Pyrrolizidine alkaloids in Crotalaria taxa from northern Australia: risk to grazing livestock

UHPLC-Q-TOF analysis of pyrrolizidine alkaloids in North-Macedonian honey

Honey contaminated with pyrrolizidine alkaloids (PAs) could pose a risk for human consumption, being a widely consumed food product. A fast and simple LC/MS method for the analysis of pyrrolizidine alkaloids in honey was optimised to collect occurrence data. The extraction efficiency was evaluated by a systematic study of multiple solvent mixtures and clean-up procedures. The best results for PA extraction were obtained using a formic acid/methanol mixture with subsequent clean-up by the QuEChERS method, resulting in a mean recovery range of 91.8-102%. The method validation showed satisfactory intra-day (RSD < 5.1%) and inter-day precision (RSD < 9.1%). The proposed method was applied to 14 samples. A total of six PAs and two N-oxides were detected, with levels between 89 and 8188 µg/kg. This assessment highlights the potential risk of intoxication and the need for further investigations regarding an effective quality system for manufacturers to control PAs in honey.

Mycotoxins, Phytoestrogens and Other Secondary Metabolites in Austrian Pastures: Occurrences, Contamination Levels and Implications of Geo-Climatic Factors

Pastures are key feed sources for dairy production and can be contaminated with several secondary metabolites from fungi and plants with toxic or endocrine-disrupting activities, which possess a risk for the health, reproduction and performance of cattle. This exploratory study aimed to determine the co-occurrences and concentrations of a wide range of mycotoxins, phytoestrogens and other secondary metabolites in grazing pastures. Representative samples of pastures were collected from 18 Austrian dairy farms (one sample per farm) between April to October 2019. After sample preparation (drying and milling) the pastures were subjected to multi-metabolite analysis using LC-MS/MS. In total, 68 metabolites were detected, including regulated zearalenone and deoxynivalenol (range: 2.16-138 and 107-505 μg/kg on a dry matter (DM) basis, respectively), modified (3-deoxynivalenol-glucoside, HT-2-glucoside) and emerging Fusarium mycotoxins (e.g., enniatins), ergot alkaloids and Alternaria metabolites along with phytoestrogens and other metabolites. Aflatoxins, fumonisins, T-2 toxin, HT-2 toxin and ochratoxins were not detected. Of the geo-climatic factors and botanical diversity investigated, the environment temperature (average of 2 pre-sampling months and the sampling month) was the most influential factor. The number of fungal metabolites linearly increased with increasing temperatures and temperatures exceeding 15 °C triggered an exponential increment in the concentrations of Fusarium and Alternaria metabolites and ergot alkaloids. In conclusion, even though the levels of regulated mycotoxins detected were below the EU guidance levels, the long-term exposure along with co-occurrence with modified and emerging mycotoxins might be an underestimated risk for grazing and forage-fed livestock. The one-year preliminary data points out a dominant effect of environmental temperature in the diversity and contamination level of fungal metabolites in pastures.

Pyrrolizidine-Derived Alkaloids: Highly Toxic Components in the Seeds of Crotalaria cleomifolia Used in Popular Beverages in Madagascar

Seeds of Crotalaria cleomifolia (Fabaceae) are consumed in Madagascar in preparation of popular beverages. The investigation of extracts from the seeds of this species revealed the presence of high amounts of alkaloids from which two pyrrolizidine-derived alkaloids were isolated. One of them was fully characterized by spectroscopic and spectrometric methods, which was found to be usaramine. Owing to the high toxicity of these alkaloids, issuing a strong warning among populations consuming the seeds of Crotalaria cleomifolia must be considered.

