Chronic toxicity/carcinogenicity study of trans-anethole in rats

FEMA GRAS assessment of natural flavor complexes: Allspice, anise, fennel-derived and related flavoring ingredients

The FEMA Expert Panel program to re-evaluate the safety of natural flavor complexes (NFCs) used as flavoring ingredients in food has resulted in the publication of an updated constituent-based procedure as well as publications on the safety evaluation of many botanical-derived NFCs. This publication, ninth in the series and related to the ninth publication, describes the affirmation of the generally recognized as safe (GRAS) status for NFCs with propenylhydroxybenzene and allylalkoxybenzene constituents under their conditions of intended use as flavoring ingredients added to food. The Panel's procedure applies the threshold of toxicological concern (TTC) concept and evaluates relevant data on absorption, metabolism, genotoxic potential and toxicology for the NFCs themselves and their respective constituent congeneric groups. For NFCs containing allylalkoxybenzene constituent(s) with suspected genotoxic potential, the estimated intake of the individual constituent is compared to the TTC for compounds with structural alerts for genotoxicity and if exceeded, a margin of exposure is calculated using BMDL10 values derived from benchmark dose analyses using Bayesian model averaging, as presented in the tenth article of the series. Safety evaluations for NFCs derived from allspice, anise seed, star anise, sweet fennel seed and pimento leaves were conducted and their GRAS status was affirmed for use as flavoring ingredients. The scope of the safety evaluation contained herein does not include added use in dietary supplements or any products other than food.

FEMA GRAS assessment of derivatives of basil, nutmeg, parsley, tarragon and related allylalkoxybenzene-containing natural flavor complexes

In 2015, the Expert Panel of the Flavor and Extract Manufacturers Association (FEMA) initiated a program for the re-evaluation of the safety of over 250 natural flavor complexes (NFCs) used as flavoring ingredients in food. In this publication, tenth in the series, NFCs containing a high percentage of at least one naturally occurring allylalkoxybenzene constituent with a suspected concern for genotoxicity and/or carcinogenicity are evaluated. In a related paper, ninth in the series, NFCs containing anethole and/or eugenol and relatively low percentages of these allylalkoxybenzenes are evaluated. The Panel applies the threshold of toxicological concern (TTC) concept and evaluates relevant toxicology data on the NFCs and their respective constituent congeneric groups. For NFCs containing allylalkoxybenzene constituent(s), the estimated intake of the constituent is compared to the TTC for compounds with structural alerts for genotoxicity and when exceeded, a margin of exposure (MOE) is calculated. BMDL₁₀ values are derived from benchmark dose analyses using Bayesian model averaging for safrole, estragole and methyl eugenol using EPA's BMDS software version 3.2. BMDL₁₀ values for myristicin, elemicin and parsley apiole were estimated by read-across using relative potency factors. Margins of safety for each constituent congeneric group and MOEs for each allylalkoxybenzene constituent for each NFC were determined that indicate no safety concern. The scope of the safety evaluation contained herein does not include added use in dietary supplements or any products other than food. Ten NFCs, derived from basil, estragon (tarragon), mace, nutmeg, parsley and Canadian snakeroot were determined or affirmed as generally recognized as safe (GRAS) under their conditions of intended use as flavor ingredients based on an evaluation of each NFC and the constituents and congeneric groups therein.

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.

Network pharmacology-based evaluation of natural compounds with paclitaxel for the treatment of metastatic breast cancer

