In vitro studies of biological effects of cigarette smoke condensate. II. Induction of sister-chromatid exchanges in human lymphocytes by weakly acidic, semivolatile constituents

A weight of evidence evaluation of the mode of action of isoeugenol

Isoeugenol is one of several phenylpropenoid compounds that is used as a fragrance, food flavoring agent and in aquaculture as a fish anesthetic. Carcinogenicity testing in rats and mice by NTP resulted in clear evidence of carcinogenicity (hepatic adenomas/carcinomas) in male mice only. A nongenotoxic threshold mode of action (MOA) is postulated for isoeugenol and is discussed considering the IPCS MOA and Human Relevance Framework. The weight of evidence indicates that isoeugenol is not genotoxic and that the carcinogenic outcome in male mice relates directly to the metabolism of individual compounds. Benchmark Dose (BMD) modeling was conducted to determine a Point of Departure (POD) and potential threshold of carcinogenicity. The results of the BMD evaluation for isoeugenol resulted in an estimated POD for carcinogenicity in the male mouse of 8 mg/kg with a lower limit of 4 mg/kg, representing a POD for the determination of an acceptable daily intake. With application of uncertainty factors, an ADI of 40 μg/kg is calculated. This daily dose in humans would be protective of human health, including carcinogenicity. A corresponding maximum residual level (MRL) of 3200 μg/kg fish is also estimated based on this POD that considers the threshold MOA.

Risk Assessment of Isoeugenol in Food Based on Benchmark Dose-Response Modeling

Isoeugenol has recently been evaluated as possibly carcinogenic (Group 2B) by the WHO International Agency for Research on Cancer (IARC). In light of this evaluation, an updated risk assessment of this common food constituent was conducted using the benchmark dose (BMD) approach as recommended by the European Food Safety Authority (EFSA) for point of departure (POD) determination, as an alternative to the no observed adverse effect level (NOAEL). This approach was specifically chosen, as for the relevant neoplastic endpoints only lowest observed adverse effect level (LOAEL) values are available. The toxicological endpoint from the animal studies with the most conservative BMD lower confidence limit (BMDL) value was identified. Using the obtained BMDL value of 8 mg/kg body weight/day as POD, an acceptable daily intake (ADI) of 16 µg/kg body weight/day was obtained, which-despite being more conservative than previous approaches-is still clearly above the estimated daily exposure level to isoeugenol in the USA and in Europe. These results confirm a low risk of the estimated daily exposure levels of isoeugenol.

Antioxidant and in vitro cytogenotoxic properties of Amburana cearensis (Allemão) A.C.Sm. leaf extract

Amburana cearensis leaves have been used in folk medicine to treat respiratory diseases and inflammations. This study aimed to evaluate the biological potential of A. cearensis leaves by antioxidant and in vitro cytogenotoxic analyses of ethanolic crude extract (EE) and its fractions in healthy human cells. The EE was obtained by percolation, followed by fractionation using dichloromethane, cyclohexane, ethyl acetate (EtOAc), and methanol (MeOH) as organic solvents. Extract and all fractions were evaluated for their antioxidant potential by DPPH and reducing power tests. In vitro cytotoxic activity was determined in human peripheral blood mononuclear cells by MTT assay for the extract, EtOAc and MeOH fractions. In turn, the genotoxic activity was determined in human lymphocytes by the Cytokinesis Block Micronucleus assay only for the EtOAc fraction. Only EtOAc fraction was analyzed via gas chromatography coupled to mass spectrometry due to its higher biological activity. Considering the antioxidant potential, the EtOAc fraction was most effective in DPPH (EC₅₀ 43.37 µg/mL) and reducing power (EC₅₀ 89.80 µg/mL) assays. GC-MS analysis of the EtOAc fraction led to the identification of guaiacol, 2,3-dihydro-benzofuran, 2-methoxy-4-vinylphenol, isovanillic acid methyl ester, 4-hydroxybenzaldehyde, and 4-(ethoxymethyl)-phenol. The EE (400-1000 µg/mL), EtOAc (≤150 µg/mL) and MeOH (50 and 150-600 µg/mL) fractions were not cytotoxic by MTT test. Additionally, the EtOAc fraction (100-400 µg/mL) did not induce significant genotoxic damage. Concentrations of the EtOAc fraction with antioxidant activity showed no cytotoxicity, nor genotoxicity potential, indicating them as a nontoxic natural antioxidant source.

