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

Interactions of Betel Quid Constituents with Drug Disposition Pathways: An Overview

Global estimates indicate that over 600 million individuals worldwide consume the areca (betel) nut in some form. Nonetheless, its consumption is associated with a myriad of oral and systemic ailments, such as precancerous oral lesions, oropharyngeal cancers, liver toxicity and hepatic carcinoma, cardiovascular distress, and addiction. Users commonly chew slivers of areca nut in a complex consumable preparation called betel quid (BQ). Consequently, the user is exposed to a wide array of chemicals with diverse pharmacokinetic behavior in the body. However, a comprehensive understanding of the metabolic pathways significant to BQ chemicals is lacking. Henceforth, we performed a literature search to identify prominent BQ constituents and examine each chemical's interplay with drug disposition proteins. In total, we uncovered over 20 major chemicals (e.g., arecoline, nicotine, menthol, quercetin, tannic acid) present in the BQ mixture that were substrates, inhibitors, and/or inducers of various phase I (e.g., CYP, FMO, hydrolases) and phase II (e.g., GST, UGT, SULT) drug metabolizing enzymes, along with several transporters (e.g., P-gp, BCRP, MRP). Altogether, over 80 potential interactivities were found. Utilizing this new information, we generated theoretical predictions of drug interactions precipitated by BQ consumption. Data suggests that BQ consumers are at risk for drug interactions (and possible adverse effects) when co-ingesting other substances (multiple therapeutic classes) with overlapping elimination mechanisms. Until now, prediction about interactions is not widely known among BQ consumers and their clinicians. Further research is necessary based on our speculations to elucidate the biological ramifications of specific BQ-induced interactions and to take measures that improve the health of BQ consumers.

Essential Oils as Multicomponent Mixtures and Their Potential for Human Health and Well-Being

Essential oils (EOs) and their individual volatile organic constituents have been an inherent part of our civilization for thousands of years. They are widely used as fragrances in perfumes and cosmetics and contribute to a healthy diet, but also act as active ingredients of pharmaceutical products. Their antibacterial, antiviral, and anti-inflammatory properties have qualified EOs early on for both, the causal and symptomatic therapy of a number of diseases, but also for prevention. Obtained from natural, mostly plant materials, EOs constitute a typical example of a multicomponent mixture (more than one constituent substances, MOCS) with up to several hundreds of individual compounds, which in a sophisticated composition make up the property of a particular complete EO. The integrative use of EOs as MOCS will play a major role in human and veterinary medicine now and in the future and is already widely used in some cases, e.g., in aromatherapy for the treatment of psychosomatic complaints, for inhalation in the treatment of respiratory diseases, or topically administered to manage adverse skin diseases. The diversity of molecules with different functionalities exhibits a broad range of multiple physical and chemical properties, which are the base of their multi-target activity as opposed to single isolated compounds. Whether and how such a broad-spectrum effect is reflected in natural mixtures and which kind of pharmacological potential they provide will be considered in the context of ONE Health in more detail in this review.

Synergic effects of aerobic exercise and eugenol supplement on germ cell development and testicular tissue structure in chlorpyrifos-treated animal model

Insecticide chlorpyrifos (CPF) with increased oxidative stress, structural destruction, and hemostasis of testicular tissue leads to male infertility. The present study investigated the protective effect of exercise (Exe) and eugenol supplementation (Sup) on CPF-induced testicular spermatogenic disorders in male rats. In this experimental study, 21 adult male albino rats were divided into seven groups, control (Co: 6 weeks), CPF (6 weeks), Co + Oil (2 weeks healthy food and 4 weeks oil), Co + Dimethylsulfoxide (DMSO: 6 weeks), CPF + Sup (2 weeks CPF and 4 weeks CPF + Sup), CPF + Exe (2 weeks CPF and 4 weeks CPF + Exe), and CPF + Exe + Sup (2 weeks CPF and 4 weeks CPF + Exe + Sup) group. All treatments were done intraperitoneally (5 days a week). Exe groups were subjected to run at moderate exercise intensity for 5 days per week over 6 weeks. DMSO groups were administered to the equal volume of vehicle for 6 consecutive weeks. Finally, the animals were sacrificed with Co2 gas and then alterations in testicular histology and sperm parameters were evaluated. Protein expression of PLZF and IGFα in the CPF group showed a significant decrease compared with the control group (p ˂ 0.001 for both). It was shown that CPF + Exe + Sup (p ˂ 0.001) and CPF + Sup (p ˂ 0.01) groups had a significant increase in protein expression of PLZF, but the protein expression of IGFα showed a significant increase just in the CPF + Exe + Sup group (p ˂ 0.001). Also, CPF caused a significant decrease in Leydig counts, Sertoli cell count, spermatogonium counts, spermatocyte cell count, spermatid cell count, and tunica thickness as well as a significant increase in testicle diameter (p ˂ 0.01) and ducts diameter compared with the control group. It seems that aerobic exercise with eugenol supplementation suppresses the disruption effects of CPF on testicular tissue (cellular and structural) by increasing the antioxidant capacity and improving the secretion of sex hormones. Therefore, the aerobic exercise with supplement of the eugenol has potential therapeutic targets for male infertility that need further study.

