Species Differences in the in Vitro Metabolic Activation of the Hepatotoxic Pyrrolizidine Alkaloid Clivorine

Lin, Ge; Cui, Yanyan; Liu, Xiaoquan; Wang, Zhentao

doi:10.1021/tx0255370

Cited by 39 publications

(50 citation statements)

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“…It is well established that the metabolic activation of clivorine is via oxidative N-demethylation to generate pyrrolic ester, which then undergoes adduct formation leading to hepatotoxicity (Mori et al, 1985;Buhler et al, 1990;Huxtable, 1990;Lin et al, 2000aLin et al, , 2002Lin et al, , 2003Fu et al, 2002Fu et al, , 2004. Because further metabolisms of pyrrolic ester, including adduct formations, all produce clivoric acid (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Quantities of individual analytes present in different incubates were determined from the corresponding calibration curves constructed at the detection wavelength of 230 nm. Furthermore, DHR-derived bound pyrroles were determined by adopting a previously published method using a spectrophotometric analysis of the specific chromophore formed via reacting pyrrole functional group with Ehrlich reagent (Yan and Huxtable, 1995;Lin et al, 2000aLin et al, , 2002Lin et al, , 2003.…”

Section: Animals and Preparation Of Liver Microsomesmentioning

confidence: 99%

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Deacetylclivorine: A Gender-Selective Metabolite of Clivorine Formed in Female Sprague-Dawley Rat Liver Microsomes

Lin

Tang²,

Liu³

et al. 2007

Drug Metab Dispos

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ABSTRACT:Clivorine, a naturally occurring pyrrolizidine alkaloid, causes liver toxicity via its metabolic activation to generate toxic metabolite (pyrrolic ester). Female Sprague-Dawley (SD) rats are reported to be less susceptible to clivorine intoxication than male SD rats. However, the biochemical mechanism causing such gender difference is largely unknown. The present study investigated hepatic microsomal metabolism of clivorine in female rats to delineate the mechanism of the gender difference. Two pathways, which directly metabolize clivorine, were observed. First, the metabolic activation to produce the toxic pyrrolic ester followed by formations of bound pyrroles, dehydroretronecine, 7-glutathionyldehydroretronecine, and clivoric acid were found in female rats, and CYP3A1/2 isozymes were identified to catalyze the metabolic activation. Compared with male rats (ϳ21%), the metabolic activation in female rats was significantly lower (ϳ4%) possibly because of significantly lower CYP3A1/2 levels expressed in female rats. Second, a direct hydrolysis to generate the novel female rat-specific metabolite deacetylclivorine was shown as the predominant pathway (ϳ16% clivorine metabolism) in female rat liver microsomes and was determined to be mediated by microsomal hydrolase A. Furthermore, when the metabolic activation was completely inhibited by ketoconazole, the amount of deacetylclivorine formed in a 1-h incubation significantly increased from 19.44 ؎ 3.00 to 54.87 ؎ 9.30 nmol/mg protein, suggesting that the two pathways compete with each other. Therefore, the lower susceptibility of female SD rats to clivorine intoxication is suggested to be caused by the significantly higher extent of the direct hydrolysis and a lower degree of the metabolic activation.Pyrrolizidine alkaloid (PA) poisoning has drawn worldwide attention because of a wide distribution of PA-containing plants and their induced serious and diversified toxicities, especially hepatotoxicity and carcinogenicity (Mattocks, 1968;Mori et al., 1985;Huxtable, 1989;Buhler et al., 1990;Fu et al., 2002Fu et al., , 2004, as well as pneumotoxicity (Huxtable, 1990;Taylor et al., 1997), neurotoxicity (Roeder, 2000), and embryotoxicity (Tu et al., 1988). Two types of PA, namely, retronecine and otonecine, are mainly responsible for the PA-induced hepatotoxicity (Mori et al., 1985;Huxtable, 1989;Buhler et al., 1990;Fu et al., 2004). Clivorine, a representative toxic otonecine-type PA, is present in many Ligularia species and especially exists as a predominant PA in the traditional Chinese medicinal herb Ligularia hodgsonii Hook (Lin et al., 2000b;Xia et al., 2004). Clivorine has been reported to cause hepatotoxicity and carcinogenicity in rodents and a positive mutagenic response in the Ames test in the presence of rat liver homogenates, suggesting the importance of hepatic metabolic activation in its intoxication (Yamanaka et al., 1979;Kuhara et al., 1980;Xia et al., 2004). In our previous studies, hepatic microsomal metabolism of clivorine in male Sprague-Dawle...

