Possible reasons for differences in phototoxic potential of a 5 quinolone antibacterial agents: generation of toxic oxygen

The reason for the differences in phototoxic potential between the 5 quinolone antibacterial agents lomefloxacin, enoxacin, ciprofloxacin, ofloxacin and DR-3355 (the s-isomer of ofloxacin) in mice was investigated. Superoxide anion, hydrogen peroxide (H2O2), and bleaching of p-nitrosodimethylaniline (B-NDMA) were detected in quinolone solutions during irradiation with ultraviolet-A (UVA). Apparent levels of H2O2 and the B-NDMA per mole of quinolone paralled the phototoxic potentials in the mice. The N-NDMA induced by quinolones and UVA was inhibited partially by treatment with D-mannitol and dimethylsulfoxide, and also with diethylenetriamine-pentaaceticacid (DTPA), suggesting that Haber-Weiss and Fenton reactions occurred. UVA concentration-dependently increased the level of the B-NMDA in H2O2 solution and the swelling in the ear pretreated by intra-auricular injection of H2O2. Both augmentations were inhibited by DTPA or DMSO. The swelling induced by the 5 quinolones and UVA was completely inhibited by pretreatment with dimethylsulfoxide. Oxygen consumption was detectable during the photodegradation, and increased with time. These results showed that the phototoxic potentials of the 5 quinolones were probably related to the amounts of toxic oxygens generated in the target cells during irradiation.

Review of the occurrence and formation of non-volatile N-nitroso compounds in foods

A review of the literature published prior to July 1991 covers the occurrence and formation of non-volatile N-nitrosamines occurring in foods and beverages. The presence of identified volatile and non-volatile N-nitrosamines accounts for less than 10% of the total apparent N-nitrosamine concentration. N-Nitrosoproline and N-nitrosothiazolidine-4-carboxylic acid are the most commonly identified non-volatile N-nitrosamines in the diet. Non-volatile N-nitrosamines account for 12 of the 21 currently identified N-nitroso compounds in foods and beverages.

International N-nitroso compounds check sample programme: report on the performance in the second study dedicated to their determination in beer and malt

The second check sample survey for the determination of N-nitrosamines in beer and malt has been initiated. Each laboratory received four samples: two beer, from the same batch, spiked respectively with 0.5 microgram/l N-nitrosodimethylamine (NDMA) and 4 micrograms/l NDMA plus 30 micrograms/l N-nitrosoproline (NPRO) and two naturally contaminated malts. Sixteen laboratories sent their results and two apologized in view of analytical problems. Results from this have been statistically evaluated. Comparison to those from the previous study demonstrated a distinct improvement in the results from the analysis of NDMA in beer and malt. Little has been achieved for the other two common contaminants of beer and malt, N-nitrosopyrrolidine (NPYR) and NPRO. For this latter compound in beer, however, some hope came from the data produced by the method of Sen et al. (1983), but the number of results is insufficient to allow firm conclusions to be drawn.

Volatile, non-volatile and total N-nitroso compounds in bacon

Twenty-five smoked and unsmoked fried bacon samples have been analysed by a group selective procedure to measure the concentration of apparent total N-nitroso compounds (ATNC). The levels of a range of individual N-nitroso compounds, including simple volatile N-nitrosamines, N-nitrosothiazolidines, N-nitrosamino acids and N-nitrosothiazolidine carboxylic acids have also been examined. Concentrations of ATNC varied from 430 to 6800 micrograms(N-NO)/kg with a mean of 2700 micrograms(N-NO)/kg. Protein-bound N-nitrosoproline was the most abundant compound detected in unsmoked bacon, mean 260 micrograms/kg, and on average accounted for 4% of the ATNC concentration. For smoked bacon, bound N-nitrosoproline was detected in levels of up to 890 micrograms/kg and contributed 5% to the ATNC total. The most abundant compound present in smoked bacon was N-nitrosothiazolidine-4-carboxylic acid, mean 660 micrograms/kg, and this accounted for 6% of the ATNC. N-Nitrosothiazolidine, mean 340 micrograms/kg, and 2-(hydroxymethyl)-3-nitrosothiazolidine-4-carboxylic acid, mean 180 micrograms/kg, were the next most prominent compounds detected in smoked bacon. The combined sum of all the individual N-nitroso compounds measured accounted for, on average, 16% of the total ATNC. The identities of the N-nitroso compounds comprising the majority of the ATNC in bacon remain unknown.