Metastatic breast cancer is a prevalent life-threatening disease. Paclitaxel (PTX) is widely used in metastatic breast cancer therapy, but the side effects limit its chemotherapeutic application. Multidrug strategies have recently been used to maximize potency and decrease the toxicity of a particular drug by reducing its dosage. Therefore, we have evaluated the combined anti-cancerous effect of PTX with tested natural compounds (andrographolide (AND), silibinin (SIL), mimosine (MIM) and trans-anethole (TA)) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, trypan blue dye exclusion assay, proliferating cell nuclear antigen (PCNA) staining, network pharmacology, molecular docking, molecular dynamics (MD) and in vivo chick chorioallantoic membrane (CAM) angiogenesis assay. We observed a reduction in the IC₅₀ value of PTX with tested natural compounds. Further, the network pharmacology-based analysis of compound-disease-target (C-D-T) network showed that PTX, AND, SIL, MIM and TA targeted 55, 61, 56, 31 and 18 proteins of metastatic breast cancer, respectively. Molecular docking results indicated that AND and SIL inhibited the C-D-T network's core target kinase insert domain receptor (KDR) protein more effectively than others. While MD showed that the binding of AND with KDR was stronger and more stable than others. In trypan blue dye exclusion assay and PCNA staining, AND and SIL along with PTX were found to be more effective than PTX alone. CAM assay results suggested that AND, SIL and TA increase the anti-angiogenic potential of PTX. Thus, natural compounds can be used to improve the anti-cancer potential of PTX.

Trans-anethole ameliorates obesity via induction of browning in white adipocytes and activation of brown adipocytes

To treat obesity, suppression of white adipose tissue (WAT) expansion and activation of brown adipose tissue (BAT) are considered as potential therapeutic targets. Recent advances have been made in the induction of brown fat-like adipocytes (beige) in WAT, which represents an attractive potential strategy for the management and treatment of obesity. Use of natural compounds for browning of white adipocytes can be considered as a safe and novel strategy against obesity. Here, we report that trans-anethole (TA), a flavoring substance present in the essential oils of various plants, alleviated high fat diet (HFD)-induced obesity in mice models via elevation of the expression of beige-specific genes such as Ppargc1α, Prdm16, Ucp1, Cd137, Cited1, Tbx1, and Tmem26. TA also regulated lipid metabolism in white adipocytes via reduction of adipogenesis and lipogenesis as well as elevation of lipolysis and fat oxidation. Moreover, TA exhibited thermogenic activity by increasing mitochondrial biogenesis in white adipocytes and activating brown adipocytes. In addition, molecular docking analysis enabled us to successfully predict core proteins for fat browning such as β3-adrenergic receptor (β3-AR) and sirtuin1 (SIRT1) based on their low binding energy interactions with TA for promotion of regulatory mechanisms. Indeed, agonistic and antagonistic studies demonstrated that TA induced browning of 3T3-L1 adipocytes through activation of β3-AR as well as the AMPK-mediated SIRT1 pathway regulating PPARα and PGC-1α. In conclusion, TA possesses potential therapeutic implications for treatment of obesity by playing multiple modulatory roles in the induction of white fat browning, activation of brown adipocytes, and promotion of lipid catabolism.

The effect of fennel essential oil in combination with antibiotics on Staphylococcus aureus strains isolated from carriers

An increase in the number of staphylococcal infections and carriers among medical staff has forced us to seek more and more effective antibacterial agents. Bacteria from the Staphylococcus genus possessing different mechanisms of resistance are the cause of nosocomial infections. The objective of our investigations was susceptibility of S. aureus strains isolated from nasal vestibule of medical students to fennel essential oil. The GC-MS analysis of fennel essential oil revealed eleven constituents among which a majority of trans-anethole (80%) was found. The D-tests showed iMLS_B (80%), cMLS_B and MS_B (10%) resistant phenotypes of S. aureus. The S. aureus isolates were intermediate to mupirocin (45%). Fennel essential oil increased the inhibition zone around cefoxitin, mupirocin, co-trimoxazole and ciprofloxacin with statistical significance. Our research showed that the fennel essential oil in combination with mupirocin may be considered as a natural alternative in eradication of S. aureus with iMLS_B, cMLS_B, MS_B resistant phenotypes and is able to decrease the growth rate of antibiotic resistance.

