Genotoxicity testing of four benzyl derivatives in the Drosophila wing spot test.

Food flavourings are an essential element in foods. Benzyl derivatives are the food additives which are used for increasing the taste of foods and beverages. In this study, different concentrations of four benzyl derivatives (benzaldehyde, benzyl acetate, benzyl alcohol and benzoic acid) used as flavour ingredients have been evaluated for genotoxicity in the wing somatic mutation and recombination test (SMART) of Drosophila melanogaster. Third-instar larvae trans-heterozygous for two genetic markers mwh and flr, were treated at different concentrations (0.1, 0.5, 1, 10, 25 and 50mM) of the test compounds. Wings of the emerging adult flies were scored for the presence of spots of mutant cells, which can result from either somatic mutation or mitotic recombination. Also lethal doses of benzyl derivatives used as flavour ingredients were determined in the experiments. For the evaluation of genotoxic effects, the frequencies of spots per wing in the treated series were compared to the control group, which is distilled water. Chemicals used were ranked as benzaldehyde, benzyl acetate, benzyl alcohol and benzoic acid according to their genotoxic effects. The present study shows that intensive administration of benzyl derivatives used as flavouring agents may have a significant genotoxic effects.     

Toluene metabolism in isolated rat hepatocytes: effects of in vivo pretreatment with acetone and phenobarbital

Hepatocytes isolated from control, acetone- and phenobarbital-pretreated rats were used to study the metabolic conversion of toluene to benzyl alcohol, benzaldehyde, benzoic acid and hippuric acid at low (<100 M) and high (100–500 M) toluene concentrations. The baseline formation rates of toluene metabolites (benzyl alcohol, benzoic acid and hippuric acid) were 2.9±01.7 and 10.0±2.3 nmol/mg cell protein/60 min at low and high toluene concentrations, respectively. In vivo pretreatment of rats with acetone and phenobarbital increased the formation of metabolites: at low toluene concentrations 3- and 5-fold, respectively; at high toluene concentrations no significant increase (acetone) and 8-fold increase (phenobarbital). Apparent inhibition by ethanol, 7 and 60 mM, was most prominent at low toluene concentrations: 63% and 69%, respectively, in control cells; 84% and 91% in acetone-pretreated cells, and 32% (not significant) and 51% in phenobarbital-pretreated cells. Ethanol also caused accumulation of benzyl alcohol. The apparent inhibition by isoniazid was similar to that of ethanol at low toluene concentrations. Control and acetone-pretreated cells were apparently resistant towards metyrapone; the decrease was 49% and 64% in phenobarbital-pretreated cells at low and high toluene concentrations, respectively. In these cells, the decrease in presence of combined ethanol and metyrapone was 95% (low toluene concentrations). 4-Methylpyrazole decreased metabolite formation extensively in all groups. Benzaldehyde was only found in the presence of an aldehyde dehydrogenase inhibitor. Increased ratio benzoic/hippuric acid was observed at high toluene concentrations. These results demonstrate that toluene oxidation may be studied by product formation in isolated hepatocytes. However, the influence of various enzymes in the overall metabolism could not be ascertained due to lack of inhibitor specificity.     

HPLC法快速检测苦参素注射液中8种抑菌剂及苯甲醛

目的:建立快速筛查和同时测定苦参素注射剂中8种抑菌剂(苯甲醇、苯酚、苯甲酸、山梨酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯)及苯甲醇降解产物———苯甲醛含量的高效液相色谱法。方法:应用WelchMaterials XB-C18色谱柱(4.6 mm×250 mm,5μm);流动相为乙腈-0.02 mol.L-1醋酸铵(冰醋酸调pH至5.0)梯度洗脱,流速1.0 mL.min-1,检测波长为211 nm(苯甲醇、苯酚),225 nm(苯甲酸),248 nm(苯甲醛),256 nm(山梨酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯)。结果:9种成分的峰面积与浓度的线性关系良好(r>0.9998),加样回收率为95.6%～102.2%。结论:本方法灵敏,快捷,准确,重复性好,可用于注射剂中抑菌剂的快速筛查与含量分析。     

Time-dependent conversion of benzyl alcohol to benzaldehyde and benzoic acid in aqueous solutions

The oxidative reaction: benzyl alcohol-benzaldehyde-benzoic acid was investigated in time in aqueous solutions of benzyl alcohol widely used as a preservative in medicine and cosmetology. The solutions of benzyl alcohol were stored at concentrations from 0.005 to 2.09 mg/ml for a long time under different conditions. The presence of benzaldehyde and benzoic acid in these solutions was controlled by liquid chromatography on silica sorbent in water. The content of benzoic acid and potentially toxic benzaldehyde in solutions depending on the initial concentration of benzyl alcohol, on time, and on storage conditions was evaluated quantitatively.     

