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

Anethole in cancer therapy: Mechanisms, synergistic potential, and clinical challenges

Cancer remains a major global health challenge, prompting the search for effective and less toxic treatments. Anethole, a bioactive compound found in essential oils of anise and fennel, commonly used as a food preservative, has recently garnered attention for its potential anti-cancer properties. This comprehensive review aims to systematically assess the anti-cancer effects of anethole, elucidating its mechanisms of action, pharmacokinetics, bioavailability, and synergistic potential with conventional cancer therapies. A detailed literature search was conducted across databases including PubMed, Embase, Scopus, Science Direct, Web of Science, and Google Scholar. Criteria for inclusion were experimental studies in peer-reviewed journals focusing on the anti-cancer properties of anethole. Extracted data included study design, intervention specifics, measured outcomes, and mechanistic insights. Anethole demonstrates multiple anti-cancer mechanisms, such as inducing apoptosis, causing cell cycle arrest, exhibiting anti-proliferative and anti-angiogenic effects, and modulating critical signaling pathways including NF-κB, PI3K/Akt/mTOR, and caspases. It enhances the efficacy of chemotherapeutic agents like cisplatin and doxorubicin while reducing their toxicity. In vitro and in vivo studies have shown its effectiveness against various cancers, including breast, prostate, lung, and colorectal cancers. Anethole shows significant potential as an anti-cancer agent, with its multi-faceted mechanisms of action and ability to synergize with existing chemotherapy. Further clinical research is essential to fully understand its therapeutic potential and application in oncology.

Maternal Reproductive Toxicity of Some Essential Oils and Their Constituents

Even though several plants can improve the female reproductive function, the use of herbs, herbal preparations, or essential oils during pregnancy is questionable. This review is focused on the effects of some essential oils and their constituents on the female reproductive system during pregnancy and on the development of the fetus. The major concerns include causing abortion, reproductive hormone modulation, maternal toxicity, teratogenicity, and embryo-fetotoxicity. This work summarizes the important studies on the reproductive effects of essential oil constituents anethole, apiole, citral, camphor, thymoquinone, trans-sabinyl acetate, methyl salicylate, thujone, pulegone, β-elemene, β-eudesmol, and costus lactone, among others.

Antitumor phenylpropanoids found in essential oils

The search for new bioactive substances with anticancer activity and the understanding of their mechanisms of action are high-priorities in the research effort toward more effective treatments for cancer. The phenylpropanoids are natural products found in many aromatic and medicinal plants, food, and essential oils. They exhibit various pharmacological activities and have applications in the pharmaceutical industry. In this review, the anticancer potential of 17 phenylpropanoids and derivatives from essential oils is discussed. Chemical structures, experimental report, and mechanisms of action of bioactive substances are presented.

Development of antiproliferative nanohybrid compound with controlled release property using ellagic acid as the active agent

An ellagic acid (EA)–zinc layered hydroxide (ZLH) nanohybrid (EAN) was synthesized under a nonaqueous environment using EA and zinc oxide (ZnO) as the precursors. Powder X-ray diffraction showed that the basal spacing of the nanohybrid was 10.4 Å, resulting in the spatial orientation of EA molecules between the interlayers of 22.5° from z-axis with two negative charges at 8,8′ position of the molecules pointed toward the ZLH interlayers. FTIR study showed that the intercalated EA spectral feature is generally similar to that of EA, but with bands slightly shifted. This indicates that some chemical bonding of EA presence between the nanohybrid interlayers was slightly changed, due to the formation of host–guest interaction. The nanohybrid is of mesopores type with 58.8% drug loading and enhanced thermal stability. The release of the drug active, EA from the nanohybrid was found to be sustained and therefore has good potential to be used as a drug controlled-release formulation. In vitro bioassay study showed that the EAN has a mild effect on the hepatocytes cells, similar to its counterpart, free EA.

