1,2-Dehydropyrrolizidine Alkaloids: Their Potential as a Dietary Cause of Sporadic Motor Neuron Diseases

Sporadic motor neuron diseases (MNDs), such as amyotrophic lateral sclerosis (ALS), can be caused by spontaneous genetic mutations. However, many sporadic cases of ALS and other debilitating neurodegenerative diseases (NDDs) are believed to be caused by environmental factors, subject to considerable debate and requiring intensive research. A common pathology associated with MND development involves progressive mitochondrial dysfunction and oxidative stress in motor neurons and glial cells of the central nervous system (CNS), leading to apoptosis. Consequent degeneration of skeletal and respiratory muscle cells can lead to death from respiratory failure. A significant number of MND cases present with cancers and liver and lung pathology. This Perspective explores the possibility that MNDs could be caused by intermittent, low-level dietary exposure to 1,2-dehydropyrrolizidine alkaloids (1,2-dehydroPAs) that are increasingly recognized as contaminants of many foods consumed throughout the world. Nontoxic, per se, 1,2-dehydroPAs are metabolized, by particular cytochrome P450 (CYP450) isoforms, to 6,7-dihydropyrrolizines that react with nucleophilic groups (-NH, -SH, -OH) on DNA, proteins, and other vital biochemicals, such as glutathione. Many factors, including aging, gender, smoking, and alcohol consumption, influence CYP450 isoform activity in a range of tissues, including glial cells and neurons of the CNS. Activation of 1,2-dehydroPAs in CNS cells can be expected to cause gene mutations and oxidative stress, potentially leading to the development of MNDs and other NDDs. While relatively high dietary exposure to 1,2-dehydroPAs causes hepatic sinusoidal obstruction syndrome, pulmonary venoocclusive disease, neurotoxicity, and diverse cancers, this Perspective suggests that, at current intermittent, low levels of dietary exposure, neurotoxicity could become the primary pathology that develops over time in susceptible individuals, along with a tendency for some of them to also display liver and lung pathology and diverse cancers co-occurring with some MND/NDD cases. Targeted research is recommended to investigate this proposal.

Guidelines for unequivocal structural identification of compounds with biological activity of significance in food chemistry (IUPAC Technical Report)

Isolation of endogenous constituents of foods is generally performed in order to elucidate the biological activity of individual compounds and their role with respect to factors such as organoleptic qualities, health and nutritional benefits, plant protection against herbivores, pathogens and competition, and presence of toxic constituents. However, unless such compounds are unequivocally defined with respect to structure and purity, any biological activity data will be compromised. Procedures are therefore proposed for comprehensive elucidation of food-based organic structures using modern spectroscopic and spectrometric techniques. Also included are guidelines for the experimental details and types of data that should be reported in order for subsequent investigators to repeat and validate the work. Because food chemistry usually involves interdisciplinary collaboration, the purpose is to inform chemists and scientists from different fields, such as biological sciences, of common standards for the type and quality of data to be presented in elucidating and reporting structures of biologically active food constituents. The guidelines are designed to be understandable to chemists and non-chemists alike. This will enable unambiguous identification of compounds and ensure that the biological activity is based on a secure structural chemistry foundation.

Pyrrolizidine alkaloids in medicinal plants from North America

Pyrrolizidine alkaloids (PAs) are mutagenic, carcinogenic, pneumotoxic, teratogenic and fetotoxic. Plants containing PAs commonly poison livestock in many countries, including the USA and Canada. In some regions of the world PA-producing plants sometimes grow in grain crops and items of food made with PA contaminated grain, such as bread baked using contaminated flour, have been, and continue to be, responsible for large incidents of acute, often fatal human poisoning. Herbal medicines and food supplements containing PAs are also recognized as a significant cause of human poisoning and it is desirable that such medications are identified and subjected to strict regulation. In this review we consider the PAs known to be, or likely to be, present in both the traditionally used medicinal plants of North America and also medicinal plants that have been introduced from other countries and are being recommended and used as phytopharmaceuticals in the USA and Canada.