LC/MS study of the diversity and distribution of pyrrolizidine alkaloids in Crotalaria species growing in Colombia

Hepatotoxic and genotoxic pyrrolizidine alkaloids have been involved in the acute poisoning of animals and humans. Crotalaria (Fabaceae) species contain these alkaloids. In this work, the diversity and distribution of pyrrolizidine alkaloids in roots, leaves, flowers, and seeds of Crotalaria pallida, Crotalaria maypurensis, Crotalaria retusa, Crotalaria spectabilis, Crotalaria incana, and Crotalaria nitens were studied. Matrix solid-phase dispersion and ultra-high-performance liquid chromatography coupled with Orbitrap mass spectrometry were successfully employed in pyrrolizidine alkaloids extraction and analysis, respectively. Forty-five pyrrolizidine alkaloids were detected and their identification was based on the mass spectrometry accurate mass measurement and fragmentation pattern analysis. The cyclic retronecine-type diesters monocrotaline, crotaleschenine, integerrimine, usaramine, and their N-oxides were predominantly present. Five novel alkaloids were identified for the first time in Crotalaria species, namely 14-hydroxymonocrotaline, 12-acetylcrotaleschenine, 12-acetylmonocrotaline, 12-acetylintegerrimine, and dihydrointegerrimine. Due to a lack of commercially available standards, the response factor of monocrotaline was used for quantification of pyrrolizidine alkaloids and their N-oxides. Seeds and flowers possessed higher pyrrolizidine alkaloids amounts than roots and leaves. Due to their 1,2-unsaturated pyrrolizidine alkaloids content, the ingestion of Crotalaria plant seeds or other parts through herbal products, infusions, or natural remedies is a serious health threat to humans and livestock.

Crotalaria spectabilis as a source of pyrrolizidine alkaloids and phenolic compounds: HPLC-MS/MS dereplication and monocrotaline quantification of seed and leaf extracts

INTRODUCTION

Crotalaria spectabilis is an important species used as a pre-plant cover for soybean crops to control the proliferation of endoparasitic nematodes. Species from the Crotalaria genus are known for presenting pyrrolizidine alkaloids (PAs) in their composition, however, C. spectabilis is still considered chemically under-explored.

OBJECTIVE

The goal of this manuscript is the development and validation of a method for PAs and flavonoids identification and quantification of C. spectabilis seeds and leaves, a toxic plant used for nematode proliferation control in soil, especially in soybean crops.

MATERIALS AND METHODS

Seeds and leaves extracts were analysed by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) for the identification of the compounds.

RESULTS

PAs and phenolic compounds could be identified in both samples based on the MS/MS fragmentation pattern. Molecular formulas of the annotated compounds were confirmed by ultra-high-performace liquid chromatography-quadrupole time-of-flight (UHPLC-QToF), and monocrotaline could also be confirmed by standard comparison. The quantification of monocrotaline was performed by HPLC-MS/MS, resulting in 123 times higher monocrotaline content in seeds than in the leaves, which could explain its efficiency in combating nematode proliferation in soil.

CONCLUSION

This was the first report of phenolic compounds in C. spectabilis. The current study highlights the importance of C. spectabilis for nematode control due to the presence of toxic PAs, and the employment of analytical techniques for identification and quantification of compounds present in the extracts.

Analysis of Pyrrolizidine Alkaloids in Queensland Honey: Using Low Temperature Chromatography to Resolve Stereoisomers and Identify Botanical Sources by UHPLC-MS/MS

Pyrrolizidine alkaloids (PAs) are a diverse group of plant secondary metabolites with known varied toxicity. Consumption of 1,2-unsaturated PAs has been linked to acute and chronic liver damage, carcinogenicity and death, in livestock and humans, making their presence in food of concern to food regulators in Australia and internationally. In this survey, honey samples sourced from markets and shops in Queensland (Australia), were analysed by high-resolution Orbitrap UHPLC-MS/MS for 30 common PAs. Relationships between the occurrence of pyrrolizidine alkaloids and the botanical origin of the honey are essential as pyrrolizidine alkaloid contamination at up to 3300 ng/g were detected. In this study, the predominant alkaloids detected were isomeric PAs, lycopsamine, indicine and intermedine, exhibiting identical MS/MS spectra, along with lesser amounts of each of their N-oxides. Crucially, chromatographic UHPLC conditions were optimised by operation at low temperature (5 °C) to resolve these key isomeric PAs. Such separation of these isomers by UHPLC, enabled the relative proportions of these PAs present in honey to be compared to alkaloid levels in suspect source plants. Overall plant pyrrolizidine alkaloid profiles were compared to those found in honey samples to help identify the most important plants responsible for honey contamination. The native Australian vines of Parsonsia spp. are proposed as a likely contributor to high levels of lycopsamine in many of the honeys surveyed. Botanical origin information such as this, gained via low temperature chromatographic resolution of isomeric PAs, will be very valuable in identifying region of origin for honey samples.