Flavored little cigar smoke induces cytotoxicity and apoptosis in airway epithelia

Addition of flavors reduces the harsh taste of tobacco, facilitating the initiation and maintenance of addiction among youths. Flavored cigarettes (except menthol) are now banned. However, the legislation on little cigars remains unclear and flavored little cigars are currently available for purchase. Since inhaled tobacco smoke directly exerts toxic effects on the lungs, we tested whether non-flavored and flavored little cigar smoke exposure had the potential for harm in cultured pulmonary epithelia. We cultured Calu-3 lung epithelia on both 96-well plates and at the air–liquid interface and exposed them to smoke from non-flavored Swisher Sweets and flavored (sweet cherry, grape, menthol, peach and strawberry) Swisher Sweets little cigars. Irrespective of flavor, acute little cigar smoke exposure (10×35 ml puffs) significantly increased cell death and decreased the percentage of live cells. Chronic exposure (10×35 ml puffs per day for 4 days) of smoke to Calu-3 cultures significantly increased lactate dehydrogenase release, further indicating toxicity. To determine whether this exposure was associated with increased cell death/apoptosis, a protein array was used. Chronic exposure to smoke from all types of little cigars induced the activation of the two major apoptosis pathways, namely the intrinsic (mitochondrial-mediated) and the extrinsic (death receptor-mediated) pathways. Both flavored and non-flavored little cigar smoke caused similar levels of toxicity and activation of apoptosis, suggesting that flavored and non-flavored little cigars are equally harmful. Hence, the manufacture, advertisement, sale and use of both non-flavored and flavored little cigars should be strictly controlled.

Anti-ulcer activity of essential oil constituents

Essential oils have attracted considerable worldwide attention over the last few decades. These natural products have wide-ranging pharmacological activities and biotechnological applications. Faced with the need to find new anti-ulcer agents and the great effort on the development of drugs for the treatment of ulcers, in this review, the anti-ulcer activities of 21 bioactive compounds found in essential oils are discussed.

Toxic effects of some synthetic food colorants and/or flavor additives on male rats

The objective of the present work was to evaluate the broadest toxic effect of some synthetic additives of colorants and/or flavors on different body organs and metabolic aspects in rats. A number of chemical food color and flavor additives are routinely added during processing to improve the aesthetic appearance of the dietary items. However, many of them are toxic after prolonged use. In this experiment, a total of 100 male albino rats of Spargue Dawley strain were divided into 10 groups: G(1) was fed basal diet and served as control, G(2): basal diet + Brilliant blue (blue dye, No. 2, 124 mg/kg diet), G(3): basal diet + carmoisine (red dye, No. 3, 70 mg/kg diet), G(4): basal diet + tartrazine (yellow dye, FD & C yellow No. 5, 75 mg/kg diet), G(5): basal diet + trans-anethole (4.5 g/kg diet) G(6): basal diet + propylene glycol (0.25 g/kg diet), G(7): basal diet + vanillin(1.25 g/kg diet), G(8): basal diet + Brilliant blue + propylene glycol, G(9): basal diet + carmoisine + trans-anethole, G(10): basal diet + tartrazine + vanillin for 42 successive days. All food colorants mixed with or without flavor additives induced a significant decrease in body weight, hemoglobin concentration and red blood cell count. Also there was a significant decrease in reduced glutathione content; glutathione-S-transferase and superoxide dismutase activities in both blood and liver compared to control group. On the other hand, a significant increase in serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase activities, bilirubin, urea, creatinine, total protein and albumin were observed in all test groups when compared to control group. Finally, it is advisable to limit the uses of these food colorants and/or food flavor additives especially those used by children.

Potentiation of fungicidal activities of trans-anethole against Saccharomyces cerevisiae under hypoxic conditions

A naturally occurring phenylpropanoid, trans-anethole (anethole), was assayed for its fungicidal activity in Saccharomyces cerevisiae grown under hypoxic and aerobic conditions. Anethole killed the growing cells in malt extract broth only under hypoxic conditions. Anethole did not exhibit fungicidal effects against non-growing cells. The cells of a mitochondrial-DNA-lacking rho0 mutant, which grew fermentatively even in the presence of O2, were killed by anethole regardless of aeration. The fungicidal potency of anethole against a strain capable of respiration under aerobic conditions was enhanced by the addition of a respiratory inhibitor antimycin A3. Therefore, anethole possibly expresses fungicidal activities only against fermentatively growing cells of S. cerevisiae.