The Dual Antioxidant/Prooxidant Effect of Eugenol and Its Action in Cancer Development and Treatment

The formation of reactive oxygen species (ROS) during metabolism is a normal process usually compensated for by the antioxidant defense system of an organism. However, ROS can cause oxidative damage and have been proposed to be the main cause of age-related clinical complications and diseases such as cancer. In recent decades, the relationship between diet and cancer has been more studied, especially with foods containing antioxidant compounds. Eugenol is a natural compound widely found in many aromatic plant species, spices and foods and is used in cosmetics and pharmaceutical products. Eugenol has a dual effect on oxidative stress, which can action as an antioxidant or prooxidant agent. In addition, it has anti-carcinogenic, cytotoxic and antitumor properties. Considering the importance of eugenol in the area of food and human health, in this review, we discuss the role of eugenol on redox status and its potential use in the treatment and prevention of cancer.

Use of Polyphenolic Compounds in Dermatologic Oncology

Polyphenols are a widely used class of compounds in dermatology. While phenol itself, the most basic member of the phenol family, is chemically synthesized, most polyphenolic compounds are found in plants and form part of their defense mechanism against decomposition. Polyphenolic compounds, which include phenolic acids, flavonoids, stilbenes, and lignans, play an integral role in preventing the attack on plants by bacteria and fungi, as well as serving as cross-links in plant polymers. There is also mounting evidence that polyphenolic compounds play an important role in human health as well. One of the most important benefits, which puts them in the spotlight of current studies, is their antitumor profile. Some of these polyphenolic compounds have already presented promising results in either in vitro or in vivo studies for non-melanoma skin cancer and melanoma. These compounds act on several biomolecular pathways including cell division cycle arrest, autophagy, and apoptosis. Indeed, such natural compounds may be of potential for both preventive and therapeutic fields of cancer. This review evaluates the existing scientific literature in order to provide support for new research opportunities using polyphenolic compounds in oncodermatology.

Review of Scientific Evidence of Medicinal Convoy Plants in Traditional Persian Medicine

One concept used in traditional Persian medicine (TPM) for multidrug therapy is that of the convoy drug (Mobadregh). According to TPM texts, convoy drugs are substances (or drugs), which facilitate the access of drugs or foods to the whole body or to specific organs. This study reviewed some convoy drugs presented in TPM, their biological effects, and their probable interactions with main drugs, considering the increased absorption through inhibition of P-glycoprotein (P-gp) efflux function, bioavailability-enhancing effects, and decreased metabolism of the main drug using electronic databases including PubMed, Scopus, ScienceDirect, and Google Scholar in November and December, 2013. Recent studies have proven the beneficial effects of Crocus sativus L. (saffron) and camphor on the heart and brain, the cerebral therapeutic effects of Asarum europaeum (hazelwort), the hepatoprotective effects of Cichorium intybus (chicory), and Apium graveolens (celery) seeds, and the diuretic effects of Cinnamomum zeylanicum (cinnamon), and Cucumis melo (melon) seeds. The effects of vinegar in targeting the liver and brain have also been demonstrated. An evaluation of the results demonstrated that the suggested convoy drugs, including Piper nigrum (black pepper), Piper longum (long pepper), red wine, Camellia sinensis (tea), hazelwort, Mentha longifolia (pennyroyal), Anethum graveolens (dill), Foeniculum vulgare (fennel), cinnamon, and Sassafras albidum (sassafras) can increase the bioavailability of coadministered drugs by inhibition of P-gp or cytochrome P450s (CYP450s) or both of them. This evidence could be a good basis for the use of these agents as convoys in TPM.