Pyrrolizidine Alkaloids of Blue Heliotrope (Heliotropium amplexicaule) and Their Presence in Australian Honey

Blue heliotrope (Heliotropium amplexicaule) is an invasive environmental weed that is widely naturalized in eastern Australia and has been implicated as a source of pyrrolizidine alkaloid (PA) poisoning in livestock. Less well-documented is the potential of such carcinogenic alkaloids to contaminate honey from bees foraging on this plant species. In this study, the PA profile of H. amplexicaule plant material, determined by HRAM LC-MS/MS, revealed the presence of nine PAs and PA-N-oxides, including several PAs and PA-N-oxides of the indicine class, which have not previously been reported. The predominant alkaloid, indicine, represents 84% of the reduced PA content, with minor alkaloids identified as intermedine and the newly reported helioamplexine, constituting 7 and 9%, respectively. NMR analysis confirmed the identity of helioamplexine as a previously unreported indicine homologue. This is the first report of the isolation of intermedine, helioamplexine, and 3'-O-angelylindicine from H. amplexicaule. Also described is the identification of N-chloromethyl analogues of the major alkaloids as isolation-derived artifacts from reactions with dichloromethane. Analysis of regional-market honey samples revealed a number of honey samples with PA profiles analogous to that seen in H. amplexicaule, with measured PA contents of up to 2.0 μg of PAs per gram of honey. These results confirm the need for honey producers to be aware of H. amplexicaule as a potential PA source, most particularly in products where honey is sourced from a single location.

Toxicity of plant extracts containing pyrrolizidine alkaloids using alternative invertebrate models

Pyrrolizidine alkaloids (PAs) are a widespread class of hepatotoxic heterocyclic organic compounds found in approximately 3% of world flora. Some PAs have been shown to have genotoxic and carcinogenic effects. The present study focuses on the toxicity effects of four dry extracts obtained from medicinal plants (Senecio vernalis, Symphytum officinale, Petasites hybridus and Tussilago farfara), on two aquatic organisms, Artemia salina and Daphnia magna, and the correlation with their PAs content. A new GC‑MS method, using a retention time (TR)‑5MS type capillary column was developed. PAs Kovats retention indices, for this type of column were computed for the first time. The lethal dose 50% (LC50) values for the two invertebrate models were correlated (Pearson 's coefficient, >0.9) and the toxicity was PA concentration-dependent, for three of the four extracts. All tested extracts were found to be toxic in both aquatic organism models. The results can be used to develop a GC‑MS validated method for the assay of PAs in medicinal plants with a further potential application in the risk assessment study of PAs toxicity in humans.

Low pyrrolizidine alkaloid levels in perennial ryegrass is associated with the absence of a homospermidine synthase gene

BACKGROUND

Pyrrolizidine alkaloids (PAs) are a class of secondary metabolites that function as feeding deterrents in a range of different plant species. In perennial ryegrass (Lolium perenne L.) the only PAs that have been identified are the thesinine-rhamnoside group, which displays significant genetic variation. Homospermidine synthase (HSS) has evolved from deoxyhypusine synthase (DHS) and catalyses the first step in the PA pathway, making it a key candidate for the investigation of genes influencing observed PA trait variation.

RESULTS

During PCR amplification and sequence analysis of DHS we identified two putative HSS genes in perennial ryegrass. One of the genes (LpHSS1) was absent in some perennial ryegrass plants. Thesinine-rhamnoside levels were measured using liquid chromatography coupled with mass spectrometry in a diverse association mapping population, consisting of 693 plants free of fungal endophytic symbionts. Association tests that accounted for population structure identified a significant association of absence of the LpHSS1 gene with lower levels of thesinine-rhamnoside PAs. HSS-like gene sequences were identified for other grass species of the Poaceae, including tall fescue, wheat, maize and sorghum.

CONCLUSION

HSS is situated at the crucial first step in the PA pathway making it an important candidate gene for investigation of involvement in PA phenotypic variation. In this study, PA level in perennial ryegrass was strongly associated with the presence or absence of the LpHSS1 gene. A genetic marker, developed for the presence/absence of LpHSS1, may be used for marker-assisted breeding to either lower or increase PAs in breeding populations of perennial or Italian ryegrass to investigate a potential role in the deterrence of herbivore pests. The presence of HSS-like genes in several other Poaceae species suggests that PA biosynthesis may occur in plant family members beyond perennial ryegrass and tall fescue and identifies a potential route for manipulating PA levels.

