Lack of effect of coumarin on unscheduled DNA synthesis in the in vivo rat hepatocyte DNA repair assay

Umbelliferone (7-hydroxycoumarin): A non-toxic antidiarrheal and antiulcerogenic coumarin

Gastrointestinal diseases are very common problems; available treatments are very limited and come with a range of side effects. Coumarins are an extensive class of phenolic compounds that can be found in plants, fungi and bacteria. The 7-hydroxycoumarin, also known as umbelliferone (UMB), is a compound that comes from coumarin and has been showing biological activities in other studies. As of this scenario, the present study was designed to evaluate the acute oral toxicity, mutagenic, antidiarrheal, anti-bacterial, and antiulcerogenic effects, and antioxidant capacity of UMB. An investigation was conducted through the hippocratic screening method and through histopathological analysis in animals to evaluate the effects of acute oral administration of a dose of 50, 100 and 200 mg/kg of UMB. A micronucleus test on peripheral blood of Swiss mice, which were orally treated with three doses (50, 100 and 200 mg/kg), was conducted to evaluate mutagenic activities. The antiulcerogenic activity was accomplished through the ethanol-induced damage method. Antidiarrheal activities were tested for inducing diarrhea with castor oil and evaluating intestinal transit duration; additionally, the antimicrobial effect against some enteropathogenic bacteria was analyzed. Finally, the antioxidant capability was determined by the capacity of the UMB sample to kidnap the stable radical 2,2-diphenyl-1-picrylhydrazyl. Of the evaluated doses, signs of toxicity after acute administration of the compound were not observed. UMB presented antiulcerogenic activity (100 and 200 mg/kg), which was explained because of its antioxidant capacity. A gastro protective effect was similar to the positive control, and the UMB was able to significantly reduce intestinal transit, and also diarrheal symptoms. Furthermore, UMB had an anti-bacterial effect with minimum inhibitory concentration fluctuating between 62.5 and 1000 μg/mL. Based on these findings, we can suggest that UMB has important biological activities in vivo and in vitro and is not toxic under the evaluated circumstances, which demonstrates its large potential for pharmacological use.

Cancer Hazard Identification Integrating Human Variability: The Case of Coumarin

Coumarin is a naturally occurring sweet-smelling benzopyrone that may be extracted from plants or synthesized for commercial uses. Its uses include as a flavoring agent, fragrance enhancer, and odor-masking additive. We reviewed and evaluated the scientific evidence on the carcinogenicity of coumarin, integrating information from carcinogenicity studies in animals with mechanistic and other relevant data, including data from toxicogenomic, genotoxicity, and metabolism studies, and studies of human variability of a key enzyme, CYP2A6. Increases in tumors were observed in multiple studies in rats and mice in multiple tissues. Our functional pathway analysis identified several common cancer-related biological processes/pathways affected by coumarin in rat liver following in vivo exposure and in human primary hepatocytes exposed in vitro. When coumarin 7-hydroxylation by CYP2A6 is compromised, this can lead to a shift in metabolism to the 3,4-epoxidation pathway and increased generation of electrophilic metabolites. Mechanistic data align with 3 key characteristics of carcinogens, namely formation of electrophilic metabolites, genotoxicity, and induction of oxidative stress. Considerations of metabolism, human variability in CYP2A6 activity, and coumarin hepatotoxicity in susceptible individuals provide additional support for carcinogenicity concern. Our analysis illustrates the importance of integrating information on human variability in the cancer hazard identification process.

Effect of the metabolic capacity in rat liver S9 on the positive results of in vitro micronucleus tests

A high incidence of positive results is obtained with in vitro genotoxicity tests, which do not correlate with the in vivo negative results in many cases. To address this issue, the metabolic profile of rat liver 9000 × g supernatant fraction (S9) pretreated with phenobarbital (PB) and 5,6-benzoflavone (BNF) was characterized. Furthermore, the in vitro micronucleus tests of 10 compounds were performed with PB-BNF-induced rat S9. PB-BNF increased cytochrome P450 (CYP) activity and CYP1A1, CYP1A2, CYP2B1/2, CYP2C6, CYP3A1, and CYP3A2 expression in rat S9, whereas it decreased CYP2C11 and CYP2E1 expression. PB-BNF-induced S9 enhanced the micronucleus induction (MI) of benzo[a]pyrene (BaP), cyclophosphamide (CPA), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine hydrochloride (PhIP), which are metabolized by CYP1A1, CYP2C6, and CYP1A2, respectively. In contrast, coumarin and chlorpheniramine showed MI with PB-BNF-induced S9 despite the fact that they show negative results in the in vivo studies. Furthermore, diclofenac, piroxicam, lansoprazole, and caffeine showed MI regardless of the enzyme induction by PB-BNF, whereas phenacetin did not show MI. These results indicate that PB-BNF-induced rat S9 is effective in detecting the genotoxic potential of promutagens, such as BaP, CPA, and PhIP, but not of coumarin and chlorpheniramine, probably due to the differences in the in vitro and in vivo metabolic profile and its exposure levels of the drugs.