Citral and eugenol modulate DNA damage and pro-inflammatory mediator genes in murine peritoneal macrophages

Citral and eugenol have been broadly studied because of their anti-inflammatory, antioxidant and antiparasitic potentials. In this study, the effects of citral (25, 50 and 100 µg/mL) and eugenol (0.31, 0.62, 1.24 and 2.48 µg/mL) on the expression (RT-PCR) of the pro-inflammatory mediator genes NF-κB1, COX-2 and TNF-α were evaluated in mouse peritoneal macrophages with or without activation by a bacterial lipopolysaccharide (LPS). Additionally, the genotoxic potentials of two compounds and their capacities to modulate the DNA damage induced by doxorubicin (DXR) were investigated using the comet assay. The data revealed that neither citral nor eugenol changed COX-2, NF-κB1 or TNF-α expression in resting macrophages. However, in LPS-activated cells, citral induced the hypoexpression of COX-2 (100 µg/mL) and TNF-α (50 and 100 µg/mL). Hypoexpression of TNF-α was also detected after cellular exposure to eugenol at the highest concentration (2.48 µg/mL). Both compounds exhibited genotoxic potential (citral at 50 and 100 µg/mL and eugenol at all concentrations) but also showed chemopreventive effects, in various treatment protocols. Both citral and eugenol might modulate inflammatory processes and DXR-induced DNA damage, but the use of these compounds must be viewed with caution because they are also able to induce primary DNA lesions.

The influence of essential oil of aniseed (Pimpinella anisum, L.) on drug effects on the central nervous system

Anise (Pimpinella anisum L.; Apiaceae) and its essential oil have been widely used in folk medicine, pharmacy and food industry. Since there are some data about the impact of anise on functions of central nervous system (CNS), the issue of possible interactions with drugs acting in CNS should be considered. This survey aimed to examine the influence of aniseed essential oil (EO) intake on the effects of drugs that act in CNS. The chemical profile of essential oil determined by GC-MS revealed as the main components: trans-anethole (88.49%), γ-himachalene (3.13%), cis-isoeugenol (1.99%), and linalool (1.79%). The effects of codeine, diazepam, midazolam, pentobarbital, imipramine and fluoxetine were tested in mice after 5days of peroral pretreatment with human equivalent dose of aniseed EO (0.3mg/kg). The intake of EO led to significant increase of analgesic effect of codeine. The motor impairment caused by midazolam was enhanced in the group treated by EO. The application of diazepam decreased the number and percentage of entries in open arm in elevated maze plus test in the group pretreated with EO indicating augmented effect of drug on motor activity. EO pretreatment caused significant shortage of pentobarbital induced sleeping time when compared to control. The decrease in antidepressant effect of imipramine and fluoxetine was diminished by the pretreatment with aniseed EO. Based on the results of this study we conclude that concomitant intake of aniseed EO preparations and drugs that act on CNS should be avoided due to potential herb-drug interactions, which also need further clinical confirmation.

Cross talk between keratinocytes and dendritic cells: impact on the prediction of sensitization

Understanding the mechanistic aspects involved in sensitization by chemicals will help to develop relevant preventive strategies. Many potential sensitizers are not directly immunogenic but require activation outside or inside the skin by nonenzymatic oxidation (prehaptens) or metabolic transformation (prohaptens) prior to being able to induce an immune response. This necessary activation step has not yet been actively integrated into a cell line-based prediction approach. We cocultured HaCaT keratinocytes with THP-1 as dendritic cell-like cells allowing intercellular interactions. The sensitizing potential was determined by analyzing differences in the expression of CD86, CD40, and CD54 on cocultured THP-1 cells. This new assay setup allowed (1) to distinguish irritants from allergens without influencing cell viability and (2) to discriminate pre/prohaptens from haptens. Under coculture conditions, the prohaptens eugenol, 2-methoxy-4-methylphenol, and benzo[a]pyrene induced a significantly higher upregulation of CD86 expression on THP-1. In agreement with the hapten concept, responses to 2,4-dinitrochlorobenzene, Bandrowski's base, and the prehapten isoeugenol were not significantly modified. Inhibition of cytochrome P450 or NAD(P)H:quinone oxidoreductase (NQO1) activity reduced the prohapten-mediated upregulation of CD86 on cocultured THP-1 cells. This coculture assay allowing cross talk between HaCaT and THP-1 cells appears to be suitable for the detection of prohaptens, is reproducible, easy to perform, and avoids donor variations. In addition, this assay is a promising approach to understand the impact of cross talk on the prediction of sensitization and once established may be integrated in a future in vitro toolbox to detect potential skin sensitizers and may thus contribute to reduce animal testing.