Ultra-Performance Liquid Chromatography Hyphenated with Quadrupole-Orbitrap Mass Spectrometry for Simultaneous Determination of Necine-Core-Structure Pyrrolizidine Alkaloids in Crotalaria sessiliflora L. without all Corresponding Standards

INTRODUCTION

Crotalaria sessiliflora L. is a Chinese traditional herb for treatment of cutaneum carcinoma and cervical carcinoma. In addition to monocrotaline, coexisting pyrrolizidine alkaloids (PAs) also require further quantification for quality control and pharmaceutical uses of the herb.

OBJECTIVE

To establish a UPLC-Q-Orbitrap/MS method of simultaneous determination of coexisting PAs with same parent structure for quality control and comprehensive researches of Crotalaria sessiliflora L.

METHODOLOGY

PAs in Crotalaria sessiliflora L. were analysed by UPLC-Q-Orbitrap/MS method. Coexisting PAs were identified by mass data of full MS-dd-MS² based on the characteristic fragmentation pattern and necine-core structure. Moreover, quantification of PAs was conducted by parallel reaction monitoring (PRM) mode using m/z 138, m/z 120 and m/z 94 from identical necine-core structure as quantitative ions with single monocrotaline standard for accurate calibration.

RESULTS

Five PAs, named monocrotaline, retrorsine, senecionine, integerrimine, O-9-angeloylretronecine, were indentified and confirmed. Quantitative ions of m/z 138, m/z 120 and m/z 94 were used for quantification of PAs containing the necine-core structure in Crotalaria sessiliflora L. The results demonstrated that contents, precision and recoveries of the five PAs mentioned earlier were respectively 3.307-30.35 μg/g, 1.1-4.5% and 88.91-92.33% while using m/z 120 as the best quantitative ion.

CONCLUSION

The UPLC-Q-Orbitrap/MS method was established for simultaneous determination of five PAs in Crotalaria sessiliflora L. without all corresponding standards, and was proved that it was simple, convenient and effective for comprehensive quality control and pharmaceutical uses. Copyright © 2017 John Wiley & Sons, Ltd.

Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study

Objective To determine the association of different types of meat intake and meat associated compounds with overall and cause specific mortality.Design Population based cohort study.Setting Baseline dietary data of the NIH-AARP Diet and Health Study (prospective cohort of the general population from six states and two metropolitan areas in the US) and 16 year follow-up data until 31 December 2011.Participants 536 969 AARP members aged 50-71 at baseline.Exposures Intake of total meat, processed and unprocessed red meat (beef, lamb, and pork) and white meat (poultry and fish), heme iron, and nitrate/nitrite from processed meat based on dietary questionnaire. Adjusted Cox proportional hazards regression models were used with the lowest fifth of calorie adjusted intakes as reference categories.Main outcome measure Mortality from any cause during follow-up.Results An increased risk of all cause mortality (hazard ratio for highest versus lowest fifth 1.26, 95% confidence interval 1.23 to 1.29) and death due to nine different causes associated with red meat intake was observed. Both processed and unprocessed red meat intakes were associated with all cause and cause specific mortality. Heme iron and processed meat nitrate/nitrite were independently associated with increased risk of all cause and cause specific mortality. Mediation models estimated that the increased mortality associated with processed red meat was influenced by nitrate intake (37.0-72.0%) and to a lesser degree by heme iron (20.9-24.1%). When the total meat intake was constant, the highest fifth of white meat intake was associated with a 25% reduction in risk of all cause mortality compared with the lowest intake level. Almost all causes of death showed an inverse association with white meat intake.Conclusions The results show increased risks of all cause mortality and death due to nine different causes associated with both processed and unprocessed red meat, accounted for, in part, by heme iron and nitrate/nitrite from processed meat. They also show reduced risks associated with substituting white meat, particularly unprocessed white meat.