Criteria for the safety evaluation of flavoring substances

The current status of the GRAS evaluation program of flavoring substances operated by the Expert Panel of FEMA is discussed. The Panel maintains a rigorous rotating 10-year program of continuous review of scientific data related to the safety evaluation of flavoring substances. The Panel concluded a comprehensive review of the GRAS (GRASa) status of flavors in 1985 and began a second comprehensive review of the same substances and any recently GRAS materials in 1994. This second re-evaluation program of chemical groups of flavor ingredients, recognized as the GRAS reaffirmation (GRASr) program, is scheduled to be completed in 2005. The evaluation criteria used by the Panel during the GRASr program reflects the significant impact of advances in biochemistry, molecular biology and toxicology that have allowed for a more complete understanding of the molecular events associated with toxicity. The interpretation of novel data on the relationship of dose to metabolic fate, formation of protein and DNA adducts, enzyme induction, and the cascade of cellular events leading to toxicity provides a more comprehensive basis upon which to evaluate the safety of the intake of flavor ingredients under conditions of intended use. The interpretation of genotoxicity data is evaluated in the context of other data such as in vivo animal metabolism and lifetime animal feeding studies that are more closely related to actual human experience. Data are not viewed in isolation, but comprise one component that is factored into the Panel's overall safety assessment. The convergence of different methodologies that assess intake of flavoring substances provides a greater degree of confidence in the estimated intake of flavor ingredients. When these intakes are compared to dose levels that in some cases result in related chemical and biological effects and the subsequent toxicity, it is clear that exposure to these substances through flavor use presents no significant human health risk.

Concentrations of nine alkenylbenzenes, coumarin, piperonal and pulegone in Indian bidi cigarette tobacco

Indian-made bidi cigarettes sold in the United States are available in a variety of exotic (e.g. clove, mango) and candy-like (e.g. chocolate, raspberry) flavors. Because certain tobacco flavorings contain alkenylbenzenes and other toxic or carcinogenic chemicals, we measured the concentration of flavor-related compounds in bidi tobacco using a previously developed method. Twenty-three brands of bidis were sampled using automated headspace solid-phase microextraction and subsequently analyzed for 12 compounds by gas chromatography-mass spectrometry. Two alkenylbenzene compounds, trans-anethole and eugenol, were found in greater than 90% of the brands analyzed. Methyleugenol, pulegone and estragole were each detected in 30% or more of the brands, whereas safrole and elemicin were not detected in any of the brands. The flavor-related compounds with the highest tobacco concentrations were eugenol (12,000 microg/g tobacco) and trans-anethole (2200 microg/g tobacco). The highest eugenol and trans-anethole concentrations found in bidi tobacco were about 70,000 and 7500 times greater, respectively, than the highest levels previously found in US cigarette brands. Measurement of these compounds is crucial to evaluation of potential risks associated with inhaling highly concentrated flavor-related compounds from bidis or other tobacco products.

Focal nodular hyperplasia of the liver after intraconazole treatment

A 38-year-old woman developed focal nodular hyperplasia of the liver after she had received a 4-month treatment with intraconazole 200 mg/d for a fungal infection of her fingernails. Because the patient underwent yearly liver ultrasound examinations because of the removal of a breast carcinoma, when the tumor was discovered incidentally, it was clear that it had developed within the past year after she had begun receiving intraconazole. Although various chemical agents and drugs have been considered as possible etiologic factors in the development of focal nodular hyperplasia of the liver, cases occurring after intraconazole therapy have not been reported before. Apart from the theoretical considerations with regard to the pathogenesis of nodular hyperplasia of the liver, this case could gain practical importance, as it shows a new adverse effect of a drug that has been used in more than 34 million patients over the past 10 years. Furthermore, this case should draw attention to the possibility of drug-induced benign hepatic tumors, as they may mimic malignant and metastatic disorders, which might be especially alarming in patients undergoing routine examinations after removal of malignant tumors, such as our patient.