Pyrrolizidine Alkaloids: Potential Role in the Etiology of Cancers, Pulmonary Hypertension, Congenital Anomalies, and Liver Disease

Large outbreaks of acute food-related poisoning, characterized by hepatic sinusoidal obstruction syndrome, hemorrhagic necrosis, and rapid liver failure, occur on a regular basis in some countries. They are caused by 1,2-dehydropyrrolizidine alkaloids contaminating locally grown grain. Similar acute poisoning can also result from deliberate or accidental consumption of 1,2-dehydropyrrolizidine alkaloid-containing herbal medicines, teas, and spices. In recent years, it has been confirmed that there is also significant, low-level dietary exposure to 1,2-dehydropyrrolizidine alkaloids in many countries due to consumption of common foods such as honey, milk, eggs, salads, and meat. The level of 1,2-dehydropyrrolizidine alkaloids in these foods is generally too low and too intermittent to cause acute toxicity. However, these alkaloids are genotoxic and can cause slowly developing chronic diseases such as pulmonary arterial hypertension, cancers, cirrhosis, and congenital anomalies, conditions unlikely to be easily linked with dietary exposure to 1,2-dehydropyrrolizidine alkaloids, especially if clinicians are unaware that such dietary exposure is occurring. This Perspective provides a comprehensive review of the acute and chronic toxicity of 1,2-dehydropyrrolizidine alkaloids and their potential to initiate certain chronic diseases, and suggests some associative considerations or indicators to assist in recognizing specific cases of diseases that may have resulted from dietary exposure to these hazardous natural substances. If it can be established that low-level dietary exposure to 1,2-dehydropyrrolizidine alkaloids is a significant cause of some of these costly and debilitating diseases, then this should lead to initiatives to reduce the level of these alkaloids in the food chain.

Pyrrolizidine alkaloids in food: a spectrum of potential health consequences

Contamination of grain with 1,2-dehydropyrrolizidine ester alkaloids (dehydroPAs) and their N-oxides is responsible for large incidents of acute and subacute food poisoning, with high morbidity and mortality, in Africa and in central and south Asia. Herbal medicines and teas containing dehydroPAs have also caused fatalities in both developed and developing countries. There is now increasing recognition that some staple and widely consumed foods are sometimes contaminated by dehydroPAs and their N-oxides at levels that, while insufficient to cause acute poisoning, greatly exceed maximum tolerable daily intakes and/or maximum levels determined by a number of independent risk assessment authorities. This suggests that there may have been cases of disease in the past not recognised as resulting from dietary exposure to dehydroPAs. A review of the literature shows that there are a number of reports of liver disease where either exposure to dehydroPAs was suspected but no source was identified or a dehydroPA-aetiology was not considered but the symptoms and pathology suggests their involvement. DehydroPAs also cause progressive, chronic diseases such as cancer and pulmonary arterial hypertension but proof of their involvement in human cases of these chronic diseases, including sources of exposure to dehydroPAs, has generally been lacking. Growing recognition of hazardous levels of dehydroPAs in a range of common foods suggests that physicians and clinicians need to be alert to the possibility that these contaminants may, in some cases, be a possible cause of chronic diseases such as cirrhosis, pulmonary hypertension and cancer in humans.

Safety assessment of food and herbal products containing hepatotoxic pyrrolizidine alkaloids: interlaboratory consistency and the importance of N-oxide determination

INTRODUCTION

Two recent mass spectrometry-based reports concerning Senecio scandens yielded remarkably dissimilar pyrrolizidine alkaloid constituents. In both studies, and in a related analysis of Senecio scandens and Tussilago farfara using micellar electrokinetic chromatography, the presence of hazardous N-oxides of the alkaloids was either not considered or was inadequately considered. This raises concerns about the effectiveness of the methodologies used in these, and similar, studies in assessing the pyrrolizidine alkaloid content and the safety of food, food supplements and medicines for human use.

