Generation of the Antioxidant Hydroxytyrosol from Tyrosol Present in Beer and Red Wine in a Randomized Clinical Trial.

Beer and wine contains the simple phenol tyrosol (TYR) which is endogenously converted into hydroxytyrosol (HT), one of the strongest dietary antioxidants, by CYP2A6 and CYP2D6 polymorphic enzymes. We investigated in humans the rate of this bioconversion after beer and red wine (RW) intake. In a single blind, randomized, crossover, controlled clinical trial (n = 20 healthy subjects), we evaluated TYR absorption and biotransformation into HT following a single dose of (i) RW, (ii) Indian pale ale beer (IPA), (iii) blonde beer, and (iv) non-alcoholic beer (free). Individuals were genotyped for CYP2A6 and CYP2D6, and a polygenic activity score (PAS) was derived. RW triggered the highest increase in total TYR recovered, followed by IPA, blonde, and free beers. Although the HT content in beer was minimal, an increase in HT production was observed in all beers following TYR in a dose-response manner, confirming TYR to HT biotransformation. Sex differences were identified in the rate of the conversion following RW. PAS scores correlated linearly with the recoveries of HT (HT:TYR ratios) after RW intake. In conclusion, after beer and RW consumption, TYR is absorbed and endogenously biotransformed into HT. This mechanism could be modulated by sex, genetics, and matrix components.

Protective effect of homovanillyl alcohol on cardiovascular disease and total mortality: virgin olive oil, wine, and catechol-methylation.

Background: Hydroxytyrosol is a phenolic compound that is present in virgin olive oil (VOO) and wine. Hydroxytyrosol-related foods have been shown to protect against cardiovascular disease (CVD).Objective: We investigated the associations between hydroxytyrosol and its biological metabolite, 3-O-methyl-hydroxytyrosol, also known as homovanillyl alcohol (HVAL), with CVD and total mortality.Design: We included 1851 men and women with a mean ± SD age of 66.8 ± 6 y at high risk of CVD from prospective cohort data. The primary endpoint was a composite of myocardial infarction, stroke, and death from cardiovascular causes; the secondary endpoint was all-cause mortality. Twenty-four-hour urinary hydroxytyrosol and HVAL and catechol-O-methyltransferase (COMT) rs4680 genotypes were measured.Results: After multivariable adjustment, all biomarkers were associated, as a continuous variable, with lower CVD risk, but only HVAL showed a strong inverse association (HR: 0.44; 95% CI: 0.25, 0.80) for the comparison between quintiles. Only HVAL, as a continuous variable, was associated with total mortality (HR: 0.81; 95% CI: 0.70, 0.95). Individuals in the highest quintile of HVAL compared with the lowest had 9.2 (95% CI: 3.5, 20.8) and 6.3 (95% CI: 2.3, 12.1) additional years of life or years free of CVD, respectively, after 65 y. Individuals with the rs4680GG genotype had the highest HVAL concentrations (P = 0.05). There was no association between COMT genotypes and events or interaction between COMT genotypes and HVAL concentrations.Conclusions: We report, for the first time to our knowledge, an independent association between high urinary HVAL concentrations and a lower risk of CVD and total mortality in elderly individuals. VOO and wine consumption and a high metabolic COMT capacity for methylation are key factors for high HVAL concentrations. The association that stems from our results reinforces the benefits of 2 key components of the Mediterranean diet (wine and VOO). This trial was registered at www.predimed.es as ISRCTN35739639.

Metabolic disposition and biological significance of simple phenols of dietary origin: hydroxytyrosol and tyrosol.

