentrations of a few hundred ng/L may be expected. Possible ecotoxicological risks associated with such environmental concentrations, can, however, not be assessed at present as data on effects on aquatic organisms are very limited, in particular on long-term effects.     

Smilax China Root Extract Detoxifies Nicotine by Reducing Reactive Oxygen Species and Inducing CYP2A6

Resveratrol has a beneficial effect of lowering reactive oxygen species (ROS) and reduces cellular oxidative stress. We hypothesized that ethanol extract of Smilax china root (EESC) rich in resveratrol (RES) and oxyresveratrol (OXY) could reduce ROS caused by nicotine and promoting nicotine turnover by induction of CYP2A6. The amount of cotinine converted from nicotine was quantified by the direct barbiturate assay method. Expression of CYP2A6 was unregulated by RES, OXY, or EESC, respectively. Pretreatment of RES (50, 100, and 250 μM), OXY (50, 100, and 250 μM), and RES+OXY (50 and 100 μM) inhibited cytotoxicity and ROS production caused by nicotine in a dose‐dependent manner. EESC pretreatment (1.8 mg/mL) increased cell viability by 1.5‐fold higher than the control (nicotine only), and lowered cellular ROS levels. A significant amount of the conversion of nicotine to cotinine was observed in EESC pretreatment by CYP2A6 induction in HepG2 cells. These results suggested that hepatic induction of CYP2A6 and ROS reduction by EESC activate nicotine metabolism and reduce cellular oxidative stress.     

Waterpipe smoking and nicotine exposure: a review of the current evidence.

The waterpipe, also known as shisha, hookah, narghile, goza, and hubble bubble, has long been used for tobacco consumption in the Middle East, India, and parts of Asia, and more recently has been introduced into the smokeless tobacco market in western nations. We reviewed the published literature on waterpipe use to estimate daily nicotine exposure among adult waterpipe smokers. We identified six recent studies that measured the nicotine or cotinine levels associated with waterpipe smoking in four countries (Lebanon, Jordan, Kuwait, and India). Four of these studies directly measured nicotine or cotinine levels in human subjects. The remaining two studies used smoking machines to measure the nicotine yield in smoking condensate produced by the waterpipe. Meta-analysis of the human data indicated that daily use of the waterpipe produced a 24-hr urinary cotinine level of 0.785 microg/ml (95% CI = 0.578-0.991 microg/ml), a nicotine absorption rate equivalent to smoking 10 cigarettes/day (95% CI = 7-13 cigarettes/day). Even among subjects who were not daily waterpipe smokers, a single session of waterpipe use produced a urinary cotinine level that was equivalent to smoking two cigarettes in one day. Estimates of the nicotine produced by waterpipe use can vary because of burn temperature, type of tobacco, waterpipe design, individual smoking pattern, and duration of the waterpipe smoking habit. Our quantitative synthesis of the limited human data from four nations indicates that daily use of waterpipes produces nicotine absorption of a magnitude similar to that produced by daily cigarette use.     

Determinants of salivary cotinine levels among current smokers in Mexico.

The present study describes salivary cotinine levels and their relationship to cigarettes smoked per day in Mexican smokers. Using a sampling strategy based on the number of cigarettes per day, we recruited 1,222 smokers from Mexico City and the state of Morelos in Mexico during 1999. Smoking behaviors and other factors known to affect nicotine intake and cotinine level were identified in an interview using a standardized questionnaire. Salivary cotinine was measured by capillary gas chromatography with nitrogen-phosphorus detection. We used generalized additive models to describe the relationship between salivary cotinine levels and variables of interest. The mean age of the population was 39.7 years (SD=15.6 years), with a mean cotinine level of 194.7 ng/ml (SD=134.8; range=10.1-767). Participants smoked a mean of 15.5 cigarettes per day (SD=11.3). Salivary cotinine and cigarettes smoked per day were positively related, although the association was not linear, flattening above 20 cigarettes per day. After adjusting for cigarettes per day, we found that significant predictors of cotinine levels included age, body mass index, cigarette producer, and smoking behavior variables. These results may have implications for dosing with nicotine medications to aid smoking cessation in Mexican smokers and suggest that whether the cigarette is labeled light or regular has no relationship to nicotine dose from smoking cigarettes.     

Glucuronidation of curcuminoids by human microsomal and recombinant UDP-glucuronosyltransferases

Glucuronidation is an important pathway in the metabolism of curcumin, but the isoforms of uridine-5'-diphosphoglucuronosyltransferase (UGT) involved are not known. Here, we report on the glucuronidation of the three natural curcuminoids and their major phase I metabolites with microsomes from human liver and intestine as well as with human recombinant UGTs. Microsomes from human liver generated predominantly the phenolic and small amounts of the alcoholic glucuronide of each curcuminoid, whereas intestinal microsomes formed only the phenolic conjugates but with higher activities. The phenolic glucuronidation of the curcuminoids was predominantly catalyzed by hepatic UGT1A1 and intestinal UGT1A8 and 1A10, whereas UGT1A9, 2B7, and 1A8 exhibited high activities for hexahydro-curcuminoids. UGT1A9 was able to form the alcoholic glucuronide of each curcuminoid in addition to the phenolic conjugate. These data suggest that the gastrointestinal tract contributes substantially to the glucuronidation of curcuminoids in humans, which may have important implications for their pharmacokinetic fate in vivo.     