Anethole exerts antimetatstaic activity via inhibition of matrix metalloproteinase 2/9 and AKT/mitogen-activated kinase/nuclear factor kappa B signaling pathways

Anethole is known to possess anti-inflammatory and anti-tumor activities and to be a main constituent of fennel, anise, and camphor. In the present study, we evaluated anti-metastatic and apoptotic effects of anethole on highly-metastatic HT-1080 human fibrosarcoma tumor cells. Despite weak cytotoxicity against HT-1080 cells, anethole inhibited the adhesion to Matrigel and invasion of HT-1080 cells in a dose-dependent manner. Anethole was also able to down-regulate the expression of matrix metalloproteinase (MMP)-2 and -9 and up-regulate the gene expression of tissue inhibitor of metalloproteinase (TIMP)-1. The similar inhibitory effect of anethole on MMP-2 and -9 activities was confirmed by zymography assay. Furthermore, anethole significantly decreased mRNA expression of urokinase plasminogen activator (uPA), but not uPA receptor (uPAR). In addition, anethole suppressed the phosphorylation of AKT, extracellular signal-regulated kinase (ERK), p38 and nuclear transcription factor kappa B (NF-κB) in HT-1080 cells. Taken together, our findings indicate that anethole is a potent anti-metastatic drug that functions through inhibiting MMP-2/9 and AKT/mitogen-activated protein kinase (MAPK)/NF-κB signal transducers.

Isoeugenol suppression of inducible nitric oxide synthase expression is mediated by down-regulation of NF-kappaB, ERK1/2, and p38 kinase

Isoeugenol, which is a naturally occurring o-methoxyphenol in a variety of foods and essential oils, is known to have anti-inflammatory effects, although the mechanism is not clear. In the present study, we investigated the effect of isoeugenol on NF-kappaB signaling leading to inducible nitric oxide synthase (iNOS) expression in RAW 264.7 murine macrophages stimulated with lipopolysaccharide (LPS). Isoeugenol markedly inhibited nitric oxide (NO) production in dose- and time-dependent manners. The decrease in NO production was found to correlate with a decrease in iNOS expression, as determined by Western blot analysis and real-time RT-PCR. To characterize further the inhibitory mechanisms of isoeugenol at the transcriptional level, we examined the DNA-binding and transcriptional activities of NF-kappaB. Isoeugenol inhibited NF-kappaB-dependent transcriptional activity and DNA-binding activity by decreasing the nuclear translocation of p65, which is a component of NF-kappaB. In addition, isoeugenol blocked signaling upstream of NF-kappaB activation, such as degradation of I-kappaBalpha and the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK), in LPS-stimulated RAW 264.7 cells. The isoeugenol analogues eugenol and allylbenzene also inhibited LPS-induced NF-kappaB signaling and iNOS expression, albeit with less potency than isoeugenol. These results suggest that isoeugenol and its analogues inhibit NO production and iNOS expression in LPS-stimulated RAW 264.7 cells, and that these effects are mediated, at least in part, by blocking the phosphorylation of ERK1/2 and p38 kinase, degradation of I-kappaBalpha, and activation of NF-kappaB.

Eugenol inhibit 7,12-dimethylbenz[a]anthracene-induced genotoxicity in MCF-7 cells: Bifunctional effects on CYP1 and NAD(P)H:quinone oxidoreductase

Typically, chemopreventive agents either inhibit the cytochrome P450s (CYPs) that are essential for the metabolism of carcinogens or induce phase II detoxifying enzymes. This study examined the chemopreventive effect of eugenol on 7,12-dimethylbenz[a]anthracene (DMBA)-induced DNA damage in MCF-7 cells. Eugenol inhibited the formation of the DMBA-DNA adduct in a dose dependent manner. CYP1A1 and CYP1B1 activity, which catalyze the biotransformation of DMBA, were strongly inhibited by eugenol. Eugenol also suppressed the CYP1A induction by DMBA through decreased aryl hydrocarbon receptor activation and subsequent DNA binding. Furthermore, eugenol increased the expression and activity of NAD(P)H:quinone oxidoreductase (QR), a major detoxifying enzyme for DMBA, through NF-E2 related factor2 binding to antioxidant response element in QR gene. Therefore, eugenol has a potent protective effect against DMBA-induced genotoxicity, presumably through the suppression of the DMBA activation and the induction of its detoxification. These results suggest that eugenol has potential as a chemopreventive.