Hydroxytyrosol and tyrosol are dietary phenolic compounds present in virgin olive oil and wine. Both compounds are also endogenously synthesized in our body as byproducts of dopamine and tyramine metabolisms, respectively. Over the last decades, research into hydroxytyrosol and tyrosol has experienced an increasing interest due to the role that these compounds may play in the prevention of certain pathologies (e.g. cardiovascular, metabolic, neurodegenerative diseases and cancer). The translation of promising in vitro and in vivo biological effects from preclinical studies to the context of human disease prevention initially depends on whether the dose ingested becomes available at the site of action. In this regard, information regarding the bioavailability and metabolic disposition of hydroxytyrosol and tyrosol is of most importance to evaluate the impact they may have on human health. In this review, we discuss and summarize the state of the art of the scientific evidence regarding the processes of absorption, distribution, metabolism and excretion of both hydroxytyrosol and tyrosol. We also examine the impact of these compounds and their metabolites on biological activity in terms of beneficial health effects. Finally, we evaluate the different analytical approaches that have been developed to measure the plasma and urinary levels of hydroxytyrosol, tyrosol and their metabolites.

Anti-inflammatory effect of white wine in CKD patients and healthy volunteers.

BACKGROUND: Mediterranean-style diet has been considered for its important beneficial effects on the progression of CV disease. Wine is an important component of the Mediterranean diet, and moderate wine drinkers have lower mortality rates than nondrinkers and heavy drinkers in epidemiologic studies. The beneficial effects of red wine are thought to be dependent on the polyphenol compounds such as resveratrol that exhibit potent antioxidant activity. However, white wine, although lacking polyphenols, contains simple phenols, such as tyrosol (Tyr) and hydroxytyrosol (OH-Tyr), characteristic also of extra-virgin olive oil, which may share similar antioxidant and inflammatory properties. PATIENTS AND METHODS: The effect of white wine and extra-virgin olive oil on inflammatory markers was evaluated in 10 healthy volunteers and in 10 patients with CKD (chronic kidney disease) K-DOQI stage III-IV in a prospective, single blind, randomized, cross-over trial. After two weeks of wash-out from alcoholic beverages, subjects were randomized to a cross-over design A-B or B-A of a 2-week treatment with white wine (4 ml/kg body weight, 0.48 g/kg of alcohol 12%, corresponding to 2-3 glasses/daily) and extra-virgin olive oil (treatment A) or extra-virgin olive oil alone (treatment B). The two study periods were separated by a two-week wash-out period. At baseline and at the end of each treatment, plasma levels of inflammatory markers C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interleukin-8 (IL-8) concentration were determined. Urinary levels of Tyr, OH-Tyr, and their metabolites were measured at the same time. RESULTS: During combined consumption of white wine and extra-virgin olive oil (treatment A), plasma levels of CRP and IL-6 decreased from 4.1 ± 1.8 to 2.4 ± 1.9 mg/l (p < 0.05) and from 5.3 ± 3.2 to 3.4 ± 2.3 mg/l (p < 0.05) in CKD patients. CRP decreased from 2.6 ± 1.2 to 1.9 ± 0.9 mg/l (p < 0.05), and IL-6 decreased from 2.2 ± 1.8 to 1.7 ± 1.3 mg/l (p = ns) in healthy volunteers. No significant variation versus baseline was observed during treatment B. A significant increase in urinary Tyr and OH-Tyr was observed during treatment A (white wine and extra-virgin olive oil). CONCLUSIONS: Plasma markers of chronic inflammation were significantly reduced in CKD patients during the combined consumption of white wine and olive oil, suggesting a possible anti-inflammatory effect of this nutritional intervention.

Dose-dependent metabolic disposition of hydroxytyrosol and formation of mercapturates in rats.

Hydroxytyrosol (HT), one of the major polyphenols present in olive oil, is known to possess a high antioxidant capacity. The aim of the present study was to investigate dose dependent (0, 1, 10 and 100 mg/kg) alterations in the metabolism of HT in rats since it has been reported that metabolites may contribute to biological effects. Special attention was paid to the activation of the semiquinone-quinone oxidative cycle and the formation of adducts with potential deleterious effects. Thus, we developed a novel analytical methodology to monitor the in vivo formation of the HT mercapturate, N-acetyl-5-S-cysteinyl-hydroxytyrosol in urine samples. Biomarkers of hepatic and renal toxicity were evaluated within the dose range tested. Following HT administration, dose-dependent effects were observed for the recovery of all the metabolites studied. At the lowest dose of 1 mg/kg, the glucuronidation pathway was the most relevant (25-30%), with lower recoveries for sulfation (14%), while at the highest dose of 100 mg/kg, sulfation was the most prevalent (75%). In addition, we report for the first time the formation of the mercapturate conjugate of HT in a dose-dependent manner. The biochemical data did not reveal significant toxic effects of HT at any of the doses studied. An increase in the GSH/GSSG ratio at the highest dose was observed indicating that the products of HT autoxidation are counteracted by glutathione, resulting in their detoxification. These results indicate that the metabolic disposition of HT is highly dependent on the dose ingested.