Toxicosis by Plant Alkaloids in Humans and Animals in Colombia

Due to its tropical location, chains of mountains, inter-Andean valleys, Amazon basin area, eastern plains and shores on both the Atlantic and Pacific Oceans, Colombia has many ecosystems and the second largest plant biodiversity in the world. Many plant species, both native and naturalized, are currently recognized as toxic for both animals and humans, and some of them are known to cause their toxic effects due to their alkaloid content. Among these, there are plants containing the hepatotoxic pyrrolizidine alkaloids, neurotoxins such as the indolizidine alkaloid swainsonine and the piperidine alkaloids coniine and γ-coniceine and tropane alkaloids. Unfortunately, the research in toxic plants in Colombia is not nearly proportional to its plant biodiversity and the scientific information available is only very scarce. The present review aims at summarizing the scarce information about plant alkaloid toxicosis in animals and humans in Colombia.

New aspect of plant-rhizobia interaction: alkaloid biosynthesis in Crotalaria depends on nodulation

Infection of legume hosts by rhizobial bacteria results in the formation of a specialized organ, the nodule, in which atmospheric nitrogen is reduced to ammonia. Nodulation requires the reprogramming of the plant cell, allowing the microsymbiont to enter the plant tissue in a highly controlled manner. We have found that, in Crotalaria (Fabaceae), this reprogramming is associated with the biosynthesis of pyrrolizidine alkaloids (PAs). These compounds are part of the plant's chemical defense against herbivores and cannot be regarded as being functionally involved in the symbiosis. PAs in Crotalaria are detectable only when the plants form nodules after infection with their rhizobial partner. The identification of a plant-derived sequence encoding homospermidine synthase (HSS), the first pathway-specific enzyme of PA biosynthesis, suggests that the plant and not the microbiont is the producer of PAs. Transcripts of HSS are detectable exclusively in the nodules, the tissue with the highest concentration of PAs, indicating that PA biosynthesis is restricted to the nodules and that the nodules are the source from which the alkaloids are transported to the above ground parts of the plant. The link between nodulation and the biosynthesis of nitrogen-containing alkaloids in Crotalaria highlights a further facet of the effect of symbiosis with rhizobia on the ecologically important trait of the plant's chemical defense.

A field investigation into a suspected outbreak of pyrrolizidine alkaloid toxicosis in horses in western Queensland

A disease outbreak investigation was conducted in western Queensland to investigate a rare suspected outbreak of pyrrolizidine alkaloid (PA) toxicosis in horses. Thirty five of 132 horses depastured on five properties on the Mitchell grass plains of western Queensland died in the first six months of 2010. Clinical-pathological findings were consistent with PA toxicosis. A local variety of Crotalaria medicaginea was the only hepatotoxic plant found growing on affected properties. Pathology reports and departure and arrival dates of two brood mares provided evidence of a pre wet season exposure period. All five affected properties experienced a very dry spring and early summer preceded by a large summer wet season. The outbreak was characterised as a point epidemic with a sudden peak of deaths in March followed by mortalities steadily declining until the end of June. The estimated morbidity (serum IGG>50IU/L) rate was 76%. Average crude mortality was 27% but higher in young horses (67%) and brood mares (44%). Logistic regression analysis showed that young horses and brood mares and those grazing denuded pastures in December were most strongly associated with dying whereas those fed hay and/or grain based supplements were less likely to die. This is the first detailed study of an outbreak of PA toxicosis in central western Queensland and the first to provide evidence that environmental determinants were associated with mortality, that the critical exposure period was towards the end of the dry season, that supplementary feeding is protective and that denuded pastures and the horses physiological protein requirement are risk factors.

Suspected pyrrolizidine alkaloid hepatotoxicosis in wild southern hairy-nosed wombats (Lasiorhinus latifrons)

Southern hairy-nosed wombats (Lasiorhinus latifrons) inhabiting degraded habitat in South Australia were recently identified with extensive hair loss and dermatitis and were in thin to emaciated body condition. Pathological and clinicopathological investigations on affected juvenile wombats identified a toxic hepatopathy suggestive of plants containing pyrrolizidine alkaloids, accompanied by photosensitive dermatitis. Hepatic disease was suspected in additional wombats on the basis of serum biochemical analysis. Preliminary toxicological analysis performed on scats and gastrointestinal contents from wombats found in this degraded habitat identified a number of toxic pyrrolizidine alkaloids consistent with ingestion of Heliotropeum europaeum. Although unpalatable, ingestion may occur by young animals due to decreased availability of preferred forages in degraded habitats and the emergence of weeds around the time of weaning of naive animals. Habitat degradation leading to malnutrition and ingestion of toxic weed species is a significant welfare issue in this species.