高效液相色谱法测定药用辅料苯甲醇中苯甲酸和苯甲醛含量

目的建立HPLC法同时测定药用辅料苯甲醇中苯甲酸和苯甲醛的含量。方法采用Acclaim 120 C18柱(4.6 mm×250 mm,5μm),流动相为乙腈-0.02%甲酸(用氨水调至p H=4.5)(30:70),流速为1.0 m L·min-1,检测波长为230 nm,柱温为35℃,进样量为20μL。结果苯甲酸在0.500 6¹5.02μg·m L-1内与峰面积线性关系良好,平均回收率均>100%,RSD均<1.3%(n=3);苯甲醛在0.505 215.02μg·m L-1内与峰面积线性关系良好,平均回收率均>100%,RSD均<1.3%(n=3);苯甲醛在0.505 2¹5.16μg·m L-1内与峰面积的线性关系良好,平均回收率均>108%,RSD均<0.15%(n=3)。结论本方法准确度高、重现性好,可用于苯甲醇中苯甲酸和苯甲醛的含量测定。     

HPLC法快速检测苦参素注射液中8个抑菌剂及苯甲醛

目的:建立快速筛查和同时测定苦参素注射液中8个抑菌剂(苯甲醇、苯酚、苯甲酸、山梨酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯)及苯甲醇降解产物—苯甲醛含量的高效液相色谱法。方法:应用Welch Materials XB-C18色谱柱(4.6 mm×250 mm,5μm),流动相为乙腈-0.02 mol.L-1醋酸铵溶液(冰醋酸调pH至5.0)梯度洗脱,流速1.0 mL.min-1,检测波长为211 nm(苯甲醇、苯酚),225 nm(苯甲酸),248 nm(苯甲醛),256 nm(山梨酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯)。结果:9个成分的峰面积与浓度的线性关系良好(r﹥0.9998),加样回收率为95.6%～102.2%。结论:本方法灵敏,快捷,准确,重复性好,可用于注射剂中抑菌剂的快速筛查与含量分析。     

Comet assay in murine bone-marrow cell line (FDC-P2)

The comet assay, also known as the single cell gel electrophoresis (SCGE) assay, is a rapid, simple, visual and sensitive technique for measuring DNA damage in mammalian cells. In the present study, Methyl methanesulfonate (MMS), 4-Nitrosoquinoline-Oxide (4NQO), Cyclophosphamide (CPA), and Benzo(a)pyrene (BP)-induced DNA damage was assayed in vitro in a murine bone-marrow cell line (FDC-P2), with or without an activation mixture (rat liver S9). All compounds caused significant DNA damage. With MMS and 4NQO, the frequency of comet tails, scored manually under a fluorescence microscope, increased dose-dependently, and reached a maximum of 53.2 and 74.8% respectively. Three parameters indicating DNA damage in the comet assay with the two-layer method, tail length, %DNA in tail, and tail moment, calculated using the automated image analysis software “Comet Analyzer v1.5” increased with all compounds. With MMS and 4NQO, all parameters increased at concentrations over 40 and 0.25 μmol/L, respectively. The in vitro comet assay with rat liver S9 could detect DNA damage caused by the metabolites of CPA and BP. The comet assay using the two-layer method is easy and efficient, and so can be conducted on a routine as basis. The assay with FDC-P2 cells was highly sensitive in detecting DNA damage with the frequency of comet tails, tail moment, %DNA in tail and tail length as indicators of the damage. Metabolism-mediated DNA damage could be detected with the addition of a rat S9 mixture at a final concentration of 6% for 6 h exposure.     