Protection of LDL from oxidation by olive oil polyphenols is associated with a downregulation of CD40-ligand expression and its downstream products in vivo in humans.

BACKGROUND: Recently, the European Food Safety Authority approved a claim concerning the benefits of olive oil polyphenols for the protection of LDL from oxidation. Polyphenols could exert health benefits not only by scavenging free radicals but also by modulating gene expression. OBJECTIVE: We assessed whether olive oil polyphenols could modulate the human in vivo expressions of atherosclerosis-related genes in which LDL oxidation is involved. DESIGN: In a randomized, crossover, controlled trial, 18 healthy European volunteers daily received 25 mL olive oil with a low polyphenol content (LPC: 2.7 mg/kg) or a high polyphenol content (HPC: 366 mg/kg) in intervention periods of 3 wk separated by 2-wk washout periods. RESULTS: Systemic LDL oxidation and monocyte chemoattractant protein 1 and the expression of proatherogenic genes in peripheral blood mononuclear cells [ie, CD40 ligand (CD40L), IL-23α subunit p19 (IL23A), adrenergic ß-2 receptor (ADRB2), oxidized LDL (lectin-like) receptor 1 (OLR1), and IL-8 receptor-α (IL8RA)] decreased after the HPC intervention compared with after the LPC intervention. Random-effects linear regression analyses showed 1) a significant decrease in CD40, ADRB2, and IL8RA gene expression with the decrease of LDL oxidation and 2) a significant decrease in intercellular adhesion molecule 1 and OLR1 gene expression with increasing concentrations of tyrosol and hydroxytyrosol in urine. CONCLUSIONS: In addition to reducing LDL oxidation, the intake of polyphenol-rich olive oil reduces CD40L gene expression, its downstream products, and related genes involved in atherogenic and inflammatory processes in vivo in humans. These findings provide evidence that polyphenol-rich olive oil can act through molecular mechanisms to provide cardiovascular health benefits. This trial was registered at www.controlled-trials.com as ISRCTN09220811.

The effect of polyphenols in olive oil on heart disease risk factors: a randomized trial.

BACKGROUND: Virgin olive oils are richer in phenolic content than refined olive oil. Small, randomized, crossover, controlled trials on the antioxidant effect of phenolic compounds from real-life daily doses of olive oil in humans have yielded conflicting results. Little information is available on the effect of the phenolic compounds of olive oil on plasma lipid levels. No international study with a large sample size has been done. OBJECTIVE: To evaluate whether the phenolic content of olive oil further benefits plasma lipid levels and lipid oxidative damage compared with monounsaturated acid content. DESIGN: Randomized, crossover, controlled trial. SETTING: 6 research centers from 5 European countries. PARTICIPANTS: 200 healthy male volunteers. MEASUREMENTS: Glucose levels, plasma lipid levels, oxidative damage to lipid levels, and endogenous and exogenous antioxidants at baseline and before and after each intervention. INTERVENTION: In a crossover study, participants were randomly assigned to 3 sequences of daily administration of 25 mL of 3 olive oils. Olive oils had low (2.7 mg/kg of olive oil), medium (164 mg/kg), or high (366 mg/kg) phenolic content but were otherwise similar. Intervention periods were 3 weeks preceded by 2-week washout periods. RESULTS: A linear increase in high-density lipoprotein (HDL) cholesterol levels was observed for low-, medium-, and high-polyphenol olive oil: mean change, 0.025 mmol/L (95% CI, 0.003 to 0.05 mmol/L), 0.032 mmol/L (CI, 0.005 to 0.05 mmol/L), and 0.045 mmol/L (CI, 0.02 to 0.06 mmol/L), respectively. Total cholesterol-HDL cholesterol ratio decreased linearly with the phenolic content of the olive oil. Triglyceride levels decreased by an average of 0.05 mmol/L for all olive oils. Oxidative stress markers decreased linearly with increasing phenolic content. Mean changes for oxidized low-density lipoprotein levels were 1.21 U/L (CI, -0.8 to 3.6 U/L), -1.48 U/L (-3.6 to 0.6 U/L), and -3.21 U/L (-5.1 to -0.8 U/L) for the low-, medium-, and high-polyphenol olive oil, respectively. LIMITATIONS: The olive oil may have interacted with other dietary components, participants' dietary intake was self-reported, and the intervention periods were short. CONCLUSIONS: Olive oil is more than a monounsaturated fat. Its phenolic content can also provide benefits for plasma lipid levels and oxidative damage. International Standard Randomised Controlled Trial number: ISRCTN09220811.