Alkenylbenzenes in Foods: Aspects Impeding the Evaluation of Adverse Health Effects

Alkenylbenzenes are naturally occurring secondary plant metabolites, primarily present in different herbs and spices, such as basil or fennel seeds. Thus, alkenylbenzenes, such as safrole, methyleugenol, and estragole, can be found in different foods, whenever these herbs and spices (or extracts thereof) are used for food production. In particular, essential oils or other food products derived from the aforementioned herbs and spices, such as basil-containing pesto or plant food supplements, are often characterized by a high content of alkenylbenzenes. While safrole or methyleugenol are known to be genotoxic and carcinogenic, the toxicological relevance of other alkenylbenzenes (e.g., apiol) regarding human health remains widely unclear. In this review, we will briefly summarize and discuss the current knowledge and the uncertainties impeding a conclusive evaluation of adverse effects to human health possibly resulting from consumption of foods containing alkenylbenzenes, especially focusing on the genotoxic compounds, safrole, methyleugenol, and estragole.

In vitro and in silico genetic toxicity screening of flavor compounds and other ingredients in tobacco products with emphasis on ENDS

Electronic nicotine delivery systems (ENDS) are regulated tobacco products and often contain flavor compounds. Given the concern of increased use and the appeal of ENDS by young people, evaluating the potential of flavors to induce DNA damage is important for health hazard identification. In this study, alternative methods were used as prioritization tools to study the genotoxic mode of action (MoA) of 150 flavor compounds. In particular, clastogen-sensitive (γH2AX and p53) and aneugen-sensitive (p-H3 and polyploidy) biomarkers of DNA damage in human TK6 cells were aggregated through a supervised three-pronged ensemble machine learning prediction model to prioritize chemicals based on genotoxicity. In addition, in silico quantitative structure-activity relationship (QSAR) models were used to predict genotoxicity and carcinogenic potential. The in vitro assay identified 25 flavors as positive for genotoxicity: 15 clastogenic, eight aneugenic and two with a mixed MoA (clastogenic and aneugenic). Twenty-three of these 25 flavors predicted to induce DNA damage in vitro are documented in public literature to be in e-liquid or in the aerosols produced by ENDS products with youth-appealing flavors and names. QSAR models predicted 46 (31%) of 150 compounds having at least one positive call for mutagenicity, clastogenicity or rodent carcinogenicity, 49 (33%) compounds were predicted negative for all three endpoints, and remaining compounds had no prediction call. The parallel use of these predictive technologies to elucidate MoAs for potential genetic damage, hold utility as a screening strategy. This study is the first high-content and high-throughput genotoxicity screening study with an emphasis on flavors in ENDS products.

Final Report on the Safety Assessment of Sodium p -Chloro- m -Cresol, p -Chloro- m -Cresol, Chlorothymol, Mixed Cresols, m -Cresol, o -Cresol, p -Cresol, Isopropyl Cresols, Thymol, o -Cymen-5-ol, and Carvacrol1