Synthesis and HPLC assessment of N-nitrosoderivatives from six beta-adrenergic antagonists

At first N-nitrosoderivatives from six beta-adrenergic antagonists of large consumption were prepared. Secondly the standard nitrosation reactions recommended by WHO were performed to get information about their possible in vivo production and the yields of N-nitrosoderivatives were evaluated by HPLC analyses. Pharmacological tests confirm the potential risk to man of the N-nitrosoderivatives studied.

Endogenous N-nitrosation in man assessed by measurement of apparent total N-nitroso compounds in faeces

The faecal concentration of substances responding to the chemical test for N-nitroso compounds (apparent total N-nitroso compounds, ATNC) was investigated in human subjects consuming their normal free-choice diet. Concentrations ranged from 40 to 590 micrograms (N-NO)/kg faeces. To ascertain the likely relative contributions of endogenous ATNC formation and preformed, dietary ATNC, the subjects consumed a diet low in nitrate and ATNC for 8 days. At the end of this period, ATNC had decreased substantially with concentrations ranging from below the 40 micrograms (N-NO)/kg detection limit up to 143 micrograms (N-NO)/kg, mean 82 micrograms (N-NO)/kg. On supplementing this diet with 300 mg nitrate/day, faecal ATNC levels increased markedly. On the third day of this regime, values were in the range 73-714 micrograms (N-NO)/kg with a mean of 307 micrograms (N-NO)/kg. The results, together with the known limited occurrence of ATNC in the majority of foodstuffs so far tested, generally non-detectable or less than 100 micrograms (N-NO)/kg, suggest that endogenous formation via species derived from dietary nitrate is likely to be an important source of ATNC in human faeces.

Analytical methods for the determination and mass spectrometric confirmation of 1-methyl-2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid and 2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in foods

A method is described for the determination of the two title compounds that is based on: (a) extraction of the acidified sample with methanol, (b) removal of fats and lipids by partitioning of the extract with n-hexane, (c) clean-up on acidic alumina extraction cartridge, and (d) determination by a post-HPLC column chemical denitrosation-thermal energy analyser (TEA) technique or by conventional HPLC-TEA analysis after derivatization of the compounds with diazomethane. Confirmation was carried out by HPLC-mass spectrometry of the free acids and also by gas chromatography-mass spectrometry of the methyl esters. The formation of both 1-methyl-2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid and 2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in nitrosated samples of several Japanese and Chinese pickled vegetables, one soy sauce, and two cheeses was demonstrated.

Long-chain N-nitroso-N-methylalkylamines in commercial cosmetics, light-duty dishwashing liquids and household cleaning preparations

A method for the determination of long-chain N-nitroso-N-methylalkylamines in a range of commercial cosmetic and cleaning emulsions is described. The clean-up consists of solid-phase extraction and column chromatography. N-Nitroso-N-methyldodecylamine, N-nitroso-N-methyltetradecylamine and N-nitroso-N-methylhexadecylamine are detected by gas-liquid chromatography using a Thermal Energy Analyzer. N-Nitroso-N-ethyldodecylamine is used as an internal standard. Analysis of 86 products produced and marketed in the FRG did not indicate significant contamination. In contrast, of 26 consumer products from the USA, three (one hair-care product and two dishwashing liquids), which contained fatty amine oxides, were contaminated with substantial amounts of N-nitroso-N-methylalkylamines.