Genotoxic effects of eugenol, isoeugenol and safrole in the wing spot test of Drosophila melanogaster

In the present study, the phenolic compounds eugenol, isoeugenol and safrole were investigated for genotoxicity in the wing spot test of Drosophila melanogaster. The Drosophila wing somatic mutation and recombination test (SMART) provides a rapid means to evaluate agents able to induce gene mutations and chromosome aberrations, as well as rearrangements related to mitotic recombination. We applied the SMART in its standard version with normal bioactivation and in its variant with increased cytochrome P450-dependent biotransformation capacity. Eugenol and safrole produced a positive recombinagenic response only in the improved assay, which was related to a high CYP450-dependent activation capacity. This suggests, as previously reported, the involvement of this family of enzymes in the activation of eugenol and safrole rather than in its detoxification. On the contrary, isoeugenol was clearly non-genotoxic at the same millimolar concentrations as used for eugenol in both the crosses. The responsiveness of SMART assays to recombinagenic compounds, as well as the reactive metabolites from eugenol and safrole were considered responsible for the genotoxicity observed.

A gene expression signature for oxidant stress/reactive metabolites in rat liver

Formation of free radicals and other reactive molecules is responsible for the adverse effects produced by a number of hepatotoxic compounds. cDNA microarray technology was used to compare transcriptional profiles elicited by training and testing sets of 15 oxidant stressors/reactive metabolite treatments to those produced by approximately 85 other paradigm compounds (mostly hepatotoxicants) to determine a shared signature profile for oxidant stress-associated hepatotoxicity. Initially, 100 genes were chosen that responded significantly different to oxidant stressors/reactive metabolites (OS/RM) compared to other samples in the database, then a 25-gene subset was selected by multivariate analysis. Many of the selected genes (e.g., aflatoxin aldehyde reductase, diaphorase, epoxide hydrolase, heme oxgenase and several glutathione transferases) are well-characterized oxidant stress/Nrf-2-responsive genes. Less than 10 other compounds co-cluster with our training and testing set compounds and these are known to generate OS/RMs as part of their mechanisms of toxicity. Using OS/RM signature gene sets, compounds previously associated with macrophage activation formed a distinct cluster separate from OS/RM and other compounds. A 69-gene set was chosen to maximally separate compounds in control, macrophage activator, peroxisome proliferator and OS/RM classes. The ease with which these 'oxidative stressor' classes can be separated indicates a role for microarray technology in early prediction and classification of hepatotoxicants. The ability to rapidly screen the oxidant stress potential of compounds may aid in avoidance of some idiosyncratic drug reactions as well as overtly toxic compounds.

Eugenol as an in vivo radioprotective agent

In the present work, an attempt has been made to evaluate the possible in vivo radioprotection by eugenol. Swiss albino mice were administered different doses of eugenol (75,150 and 300 mg/kg) before exposure to 1.5 Gy of gamma radiation. The micronucleus test was carried out to determine the genetic damage in bone marrow. Our results demonstrated significant reduction in the frequencies of micronucleated polychromatic erythrocytes (MnPCEs) with all three eugenol doses. Eugenol (150 mg/kg) was also tested against different doses of radiation (0.5, 1, 1.5, and 2 Gy) and was found to afford significant radioprotection. Reduction in the incidence of MnPCEs could be noticed up to 72 h postirradiation (1.5 Gy). Moreover, the level of peroxidative damage and the specific activities of lactate dehydrogenase (LDH) and methylglyoxalase I (Gly I) were observed in the liver of mice treated with eugenol for seven days in comparison to untreated mice. The results revealed that eugenol exerted significant protection against oxidative stress. This possibility was further supported by the enhanced response of Gly I and the lowered activity of LDH. The present findings suggested that eugenol has a radioprotective potential.

Inhibition of benzo[a]pyrene- and cyclophoshamide-induced mutagenicity by Cinnamomum cassia

Cinnamomum cassia is used as a flavoring spice with some established medicinal properties. In this study, we evaluated the antimutagenic effect of C. cassia against two mutagens, viz. benzo[a]pyrene (B[a]P) and cyclophosphamide (CP). The antimutagenic properties of C. cassia were examined by the Ames test. In vivo chromosomal aberration (CA) and micronuclei tests were also employed to assess the antimutagenic effect of C. cassia in mice after pretreatment with the extract orally for seven consecutive days. To elucidate the mechanism by which C. cassia exerts its antimutagenic effect, certain key enzymes involved in bioactivation and detoxification processes were also investigated. Changes in liver cytochrome P450 (Cyt P450), glutathione content (GSH), glutathione S-transferase (GST), glutathione reductase (GR), and glutathione peroxidase (GPX) were evaluated in pretreated animals. It was observed in the Ames test, bone marrow chromosomal aberration assay, and micronucleus test that C. cassia exerted significant antimutagenic effects against B[a]P and CP in animals treated with the plant extract. C. cassia pretreatment decreased Cyt P450 content but increased GSH content and the activity of glutathione-dependent antioxidant enzymes, viz. GST, GR, and GPX. The present findings demonstrate that the antimutagenic potential of C. cassia could be attributed to its modulatory effect on the xenobiotic bioactivation and detoxification processes.