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Section: Resultsmentioning

confidence: 99%

Section: Animals and Preparation Of Liver Microsomesmentioning

confidence: 99%

Deacetylclivorine: A Gender-Selective Metabolite of Clivorine Formed in Female Sprague-Dawley Rat Liver Microsomes

Lin

Tang²,

Liu³

et al. 2007

Drug Metab Dispos

Self Cite

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“…The species-, strain-or gender-depending variations in enzymatic activities or expressions, resulting in different overall balances of the detoxification and activation pathways, can influence the higher susceptibility of certain animals (e.g. male rat > guinea pig) to PA toxicity (Huan et al, 1998a;Lin et al, 2002Lin et al, , 2003Chung and Buhler, 2004;Lin et al, 2007).…”

Section: Metabolismmentioning

confidence: 99%

“…Several studies attempted to correlate the formation of reactive pyrrole metabolites to the marked differences in PA toxicity observed in different species (Shull et al, 1976;Cheeke, 1988;Huan et al, 1998aHuan et al, , 1998bLin et al, 2002;Fu et al, 2004). Species differences in the formation of pyrrolic metabolites and N-oxide from senecionine were studied in vitro in hepatic microsome fractions from hamsters, rats, rabbits, chickens, Japanese quail, sheep and cattle by Huan et al (1998a).…”

Section: Metabolismmentioning

confidence: 99%

Scientific Opinion on Pyrrolizidine alkaloids in food and feed

2011

EFS2

222

130

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The European Food Safety Authority (EFSA) was asked by the European Commission to deliver a scientific opinion on pyrrolizidine alkaloids (PA) in food and feed. PAs are toxins exclusively biosynthesised by plants. To date, approximately 600 different PAs are known. Results for 13,280 bulk honey and 1324 retail honey samples were provided to EFSA by one Member State and 351 feed samples were provided by a second Member State. The EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) performed estimates of both acute and chronic exposure to PAs through honey for three different age groups. Although there might be other sources of PA exposure, due to lack of data the CONTAM Panel was not able to quantify dietary exposure from food other than honey. A number of PAs were identified as being of particular importance for food and feed. Based on the present knowledge of metabolism, activation, DNA adduct-formation, genotoxicity and carcinogenicity, the CONTAM Panel concluded that 1,2-unsaturated PAs may act as genotoxic carcinogens in humans. Therefore, the CONTAM Panel decided to apply the Margin of Exposure (MOE) approach. A benchmark dose lower confidence limit for a 10 % excess cancer risk (BMDL 10 ) of 70 µg/kg b.w. per day for induction of liver haemangiosarcomas by lasiocarpine in male rats was calculated as the reference point for comparison with the estimated dietary exposure. The CONTAM Panel concluded that there is a possible health concern for those toddlers and children who are high consumers of honey. There is generally a low risk of PA poisoning in livestock and companion animals in the EU as most PA poisonings reported recently are due to accidental exposure. © European Pyrrolizidine alkaloids in food and feedEFSA Journal 2011;9(11):2406 2 SUMMARYFollowing a request from the European Commission, the Panel on Contaminants in the Food Chain (CONTAM Panel) was asked to deliver a scientific opinion on the risks to human and animal health related to the presence of pyrrolizidine alkaloids (PA) in food and feed. PAs are toxins exclusively biosynthesised by plants. They are typical plant secondary metabolites against herbivores. It has been estimated that approximately 6000 plant species world wide, representing 3 % of all flowering plants, may contain pyrrolizidine alkaloids. PAs are mainly found in the distantly related angiosperm families of the Boraginaceae (all genera), Asteraceae (tribes Senecioneae and Eupatorieae) and Fabaceae (genus Crotalaria). The PA-content of plant material depends on a large number of factors (species, plant organ, harvest, storage, extraction procedures). Reported contents vary from trace amounts up to 19 % based on dry weight. The name pyrrolizidine is the chemical description of two-fused 5-membered rings with a nitrogen atom at the bridgehead. This motif is the central structure of a variety of PAs. PAs generally consist of an amino alcohol which is referred to as necine or necine base and an acid part which is called a necic acid. Most of the known PAs are este...