Trace analysis of nitrosated foodstuffs for nitrosamides

An analytical procedure previously developed for the trace determination of nitrosamides was applied to a screening of nitrosated foodstuffs for nitrosoureas. Different types of foodstuffs were nitrosated both under chemical conditions using a high nitrite concentration, and under simulated gastric conditions. Methylating activity corresponding to N-nitroso-N-methylurea (MNU) was detected in most samples. Under chemical conditions, the yields spanned several orders of magnitude with processed fish and meat products being at the top, and plant products at the bottom of the scale. After nitrosation under simulated gastric conditions, the range of MNU activity was significantly smaller. No correlation exists between the yields determined under chemical and simulated gastric conditions.

N-nitroso compounds in cigarette tobacco and their occurrence in mainstream tobacco smoke

The tobacco and mainstream smoke of 20 commercial brands of filter and non-filter cigarettes were analysed for N-nitroso compounds. The concentrations of N-nitrosodimethylamine (NDMA), N-nitrosoethylmethylamine (NEMA) and N-nitrosopyrrolidine (NPYR) in cigarette tobacco were very much lower than in mainstream smoke, where the levels were 6.3-76.4 ng/cig NDMA, less than 1.0-7.1 ng/cig NEMA and 3.9-41.2 ng/cig NPYR. N-Nitrosodiethylamine was not detected in mainstream smoke and N-nitrosopiperidine (less than 1.0 ng/cig) was detected in the smoke of four unfiltered cigarette brands. The five major non-volatile nitrosamines present in cigarette tobacco were 4-(N-nitroso-N-methylamino)butyric acid (not detected to 200 ng/cig), N-nitrosopipecolic acid (not detected to 670 ng/cig), N-nitrososarcosine (22-460 ng/cig), 3-(N-nitroso-N-methylamino)propionic acid (110-4990 ng/cig) and N-nitrosoproline (580-15000 ng/cig). The tobacco-specific nitrosamines N-nitrosoanabasine and N-nitrosoanatabine were found at levels of 270-2330 ng/cig and 18-205 ng/cig in cigarette tobacco and mainstream smoke respectively. N-Nitrosonornicotine was present at 400-5340 ng/cig and 19-855 ng/cig in cigarette tobacco and mainstream smoke respectively. 4-(N-Nitrosomethyl-amino)-1-(3-pyridyl)-1-butanone concentrations of 100-960 ng/cig and 21-470 ng/cig in cigarette tobacco and mainstream smoke were determined. 4-(N-Nitrosomethyl-amino)-4-(3-pyridyl)-1-butanol (iso-NNAL) was detected in four dark (French) tobacco unfiltered cigarettes at a concentration range of 140-240 ng/cig and 5-11 ng/cig in the corresponding mainstream smoke. For non-filter cigarettes, a transfer rate of 3.4-4.6% for iso-NNAL was calculated.

Nitrates, nitrites and N-nitrosocompounds: a review of the occurrence in food and diet and the toxicological implications

Data on occurrence of nitrate, nitrite and N-nitrosocompounds in food and drinking water, and on total dietary intakes are reviewed. Metabolic, toxicological and epidemiological studies are surveyed and the implications with respect to safety evaluation are addressed. It is concluded that, on the basis of recent long-term animal studies and of clinical experience in man, the current Acceptable Daily Intake (ADI) allocated to nitrate by the Joint FAO/WHO Expert Committee on Food Additives of 0-5 mg/kg body weight/day (expressed as sodium nitrate) might be increased to 0-25 mg/kg body weight/day. Based on similar criteria, the ADI for nitrite would be 0-0.1 mg/kg body weight/day (expressed as sodium nitrite). In view of the known carcinogenicity of N-nitrosocompounds, exposure to these compounds in food should be minimized by appropriate technological means, such as lowering the nitrite concentration in preserved foods to the minimum required to ensure microbiological safety and use of inhibitors of nitrosation like alpha-tocopherol or ascorbic acid. Further work is needed to define the minimal levels of nitrite in foods needed to inhibit outgrowth of Clostridium botulinum and toxin production.