Development of a sensitive and specific solid phase extraction--gas chromatography-tandem mass spectrometry method for the determination of elenolic acid, hydroxytyrosol, and tyrosol in rat urine.

A novel gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed, using an ion trap mass spectrometer, for the simultaneous determination of olive oil bioactive components, elenolic acid, hydroxytyrosol, and tyrosol, in rat urine. Samples were analyzed by GC-MS/MS prior to and after enzymatic treatment. A solid phase extraction sample pretreatment step with greater than 80% analytical recoveries for all compounds was performed followed by a derivatization reaction prior to GC-MS/MS analysis. The calibration curves were linear for all compounds studied for a dynamic range between 1 and 500 ng. The limit of detection was in the mid picogram level for tyrosol and elenolic acid (300 pg) and in the low picogram level for hydroxytyrosol (2.5 pg). The method was applied to the analysis of rat urine samples after sustained oral intake of oleuropein or extra virgin olive oil as a diet supplement.

Tyrosol and hydroxytyrosol are absorbed from moderate and sustained doses of virgin olive oil in humans.

OBJECTIVE: To investigate the absorption of tyrosol and hydroxytyrosol from moderate and sustained doses of virgin olive oil consumption. The study also aimed to investigate whether these phenolic compounds could be used as biomarkers of virgin olive oil intake. DESIGN AND INTERVENTIONS: Ingestion of a single dose of virgin olive oil (50 ml). Thereafter, for a week, participants followed their usual diet which included 25 ml/day of the same virgin olive oil as the source of raw fat. SETTING: Unitat de Recerca en Farmacologia. Institut Municipal d'Investigació Mèdica (IMIM). SUBJECTS: Seven healthy volunteers. RESULTS: An increase in 24 h urine of tyrosol and hydroxytyrosol, after both a single-dose ingestion (50 ml) and short-term consumption (one week, 25 ml/day) of virgin olive oil (P<0.05) was observed. Urinary recoveries for tyrosol were similar after a single dose and after sustained doses of virgin olive oil. Mean recovery values for hydroxytyrosol after sustained doses were 1.5-fold those obtained after a single 50 ml dose. CONCLUSIONS: Tyrosol and hydroxytyrosol are absorbed from realistic doses of virgin olive oil. With regard to the dose-effect relationship, 24 h urinary tyrosol seems to be a better biomarker of sustained and moderate doses of virgin olive oil consumption than hydroxytyrosol.

Bioavailability of tyrosol, an antioxidant phenolic compound present in wine and olive oil, in humans.