HPLC法同时测定地西泮直肠凝胶中地西泮、 苯甲酸、苯甲醇含量

目的:建立了同时测定地西泮直肠凝胶中地西泮、苯甲酸、苯甲醇含量的高效液相色谱方法。方法:色谱柱为Agilent Eclipse Plus C18(4.6 mm×150 mm,3.5μm),以甲醇-0.05 mol·L^-1乙酸铵缓冲溶液(pH 4.0)为流动相,梯度洗脱,流速1.0 mL·min^-1,检测波长254 nm,柱温30℃,进样量10μL。结果:地西泮、苯甲酸、苯甲醇分离度均大于1.5,地西泮在0.010~0.200 mg·mL^-1范围内线性关系良好(r≥0.9999);苯甲酸在0.030~0.600 mg·mL^-1范围内线性关系良好(r≥0.9999);苯甲醇在0.0718~1.436 mg·mL^-1范围内线性关系良好(r≥0.9999);且地西泮、苯甲酸、苯甲醇的平均回收率均在98%~101%,RSD均小于2.0%(n=9)。结论:本法简单准确可靠,可用于地西泮直肠凝胶中地西泮、苯甲酸、苯甲醇的含量测定。     

铅对小鼠睾丸细胞DNA损伤作用研究

目的:通过建立亚慢性铅中毒动物模型探讨醋酸铅对雄性小鼠睾丸细胞DNA的损伤,为进一步了解其毒性作用机制提供科学依据。方法:将45只雄性小鼠分为0.2%、0.4%染铅组及空白对照组,每组各5只。实验组醋酸铅溶于去离子水中供小鼠自由摄取,空白对照组饮用自来水。分别于第2、4、6周分别处死动物,用单细胞凝胶电泳实验(彗星实验)检测小鼠睾丸细胞DNA损伤情况。结果:醋酸铅染毒后小鼠睾丸细胞DNA单链断裂,出现彗星状拖尾。无论是拖尾细胞的百分率,DNA迁移的长度,还是olive尾矩与空白对照组相比其差异具有极显著性(P<0.01),并且随着醋酸铅染毒浓度和时间的增加DNA的损伤越重,呈现出时间-效应关系。但0.2%与0.4%各周染毒组的拖尾细胞百分率、彗星尾长、olive尾矩的差异并无显著性(P>0.05)。结论:醋酸铅可诱导睾丸生殖细胞DNA损伤,并且其损伤作用呈现出时间依赖性。     

In vivo genotoxicity study of single-wall carbon nanotubes using comet assay following intratracheal instillation in rats

The genotoxicity of single-wall carbon nanotubes (SWCNTs) was evaluated in vivo using the comet assay after intratracheal instillation in rats. The SWCNTs were instilled at a dosage of 0.2 or 1.0 mg/kg body weight (single instillation group) and 0.04 or 0.2 mg/kg body weight once a week for 5 weeks (repeated instillation group). As a negative control, 1% Tween 80 was instilled in a similar manner. As a positive control, ethyl methanesulfonate (EMS) at 500 mg/kg was administered once orally 3 h prior to dissection. Histopathologically, inflammation in the lung was observed for all the SWCNTs in both single and repeated groups. In the comet assay, there was no increase in% tail DNA in any of the SWCNT-treated groups. In the EMS-treated groups, there was a significant increase in% tail DNA compared with the negative control group. The present study indicated that a single intratracheal instillation of SWCNTs (1.0 mg/kg) or repeated intratracheal instillation (0.2 mg/kg) once a week for five weeks induced a clear inflammatory response (hemorrhage in the alveolus, infiltration of alveolar macrophages and neutrophiles), but no DNA damage, in the lungs in rats. Under the conditions of the test, SWCNTs were not genotoxic in the comet assay following intratracheal instillation in rats.     

Combined effects of curcumin and piperine in ameliorating benzo(a)pyrene induced DNA damage

The present study was planned to investigate the antigenotoxic effects of curcumin and piperine separately and in combination against benzo(a)pyrene (BaP) induced DNA damage in lungs and livers of mice. Male Swiss albino mice received curcumin (100 mg kg⁻¹ body weight) and piperine (20 mg kg⁻¹ body weight) separately as well as in combination orally in corn oil for 7 days as pretreatments and subsequently, 2 h after, BaP was administered orally in corn oil (125 mg kg⁻¹ body weight). A single dose of BaP to normal mice increased the level of 8-oxo-2′-deoxyguanosine (8-oxo-dG) content and % DNA in the comet tail in the lungs and liver. Pretreatments of curcumin and curcumin plus piperine before administration of single dose of BaP significantly decreased the levels of 8-oxo-dG content and % DNA in the comet tail in both the tissues. Moreover, the genoprotective potential of curcumin plus piperine was significantly higher as compared to curcumin alone against BaP induced DNA damage.     