Anti-genotoxicity of trans-anethole and eugenol in mice

The naturally occurring flavouring agents trans-anethole and eugenol were evaluated for antigenotoxic effects in mice. The test doses of trans-anethole (40-400 mg/kg body weight) and eugenol (50-500 mg/kg weight) were administered by gavage 2 and 20 h before the genotoxins were injected intraperitoneally. Anti-genotoxic effects were assessed in the mouse bone marrow micronucleus test. Pretreatment with trans-anethole and eugenol led to significant antigenotoxic effects against cyclophosphamide (CPH), procarbazine (PCB), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and urethane (URE). In addition, trans-anethole inhibited the genotoxicity of ethyl methane sulfonate (EMS). Both trans-anethole and eugenol exerted dose-related antigenotoxic effects against PCB and URE. There was no significant increase in genotoxicity when trans-anethole (40-400 mg/kg body weight) and eugenol (50-500 mg/kg body weight) were administered alone.

In vitro and in vivo activity of eugenol on human herpesvirus

Eugenol (4-allyl-1-hydroxy-2-methoxybenzene) was tested for antiviral activity against HSV-1 and HSV-2 viruses. In vitro, it was found that the replication of these viruses was inhibited in the presence of this compound. Inhibitory concentration 50% values for the anti-HSV effects of eugenol were 25.6 microg/mL and 16.2 microg/mL for HSV-1 and HSV-2 respectively, 250 microg/mL being the maximum dose at which cytotoxicity was tested. Eugenol was virucidal and showed no cytotoxicity at the concentrations tested. Eugenol-acyclovir combinations synergistically inhibited herpesvirus replication in vitro. Topical application of eugenol delayed the development of herpesvirus induced keratitis in the mouse model.

Anethole blocks both early and late cellular responses transduced by tumor necrosis factor: effect on NF-kappaB, AP-1, JNK, MAPKK and apoptosis

Anethole, a chief constituent of anise, camphor, and fennel, has been shown to block both inflammation and carcinogenesis, but just how these effects are mediated is not known. One possibility is TNF-mediated signaling, which has also been associated with both inflammation and carcinogenesis. In the present report we show that anethole is a potent inhibitor of TNF-induced NF-kappaB activation (an early response) as monitored by electrophoretic mobility shift assay, IkappaBalpha phosphorylation and degradation, and NF-kappaB reporter gene expression. Suppression of IkappaBalpha phosphorylation and NF-kappaB reporter gene expression induced by TRAF2 and NIK, suggests that anethole acts on IkappaBalpha kinase. Anethole also blocked the NF-kappaB activation induced by a variety of other inflammatory agents. Besides NF-kappaB, anethole also suppressed TNF-induced activation of the transcription factor AP-1, c-jun N-terminal kinase and MAPK-kinase. In addition, anethole abrogated TNF-induced apoptosis as measured by both caspase activation and cell viability. The anethole analogues eugenol and isoeugenol also blocked TNF signaling. Anethole suppressed TNF-induced both lipid peroxidation and ROI generation. Overall, our results demonstrate that anethole inhibits TNF-induced cellular responses, which may explain its role in suppression of inflammation and carcinogenesis. Oncogene (2000).

The role of biotransformation in dietary (anti)carcinogenesis

The fact that dietary compounds influence the susceptibility of human beings to cancer, is widely accepted. One of the possible mechanisms that is responsible for these (anti)carcinogenic effects is that dietary constituents may modulate biotransformation enzymes, thereby affecting the (anti)carcinogenic potential of other compounds. This ambiguous theme is the basis for the present paper. The possible effects of enzymatic bioactivation and detoxification of dietary constituents are discussed using two representative examples of phase I and phase II biotransformation enzymes i.e., cytochrome P450 and glutathione S-transferase. Furthermore, the impact of genetic polymorphisms of these two enzyme systems is considered. Although it is very difficult on the basis of the enzyme inducing or inhibiting properties of dietary compounds, especially to characterize them as anticarcinogenic, for certain constituents it is acknowledged that they have anticarcinogenic properties. As such, this provides for an important mechanistic substantiation of the established cancer chemopreventive effect of a diet rich in fruits and vegetables.