Sodium p -Chloro- m -Cresol, p -Chloro- m -Cresol (PCMC), Mixed Cresols, m -Cresol, o -Cresol, p -Cresol, Isopropyl Cresols, Thymol, Chlorothymol, o -Cymen-5-ol, and Carvacrol are substituted phenols used as cosmetic biocides/preservatives and/or fragrance ingredients. Only PCMC, Thymol, and o -Cymen-5-ol are reported to be in current use, with the highest concentration of use at 0.5% for o -Cymen-5-ol in perfumes. The use of PCMC in cosmetics is restricted in Europe and Japan. Cresols can be absorbed through skin, the respiratory tract, and the digestive tract; metabolized by the liver; and excreted by the kidney as glucuronide and sulfate metabolites. Several of these cresols increase the dermal penetration of other agents, including azidothymidine. In acute oral toxicity studies, LD50 values were in the 200 to 5000 mg/kg day-1 range across several species. In short-term studies in rats and mice, an o -Cresol, m -Cresol, p -Cresol or m -Cresol/ p -Cresol mixture at 30,000 ppm in the diet produced increases in liver and kidney weights, deficits in liver function, bone marrow hypocellularity, irritation to the gastrointestinal tract and nasal epithelia, and atrophy of female reproductive organs. The no observed effect levels (NOEL) of o -Cresol was 240 mg/kg in mink and 778 mg/kg in ferrets in short-term feeding studies, with no significant dose-related toxicity (excluding body weight parameters). In mice, 0.5% p -Cresol, but neither m -Cresol nor o -Cresol, caused loss of pigmentation. Short-term and subchronic oral toxicity tests performed with various cresols using mice, rats, hamsters, and rabbits resulted in no observed adverse effect levels (NOAELs) for mice of 625 ppm and rats of 50 mg/kg day -1, although the NOEL was 2000 ppm ina chronic study using rats. In rabbits, 160 mg/kg PCMC was found to produce irritation and erythema, but no systemic effects. Hamsters dosed with 1.5% p -Cresol in diet for 20 weeks had a greater incidence of mild and moderate forestomach hyperplasia as compared to the control. Acute inhalation toxicity studies using rats yielded LC50 values ranging from > 20 mg/m3 for o -Cresol to > 583 mg/m3 for PCMC. No deaths were recorded in mice given o -Cresol at 50 mg/m3. Cats exposed (short-term) to 9 to 50 mg/m3 of o -Cresol developed inflammation and irritation of the upper respiratory tract, pulmonary edema, and hemorrhage and perivascular sclerosis in the lungs. Rats exposed (subchronic) to o -Cresol at 9 mg/m3 had changes in leukocytes, spinal cord smears, nervous activity, liver function, blood effects, clinical signs, and neurological effects. In guinea pigs, exposure to 9 mg/m3 produced changes in hemoglobin concentrations and electrocardiograms (EKGs). Rats exposed (subchronic) to 0.05 mg/m3 Mixed Cresols by inhalation exhibited central nervous system (CNS) excitation, denaturation of lung protein, and decreased weight gain. All cresols appear to be ocular irritants. Numerous sensitization studies have been reported and most positive reactions were seen with higher concentrations of Cresol ingredients. Developmental toxicity is seen in studies of m -Cresol, o -Cresol, and p -Cresol, but only at maternally toxic levels. In a reproductive toxicity study of a mixture of m -Cresol and p -Cresol using mice under a continuous breeding protocol, 1.0% caused minimal adult reproductive and significant postnatal toxicity in the presence of systemic maternal toxicity. The o -Cresol NOAEL was 0.2% for both reproductive and general toxicity in both generations. Cresol ingredients were generally nongenotoxic in bacterial, fruit fly, and mammalian cell assays. Thymol did not induce primary lung tumors in mice. No skin tumors were found in mice exposed dermally to m -Cresol, o -Cresol, or p -Cresol for 12 weeks. In the tryphan blue exclusion assay, antitumor effects were observed for Thymol and Carvacrol. Clinical patch testing with 2% PCMC may produce irritant reactions, particularly in people with multiple patch test reactions, that are misinterpreted as allergic responses. o -Cresol, p -Cresol, Thymol, Carvacrol, and o -Cymen-5-ol caused no dermal irritation at or above use concentrations. In two predictive patch tests, PCMC did not produce a sensitization reaction. Overall, these ingredients are not significant sensitizing or photosensitizing agents. The Cosmetic Ingredient Review (CIR) Expert Panel noted some of these ingredients may increase the penetration of other cosmetic ingredients and advised cosmetic formulators to take this into consideration. The CIR Expert Panel concluded that the toxic effects of these ingredients are observed at doses higher than would be available from cosmetics. A concentration limitation of 0.5% was chosen to ensure the absence of a chemical leukoderma effect. For p -Cresol and Mixed Cresols (which contain p -Cresol), the Panel considered that the available data are insufficient to support the safety of these two ingredients in cosmetics. Studies that would demonstrate no chemical leukoderma at concentrations of use of p -Cresol and Mixed Cresols, or would demonstrate a dose response from which a safe concentration could be derived, are needed.

RIFM fragrance ingredient safety assessment, isoeugenol, CAS Registry Number 97-54-1

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Repeated dose toxicity was determined to have the most conservative systemic exposure derived NO[A]EL of 37.5 mg/kg/day. A gavage 13-week subchronic toxicity study conducted in mice resulted in a MOE of 5769 while considering 38.4% absorption from skin contact and 100% from inhalation. A MOE of >100 is deemed acceptable.

RIFM fragrance ingredient safety assessment, Eugenol, CAS Registry Number 97-53-0

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Reproductive toxicity was determined to have the most conservative systemic exposure derived NO[A]EL of 230 mg/kg/day. A gavage multigenerational continuous breeding study conducted in rats on a suitable read across analog resulted in a MOE of 12,105 while considering 22.6% absorption from skin contact and 100% from inhalation. A MOE of >100 is deemed acceptable.