Single and combined genotoxicity effects of six pollutants on THP-1 cells

The objective of this study was to evaluate the single and combined genotoxic effects of six food pollutants (Chrysoidine G, Sudan I, acid orange II, malachite green, acrylamide, and potassium bromate) on THP-1 cells through comet assay. The results of the single tests indicated that the pollutants increased the percentage of tail DNA (% tail DNA) in a dose-dependent manner. Moreover, the % tail DNA values induced by synthetic colorants (Chrysoidine G, Sudan I, acid orange II, and malachite green) were significantly higher than those by acrylamide or potassium bromate at most concentrations. In the combined tests, Chrysoidine G (422 μmol/L) or acrylamide (400 μmol/L) was mixed with different concentrations of the other five pollutants respectively. In the first combined tests, most mixtures significantly increased the % tail DNA values with the exception of Chrysoidine G and acid orange II. In the second tests, there were no significant differences in the % tail DNA values between the single and combined tests at most cases.     

Metabolism and covalent binding of [14C]toluene by human and rat liver microsomal fractions and liver slices

The in vitro metabolism of [14C]toluene by liver microsomes and liver slices from male Fischer F344 rats and human subjects has been compared. Rat liver microsomes produced only benzyl alcohol from toluene. Liver microsomes from human subjects metabolized toluene to benzyl alcohol, benzaldehyde, and benzoic acid. Liver microsomes from one human donor also produced p-cresol and o-cresol. The overall rate of toluene metabolism by human liver microsomes was 9-fold greater than by rat liver microsomes. Human liver microsomal metabolism of benzyl alcohol to benzaldehyde required NADPH and was inhibited by carbon monoxide and high pH (pH 10). but was not inhibited by ADP-ribose or sodium azide. These results suggest that cytochrome P-450, rather than alcohol dehydrogenase, was responsible for the metabolism of benzyl alcohol to benzaldehyde. Human and rat liver slices metabolized toluene to hippuric acid and benzoic acid. The overall rate of toluene metabolism by human liver slices was 1.3-fold greater than by rat liver slices. Cresols and cresol conjugates were not detected in human or rat liver slice incubations. Covalent binding of [14C]toluene to human liver microsomes and slices was 21-fold and 4-fold greater than to the comparable rat liver preparations. Covalent binding did not occur in the absence of NADPH, was significantly decreased by coincubation with cysteine, glutathione, or superoxide dismutase, and was unaffected by coincubation with lysine. Protease and ribonuclease digestion decreased the amount of toluene covalently bound to human liver microsomes by 78% and 27% respectively. Acid washing of human liver microsomes had no effect on covalent binding.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genotoxicity of sodium arsenite and DNA fragmentation in ovarian cells of rat

Present study examined the genotoxic effects of arsenite in ovarian tissue of rat at 56 days of age. Immature (28 days old) female rats were exposed to different doses (50, 100, and 200 ppm) of sodium arsenite in drinking water for 28 days. DNA damage in ovarian tissue was measured by comet assay. All doses induced significant decrease in ovarian weight in a dose-dependent manner compared to control, more prominently at (P < 0.001) 100 and 200 ppm. All the comet assay parameters showed significant difference with arsenite treatment compared to control group. In treatment groups, mean number of cells with intact DNA decreased while, mean comet number increased (P < 0.001) in a dose-dependent manner compared to control. Significant decrease (P < 0.05) was observed in mean comet length, height, comet head diameter and %DNA in comet head of high dose groups compared to control group. Dose dependent increase was found in mean comet tail length, %DNA in tail, tail moment and olive tail moment in high dose groups compared to control group. The study indicates that arsenic caused DNA damage to ovarian cells particularly at high doses and ensure comet assay as an effective method to detect DNA damage in tissue caused by metals.     