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“…The two angeloyloxy groups accounted for four degrees of unsaturation. The remaining two degrees of unsaturation required the presence of a monocyclic sesquiterpene skeleton with a terminal C¼C bond The HMBC plot showed also cross-peaks for the ester C¼O atoms of the two angeloyloxy groups with HÀC(2) and HÀC (10), indicating that these two groups were attached to C(2) and C (10) H-COSY and HMBC [20 -22], which biosynthetically was probably derived from compound 3 (Scheme) [23]. The structure of 6 was finally eluci-dated as (1b,2b,3b,4a,6b) C-NMR and DEPT data of 6 showed the presence of ten Me, five CH 2 , and ten CH groups, and ten quaternary C-atoms (three ester C¼O), arising from two angeloyloxy groups (ten C-atoms), the bisabolane skeleton (fifteen C-atoms), and the extra C 10 1 H), 1.64 (s, 3 H), 1.58 -1.53 (m, 1 H), 1.31 -1.28 (m, 1 H) (Fig.…”

mentioning

confidence: 99%

Pyrrolizidine Alkaloids and Bisabolane Sesquiterpenes from the Roots of Ligularia cymbulifera

Liu

Wang

Wei

et al. 2008

Helvetica Chimica Acta

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The new pyrrolizidine alkaloid glycoside 1, and the three new highly oxygenated bisabolane sesquiterpenes 4 -6, together with the two known pyrrolizidine alkaloids 2 and 3, were isolated from the roots of Ligularia cymbulifera (W. W. Smith) Hand.-Mazz. Their structures were established on the basis of spectroscopic analysis, especially 1D-and 2D-NMR data. The cytotoxic activities of compounds 1, 2, and 4 -6 were evaluated against hepatoma (BEL-7402), human leukemia (HL-60), human ovarian carcinoma (HO-8910), and nasopharyngeal carcinoma (KB) cell lines (Tables 1 -3). Compound 6 showed weak cell-growth inhibition of BEL-7402 cell.Introduction. -Various types of sesquiterpenoids, such as eremophilane, guaiane, eudesmane, benzofurane, bisabolane (¼ 1-(1,5-dimethylhexyl)-4-methylcyclohexane), and phenolic norsesquiterpene, have been isolated from the genus Ligularia belonging to the tribe Senecioneae of the Compositae [1 -6]. Pyrrolizidine alkaloids are also widespread secondary metabolites in the genus Ligularia [7] [8]. However, in recent years, little attention has been paid to pyrrolizidine alkaloids from Ligularia. It is reported that the pyrrolizidine alkaloids possess antitumor activity, and many of them are also highly toxic and can cause poisoning in livestock and in humans [9 -13]. In the interests of public health and to systematically investigate the chemotaxonomic and bioactive components of pyrrolizidine alkaloids and sesquiterpenes of Ligularia plants, we continued to study the extract of Ligularia cymbulifera, which showed the presence of alkaloids due to a positive reaction to the Dragendorff reagent, and from which a new pyrrolizidine alkaloid 1 and the two known pyrrolizidine alkaloids 2 and 3 were obtained together with the three new highly oxygenated bisabolane sesquiterpenes 4 -6. The cytotoxicity of these compounds was screened against HL-60, BEL-7402, HO-8910, and KB cancer cell lines by using the MTT and SRB methods.

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Species Differences in the in Vitro Metabolic Activation of the Hepatotoxic Pyrrolizidine Alkaloid Clivorine

Cited by 39 publications

References 29 publications

Deacetylclivorine: A Gender-Selective Metabolite of Clivorine Formed in Female Sprague-Dawley Rat Liver Microsomes

Deacetylclivorine: A Gender-Selective Metabolite of Clivorine Formed in Female Sprague-Dawley Rat Liver Microsomes

Scientific Opinion on Pyrrolizidine alkaloids in food and feed

Pyrrolizidine Alkaloids and Bisabolane Sesquiterpenes from the Roots of Ligularia cymbulifera

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