N-nitroso compounds and their precursors in Brassica oleracea

In the present study, Brassica a dried green vegetable from Kashmir, which is a major constituent of the local diet, was analysed for nitrosatable aliphatic amines, N-nitrosamines prior to and after nitrosation) and alkylating activity due to N-nitrosamides following nitrosation. The cooked vegetable contained 11 micrograms/kg nitrosodimethylamine and 21 micrograms/kg nitrosopyrrolidine. Nitrosation under chemical conditions yielded 1200 micrograms/kg N-methylnitrosourea.

An investigation of the levels of N-nitrosodimethylamine, apparent total N-nitroso compounds and nitrate in beer

Over 170 retail samples of beer have been analysed for N-nitrosodimethylamine (NDMA), apparent total N-nitroso compounds (ATNC) and nitrate. Levels of NDMA ranged from below 0.1 up to 1.2 micrograms/kg with a mean of 0.2 micrograms/kg. ATNC was detected in 42% of the samples in concentrations of up to 569 micrograms (N-NO)/kg. The levels of nitrate ranged from less than 0.2 up to 143 mg/kg with a mean of 16.8 mg/kg. There was no correlation between the amounts of NDMA and ATNC found in the retail beers. Samples taken during the course of fermentation showed that NDMA was unaffected by the bacterial reduction of nitrate which causes ATNC formation. HPLC studies using a photolysis/chemiluminescence detector revealed that the ATNC in beer are highly polar species of as yet unknown identity.

Determination of N-nitroso compounds by high-performance liquid chromatography with postcolumn reaction and a thermal energy analyzer

Carcinogenic nonvolatile N-nitroso compounds have been difficult to determine in foods and other consumer products because of the incompatibility of aqueous high-performance liquid chromatography (HPLC) mobile phases with the thermal energy analyzer (TEA), a sensitive and selective detector for N-nitroso compounds. A postcolumn technique has been developed that permits the use of aqueous mobile phases with an interfaced liquid chromatograph/TEA. This system was linear from 3.5 to 900 ng of N-nitrosoproline injected. Coefficients of variation of 3.0 and 5.1%, respectively, were obtained when N-nitrosoproline and N-nitrosotrimethylurea were repeatedly injected at the 80- to 90-ng level. Mixtures of volatile and nonvolatile N-nitroso compounds as well as N-nitrosodipeptides were separated and quantitated by HPLC/TEA with a water/acetonitrile gradient.

Exposure of humans to endogenous N-nitroso compounds: implications in cancer etiology

Two sensitive procedures to quantitate human exposure to endogenous N-nitroso compounds (NOC) and/or methylating agents have been developed. One, the NPRO test, is based on the excretion of N-nitrosoproline (NPRO) and other N-nitrosoamino acids in the urine, that are measured as an index of endogenous nitrosation, following ingestion of precursors. The NPRO test has been applied to human subjects in clinical and epidemiological studies, and the kinetics and dietary modifiers of endogenous nitrosation have been investigated. Results obtained after application of the NPRO test to subjects at high risk for cancers of the stomach, esophagus, oral cavity and urinary bladder are summarized. In most instances, higher exposures to endogenous NOC were found in high-risk subjects, but individual exposure was greatly affected by dietary modifiers or disease state. Vitamin C efficiently lowered the body burden of intragastrically formed NOC. In experimental animals 3-methyladenine (3-MeAde) is excreted in urine following exposure to methylating NOC. Humans normally excrete 3-MeAde, the origin of which remains unknown. Recently developed analytical methodology permits large numbers of human urine samples to be analyzed and a wide variation is observed. Preliminary results suggest a weak correlation between basal NPRO excretion and background 3-MeAde excretion. Taken together, the results point to an etiological role of endogenously formed NOC in certain human cancers, and provide an interpretation of epidemiological findings that have shown protective effects of fruits and vegetables against several malignancies.