Protective Role of Comfrey Leave Extracts on UV-induced Zebrafish Fin Damage

In zebrafish, UV exposure leads to fin malformation phenotypes including fin reduction or absence. The present study evaluated UV-protective activities of comfrey leaves extracts in a zebrafish model by recording fin morphological changes. Chemopreventive effects of comfrey leave extracts were evaluated using Kaplan-Meier analysis and Cox proportional hazards regression. The results showed that (1) the mean times of return to normal fin in the UV+comfrey (50 and 100 ppm) groups were 3.43 and 2.86 days and were quicker compared with that in the UV only group (4.21 days); (2) zebrafish fins in the UV+comfrey (50 and 100 ppm) groups were 2.05 and 3.25 times more likely to return to normal than those in the UV only group; and (3) comfrey leave extracts had UV-absorbance abilities and significantly reduced ROS production in UV-exposed zebrafish embryos, which may attenuate UV-mediated apoptosis. In conclusion, comfrey leaves extracts may have the potential to be developed as UV-protective agents to protect zebrafish embryos from UV-induced damage.

Involvement of organic cation transporter 1 and CYP3A4 in retrorsine-induced toxicity

Retrorsine (RTS) is a hepatotoxic pyrrolizidine alkaloid present in plants of the Senecio genus. The present study is aimed at clarifying the role of organic cation transporters (OCTs) in the liver disposition of RTS, and the coupling of OCT1 and cytochrome P450 (CYP) 3A4 in the hepatotoxicity of RTS. MDCK or LLC-PK1 cells stably expressing liver uptake or efflux transporters were used to investigate the interaction of RTS with these transporters. Primary cultured rat hepatocytes (PCRH) and double-transfected MDCK-hOCT1-CYP3A4 cells were used to determine the contribution of OCT1 and CYP3A4 to the toxicity of RTS. The results showed that RTS inhibited the OCT1-mediated 1-methyl-4-phenylpyridinium (MPP(+)) uptake in MDCK-hOCT1 cells with the IC50 of 2.25±0.30μM. The uptake of RTS in MDCK-hOCT1 cells and PCRH was significantly inhibited by OCT1 inhibitors, while hOCT3, human multidrug and toxin extrusion (hMATE) transporter 1, multidrug resistance 1 (MDR1), and breast cancer resistance protein (BCRP) showed weak or no obvious interaction with RTS. The toxic effect of RTS on the PCRH was attenuated by OCT1 inhibitors, quinidine and (+)-tetrahydropalmatine ((+)-THP). Compared to mock cells, MDCK-CYP3A4 cells showed a decrease in viability after being treated with RTS. Furthermore, RTS showed a more severe toxicity in the OCT1/CYP3A4 double-transfected cells compared to all other cells. Our data suggests that OCT1 mediates the liver-specific uptake of RTS, and plays an important role in RTS-induced hepatotoxicity together with CYP3A4. Consequently, the OCT1 inhibitors could be applied to protect the liver from the toxicity of RTS.

Estrogenic and mutagenic activities of Crotalaria pallida measured by recombinant yeast assay and Ames test

Background

Crotalaria pallida Ailton is a plant belonging to the Fabaceae family, popularly known as “rattle or rattlesnake” and used in traditional medicine to treat swelling of the joints and as a vermifuge. Previous pharmacological studies have also reported anti-inflammatory, antimicrobial and antifungal activities. Nevertheless, scientific information regarding this species is scarce, and there are no reports related to its possible estrogenic and mutagenic effects. Thus, the purpose of the present study was to investigate the estrogenic potential of C. pallida leaves by means of the Recombinant Yeast Assay (RYA), seeking an alternative for estrogen replacement therapy during menopause; and to reflect on the safe use of natural products to assess the mutagenic activity of the crude extract from C. pallida leaves, the dichloromethane fraction and stigmasterol by means of the Ames test.