Tyrosol is a phenolic compound present in two of the traditional components of the Mediterranean diet: wine and virgin olive oil. The presence of tyrosol has been described in red and white wines. Tyrosol is also present in vermouth and beer. Tyrosol has been shown to be able to exert antioxidant activity in in vitro studies. Oxidation of low-density lipoprotein (LDL) appears to occur predominantly in arterial intima in microdomains sequestered from antioxidants of plasma. The antioxidant content of the LDL particle is critical for its protection. Thus, phenolics, which are able to bind LDL, could be effective in preventing lipid peroxidation and atherosclerotic processes. The ability of tyrosol to bind human LDL has been reported. We have demonstrated the bioavailability of tyrosol in humans from virgin olive oil in its natural form. Urinary tyrosol increased, reaching a peak at 0-4 h after virgin olive oil administration. Men and women showed a different pattern of urinary excretion of tyrosol. Moreover, tyrosol is absorbed in a dose-dependent manner after sustained and moderate doses of virgin olive oil. In summary, our results suggest that tyrosol from wine or virgin olive oil could exert beneficial effects on human health in vivo if its biological properties are confirmed in in vivo studies.

Structural characterization of the metabolites of hydroxytyrosol, the principal phenolic component in olive oil, in rats.

Hydroxytyrosol is quantitatively and qualitatively the principal phenolic antioxidant in olive oil. Recently it was shown that hydroxytyrosol and five metabolites were excreted in urine when hydroxytyrosol was dosed intravenously or orally in an olive oil solution to rats. The conclusive identification of three metabolites of hydroxytyrosol by MS/MS as a monosulfate conjugate, a 3-O-glucuronide conjugate, and 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid) has been established in this investigation. The structural configurations of the glucuronide conjugate and 4-hydroxy-3-methoxyphenylacetic acid were confirmed by (1)H NMR. The radical scavenging potencies of homovanillic acid, homovanillic alcohol, hydroxytyrosol, and the metabolites were examined with the radical 2,2-diphenyl-1-picrylhydrazyl. These studies showed them to be potent antioxidants with SC(50) values of 14.8 and 11.4 microM for homovanillic acid and homovanillic alcohol, respectively. The 3-O-glucuronide conjugate was more potent than hydroxytyrosol, with an SC(50) of 2.3 in comparison to 11.0 microM, and the monosulfate conjugate was almost devoid of radical scavenging activity.

Olive oil phenols are absorbed in humans.

Animal and in vitro studies suggest that olive oil phenols are effective antioxidants. The most abundant phenols in olive oil are the nonpolar oleuropein- and ligstroside-aglycones and the polar hydroxytyrosol and tyrosol. The aim of this study was to gain more insight into the metabolism of those phenols in humans. We measured their absorption in eight healthy ileostomy subjects. We also measured urinary excretion in the ileostomy subjects and in 12 volunteers with a colon. Subjects consumed three different supplements containing 100 mg of olive oil phenols on separate days in random order. Ileostomy subjects consumed a supplement with mainly nonpolar phenols, one with mainly polar phenols and one with the parent compound oleuropein-glycoside. Subjects with a colon consumed a supplement without phenols (placebo) instead of the supplement with oleuropein-glycoside. Ileostomy effluent and urine were collected for 24 h after supplement intake. Tyrosol and hydroxytyrosol concentrations were low (< 4 mol/100 mol of intake) in the ileostomy effluent, and no aglycones were detected. We estimated that the apparent absorption of phenols was at least 55-66% of the ingested dose. Absorption was confirmed by the excretion of tyrosol and hydroxytyrosol in urine. In ileostomy subjects, 12 mol/100 mol and in subjects with a colon, 6 mol/100 mol of the phenols from the nonpolar supplement were recovered in urine as tyrosol or hydroxytyrosol. In both subject groups, 5--6 mol/100 mol of the phenols was recovered from the polar supplement. When ileostomy subjects were given oleuropein-glycoside, 16 mol/100 mol was recovered in 24-h urine, mainly in the form of hydroxytyrosol. Thus, humans absorb a large part of ingested olive oil phenols and absorbed olive oil phenols are extensively modified in the body.

Urinary excretion of olive oil phenols and their metabolites in humans.