Nitrate, nitrite, and N-nitroso compounds in Finnish foods and the estimation of the dietary intakes

An estimate of the dietary intakes of nitrite, nitrate and N-nitroso compounds is presented, based on the analytical data supplied by the Finnish Food Quality Control. Figures on the food consumption of the Finnish population, taken from a national dietary survey, and food consumption of 1768 children and adolescents over a 48-h recall period were used. The mean daily dietary nitrate intakes were estimated to be about 55 mg for the total population and for children and adolescents. The mean nitrite intakes were 1.88 mg for the total population and 1.07 mg for children and adolescents. The intake of N-nitroso compounds (NDMA) was estimated to be 0.08 micrograms for the total population and 0.02 micrograms for children. Nitrates were found to originate mainly from vegetables (80%), nitrites from meat products (97%) and nitrosamines mostly from fish products and beer. A comparison of the estimate of dietary intake of with ADI values indicated that the nitrite intake of the total population was 23% and by children 39% of ADI. The average weight was approximately 60 kg for adults and 20 kg for children. When measured average weight (39 kg) was used, and the nitrite intake was found to be 28% of ADI. Nitrate intakes from food additives were 2.5% and 1.4% of the ADI value, respectively. When the total nitrate intake from various food sources was compared with the ADI (which is given only for food additives), the estimated nitrate intake of the total population was 25% and that of children 28% of the ADI value.

Determination of ten N-nitrosoamino acids in cured meat products

A rapid, sensitive, and accurate solid-phase extraction method was developed for the measurement of 10 N-nitrosoamino acids (NAAs) in cured meat products. In the procedure, the comminuted meat was mixed with sulfamic acid and Celite, and then added to a glass column containing anhydrous sodium sulfate. The column was washed with pentane, and the NAAs were eluted with ethyl acetate. The eluate was concentrated, then derivatized with diazomethane followed by acetic anhydride-pyridine reagent. The NAA methyl esters and their acylated hydroxy derivatives were separated by gas chromatography on a DB-5 fused silica capillary column and quantitated with a thermal energy analyzer, a chemiluminescence detector specific for nitric oxide derived from the thermal denitrosation of nitrosamines. Recovery of 10 of the NAAs exceeded 75% at the 10 ppb level. The method is applicable to a wide range of cured meat products.

Fluorescence detection of carbon-centered radicals in aqueous solution

A simple, highly sensitive method for the simultaneous determination of arrays of carbon-centered radicals in aqueous systems is described. Radicals are efficiently trapped by an amino-nitroxide to form stable products which are then reacted with fluorescamine to produce highly fluorescent adducts. The adducts are easily separated by reversed-phase high performance liquid chromatography. The detection limit for individual radical adducts (0.5 to 2 nM) is two to three orders of magnitude lower than those of current methods employing electron paramagnetic resonance detection. Results on the photolysis of ketones and alpha-keto acids demonstrate the potential of this technique. This approach should be widely applicable to the study of radical processes in biological and chemical systems.

Effect of storage conditions on nitrosated, acylated, and oxidized pyridine alkaloid derivatives in smokeless tobacco products

Very large concentration increases in nitrite (34-fold), nitrosated pyridine alkaloids, and related 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) (14- to 33-fold) occurred in moist snuff during storage at 24 degrees C for 52 weeks, whereas, decreases in all parent and some acylated pyridine alkaloids were observed in the same material. Nitrite concentrations in dry snuff decreased up to 90% during storage; increased contents of nitrosated alkaloids and NNK of 30 to 80% were also observed. Storage effects on chewing tobacco included a 75% increase in nitrite and small increases of nitrosated alkaloids and NNK. Sums of parent alkaloids in moist snuff decreased 24 and 54% after storage for 24 weeks at 24 and 32 degrees C, respectively, while sums of alkaloid derivatives increased, up to 36-fold for nitrosated alkaloids and NNK, 92% for acylated, and 133% for oxidized components. Levels of N'-nitrosonornicotine, NNK, and N'-nitrosoanatabine after 52 weeks' storage at 24 degrees C were 547, 41, and 296% higher, respectively, in ambient air-exposed moist snuff than in the nonexposed counterpart. A mathematical model was evaluated and used to calibrate nonlinear gas chromatography alkali bead detector response to the individual components. This permitted the use of a single analysis for all required individual compounds over a wide concentration range.