The structure-activity relationship of the 3-oxy site in the anticonvulsant (R)-N-benzyl 2-acetamido-3-methoxypropionamide

Lacosamide ((R)-N-benzyl 2-acetamido-3-methoxypropionamide, (R)-1) is a low molecular weight anticonvulsant recently introduced in the United States and Europe for adjuvant treatment of partial-onset seizures in adults. In this study, we define the structure-activity relationship (SAR) for the compound's 3-oxy site. Placement of small nonpolar, nonbulky substituents at the 3-oxy site provided compounds with pronounced seizure protection in the maximal electroshock (MES) seizure test with activities similar to (R)-1. The anticonvulsant activity loss that accompanied introduction of larger moieties at the 3-oxy site in (R)-1 was offset, in part, by including unsaturated groups at this position. Our findings were similar to a recently reported SAR study of the 4'-benzylamide site in (R)-1 ( J. Med. Chem. 2010 , 53 , 1288 - 1305 ). Together, these results indicate that both the 3-oxy and 4'-benzylamide positions in (R)-1 can accommodate nonbulky, hydrophobic groups and still retain pronounced anticonvulsant activities in rodents in the MES seizure model.

Effects of cytochrome p450 inhibitors on itraconazole and fluconazole induced cytotoxicity in hepatocytes

Itraconazole and fluconazole have been reported to induce hepatotoxicity in patients. The present study was designed to investigate the role of cytochrome P450 inhibitors, SKF 525A, and curcumin pretreatment on the cytotoxicity of antifungal drugs fluconazole and itraconazole. For 3 consecutive days, female rats were administered daily SKF 525A or curcumin (5 and 25 mg/kg). Control rats received an equivalent amount of dosed vehicle. The animals were anaesthetized 24 hours after receiving the last dose for liver perfusion. Hepatocytes were then exposed to various concentrations of antifungal drugs. In vitro incubation of hepatocytes with itraconazole revealed significantly lower viability when compared to fluconazole as assessed by lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase activities. The cytotoxicity of itraconazole was enhanced when incubated with hepatocytes pretreated with SKF 525A. SKF 525A had no effects on the cytotoxicity of fluconazole. Curcumin failed to either increase or decrease the cytotoxicity of both antifungal drugs. ATP levels also showed significant decrease in both itraconazole and fluconazole incubated hepatocytes. However, SKF 525A pretreated hepatocytes had significantly lower ATP levels after itraconazole incubations. Collectively, these results confirm the involvement of cytochrome P450 in the cytoprotection in itraconazole induced hepatocyte toxicity. Differences of the effects of SKF 525A on the cytotoxicity induced by itraconazole and fluconazole may be due to the differences on the metabolism of each antifungal drug in vivo.

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.

Epoxide hydrolases: their roles and interactions with lipid metabolism

The epoxide hydrolases (EHs) are enzymes present in all living organisms, which transform epoxide containing lipids by the addition of water. In plants and animals, many of these lipid substrates have potent biologically activities, such as host defenses, control of development, regulation of inflammation and blood pressure. Thus the EHs have important and diverse biological roles with profound effects on the physiological state of the host organisms. Currently, seven distinct epoxide hydrolase sub-types are recognized in higher organisms. These include the plant soluble EHs, the mammalian soluble epoxide hydrolase, the hepoxilin hydrolase, leukotriene A4 hydrolase, the microsomal epoxide hydrolase, and the insect juvenile hormone epoxide hydrolase. While our understanding of these enzymes has progressed at different rates, here we discuss the current state of knowledge for each of these enzymes, along with a distillation of our current understanding of their endogenous roles. By reviewing the entire enzyme class together, both commonalities and discrepancies in our understanding are highlighted and important directions for future research pertaining to these enzymes are indicated.

A General and Nonempirical Approach to the Determination of the Absolute Configuration of 1-Aryl-1,2-diols

We describe herein a simple, general, and reliable nonempirical approach, based on the exciton coupling method, to assign the absolute configuration of the benzylic stereogenic center of 1-aryl-1,2-diols. According to this method, it is only necessary to prepare the 4-biphenylboronic esters of the diols and to record their CD spectra in the 230-300 nm range, i.e., in the range corresponding to the long-axis (1)L(a) transition of the biphenyl chromophore. From the sign of the CD couplet or Cotton effect at 260 nm it is possible to know the chirality defined by the aryl and biphenyl chromophore transitions and then to determine the absolute configuration of the benzylic carbon. By this approach, simple rules have been formulated which allow us to establish the absolute configuration of many classes of 1-aryl-1,2-diols.