Solid phase microextraction of alkenylbenzenes and other flavor-related compounds from tobacco for analysis by selected ion monitoring gas chromatography-mass spectrometry

Some constituents found in natural flavorings are known to exhibit toxic properties. We developed a rapid method for quantifying 12 flavor-related compounds in cigarette tobacco using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. Using selected ion monitoring, we quantified and positively identified coumarin; pulegone; piperonal and nine alkenylbenzenes, including trans-anethole, safrole, methyleugenol and myristicin in one or more brands of cigarettes. In 62% of 68 brands analyzed, we detected one or more of the flavor-related compounds ranging from 0.0018 to 43 microg/g. Toxic properties of these flavor-related compounds may constitute an additional health risk related to cigarette smoking.

The FEMA GRAS assessment of trans-anethole used as a flavouring substance. Flavour and Extract Manufacturer's Association

This publication is the fourth in a series of safety evaluations performed by the Expert Panel of the Flavour and Extract Manufacturers' Association (FEMA). In 1993, the Panel initiated a comprehensive program to re-evaluate the safety of more than 1700 GRAS flavouring substances under conditions of intended use. In this review, scientific data relevant to the safety evaluation of trans-anethole (i.e. 4-methoxypropenylbenzene) as a flavouring substance is critically evaluated by the FEMA Expert Panel. The evaluation uses a mechanism-based approach in which production of the hepatotoxic metabolite anethole epoxide (AE) is used to interpret the pathological changes observed in different species and sexes of laboratory rodents in chronic and subchronic dietary studies. Female Sprague Dawley rats metabolize more trans-anethole to AE than mice or humans and, therefore, are the most conservative model for evaluating the potential for AE-induced hepatotoxicity in humans exposed to trans-anethole from use as a flavouring substance. At low levels of exposure, trans-anethole is efficiently detoxicated in rodents and humans primarily by O-demethylation and omega-oxidation, respectively, while epoxidation is only a minor pathway. At high dose levels in rats, particularly females, a metabolic shift occurs resulting in increased epoxidation and formation of AE. Lower activity of the "fast" acting detoxication enzyme epoxide hydrolase in the female is associated with more pronounced hepatotoxicity compared to that in the male. The continuous intake of high dose levels of trans-anethole (i.e. cumulative exposure) has been shown in dietary studies to induce a continuum of cytotoxicity, cell necrosis and cell proliferation. In chronic dietary studies in rats, hepatotoxicity was observed when the estimated daily hepatic production of AE exceeded 30 mg AE/kg body weight. In female rats, chronic hepatotoxicity and a low incidence of liver tumours were reported at a dietary intake of 550 mg trans-anethole/kg body weight/day. Under these conditions, daily hepatic production of AE exceeded 120 mg/kg body weight. Additionally, neither trans-anethole nor AE show any evidence of genotoxicity. Therefore, the weight of evidence supports the conclusion that hepatocarcinogenic effects in the female rat occur via a non-genotoxic mechanism and are secondary to hepatotoxicity caused by continuous exposure to high hepatocellular concentrations of AE. trans-Anethole was reaffirmed as GRAS (GRASr) based on (1) its low level of flavour intake (54 microg/kg body weight/day); (2) its metabolic detoxication pathway in humans at levels of exposure from use as a flavouring substance; (3) the lack of mutagenic or genotoxic potential; (4) the NOAEL of 120 mg trans-anethole/kg body weight/day in the female rat reported in a 2 + -year study which produces a level of AE (i.e. 22 mg AE/kg body weight/day) at least 10,000 times the level (0.002 mg AE/kg body weight day) produced from the intake of trans-anethole from use as a flavouring substance; and (5) the conclusion that a slight increase in the incidence of hepatocellular tumours in the high dose group (550 mg trans-anethole/kg body weight/day) of female rats was the only significant neoplastic finding in a 2+ -year dietary study. This finding is concluded to be secondary to hepatotoxicity induced by high hepatocellular concentrations of AE generated under conditions of the study. Because trans-anethole undergoes efficient metabolic detoxication in humans at low levels of exposure, the neoplastic effects in rats associated with dose-dependent hepatotoxicity are not indicative of any significant risk to human health from the use of trans-anethole as a flavouring substance.