Stability of Myrmecia pilosula (Jack Jumper) Ant venom for use in immunotherapy

Allergy to Myrmecia pilosula (Jack Jumper Ant) venom is common in Australia, affecting ∼2.7% of some communities. Venom immunotherapy is a highly effective treatment, but for the venom to be widely distributed for clinical use, the stability and shelf-life of formulated Jack Jumper Ant venom must be demonstrated. HPLC–UV, ELISA Inhibition, SDS-PAGE and SDS-PAGE Immunoblot were used to assess venom stability under conditions of varying temperature, pH and in the presence of various stabilising agents. Optimal stability occurred between pH 8 and 10, however the presence of benzyl alcohol within this pH range resulted in a cloudy appearance within 3 days, so a pH of 6 was used. Increasing polysorbate 80 concentrations accelerated the degradation of allergenic peptides in 100 μg/mL venom, but improved stability at concentrations of 1 μg/mL or less. Sucrose reduced degradation of allergens Myr p 1 and Myr p 3, whilst glycerol was destabilising. In the presence of 22% sucrose, 1.1 mg/mL Jack Jumper Ant venom was stable at −18 °C and 4 °C for 12 months; following dilution to 100 μg/mL with 0.9% sodium chloride, 10 mM phosphate (pH 6), 0.05% polysorbate 80 and 0.9% benzyl alcohol (giving 2% sucrose), venom was stable for 7 days when stored at 4 °C. Concentrated Jack Jumper Ant venom can be stored in 22% sucrose for 12 months, and after dilution to 100 μg/mL for clinical use, it should be discarded after 7 days.     

Ameliorative role of conjugated linolenic acid isomers against oxidative DNA damage induced by sodium arsenite in rat model

The present study was undertaken to evaluate the ameliorative role of α-eleostearic acid and punicic acid, isomers of conjugated linolenic (CLnA) acid, against oxidative stress induced DNA damage. Male albino rats were divided into six groups. Group 1 and 2 were normal control and sodium arsenite treated (Sa; 10 mg/kg BW) control respectively. Group 3–6 were orally treated with different doses of two fatty acids (0.5% and 1.0% of total lipid given for each isomer) along with sodium arsenite (Sa; 10 mg/kg BW). Comet assay of blood leukocytes showed that administration of CLnA reduced DNA damage significantly (P < 0.05) which was determined by tail DNA percent and olive tail moment. Results showed that activity of antioxidant enzymes viz. catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx) and reduced glutathione (GSH) in plasma, liver and erythrocyte lysate decreased and activity of nitric oxide synthase in plasma and liver increased significantly due to oxidative stress generated by sodium arsenite. Administration of CLnA isomers restored all the altered parameters and also reduced lipid peroxidation and leakage of transaminase enzymes from liver to blood due to liver injury. α-Eleostearic acid was more efficient antioxidant than punicic acid against oxidative DNA damage.     

Antioxidant activities of major thyme ingredients and lack of (oxidative) DNA damage in V79 Chinese hamster lung fibroblast cells at low levels of carvacrol and thymol

The leafy parts of thyme and its essential oil have been used in foods for the flavour, aroma and preservation and also in folk medicines. In the present study the genotoxicity of thymol and carvacrol was examined using comet assay. In V79 Chinese hamster lung fibroblast cells treated with 1, 5, 25 μM thymol and carvacrol, only 25 μM thymol caused some clastogenic DNA damage. For detection of oxidative DNA damage, the comet assay with formamido pyrimidine glycosylase (Fpg) protein was used: When V79 cells were treated with 1, 5, 25 μM thymol and carvacrol and post-treated with Fpg enzyme, no significant increase of Fpg-sensitive sites was observed at all concentrations studied. Reactive oxygen species (ROS) generation decreased slightly in the presence of thymol (1–100 μM) and carvacrol (5 μM) between 1 and 4 h, yet increased at the highest 100 μM concentration of carvacrol after 24 h. Thymol and carvacrol displayed a concentration dependent antioxidant capacity, whilst γ-terpinene which lacks a phenolic group did not show any antioxidant capacity in the trolox equivalent antioxidant capacity (TEAC) assay. The results of this study indicate a lack of clastogenic activity for thymol and carvacrol at biologically relevant concentrations, and a moderate antioxidant activity in vitro.     