Cytotoxic and xenoestrogenic effects via biotransformation of trans-anethole on isolated rat hepatocytes and cultured MCF-7 human breast cancer cells

The metabolism and action of trans-anethole (anethole) and the estrogen-like activity of the compound and its metabolites were studied in freshly isolated rat hepatocytes and cultured MCF-7 human breast cancer cells, respectively. The incubation of hepatocytes with anethole (0.25-2.0mM) caused a concentration- and time-dependent cell death accompanied by losses of cellular ATP and adenine nucleotide pools. Anethole at a weakly toxic level (0.5mM) was metabolized to 4-methoxycinnamic acid (4MCA), 4-hydroxy-1-propenylbenzene (4OHPB), and the monosulfate conjugate of 4OHPB; the levels of 4OHPB sulfate and 4MCA reached approximately 20 and 200 microM within 2 hr, respectively, whereas that of free unconjugated 4OHPB was less than approximately 0.5 microM. At a moderately toxic concentration (1.0mM), unconjugated 4OHPB reached approximately 10 microM, followed by abrupt loss of 3'-phosphoadenosine 5'-phosphosulphate (PAPS). Based on cell viability and adenine nucleotide levels, 4OHPB was more toxic than anethole and 4MCA. The addition of 2,6-dichloro-4-nitrophenol (50 microM), an inhibitor of sulfotransferase, enhanced the anethole-induced cytotoxicity associated with losses of ATP, PAPS, and 4OHPB sulfate, and symmetrically increased the unconjugated 4OHPB concentration. 4OHPB as well as diethylstilbestrol (DES) and bisphenol A (BPA), which are known xenoestrogenic compounds, competitively displaced 17beta-estradiol bound to the estrogen receptor alpha in a concentration-dependent manner; IC(50) values of these compounds were approximately 1 x 10(-5), 1 x 10(-8) and 5 x 10(-5)M, respectively. 4OHPB also caused a concentration (10(-8) to 10(-6)M)-dependent proliferation of MCF-7 cells, whereas neither anethole nor 4MCA (10(-9) to 10(-5)M) affected cell proliferation. However, at higher concentrations (>10(-4)M), 4OHPB rather than anethole and 4MCA was cytotoxic. These results suggest that the biotransformation of anethole induces a cytotoxic effect at higher concentrations in rat hepatocytes and an estrogenic effect at lower concentrations in MCF-7 cells based on the concentrations of the hydroxylated intermediate, 4OHPB.

Itraconazole- and fluconazole-induced toxicity in rat hepatocytes: a comparative in vitro study

This current study was to investigate the in vitro cytotoxicity of rat hepatocytes induced by the antifungal drugs, itraconazole and fluconazole. Both antifungal drugs caused dose-dependent cytotoxicity. In vitro incubation of hepatocytes with itraconazole revealed significantly higher lactate dehydrogenase (LDH) leakage when compared to fluconazole. Phenobarbital pretreated hepatocytes contained significantly higher total cytochrome P450 content than the control hepatocytes. P450 content was reduced approximately 30% for both types of hepatocytes after 6 hours incubation. Interestingly, cytotoxicity of itraconazole was reduced significantly by phenobarbital pretreatment. Phenobarbital did not have any effect on the cytotoxicity induced by fluconazole. These results demonstrate the in vitro toxicity of hepatocytes induced by itraconazole and fluconazole that were expressed in a dose- and time-dependent manner. Phenobarbital plays a role in the cytoprotection of hepatocytes to itraconazole-induced but not fluconazole-induced cytotoxicity in vitro.