We have recently demonstrated, in humans, the bioavailability of hydroxytyrosol (3,4-dihydroxyphenylethanol; HT), one of the major antioxidant components of virgin olive oil. In particular, we reported that this compound is present in lipoproteins involved in atherosclerotic processes and is excreted in the urine mainly as glucuronide-conjugate. The aim of the present study was to elucidate, in humans, the metabolic fate of HT after ingestion of virgin olive oil. After administration of virgin olive oil, 24-hour urine collections of healthy volunteers were prepared for gas chromatography-mass spectrometry analyses in order to identify and quantify HT and its metabolites homovanillic alcohol (HVA1c) and homovanillic acid (HVA). The results indicate that this compound undergoes the action of catechol-O-methyl transferase (COMT), enzymes involved in the catecholamine catabolism, resulting in an enhanced excretion of HVA1c. We also found a significant increase of HVA, indicating an oxidation of the ethanolic residue of HT and/or of HVA1c in humans. The excretion of both metabolites significantly correlated with the dose of administered HT.

Pharmacokinetics and metabolism of hydroxytyrosol, a natural antioxidant from olive oil.

3,4-Dihydroxyphenylethanol (DOPET) is the major o-diphenol detectable in extra virgin olive oil, either in free or esterified form. Despite its relevant biological effects, mainly related to its antioxidant properties, little data have been reported so far on its toxicity and metabolism. The aim of the present work is to evaluate DOPET toxicity and to investigate its molecular pharmacokinetics by using the (14)C-labeled diphenol. When orally administered to rats, the molecule does not show appreciable toxicity up to 2 g/kg b.wt. To identify and quantify its metabolites, [(14)C]DOPET has been synthesized and intravenously injected in rats. The pharmacokinetic analysis indicates a fast and extensive uptake of the molecule by the organs and tissues investigated, with a preferential renal uptake. Moreover, 90% of the administered radioactivity is excreted in urine collected up to 5 h after injection, and about 5% is detectable in feces and gastrointestinal content. The characterization of the labeled metabolites, extracted from the organs and urine, has been performed by high-pressure liquid chromatography analysis. In all the investigated tissues, DOPET is enzymatically converted in four oxidized and/or methylated derivatives. Moreover, a significant fraction of total radioactivity is associated with the sulfo-conjugated forms, which also represent the major urinary excretion products. On the basis of the reported results, an intracellular metabolic pathway of exogenously administered DOPET, implying the involvement of catechol-O-methyltransferase, alcohol dehydrogenase, aldehyde dehydrogenase, and phenolsulfotransferase, has been proposed.

The in vivo fate of hydroxytyrosol and tyrosol, antioxidant phenolic constituents of olive oil, after intravenous and oral dosing of labeled compounds to rats.

In vitro studies have shown phenolics in olive oil to be strong radical scavengers. The absorption and elimination of two radiolabeled phenolic constituents of olive oil, hydroxytyrosol and tyrosol were studied in vivo using rats. Compounds were administered intravenously (in saline) and orally (in oil- and water-based solutions). For both compounds, the intravenously and orally administered oil-based dosings resulted in significantly greater elimination of the phenolics in urine within 24 h than the oral, aqueous dosing method. There was no significant difference in the amount of phenolic compounds eliminated in urine between the intravenous dosing method and the oral oil-based dosing method for either tyrosol or hydroxytyrosol. Oral bioavailability estimates of hydroxytyrosol when administered in an olive oil solution and when dosed as an aqueous solution were 99% and 75%, respectively. Oral bioavailability estimates of tyrosol, when orally administered in an olive oil solution and when dosed as an aqueous solution were 98% and 71%, respectively. This is the first study that has used a radiolabeled compound to study the in vivo biological fates of hydroxytyrosol and tyrosol.

Capillary gas chromatography-mass spectrometry quantitative determination of hydroxytyrosol and tyrosol in human urine after olive oil intake.