Salivary cotinine concentration versus self-reported cigarette smoking: Three patterns of inconsistency in adolescence.

The present study examined the extent and sources of discrepancies between self-reported cigarette smoking and salivary cotinine concentration among adolescents. The data are from household interviews with a cohort of 1,024 adolescents from an urban school system. Histories of tobacco use in the last 7 days and saliva samples were obtained. Logistic regressions identified correlates of three inconsistent patterns: (a) Pattern 1-self-reported nonsmoking among adolescents with cotinine concentration above the 11.4 ng/mg cutpoint (n = 176), (b) Pattern 2-low cotinine concentration (below cutpoint) among adolescents reporting having smoked within the last 3 days (n = 155), and (c) Pattern 3-high cotinine concentration (above cutpoint) among adolescents reporting not having smoked within the last 3 days (n = 869). Rates of inconsistency were high among smokers defined by cotinine levels or self-reports (Pattern 1 = 49.1%; Pattern 2 = 42.0%). Controlling for other covariates, we found that reports of nonsmoking among those with high cotinine (Pattern 1) were associated with younger age, having few friends smoking, little recent exposure to smokers, and being interviewed by the same interviewer as the parent and on the same day. Low cotinine concentration among self-reported smokers (Pattern 2) was negatively associated with older age, being African American, number of cigarettes smoked, depth of inhalation, and exposure to passive smoke but positively associated with less recent smoking and depressive symptoms. High cotinine concentrations among self-reported nonsmokers was positively associated with exposure to passive smoke (Pattern 3). The data are consonant with laboratory findings regarding ethnic differences in nicotine metabolism rate. The inverse relationship of cotinine concentration with depressive symptoms has not previously been reported. Depressed adolescent smokers may take in smaller doses of nicotine than nondepressed smokers; alternatively, depressed adolescents may metabolize nicotine more rapidly.     

No evidence of substantial nicotine metabolism by Lasioderma serricorne (Fabricius) (Coleoptera: Anobiidae) reared on tobacco

The cigarette beetle, Lasioderma serricorne (Fabricius), is the most prevalent pest of stored tobacco and is responsible for substantial economic damage. Other than L. serricorne, few insects have been found to infest tobacco due to its low nutritional value and nicotine toxicity. Self, L.S., Guthrie, F.E., Hodgson, E. [1964a. Metabolism of nicotine by tobacco-feeding insects. Nature 204, 300-301] reported that L. serricorne metabolizes at least 70% of ingested nicotine to cotinine. This study re-examined nicotine metabolism by the L. serricorne using gas chromatography/flame ionization detection (GC/FID) and gas chromatography/thermal desorption with time-of-flight mass spectrometry (GC/TDS/ToF). Cigarette beetles reared on whole-wheat flour were compared with those reared on tobacco. Larvae, depurated larvae, frass, and both diets were analyzed to determine if nicotine was assimilated, sequestered, metabolized, and/or excreted. Contrary to previous findings, these data indicate that L. serricorne does not metabolize a significant amount of nicotine into cotinine. Nicotine is excreted unmodified. Older research involving nicotine metabolism by other insects should be reviewed in the light of these findings.     

Higher nicotine and carbon monoxide levels in menthol cigarette smokers with and without schizophrenia.

This study examined whether smoking menthol cigarettes was associated with increased biochemical measures of smoke intake. Expired carbon monoxide (CO) and serum nicotine and cotinine were measured in 89 smokers with schizophrenia and 53 control smokers immediately after smoking an afternoon cigarette. Serum nicotine levels (27 vs. 22 ng/ml, p = .010), serum cotinine levels (294 vs. 240 ng/ml, p = .041), and expired CO (25 vs. 21 ppm, p = .029) were higher in smokers of menthol compared with nonmenthol cigarettes, with no differences in 3-hydroxycotinine/cotinine ratios between groups when controlling for race. Backward stepwise linear regression models showed that, in addition to having a diagnosis of schizophrenia, smoking menthol cigarettes was a significant predictor of nicotine and cotinine levels. Individuals with schizophrenia or schizoaffective disorder smoked more generic or discount value brands (Basic, Doral, Monarch, USA, Wave, others) compared with control smokers (28% vs. 6%, p = .002) but did not smoke more brands with high nicotine delivery as estimated by the U.S. Federal Trade Commission method. Although rates of mentholated cigarette smoking were not higher in smokers with schizophrenia overall, they were significantly higher in non-Hispanic White people with schizophrenia compared with controls of the same ethnic/racial subgroup (51% vs. 28%, p<.0001). The higher exhaled CO in menthol smokers suggests that the higher nicotine levels are at least partly related to increased intake of smoke from menthol cigarettes, although menthol-mediated inhibition of nicotine metabolism also may be a factor. Menthol is an important cigarette additive that may help explain why some groups have lower quit rates and more smoking-caused disease.     