Evaluation of the DNA damaging effect of the heat-induced food toxicant 5-hydroxymethylfurfural (HMF) in various cell lines with different activities of sulfotransferases

5-Hydroxymethylfurfural (HMF), a heat-induced food toxicant present in a vast number of food items, has been suggested to be genotoxic after being bioactivated by the sulfotransferase SULT1A1. The comet assay was used to evaluate the DNA damaging effect of HMF in cell lines with different activities of SULT1A1: two human cell lines (Caco-2, low activity; and HEK293, higher activity), one cell line from mouse (L5178Y, no activity) and two cell lines from Chinese hamster (V79, negligible activity; and V79-hP-PST, high activity of human SULT1A1). HMF induced significant DNA damage in all cell lines after 3 h exposure to 100 mM. Most sensitive were V79 and V79-hP-PST where HMF induced significant DNA damage at 25 mM. Consequently, in the present study we have shown that HMF is a DNA damaging agent in vitro independent of the activity of SULT1A1 in the cells. The HMF-induced DNA damage was only observed at rather high concentrations which usually was associated with a concomitant decrease in cell viability.     

Genotoxicity of nicotine in cell culture of Caenorhabditis elegans evaluated by the comet assay

To assess the genotoxicity of nicotine, its DNA-damaging effect on Caenorhabditis elegans cells was tested with the alkaline single-cell microgel electrophoresis (comet) assay. The degree of DNA migration (a measure of possible DNA single-strand breaks, alkali-labile sites, and incomplete excision repair sites) was expressed as the head DNA%, tail length, and Olive tail moment. Large differences were found between experimental variants: 0, 1, 10, and 100?μM (-)-nicotine. At concentrations of 1 and 10?μM, no damages were detected by the comet assay, and the Olive tail moment and tail length were significantly lower than in the control (P?<?0.001). The highest head DNA% and the lowest tail length and Olive tail moment were observed in the presence of 1?μM of nicotine. At 100?μM of nicotine, a significant increase (P?<?0.001) was observed in Olive tail moment and tail length (up to 2.7- and 3-fold, respectively, compared to the control). The results are consistent with the lowest head DNA% among the three tested variants. This study demonstrated that nicotine treatment had dose-dependent effects on the level of DNA damage. Generally, a high dose of nicotine (100?μM) is genotoxic, while a reasonably low concentration has a protective effect. The possible participation of reactive oxygen species in the DNA-damaging potential of nicotine in C. elegans is discussed.     

Studies on benzyl acetate. I. Effect of dose size and vehicle on the plasma pharmacokinetics and metabolism of [methylene-14C]benzyl acetate in the rat

Male Fischer 344 rats received [methylene-¹⁴C]benzyl acetate by gavage in a dose of 5, 250 or 500 mg/kg, as the neat substance, in corn oil or in propylene glycol. Urine and faeces were collected and urinary metabolites were assayed by radio-TLC and HPLC. Other animals were killed at various times and exsanguinated, and plasma levels of ¹⁴C in plasma occurred earliest and were highest when benzyl acetate was given neat. Peak levels were lower and absorption was delayed with the propylene glycol vehicle. The use of corn oil as the dose vehicle at the higher doses (250 and 500 mg/kg) led to the maintenance of plateau plasma levels, at about one half of the peak levels seen with the neat compound, for up to 8 hr after administration. At the 5 mg/kg dose, the plasma levels of ¹⁴C were essentially the same whether the dose was given in corn oil or propylene glycol. At the 250- and 500-mg/kg doses, at all time points, the major metabolite in plasma was benzoic acid, accompanied by smaller amounts of hippuric acid. Benzyl alcohol was also detected in some plasma samples. At the 5-mg/kg dose, the major plasma metabolite was hippuric acid, together with a smaller amount of benzoic acid. When propylene glycol was used as the vehicle at this dose level, benzylmercapturic acid was also present in the plasma. The major urinary metabolite was hippuric acid (c. 66% of the dose), with benzoic acid (2%) and benzylmercapturic acid (1%) also present. The elimination of benzoyl glucuronide increased with increasing dose, from c. 3 to 11% of the dose.