Methods

The recombinant yeast assay with the strain BY4741 of Saccharomyces cerevisiae, was performed with the ethanolic extract, dichloromethane fraction and stigmasterol isolated from the leaves of C. pallida. Mutagenic activity was evaluated by the Salmonella/microsome assay (Ames test), using the Salmonella typhimurium tester strains TA100, TA98, TA97 and TA102, with (+S9) and without (-S9) metabolization, by the preincubation method.

Results

All samples showed estrogenic activity, mainly stigmasterol. The ethanolic extract from C. pallida leaves showed mutagenic activity in the TA98 strain (-S9), whereas dichloromethane fraction and stigmasterol were found devoid of activity.

Conclusion

Considering the excellent estrogenic activity performed by stigmasterol in the RYA associated with the absence of mutagenic activity when evaluated by the Ames test, stigmasterol becomes a strong candidate to be used in hormone replacement therapy during menopause.

Pulmonary and hepatic lesions caused by the dehydropyrrolizidine alkaloid-producing plants Crotalaria juncea and Crotalaria retusa in donkeys

The effects and susceptibility of donkeys to Crotalaria juncea and Crotalaria retusa poisoning were determined at high and low doses. Seeds of C. juncea containing 0.074% of dehydropyrrolizidine alkaloids (DHPAs) (isohemijunceines 0.05%, trichodesmine 0.016%, and junceine 0.008%) were administered to three donkeys at 0.3, 0.6 and 1 g/kg body weight (g/kg) daily for 365 days. No clinical signs were observed and, on liver and lung biopsies, the only lesion was a mild liver megalocytosis in the donkeys ingesting 0.6 and 1 g/kg/day. Two other donkeys that received daily doses of 3 and 5 g seed/kg showed initial respiratory signs 70 and 40 days after the start of the administration, respectively. The donkeys were euthanized following severe respiratory signs and the main lung lesions were proliferation of Clara cells and interstitial fibrosis. Three donkeys ingested seeds of C. retusa containing 5.99% of monocrotaline at daily doses of 0.025, 0.05 and 0.1 g/kg for 365 days. No clinical signs were observed and, on liver and lung biopsies, the only lesion was moderate liver megalocytosis in each of the three donkeys. One donkey that received a single dose of 5 g/kg of C. retusa seeds and another that received 1 g/kg daily for 7 days both showed severe clinical signs and died with diffuse centrilobular liver necrosis. No lung lesions were observed. Another donkey that received a single dose of 2.5 g/kg of C. retusa seeds showed no clinical signs. The hepatic and pneumotoxic effects observed are consistent with an etiology involving DHPAs. Furthermore, the occurrence of lung or liver lesions correlates with the type of DHPAs contained in the seeds. Similarly as has been reported for horses, the data herein suggest that in donkeys some DHPAs are metabolized in the liver causing liver disease, whereas others are metabolized in the lung by Clara cells causing lung disease.

Dehydropyrrolizidine alkaloids, including monoesters with an unusual esterifying acid, from cultivated Crotalaria juncea (Sunn Hemp cv.'Tropic Sun')

Cultivation of Crotalaria juncea L. (Sunn Hemp cv. 'Tropic Sun') is recommended as a green manure crop in a rotation cycle to improve soil condition, help control erosion, suppress weeds, and reduce soil nematodes. Because C. juncea belongs to a genus that is known for the production of toxic dehydropyrrolizidine alkaloids, extracts of the roots, stems, leaves, and seeds of 'Tropic Sun' were analyzed for their presence using HPLC-ESI/MS. Qualitative analysis identified previously unknown alkaloids as major components along with the expected macrocyclic dehydropyrrolizidine alkaloid diesters, junceine and trichodesmine. The dehydropyrrolizidine alkaloids occurred mainly as the N-oxides in the roots, stems, and, to a lesser extent, leaves, but mainly as the free bases in the seeds. Comprehensive spectrometric and spectroscopic analysis enabled elucidation of the unknown alkaloids as diastereoisomers of isohemijunceine, a monoester of retronecine with an unusual necic acid. The dehydropyrrolizidine alkaloid contents of the roots, stems, and leaves of immature plants were estimated to be 0.05, 0.12, and 0.01% w/w, respectively, whereas seeds were estimated to contain 0.15% w/w.