Oesophageal cancer in France: potential importance of hot alcoholic drinks

In France, major geographic variation exists in the incidence of oesophageal cancer, the highest incidence being reported in Normandy and Brittany. The role of alcohol in the risk of oesophageal cancer is well established in Western countries. One possible explanation for geographical variation of incidence is that higher incidence of oesophageal cancer is due to specific local alcoholic beverages. The aim of this study was to determine whether different types of alcoholic beverages exert different effects on the risk of oesophageal cancer, and whether the variation of incidence in France is due to variation in local drinking behaviour. We conducted a multicentre case-control study in 3 regions of France (Normandy, Burgundy and Midi-Pyrenees), among which there is a 5-fold variation in incidence. We selected 208 cases and 399 controls, all males. During the interview, the subject's entire alcohol history was reconstituted, noting each type of alcoholic beverage consumed throughout life. The link between the risk of oesophageal cancer and alcohol varies greatly according to the type of alcoholic beverage, with aniseed aperitifs, hot spirits (especially hot Calvados) and beer carrying the highest risk. Consumption of hot Calvados appeared to explain about 2/3 of the inter-regional and urban/rural differences in incidence, whereas total alcohol intake explained less than 1/5. Even after adjustment for all other alcoholic beverages, consumption of hot calvados explained almost half of the peak in incidence of oesophageal cancer in the Northwest of France, as well as half of the urban/rural differences in incidence.

Lack of influence of modulators of epoxide metabolism on the genotoxicity of trans-anethole in freshly isolated rat hepatocytes assessed with the unscheduled DNA synthesis assay

The aniseed food flavour trans-anethole was implicated as a weak hepatocarcinogen only in female Sprague Dawley-CD rats administered high doses (1% in the diet for 121 wk). However, this substance is apparently non-genotoxic in a range of test systems. Anethole is metabolized in the rat along three primary pathways, one of which is epoxidation across the double bond of the side-chain. The epoxides of a number of the alkenylbenzene family of food flavours, of which anethole is a member, are putative genotoxins, being bacterial mutagens but not mammalian carcinogens. The authors have previously shown that the cytotoxicity of anethole is enhanced when the cellular epoxide defence mechanisms of conjugation with reduced glutathione and hydration by cytosolic epoxide hydrolase are severely compromised. They now report, however, that modulation of epoxide metabolism in cultured cells by the same mechanisms fails to induce unscheduled DNA synthesis (UDS) by anethole nor was there a UDS response in hepatocytes of female rats dosed with anethole in vivo. The epoxide of anethole was synthesized for the first time in this investigation and tested directly. As expected, it was markedly cytotoxic but not genotoxic. Anethole epoxide has chemical characteristics that differ from those of other structurally similar epoxides being labile to hydrolysis in aqueous media at physiological pH and temperature. This gives greater relevance to tests of its genotoxicity after formation within the hepatocyte rather than by adding the epoxide extracellularly to the culture medium. The direct and indirect demonstration of the lack of induction of UDS by anethole epoxide provides further support for the hypothesis that marginal hepatocarcinogenicity observed in female rats given 1% anethole in the diet for 121 wk was not initiated by a genotoxic event.

Genotoxicity of trans-anethole in vitro

Trans-anethole genotoxicity has been evaluated previously both in vitro and in vivo. To ascertain the reproducibility and relevance of previously conducted gene mutation studies, the Salmonella/microsome test and the L5178Y mouse lymphoma TK+/- assay were repeated according to the protocols that previously produced positive results. For the mouse lymphoma TK+/- assay, standard conditions were employed. For the Salmonella/microsome tests, however, metabolic cofactors were supplemented relative to standard protocols. In addition, trans-anethole was evaluated for its ability to induce chromosome aberrations in vitro in Chinese hamster ovary cells. The results presented here indicate that trans-anethole does not increase the mutant frequency in the Salmonella/microsome test, whereas a dose-related response was confirmed in the L5178Y mouse lymphoma TK+/- assay with metabolic activation. The metabolic conditions used in each of the published gene mutation assays may explain the various responses to trans-anethole. Trans-anethole did not induce chromosome aberrations in Chinese hamster ovary cells. The molecular nature of the genetic change induced in mouse lymphoma cells by trans-anethole has not been identified but the available genotoxicity data are consistent with either a recombination event or a non-DNA reactive mechanism. Considering the trans-anethole genotoxicity data base as a whole, including the positive response observed only in the L5178Y mouse lymphoma TK+/- assay, the irreproducible response in the Salmonella/microsome test, the negative result in the chromosome aberration test in vitro and the results from 32P-postlabeling studies in vivo, as well as the occurrence of liver tumors in the rat bioassay only at doses which exceeded the MTD and caused significant liver toxicity, repeated toxic insult followed by compensatory cell proliferation is favored as an underlying mechanism for the observed rat tumorigenic response.