Formation of DNA adducts in wild-type and transgenic mice expressing human sulfotransferases 1A1 and 1A2 after oral exposure to furfuryl alcohol

Furfuryl alcohol (FFA) is present in many heat-treated foods as a result of its formation via dehydration of pentoses. It is also used legally as a flavouring agent. In an inhalation study conducted in the National Toxicology Program, FFA showed some evidence of carcinogenic activity in rats and mice. FFA was generally negative in conventional genotoxicity assays, which suggests that it may be a non-genotoxic carcinogen. However, it was recently found that FFA is mutagenic in Salmonella strains expressing appropriate sulfotransferases (SULTs), such as human or mouse SULT1A1. The same DNA adducts that were formed by FFA in these strains, mainly N (2)-((furan-2-yl)methyl)-2'-deoxyguanosine (N (2)-MF-dG), were also detected in tissues of FFA-exposed mice and even in human lung specimens. In the present study, a single oral dose of FFA (250 mg/kg body weight) or saline was administered to FVB/N mice and transgenic mice expressing human SULT1A1/1A2 on the FVB/N background. The transgenic mice were used, since human and mouse SULT1A1 substantially differ in substrate specificity and tissue distribution. DNA adducts were studied in liver, kidney, proximal and distal small intestine as well as colon, using isotope-dilution ultra performance liquid chromatography (UPLC-MS/MS). Surprisingly, low levels of adducts that may represent N (2)-MF-dG were detected even in tissues of untreated mice. FFA exposure enhanced the adduct levels in colon and liver, but not in the remaining investigated tissues of wild-type (wt) mice. The situation was similar in transgenic mice, except that N (2)-MF-dG levels were also strongly enhanced in the proximal small intestine. These different results between wt and transgenic mice may be attributed to the fact that human SULT1A1, but not the orthologous mouse enzyme, is strongly expressed in the small intestine.

Safety Assessment of Alkyl Benzoates as Used in Cosmetics

The functions of alkyl benzoates in cosmetics include fragrance ingredients, skin-conditioning agents—emollient, skin-conditioning agents—miscellaneous, preservatives, solvents, and plasticizers. The Cosmetic Ingredient Review Expert Panel reviewed the relevant animal and human data and noted gaps in the available safety data for some of the alkyl benzoates. Similar structure activity relationships, biologic functions, and cosmetic product usage allowed the available data of many of the alkyl benzoates to be extended to the entire group. Carcinogenicity data were not available, but available data indicated that these alkyl benzoate cosmetic ingredients are not genotoxic. Also benzoic acid and tested component alcohols were not reproductive or developmental toxicants, are not genotoxic in almost all assays, and are not carcinogenic. These ingredients were determined to be safe in the present practices of use and concentration.

2,4,5-trichlororophenol and its derivatives induce biochemical and morphological changes in human peripheral blood lymphocytes in vitro

In this work, the investigation of the effects of 2,4,5-trichlorophenol (2,4,5-TCP), 4,6-dichloroguaiacol (4,6-DCG), and 4,5-dichlorocatechol (4,5-DCC) on selected morphological and biochemical parameters in human peripheral blood lymphocytes were studied. All of the investigated compounds (at concentrations from 25-600 ppm) increased the size and granularity of the lymphocytes. 2,4,5-TCP induced the strongest and 4,5-DCC induced the weakest changes in these parameters. Moreover, 2,4,5-TCP induced the greatest loss of lymphocyte viability, which was statistically significant at concentrations of 125 and 600 ppm. DNA and protein damage was provoked by relatively low concentrations of the xenobiotics examined. Comet assay analysis showed that 4,6-DCG and 4,5-DCC at 5 ppm significantly increased the level of single- and/or double-strand breaks in the DNA of human lymphocytes. The increase in carbonyl group content (the marker of protein damage) was more strongly induced by 4,5-DCC and 2,4,5-TCP than by 4,6-DCG at concentrations ranging from 0.04 to 5 ppm. DNA and protein damage was most probably caused by reactive oxygen species (ROS) because it was observed that all of the compounds studied, as well as 4,5-DCC and 2,4,5-TCP in particular, were capable of oxidising fluorescent probe 6-carboxy-2',7'-dichlorodihydrofluorescein at very low concentrations (0.01-1 ppm). In summary, 2,4,5-TCP induced the greatest morphological and cytotoxic changes in human peripheral blood lymphocytes, whereas its metabolite 4,5-DCC caused the most severe biochemical alterations, such as protein and DNA damage as well as ROS formation, in the incubated cells,.