Examination of some fermented foods for the presence of apparent total N-nitroso compounds

The fermented foods yoghurt, bread and cheese were analysed for the presence of apparent total N-nitroso compounds (ATNC) by a group-selective procedure involving direct chemical denitrosation and chemiluminescence detection of the released nitric oxide. The levels of ATNC were below the 20 micrograms(N-NO)/kg detection limit in all 20 yoghurts, 23 of the 24 bread samples and 28 out of 31 different varieties of cheese analysed. ATNC were detected in most of those cheese samples manufactured with added nitrate, including Edam, Gouda and Havarti, in concentrations ranging from 30 to 210 micrograms(N-NO)/kg.

Effects of inhaled municipal refuse incinerator fly ash in the guinea pig

Fly ash was collected from two municipal refuse incinerators. It was analyzed for heavy metals, elements, and a wide range of toxic organics. It was resuspended in air for inhalation exposure of guinea pigs. These animals were exposed at high concentrations of each ash 6 h/d for 5 d, and tissues were taken 45 d after the exposure. Following the first exposure and after each daily exposure the ventilatory response of these animals upon challenge with CO2 was found to be depressed. Recovery occurred following exposure. Heavy metals, cadmium, lead, zinc, and mercury were elevated in the lungs of these animals. Histologic evaluation of pulmonary tissue revealed multifocal pneumoconiosis. Interstitial infiltration by macrophages and smooth muscle hypertrophy of blood vessels and bronchioles were also observed. There was no evidence of a dioxinlike toxic effect following inhalation of these ashes.

HPLC analysis of the nitrosation products of chlordiazepoxide

Products originated from Chlordiazepoxide (I) hydrochloride/sodium nitrite interaction were analyzed by HPLC. The studied reactions were carried out in diluted hydrochloric acid solutions at pH values ranging between 0.5-5.0. Depending on the reaction pH values and molar ratios it was possible to find and assess variable amounts of the N-nitrosochlordiazepoxide (II), the dihydroquinazoline (III) and the lactam (IV). The highest degree of N-nitrosation was found at pH 3.5. At this pH value the yields of (II) were respectively 54.8% and 18.3% when the drug (I)/nitrite molar ratios were correspondingly 0.41 and 0.25. When the reaction was performed in concentrations which is possible to find in the gastric juice of patients taking (I) together with nitrite-rich foods the yield of (II) at pH 3.5 was 2.5%. Since in the meantime the genotoxicity of (II) was proved, "in vivo" formation of N-nitrosochlordiazepoxide (II) represents a potential risk not to be underestimated.

The occurrence of N-nitroso compounds in kiwam tobacco

The concentrations of tobacco-specific nitrosamines (TSNA), volatile and non-volatile N-nitroso compounds in kiwam, a fermented Indian tobacco product are presented. Total identified N-nitroso compound concentrations in kiwam ranged from 6.19 to 25.4 mg/kg fresh weight tobacco, the concentration range of TSNA was 5.43-22.2 mg/kg tobacco which accounted for 67-87% of the total identified N-nitroso compound burden. The high concentrations of TSNA found in kiwam tobacco may present a considerable exposure source to carcinogenic N-nitroso compounds for people using this type of tobacco.

A sensitive analytical procedure for the detection of N-nitrosamides via their alkylating activity

Based on a method for trapping direct-alkylating intermediates with scavenger reagents possessing a nucleophilic side-chain and an N-nitroso group as a marker, a sensitive test system for the detection of N-nitrosamides and related compounds has been developed. N-Nitroso-N-tert-butylglycine is an effective scavenger reagent for this purpose. It reacts readily with diazoalkanes released from N-nitrosamides on treatment with alkali to form the corresponding esters which are analysed by gas-liquid chromatography using a thermal energy analyser. The method is easy to perform and specific for N-nitroso compounds that decompose to non-polar diazoalkanes on treatment with alkali. A determination limit of 2 ng solids/sample was established for methylated NTBG formed from N-methyl-N-nitro-sourea following treatment with alkali.