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.

Effect of eugenol on the mutagenicity of benzo[a]pyrene and the formation of benzo[a]pyrene-DNA adducts in the lambda-lacZ-transgenic mouse

To study the possible reduction by eugenol of the mutagenicity and genotoxicity of benzo[a]pyrene (B[a]P) in vivo, the lambda-lacZ-transgenic mouse strain 40.6 (Muta Mouse) was used. Male mice were fed a diet containing 0.4% (w/w) eugenol or a control diet for 58 days. On day 10, half of the mice received an i.p. dose of 100 mg/kg b.w. B[a]P. The lacZ mutants were recovered by packaging of DNA isolated from liver into lambda phage, and expressed in E. coli C lacZ-recA-galE- bacteria. In both control mice and mice fed the eugenol diet, B[a]P treatment resulted in a similar, significant increase in lacZ mutant frequency. Eugenol was not mutagenic by itself. By 32P-postlabelling analysis of the liver DNA using an analysis method with chromatographic conditions for B[a]P-DNA adducts, no effect of eugenol on the formation of B[a]P-DNA adducts in the lambda-lacZ-transgenic mouse was found. By 32P-postlabelling analysis using an alkenylbenzene solvent system the amount of B[a]P-DNA adducts was lower in mice fed the eugenol diet than in mice fed the control diet but the decrease was not statistically significant. However, one spot indicative of an eugenol-associated DNA adduct was detected. The present data provide no evidence for antimutagenic or antigenotoxic potential of eugenol in vivo. Furthermore, they suggest genotoxicity in vivo of eugenol per se.

Effect of short-term dietary administration of eugenol in humans

1. In order to study the antigenotoxic potential of eugenol in humans, ten healthy non-smoking males ingested a daily amount of 150 mg eugenol or the placebo for seven consecutive days. After a washout period of one week, groups ingesting eugenol or the placebo were crossed and received the other treatment for seven consecutive days. 2. On days 8 and 22 blood samples were taken for the assessment of standard clinical biochemical parameters. To study the possible antigenotoxic effect of eugenol, on day 8 and 22 blood samples were collected and exposed in vitro to the established genotoxic agents mitomycin C and vinblastine. After exposure the percentage of cells with chromosome aberrations and micronuclei was determined in cultured white blood cells. On days 8 and 22 paracetamol (500 mg p.o.) was administered as test substance to measure phase-II biotransformation capacity. Glutathione-S-transferase (GST) activities were determined in erythrocytes and blood plasma. 3. No significant differences in the clinical biochemical parameters were detected between the eugenol-period and the placebo-period, indicating that daily administration of 150 mg eugenol for 7 days has no toxic affects. 4. No significant differences on the cytogenetic parameters were found after ingestion of eugenol. Thus, there are no indications for an antigenotoxic potential of eugenol in humans, consuming daily 150 mg eugenol for 7 days. 5. A significant reduction in alpha-class GSTs in plasma (P < 0.05), but not in the other measured biotransformation parameters, was found in volunteers during the eugenol-periods as compared to the placebo-period. This may either reflect GST-inhibition by eugenol or protection against background damage of liver cells by eugenol.

Inhibition of rat, mouse, and human glutathione S-transferase by eugenol and its oxidation products

The irreversible and reversible inhibition of glutathione S-transferases (GSTs) by eugenol was studied in rat, mouse and man. Using liver cytosol of human, rat and mouse, species differences were found in the rate of irreversible inhibition of GSTs by eugenol in the presence of the enzyme tyrosinase. Tyrosinase was used to oxidize eugenol. No inhibition was observed in the absence of tyrosinase. The rate of irreversible inhibition of GSTs was highest in mouse cytosol, and lowest in rat cytosol. In addition, the irreversible inhibition of human and rat GSTs by eugenol was studied using purified isoenzymes of man and rat. The human GST isoenzymes A1-1, M1a-1a and P1-1 and the rat GST isoenzymes 1-1, 2-2, 3-3, 4-4 and 7-7 were irreversibly inhibited by eugenol in the presence of tyrosinase. In this respect human GST P1-1 and rat GST 7-7 were by far the most sensitive enzymes; human GST A2-2 was not inhibited. Indications were found that human GST P1-1 may be inhibited via three mechanisms: in addition to the well documentated nucleophilic addition of quinones and oxidation of cysteine residues, a covalent subunit cross-linking was also observed. The reversible inhibition of human and rat GST by eugenol, eugenol methyl ether, isoeugenol methyl ether, 2-allylphenol and 4-propylphenol was also studied using purified isoenzymes. The reversible inhibition of human and rat GSTs, using 1-chloro-2,4-dinitrobenzene as substrate, was expressed as I25. All compounds caused moderate reversible inhibition (I25 ranged from 0.2 to 5.4 mM for human GSTs and from 0.4 to 4.9 mM for rat GSTs). In rat, eugenol methyl ether was the strongest inhibitor. In human, the overall inhibiting capacities of eugenol, eugenol methyl ether, isoeugenol methyl ether and 4-propyl phenol were more or less similar; 2-allylphenol was the poorest inhibitor.