Pentachlorophenol and its derivatives induce oxidative damage and morphological changes in human lymphocytes (in vitro)

In this study, the effect of environmental toxins such as pentachlorophenol (PCP), tetrachlorocatechol (TeCC) and tetrachloroguaiacol (TeCG) on human peripheral blood lymphocytes was investigated. All the compounds studied increased the size and granularity of the lymphocytes in the concentrations range from 5 to 600 ppm. The PCP caused the strongest increase in the size of the cells, whereas lymphocytes granularity was more strongly increased by TeCC and PCP than by TeCG. The PCP and its derivatives in the concentrations range from 1 to 125 ppm significantly depleted ATP level. It was also observed that PCP most strongly decreased ATP content at its highest concentration of 125 ppm. Moreover, PCP caused the highest loss of lymphocytes viability in the concentrations range from 125 to 600 ppm. The TeCC in the concentrations of 1 and 5 ppm significantly increased the level of strand breaks in DNA, whereas lower damage was noted for PCP, and particularly for TeCG. The increase in carbonyl groups content was more strongly induced by TeCG and TeCC than by PCP in the concentrations range from 0.04 to 1 ppm; however, in a concentration of 5 ppm, all the compounds studied increased this parameter to a similar degree. DNA and protein damage was the most probably induced by free radical formation, as it was observed that all the compounds examined, and TeCC, in particular, were able of oxidize a fluorescent probe 6-carboxy-2',7'-dichlorodihydrofluorescein in the concentrations range from 0.01 to 1 ppm.

Chlorophenols, chlorocatechols and chloroguaiacols induce DNA base oxidation in human lymphocytes (in vitro)

Phenolic compounds are strong environmental toxicants, which are found in food, drinking water as well as in the indoor and outdoor air environment. In this work we investigated the effect of low concentrations of 0.2, 1 and 5 microg/ml of 2,4,5-trichlorophenol (2,4,5-TCP), pentachlorophenol (PCP), 4,6-dichloroguaiacol (4,6-DCG), tetrachloroguaiacol (TeCG), 4,5-dichlorocatechol (4,5-DCC) and tetrachlorocatechol (TeCC) on DNA bases oxidation in human peripheral blood lymphocytes. The analysis was performed using alkaline single cell gel electrophoresis (the comet assay). To detect oxidized pyrimidynes and purines we used the repair enzymes such as endonuclease III and formamidopyrimidine-DNA glycosylase. DNA oxidation was expressed as a percentage of comet tail, which was formed after the xenobiotics treatment. The obtained results showed that all the compounds examined were able to oxidize DNA bases in human lymphocytes. It was also observed that pyrimidine bases were more strongly oxidized in comparison to purine ones. Finally, it was found that chlorinated catechols and TeCC in particular, revealed a higher oxidative potential in comparison to chlorophenols and chloroguaiacols, and a rise in the number of chlorine atoms in the compound from each group examined led to an increase in DNA bases damage.

Sequential fractionation with concurrent chemical and toxicological characterization of the combustion products of chlorogenic acid

Chlorogenic acid is the most abundant polyphenol found in the tobacco plant. The biological effects of its combustion products remain largely unknown. In this study, chlorogenic acid was burned at 640 degrees C for 2 min and the particulate matter of the smoke was collected onto Cambridge filter pads followed by selective extraction in five different solvents. Various fractions of the chlorogenic acid combustion products were tested for induction of micronuclei in V79 Chinese hamster fibroblast cells. Over 40 compounds were identified in the dimethyl sulfoxide (DMSO) extract by high-performance liquid chromatography coupled to electrospray time-of-flight mass spectrometry (HPLC/TOF-MS). The DMSO extract was then fractionated into three major fractions by preparative LC. The fraction inducing the highest degree of toxicity was further separated into four sub-fractions. The sub-fraction responsible for the most toxic response was determined to contain catechol as its major component. The overall reproducibility of the combustion, the extraction procedure and the chemical characterization of the compounds responsible for the toxicity in the chlorogenic acid smoke were evaluated by LC/TOF-MS.