Effects of warfarin on biological processes other than haemostasis: A review

Warfarin is the world's most widely used anticoagulant drug. Its anticoagulant activity is based on the inhibition of the vitamin K-dependent (VKD) step in the complete synthesis of a number of blood coagulation factors that are required for normal blood coagulation. Warfarin also affects synthesis of VKD proteins not related to haemostasis including those involved in bone growth and vascular calcification. Antithrombotic activity of warfarin is considered responsible for some aspects of its anti-tumour activity of warfarin. Some aspects of activities against tumours seem not to be related to haemostasis and included effects of warfarin on non-haemostatic VKD proteins as well as those not related to VKD proteins. Inflammatory/immunomodulatory effects of warfarin indicate much broader potential of action of this drug both in physiological and pathological processes. This review provides an overview of the published data dealing with the effects of warfarin on biological processes other than haemostasis.

Qualitative and quantitative determination of coumarin using surface-enhanced Raman spectroscopy coupled with intelligent multivariate analysis

Coumarin is harmful to health but still used in cosmetics, tobacco, or illegally added into food as a spice in trace amounts so that it is exceedingly difficult to be determined accurately.

Evaluation of the biological activity of naturally occurring 5,8-dihydroxycoumarin

5,8-Dihydroxycoumarin (5,8-DHC) was isolated from aerial parts of sweet grass (Hierochloë odorata L.) and screened for antioxidant and genotoxic activities. A clear linear dependency of radical scavenging capacity in DPPH^• and ABTS^•+ assays was determined. 5,8-DHC was very efficient in retarding rapeseed oil oxidation (Oxipress test). TPC (total phenols content) and FRAP (the ability to reduce ferric ion to ferrous ion) assays revealed a somewhat lower antioxidant capacity of 5,8-DHC as compared with gallic acid. Genotoxic activity was tested using different genetic end-points: chromosome aberrations (CAs) and micronuclei (MN) in Wistar rat bone marrow in vivo, CAs and sister chromatid exchanges (SCEs) in human lymphocytes in vitro, and somatic mutations and recombination in Drosophila melanogaster wing cells in vivo. 5,8-DHC did not increase frequency of CAs in rat bone marrow cells, but induced a significant increase of MN. It was slightly mutagenic in the Drosophila melanogaster assay after 120 h of treatment, but not after 48 h of treatment. 5,8-DHC induced both CAs and SCEs in vitro in human lymphocytes in a clear dose-dependent manner. Thus, 5,8-DHC may be classified as weakly genotoxic both in vivo and in vitro.

Effects of subacute oral warfarin administration on peripheral blood granulocytes in rats

Warfarin affects mainly vitamin K dependent (VKD) processes, but the effects on some non-VKD-related activities such as tumor growth inhibition and mononuclear cell-mediated immune reactions were shown as well. In this study, the effect of subchronic (30 days) oral warfarin (0.35 mg/l and 3.5mg/l) intake on peripheral blood granulocytes in rats was investigated. Increase in prothrombin and partial thromboplastin time at high warfarin dose reflected its basic activity. Priming effect for respiratory burst was noted at both warfarin doses, while only high warfarin dose resulted in priming for adhesion, the rise in intracellular myeloperoxidase content/release and stimulation of nitric oxide production. Differential effects of high warfarin dose were noted on granulocyte cytokines IL-6 (lack of the effect), TNF-α (decreased release and mRNA expression) and IL-12 (increase in mRNA for IL-12 subunits p35 and p40). Changes in granulocytes seems not to rely on mitogen activated kinases p38 and ERK. Warfarin intake was associated with an increase in circulating IL-6, fibrinogen and haptoglobin and with changes in the activity of erythrocyte antioxidant enzymes superoxide dismutase and catalase. The effects of oral warfarin intake on peripheral blood granulocytes demonstrated in this study might be relevant for oral anticoagulant therapy strategies in humans.