Effect of eugenol on the genotoxicity of established mutagens in the liver

The influence of in vivo treatment with eugenol on established mutagens was studied to determine whether eugenol has antigenotoxic potential. The effects of eugenol in rats was investigated in the unscheduled DNA synthesis (UDS) assay with established mutagens and the Salmonella typhimurium mutagenicity assay. In addition, the effect of in vivo treatment with eugenol on benzo[a]pyrene (B[a]P)-induced genotoxicity in human hepatoma cell line Hep G2 was investigated in the single-cell gel electrophoresis assay. The mutagenicity of B[a]P in the S. typhimurium mutagenicity assay was lower in liver S-9 fractions from control rats. Incubation of liver S-9 fractions from eugenol-treated rats with dimethylbenzanthracene (DMBA) had no antimutagenic effect. Eugenol did not modify UDS activity in hepatocytes isolated from rats pretreated with eugenol orally after exposure of these cells in vitro to DMBA and aflatoxin B1. Four different treatment schemes of combinations of B[a]P and eugenol were examined in Hep G2 cells: pre-treatment with eugenol; simultaneous treatment with eugenol and B[a]P; a combination of these (pretreatment/simultaneous treatment); and post-treatment with eugenol. An increase in the genotoxicity of B[a]P was found in Hep G2 cells. No effect of eugenol on the genotoxicity of B[a]P was found with the pre- and post-treatments. It is concluded that the effect of eugenol on genotoxicity induced by established mutagens is not univocal; in vivo treatment of rats with eugenol resulted in a reduction of the mutagenicity of B[a]P in the S. typhimurium mutagenicity assay, while in the UDS assay no effect of eugenol was found. In vitro treatment of cultured cells with eugenol resulted in an increase in genotoxicity of B[a]P. These findings indicate that there is only limited support for the antigenotoxic potential of eugenol in vivo.

Effect of eugenol on drug-metabolizing enzymes of carbon tetrachloride-intoxicated rat liver

The chemoprotection extended by eugenol against carbon tetrachloride (CCl4) intoxication was established by studies on drug-metabolizing phase I and phase II enzymes. An overall decrease in drug-metabolizing enzymes, namely NADPH-cytochrome c reductase, NADH-cytochrome reductase, coumarin hydroxylase, 7-ethoxy coumarin-O-deethylase, UDP-glucuronyltransferase and glutathione-S-transferase, was observed with CCl4 intoxication, with a subsequent decrease in cytochrome P450 and cytochrome b5 content. CCl4 caused a significant decrease in microsomal phospholipids and the marker enzymes glucose-6-phosphatase and 5'-nucleotidase, and an increase in thiobarbituric acid reactive substances (TBARS). Simultaneous administration of eugenol with CCl4 inhibited the accumulation of TBARS and the decrease in the microsomal phospholipids and marker enzymes. Further, the chemical onslaught imposed by CCl4 on the drug-metabolizing system was removed successfully by eugenol. Eugenol appears to act as an in vivo antioxidant and as a better inducer of phase II enzymes than phase I enzymes. It is therefore suggested that eugenol could be an interesting basic structure for drug design.

Antimutagenicity of eugenol in the rodent bone marrow micronucleus test

The antimutagenic effect of eugenol on the mutagenicity of cyclophosphamide (CP), mitomycin C (MMC), ethyl methanesulfonate (EMS) and benzo[a]pyrene (B[a]P) was assessed in the rodent bone marrow micronucleus test using male Swiss mice. Oral administration of eugenol (0.4% in the diet) for 15 days was found to decrease significantly the frequency of micronucleated polychromatic erythrocytes (MPEs) elevated by CP. No effect was found on the frequency of MPEs elevated by MMC, EMS and B[a]P. The results provide some support for antimutagenic potency of eugenol in vivo.