Effects of the naturally occurring alkenylbenzenes eugenol and trans-anethole on drug-metabolizing enzymes in the rat liver

In order to study the effects of trans-anethole and eugenol on drug-metabolizing enzyme activities in vivo, male Wistar rats were treated by gavage with trans-anethole (125 or 250 mg/kg body weight) or eugenol (250, 500 or 1000 mg/kg body weight) daily for 10 days. In liver microsomes and cytosol various phase-I and phase-II biotransformation enzyme activities were determined. No effect on total cytochrome P-450 content in liver microsomes from rats treated with eugenol or trans-anethole was observed. Administration of 1000 mg eugenol/kg body weight, but not the lower doses, significantly increased cytochrome P-450-dependent 7-ethoxy-resorufin O-deethylation (EROD) and 7-pentoxyresorufin O-depentylation (PROD); administration of trans-anethole (125 or 250 mg/kg body weight) did not alter EROD and PROD activities. In rat liver cytosol, UDP-glucuronyl transferase (GT) activity towards the substrate 4-chlorophenol was significantly increased in all treated rats, and activity towards 4-hydroxybiphenyl as substrate was significantly increased in rats treated with 250 mg trans-anethole/kg or with 500 or 1000 mg eugenol/kg. DT-diaphorase (DTD) activity was only significantly enhanced in the liver cytosol of rats treated with trans-anethole at 250 mg/kg body weight. Enhancement of cytosolic glutathione S-transferase (GST) activity towards 1-chloro-2,4-dinitrobenzene was found for all eugenol- and trans-anethole-treated rats. In addition, significantly increased levels of GST subunit 2 were measured by HPLC in the liver cytosol of rats treated with eugenol (500 or 1000 mg/kg body eight) or trans-anethole (250 mg/kg body weight). It is concluded that both eugenol and trans-anethole preferentially induced phase II biotransformation enzymes in rat liver in vivo.

Perspective on the usefulness of the mouse lymphoma assay as an indicator of a genotoxic carcinogen: ten compounds which are positive in the mouse lymphoma assay but are not genotoxic carcinogens

The mouse lymphoma assay is commonly included in batteries of tests for the mutagenic and carcinogenic potential of chemicals. Unlike other bacterial and mammalian cell tests, it has an unacceptably high incidence of false positive results. This paper reviews data on ten chemicals, all of which are positive in the mouse lymphoma assay but negative in all other genotoxicity tests. Three are non-genotoxic rodent carcinogens acting through a variety of secondary mechanisms, while seven are not carcinogenic. It is concluded that a positive mouse lymphoma assay alone cannot be a barrier to the human use of drugs and other chemicals.

Influence of modulators of epoxide metabolism on the cytotoxicity of trans-anethole in freshly isolated rat hepatocytes