Risk assessment of coumarin using the bench mark dose (BMD) approach: children in Norway which regularly eat oatmeal porridge with cinnamon may exceed the TDI for coumarin with several folds

Coumarin is a naturally occurring flavouring substance in cinnamon and many other plants. It is known that coumarin can cause liver toxicity in several species, and it is considered a non-genotoxic carcinogen in rodents. By using the bench mark dose approach we re-assessed coumarin toxicity and established a new TDI for coumarin of 0.07 mg/kg bw/day. Oral intake of coumarin is related to consumption of cinnamon-containing foods and food supplements. Cinnamon is a widely used spice in Norway, and can be used as topping on oatmeal porridge. Based on analyses of coumarin in Norwegian foods, intake calculations for children and adults were conducted, and a risk assessment of coumarin in the Norwegian population was performed. Intake estimates of coumarin show that small children eating oatmeal porridge several times a week sprinkled with cinnamon could have a coumarin intake of 1.63 mg/kg bw/day and may exceeding the TDI with several folds. Adults drinking cinnamon-based tea and consuming cinnamon supplements also can exceed TDI. The coumarin intake could exceed the TDI by 7- to 20-fold in some intake scenarios. Such large daily exceedances of TDI, even for a limited time period of 1-2 weeks, cause concern of adverse health effects.

A safety assessment of coumarin taking into account species-specificity of toxicokinetics

Coumarin (1,2-benzopyrone) is a naturally occurring fragrant compound found in a variety of plants and spices. Exposure to the general public is through the diet and from its use as a perfume raw material in personal care products. High doses of coumarin by the oral route are known to be associated with liver toxicity in rodents. Chronic oral bioassays conducted in the 1990s reported liver tumors in rats and mice and lung tumors in mice, raising concerns regarding the safety of coumarin. Since then, an extensive body of research has focused on understanding the etiology of these tumors. The data support a conclusion that coumarin is not DNA-reactive and that the induction of tumors at high doses in rodents is attributed to cytotoxicity and regenerative hyperplasia. The species-specific target organ toxicity is shown to be related to the pharmacokinetics of coumarin metabolism, with data showing rats to be particularly susceptible to liver effects and mice to be particularly susceptible to lung effects. A quantitative human health risk assessment that integrates both cancer and non-cancer effects is presented, confirming the safety of coumarin exposure from natural dietary sources as well as from its use as a perfume in personal care products.

Molecular mechanisms of toxicity of important food-borne phytotoxins

At present, there is an increasing interest for plant ingredients and their use in drugs, for teas, or in food supplements. The present review describes the nature and mechanism of action of the phytochemicals presently receiving increased attention in the field of food toxicology. This relates to compounds including aristolochic acids, pyrrolizidine alkaloids, beta-carotene, coumarin, the alkenylbenzenes safrole, methyleugenol and estragole, ephedrine alkaloids and synephrine, kavalactones, anisatin, St. John's wort ingredients, cyanogenic glycosides, solanine and chaconine, thujone, and glycyrrhizinic acid. It can be concluded that several of these phytotoxins cause concern, because of their bioactivation to reactive alkylating intermediates that are able to react with cellular macromolecules causing cellular toxicity, and, upon their reaction with DNA, genotoxicity resulting in tumors. Another group of the phytotoxins presented is active without the requirement for bioactivation and, in most cases, these compounds appear to act as neurotoxins interacting with one of the neurotransmitter systems. Altogether, the examples presented illustrate that natural does not equal safe and that in modern society adverse health effects, upon either acute or chronic exposure to phytochemicals, can occur as a result of use of plant- or herb-based foods, teas, or other extracts.

Lack of effect of coumarin on the formation of micronuclei in an in vivo mouse micronucleus assay

Coumarin was tested for its potential to cause genotoxic effects in mouse bone marrow cells using an in vivo micronucleus assay. Male and female Swiss mice were administered a single oral dose of coumarin at 50, 100 or 200 mg/kg by gavage in corn oil vehicle. Control animals received only the vehicle. Groups of male mice were also administered mitomycin C at 0.75 mg/kg and served as positive controls. At 24 h after treatment, mice from all dose levels, and at 48 h after treatment, mice from the high dose level only were sacrificed. Bone marrow cells were collected and assayed for the presence of micronuclei. Coumarin did not cause any increase in the incidence of micronucleated polychromatic erythrocytes in male or female mice at any of the dose levels, the positive control mitomycin C produced a significant increase. There was no evidence of coumarin or mitomycin C treatment related cytotoxicity to bone marrow cells. The results of this study demonstrate that coumarin is negative in the mouse in vivo micronucleus assay.