Stimulatory drugs of abuse in surface waters and their removal in a conventional drinking water treatment plant

The presence of psychoactive stimulatory drugs in raw waters used for drinking water production and in finished drinking water was evaluated in a Spanish drinking water treatment plant (DWTP). Contamination of the river basin which provides raw water to this DWTP was also studied. In surface waters, illicit drugs such as cocaine, benzoylecgonine (cocaine metabolite), amphetamine, methamphetamine, MDMA (ecstasy), and MDA were detected at mean concentrations ranging from 4 to 350 ng/L. Nicotine, caffeine, and their metabolites were also found at the microg/L level. The elimination of these compounds during drinking water treatment was investigated in a real waterworks. Amphetamine-type stimulants (except MDMA) were completely removed during prechlorination, flocculation, and sand filtration steps, yielding concentrations lowerthan their limits of detection (LODs). Further, ozone treatment was shown to be effective in partially eliminating caffeine (76%), while subsequent granulated activated carbon (GAC) filtration removed cocaine (100%), MDMA(88%), benzoylecgonine (72%), and cotinine (63%). Postchlorination achieved the complete elimination of cocaine and nicotine and only one parent compound (caffeine) and two metabolites (cotinine and benzoylecgonine) persisted throughout treatment although reductions of 90% for caffeine and benzoylecgonine and 74% for cotinine were obtained.     

The reinforcing effects of nicotine and stimulant medication in the everyday lives of adult smokers with ADHD: A preliminary examination.

Whereas the smoking prevalence rates in the general population are declining, rates among people diagnosed with attention-deficit/hyperactivity disorder (ADHD) continue to be elevated. Previous research has shown that nicotine may improve attention and mood, suggesting that nicotine may help ameliorate the attentional and emotional problems associated with ADHD. The present study examined the effects of nicotine with and without stimulant medication on ADHD symptoms, moods, and arousal in the everyday lives of smokers with ADHD. A total of 10 smokers with ADHD who were being treated with stimulant medication were asked to abstain from smoking while participating in the study. Participants underwent four conditions in randomized order: (a) Nicotine patch+stimulant medication, (b) nicotine patch only, (c) placebo patch+stimulant medication, and (d) placebo patch only. Each condition continued for 2 days, during which self-reports of ADHD symptoms and moods were obtained using electronic diaries. Lightweight ambulatory monitors recorded cardiovascular activity at each diary entry. Smoking abstinence was verified by expired carbon monoxide and salivary cotinine analysis. Results showed that nicotine patches and stimulant medication alone and in combination reduced difficulty concentrating and core ADHD symptoms compared with placebo patch only. Borderline improvement in impatience and self-control was seen with nicotine patch administration primarily on day 1. Nicotine patches also tended to elevate systolic and diastolic blood pressure compared with placebo patch during day 2. The findings suggest that smokers with ADHD experience nicotine-related reductions in ADHD symptoms during their everyday lives.     

Smokeless tobacco topography and toxin exposure.

This study examined the relationship between oral smokeless tobacco (ST) topographical measures and biomarkers of tobacco and carcinogen exposure. During 2 weeks of baseline ad libitum ST use, 54 male participants (mean age=32.1+/-7.5 years) were required to record the time each dip was placed in and removed from their mouths. Urine samples were collected twice during baseline and analyzed for nicotine, cotinine, and their glucuronides (total nicotine and total cotinine) and for metabolites of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL). The results suggest that frequency and duration measures of ST use (p<.01 to p<.001), particularly total dip duration, are significantly correlated with total cotinine, total nicotine, and total NNAL. These results suggest that how long a ST user has tobacco in his mouth is most predictive of tobacco toxin exposure.     

Aromatic hydroxylation is a major metabolic pathway of the mycotoxin zearalenone in vitro

Zearalenone (ZEN) is a common mycotoxin, for which only reductive metabolites have been identified so far. We now report that ZEN is extensively monohydroxylated by microsomes from human liver in vitro. Two of the major oxidative metabolites arise through aromatic hydroxylation and are catechols. Their chemical structures have been unambiguously determined by using deuterium‐labeled ZEN and by comparison with authentic reference compounds. Moreover, both catechol metabolites of ZEN were substrates of the enzyme catechol‐O‐methyl transferase. One of the monomethyl ethers represented the major metabolite when ZEN was incubated with rat liver slices, thus demonstrating that catechol formation also takes place under in vivo‐like conditions. Out of ten major human cytochrome P450 (hCYP) isoforms only hCYP1A2 was able to hydroxylate ZEN to its catechols with high activity. Catechol formation represents a novel pathway in the metabolism of ZEN and may be of toxicological relevance.