Recent in vitro studies have demonstrated antioxidant properties of some virgin olive oil phenolic compounds. One of the prerequisites to extrapolate these data to an in vivo situation is the knowledge of their bioavailability in humans. In the present work we describe an analytical method which enables us to perform hydroxytyrosol and tyrosol quantitative determinations in human urine. This method was successfully used in bioavailability studies of both phenolic compounds after acute olive oil administration. Virgin olive oil was administered to healthy volunteers after a low phenolic diet. The dose administered of both phenolic compounds was estimated in reference to free forms of hydroxytyrosol and tyrosol present in virgin olive oil extracts before and after being submitted to hydrolytic conditions. These conditions mimic those occurring during digestion. Urine samples were collected before and after acute olive oil intake and analyzed by capillary gas chromatography-mass spectrometry. Hydroxytyrosol and tyrosol urinary recovery increased in response to olive oil administration, obtaining maximal values in the first 4 h. Our results further indicate that hydroxytyrosol and tyrosol are mainly excreted in conjugated form, since only 5.9 +/- 1.4% (hydroxytyrosol) and 13.8 +/- 5.4% (tyrosol) of the total amounts excreted in urine were in free form.

Olive oil phenolics are dose-dependently absorbed in humans.

Olive oil phenolic constituents have been shown, in vitro, to be endowed with potent biological activities including, but not limited to, an antioxidant action. To date, there is no information on the absorption and disposition of such compounds in humans. We report that olive oil phenolics, namely tyrosol and hydroxytyrosol, are dose-dependently absorbed in humans after ingestion and that they are excreted in the urine as glucuronide conjugates. Furthermore, an increase in the dose of phenolics administered increased the proportion of conjugation with glucuronide.

The impact of recent advances in diagnostic technology on the clinical presentation of phaeochromocytoma.

OBJECTIVE: To examine the impact of recent advances in diagnostic technology on the spectrum of clinical and biochemical features of patients presenting with a new diagnosis of phaeochromocytoma. DESIGN: A retrospective review of the clinical and biochemical features of patients diagnosed by our laboratory as having phaeochromocytoma within a 27-month period up to December, 1990. Noradrenaline, adrenaline and dihydroxyphenylglycol were assayed in 24-hour urine specimens (19 patients) or plasma (1 anuric patient) by gas chromatography/mass spectrometry. SETTING: A tertiary level chemical pathology department. PATIENTS: Twenty patients with a new diagnosis of phaeochromocytoma. RESULTS: The classic, episodic adrenergic symptoms traditionally associated with phaeochromocytoma were absent in 9 of the 20 patients (45%). "Atypical" phaeochromocytoma presented as a mass on computed tomography imaging (6 patients, 30%), "phaeochromocytoma crisis" (4 patients, 20%) or family screening (1 patient, 5%). Excessive adrenaline production was found in 11 patients (55%) and six (30%) had predominantly adrenaline-secreting tumours. The urinary noradrenaline:dihydroxyphenylglycol ratio was raised in all nine patients with predominantly noradrenaline-secreting tumours but was not raised in nine out of ten patients with adrenaline-secreting phaeochromocytoma. Adrenaline excretion was significantly correlated with tumour size (r = 0.8; P less than 0.05). CONCLUSIONS: Advances in diagnostic technology, particularly specific adrenaline assays and computed tomography, have made possible the early diagnosis of patients with phaeochromocytoma presenting in ways previously thought to be uncommon. All patients with adrenal masses noted incidentally on CT scan should be investigated for phaeochromocytoma. Adrenaline-secreting tumours are common and both noradrenaline and adrenaline should be assayed in all patients investigated for phaeochromocytoma.

Stereometabolism of styrene in man: gas chromatographic determination of phenylethyleneglycol enantiomers and phenylethanol isomers in the urine of occupationally-exposed persons.

A gas chromatographic procedure for the determination of phenylethyleneglycol enantiomers and phenylethanol isomers is described and applied to the investigation of urine samples from occupationally styrene-exposed workers (11 males, six females) and an unexposed control group. Phenylethyleneglycol enantiomers and 2-phenylethanol were present in the urine samples of exposed and unexposed individuals whereas 1-DL-phenylethanol was not found in control urine. The L/D enantiomer ratio of phenylethyleneglycol was found to be approximately 3 in the exposed group and 1.5 in the control group. Because of the close structural relation of these metabolites to the primarily formed epoxide, the results give further insight into the stereotoxicity of styrene in man.