Crotalaria medicaginea associated with horse deaths in northern Australia: new pyrrolizidine alkaloids

Crotalaria medicaginea has been implicated in horse poisoning in grazing regions of central-west Queensland, which resulted in the deaths of more than 35 horses from hepatotoxicosis in 2010. Liver pathology was suggestive of pyrrolizidine alkaloidosis, and we report here the isolation of two previously uncharacterized pyrrolizidine alkaloids from C. medicaginea plant specimens collected from pastures where the horses died. The first alkaloid was shown by mass spectometric and NMR analyses to be 1β,2β-epoxy-7β-hydroxy-1α-methoxymethyl-8α-pyrrolizidine, which, like other alkaloids previously isolated from C. medicaginea, lacks the requisite functionality for hepatotoxcity. The second alkaloid isolated in this investigation was a new macrocyclic diester of otonecine, which we have named cromedine. The (1)H and (13)C NMR spectra of cromedine were fully assigned by 2D NMR techniques and allowed the constitution of the macrocyclic diester to be assigned unambiguously. C. medicaginea specimens implicated in this investigation do not belong to any of the three recognized Australian varieties (C. medicaginea var. neglecta, C. medicaginea var. medicaginea, and C. medicaginea var. linearis) and appear to be a local variant or form, referred to here as C. medicaginea (chemotype cromedine).

MicroRNA expression profiles distinguish the carcinogenic effects of riddelliine in rat liver

Pyrrolizidine alkaloids (PAs) are the most common plant constituents that poison livestock, wildlife and humans. Riddelliine is a prototype genotoxic PA and has been nominated to be classified as a reasonably anticipated human carcinogen by the US National Toxicology Program (NTP) in the 12th Report on Carcinogens. Riddelliine's nomination is due to the high incidence of liver tumours that were observed in both mice and rats in the NTP tumourigenicity bioassay study. In this current study, we explored whether riddelliine treatment could alter microRNA (miRNA) expression in rat liver and whether the possible deregulation of miRNA was related to mutagenicity and carcinogenicity of riddelliine. Groups of six rats were administered riddelliine at a mutagenic dose of 1 mg/kg body weight or with control vehicle 5 days a week for 12 weeks. A group of six rats treated with aristolochic acid, a renal carcinogen, was used as a tissue-specific negative control. The animals were sacrificed 1 day after the last treatment and the livers were isolated for miRNA expression analysis using miRNA microarrays. miRNA expression was significantly altered by riddelliine treatment. Principal component analysis and hierarchical clustering analysis showed that the miRNA expression profiles were clearly classified into two groups, riddelliine treatment versus other samples. Forty-seven miRNAs were significantly dysregulated by riddelliine treatment, among which 38 were up-regulated and 9 were down-regulated. Functional analysis of these differentially expressed miRNAs by riddelliine revealed that these miRNAs were involved in liver carcinogenicity and toxicity, such as liver proliferation, liver necrosis/cell death, hepatocellular carcinoma, liver hepatomegaly, liver inflammation and liver fibrosis. These results suggest that miRNAs actively respond to a mutagenic dose of riddelliine and the pattern of miRNA expression has the potential to be used as a biomarker of genotoxicity and carcinogenicity for riddelliine and possibly other PAs.

Genotoxicity of pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) are common constituents of many plant species around the world. PA-containing plants are probably the most common poisonous plants affecting livestock and wildlife. They can inflict harm to humans through contaminated food sources, herbal medicines and dietary supplements. Half of the identified PAs are genotoxic and many of them are tumorigenic. The mutagenicity of PAs has been extensively studied in different biological systems. Upon metabolic activation, PAs produce DNA adducts, DNA cross-linking, DNA breaks, sister chromatid exchange, micronuclei, chromosomal aberrations, gene mutations and chromosome mutations in vivo and in vitro. PAs induced mutations in the cII gene of rat liver and in the p53 and K-ras genes of mouse liver tumors. It has been suggested that all PAs produce a set of (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine-derived DNA adducts and similar types of gene mutations. The signature types of mutations are G : C --> T : A transversion and tandem base substitutions. Overall, PAs are mutagenic in vivo and in vitro and their mutagenicity appears to be responsible for the carcinogenesis of PAs.