The effect of modulating epoxide metabolism by inhibiting microsomal and cytosolic epoxide hydrolases and depleting glutathione, on the cytotoxicity of trans-anethole has been examined in freshly isolated rat hepatocytes in suspension. Hepatocytes derived from female Sprague-Dawley CD rats by collagenase perfusion were incubated in suspension and sampled at intervals over a 6-hr period. Cytotoxicity was assessed by the leakage of lactate dehydrogenase into the culture medium and in the cells after lysis. Glutathione was determined by fluorimetry. Anethole showed a dose-dependent cytotoxicity at concentrations ranging from 5 x 10(-4) to 5 x 10(-3) M, with concentrations of 10(-3) M and above causing greater than 63% leakage of lactate dehydrogenase in 6 hr. Microsomal epoxide hydrolase was inhibited by trichloropropene oxide (10(-4) M) and cyclohexene oxide (10(-3) M), and cytosolic epoxide hydrolase by 4-fluorochalcone oxide (5 x 10(-4) M). Cellular glutathione was depleted by diethyl maleate (5 x 10(-4) M), and its synthesis inhibited by 2.5 x 10(-3) M-L-buthionine (S,R)-sulphoximine. Suspensions treated with a sub-cytotoxic concentration of anethole (5 x 10(-4) M) showed a rapid increase in cytotoxicity when 4-fluorochalcone oxide was present (complete loss of viability within 2 hr), while pretreatment of hepatocytes with diethyl maleate in combination with buthionine sulphoximine, to deplete glutathione, slowly increased the cytotoxic response at later times (after 4 hr of incubation). The association of the effects of 4-fluorochalcone oxide with the inhibition of cytosolic epoxide hydrolase is strengthened by the inability of chalcone oxide, a close structural analogue of 4-fluorochalcone oxide, which has no effect on epoxide hydrolase or glutathione conjugation, to influence the effects of anethole on hepatocytes. These data are discussed in terms of the role of anethole epoxide in the cytotoxicity of trans-anethole.

Structure-specificity of the genotoxicity of some naturally occurring alkenylbenzenes determined by the unscheduled DNA synthesis assay in rat hepatocytes

A number of alkenylbenzenes related to safrole and estragole are known to be hepatocarcinogenic in rats and/or mice, apparently by a genotoxic mechanism. However, they are not bacterial mutagens in the Ames test. We have studied the ability of a series of carcinogenic and non-carcinogenic congeners to induce unscheduled DNA synthesis (UDS) in freshly isolated rat hepatocytes in primary culture. The cytotoxicity of these compounds was assessed by lactate dehydrogenase leakage. There was an excellent correlation between UDS induction and known rodent hepatocarcinogenicity, with safrole, estragole and methyleugenol all inducing UDS. Anethole, isosafrole, eugenol and allylbenzene, for which evidence of carcinogenicity is equivocal or negative, did not induce UDS. All compounds were markedly cytotoxic at concentrations between 10(-3) and 10(-2) M, irrespective of their structural features. The data are discussed with reference to the known structure dependence of the disposition of the alkenylbenzenes, notably their metabolic activation, with which there are excellent correlations. The demonstration of the genotoxicity of rodent hepatocarcinogenic alkenylbenzenes in cells cultured from the in vivo target organ will allow the direct investigation of factors influencing these processes and facilitate the safety evaluation of these important natural flavours.

Histopathological evaluation of proliferative liver lesions in rats fed trans-anethole in chronic studies

In a two-year study of rats fed trans-anethole--a flavouring that is Generally Recognized As Safe by the US Food and Drug Administration--a slight increase in proliferative lesions of the liver was observed. These results were reviewed by a Pathology Working Group (PWG) and their findings are detailed here. The increased incidence of non-neoplastic lesions in male and female rats fed 0.25, 0.5 or 1.0% trans-anethole was considered by the PWG to be treatment related. Male and female rats fed 0.25% trans-anethole in their diet (25 to 29 times the postulated maximum human intake) had no significant treatment-related microscopic lesions in the liver, although there was a slight increase in parenchymal cell hyperplasia. Rats fed 0.5% trans-anethole had hepatic changes consistent with those caused by chronic exposure of rodents to compounds with enzyme-inducing activity. Male and female rats fed 1.0% trans-anethole revealed increased incidence and severity of hepatic changes as seen in the mid-dose rats, and a low incidence of hepatocellular neoplasms. These neoplasms were not increased in male rats in any dietary group or in female rats of the low- (0.25%) and mid-dose (0.5%) groups. The slightly increased incidence of hepatocellular neoplasms in the high-dose females is not considered to be of significance to human safety and it is concluded that trans-anethole does not constitute a carcinogenic risk for man. The slightly increased tumour incidence was seen only in the highest dose group of one sex; it has not been observed in studies of mice fed trans-anethole--the metabolism of trans-anethole in the mouse is similar to that in man. The extremely high exposure was associated with other liver changes which may have contributed to the findings.