Spontaneous hydrolysis reactions of cis- and trans-beta-methyl-4-methoxystyrene oxides (Anethole oxides): buildup of trans-anethole oxide as an intermediate in the spontaneous reaction of cis-anethole oxide

Rates and products of the reactions of trans- and cis-beta-methyl-4-methoxystyrene oxides (1 and 2) (anethole oxides) and beta,beta-dimethyl-4-methoxystyrene oxide (3) in water solutions in the pH range 4-12 have been determined. In the pH range ca. 8-12, each of these epoxides reacts by a spontaneous reaction. The spontaneous reaction of trans-anethole oxide (1) yields ca. 40% of (4-methoxyphenyl)acetone and 60% of 1-(4-methoxyphenyl)-1, 2-propanediols (erythro:threo ratio ca. 3:1). The spontaneous reaction of cis-anethole oxide is more complicated. The yields of diol and ketone products vary with pH in the pH range 8-11, even though there is not a corresponding change in rate. These results are interpreted by a mechanism in which 2 undergoes isomerization in part to the more reactive trans-anethole oxide (1), which subsequently reacts by acid-catalyzed and/or spontaneous reactions, depending on the pH, to yield diol and ketone products. The buildup of the intermediate trans-anethole oxide in the spontaneous reaction of cis-anethole oxide was detected by (1)H NMR analysis of the reaction mixture. Other primary products of the spontaneous reaction of 2 are (4-methoxyphenyl)acetone (73%) and threo-1-(4-methoxyphenyl)-1,2-propanediol (ca. 3%). The rates and products of the spontaneous reaction of 2 and its beta-deuterium-labeled derivative were determined, and the lack of significant kinetic and partitioning deuterium isotope effects indicates that the isomerization of 2 to ketone and to trans-anethole oxide must occur primarily by nonintersecting reaction pathways.

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.

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.

Stereochemical aspects of the hydration of trans-anethole epoxide in the rat

Racemic trans-anethole epoxide [1-(4'-methoxyphenyl)-propane-1,2-oxide] was incubated with water, buffers, and rat liver microsomes and cytosol and the stereochemistry of the diols produced was determined by HPLC as their dicamphanyl esters. The diol metabolites were isolated by HPLC from the urine of rats administered [1'-14C] trans-anethole and their stereochemistry determined after derivatization to their camphanyl esters. The stereochemical course of the metabolism of trans-anethole by rat liver microsomes and cytosol is discussed.

Genotoxicity of the alkenylbenzenes alpha- and beta-asarone, myristicin and elimicin as determined by the UDS assay in cultured rat hepatocytes

While the alkenylbenzenes alpha- and beta-asarone are hepatocarcinogenic in rodents, myristicin and elimicin, two other alkenylbenzenes, are not. The present study investigated the mechanism of genotoxicity of the asarones to elucidate the role of cytochrome P-450 and obtain further information about the relationships between the structure, metabolism and genotoxicity of the alkenylbenzenes. The data on the ability of these compounds to induce unscheduled DNA synthesis (UDS) in hepatocytes derived from male Fischer 344 rats are presented in this paper. Cytotoxicity was assessed by lactate dehydrogenase leakage. Elimicin and alpha- and beta-asarone are genotoxic in the UDS assay but myristicin is not. The genotoxicity of the asarones is inhibited by the cytochrome P-450 inhibitor cimetidine but the sulfotransferase inhibitor pentachlorophenol (PCP) is without effect. The major metabolite of the asarones in hepatocytes was identified by liquid chromatography-mass spectrometry as 2,4,5-trimethoxycinnamic acid but this was not genotoxic when tested separately. Simple allylbenzenes such as safrole, estragole and methyleugenol are activated by sequential 1-hydroxylation and sulfation, and this is the likely mechanism of the genotoxicity of elimicin. The propenyl analogues isosafrole, anethole and methylisoeugenol, which cannot undergo 1-hydroxylation, are not genotoxic. The positive results obtained with the asarones suggest the occurrence of a novel activation 'option' for alkenylbenzenes which features a 2-methoxy group in the aromatic ring.

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.