OBJECTIVE

To highlight essential analytical requirements for confident assessment of pyrrolizidine alkaloid-related safety of food and herbal products for human use.

METHODOLOGY

Direct infusion-ESI MS and HPLC-ESI MS were used to analyse samples derived from liquid-liquid partitioning experiments and from strong cation exchange, solid-phase extraction of pyrrolizidine alkaloids and their N-oxides.

RESULTS

A simple solvent partitioning experiment using pure senecionine and senecionine-N-oxide, two constituents reported in one of the mass spectrometry-based studies of S. scandens, clearly demonstrated the inadequacy of the reported method to detect and quantitate hazardous pyrrolizidine alkaloid N-oxide components. A preliminary LCMS analysis of commercially-prepared extracts of comfrey roots (Symphytum officinale and S. uplandicum s. l.) was used as a model to highlight the analytical importance of N-oxides in the safety assessment of pyrrolizidine alkaloid-containing medicinal herbs.

CONCLUSIONS

This study highlighted significant differences in the reported identification of pyrrolizidine alkaloids from the same plant species, and clearly demonstrated the inadequacy of some procedures to include N-oxides in the assessment of pyrrolizidine alkaloid-related safety of food and herbal products.

Hepatotoxic pyrrolizidine alkaloids in pollen and drying-related implications for commercial processing of bee pollen

Using HPLC-ESI-MS, several saturated and 1,2-dehydropyrrolizidine alkaloids were detected, mainly as their N-oxides, in fresh pollen collected from flowers of the pyrrolizidine alkaloid-producing plants Echium vulgare, E. plantagineum, Senecio jacobaea, S. ovatus, and Eupatorium cannabinum, and/or pollen loads from bees (bee pollen) that foraged on those plants. A major alkaloidal metabolite in S. ovatus was tentatively identified, using its mass spectrometric data and biogenic considerations, as the previously unreported, saturated alkaloid, 2-hydroxysarracine. Heating had very little effect on the 1,2-dehydropyrrolizidine alkaloids and their N-oxides from a variety of sources. Considered in conjunction with international concerns about the adverse effects of these alkaloids, the results strongly indicate a need for monitoring pollen supplies intended for human consumption, at least until conditions for processing and/or selection are clearly defined such as to significantly reduce the hepatotoxic (and potentially carcinogenic and genotoxic) pyrrolizidine alkaloid content of bee pollen.

Formation of DHP-derived DNA adducts from metabolic activation of the prototype heliotridine-type pyrrolizidine alkaloid, lasiocarpine

Pyrrolizidine alkaloids (PAs) are probably the most common poisonous plants affecting livestock, wildlife, and humans. The PAs that have been found to be tumorigenic in experimental animals belong to the retronecine-, heliotridine-, and otonecine-type PAs. Our recent mechanistic studies indicated that riddelliine, a tumorigenic retronecine-type PA, induced tumors via a genotoxic mechanism mediated by the formation of 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP)-derived DNA adducts. The same adducts were formed from clivorine, a tumorigenic otonecine-type PA from metabolism of clivorine by rat liver microsomes in the presence of calf thymus DNA. In this study, we report that metabolism of lasiocarpine, the prototype heliotridine PA, by F344 rat liver microsomes resulted in the formation of DHP. When incubated in the presence of calf thymus DNA, the same DHP-derived DNA adducts were formed. These results suggest that these DHP-derived DNA adducts are potential biomarkers of exposure and tumorigenicity for all types of PAs.

Solid-phase extraction and HPLC-MS profiling of pyrrolizidine alkaloids and their N-oxides: a case study of Echium plantagineum

Pyrrolizidine alkaloids and their N-oxides can be extracted from the dried methanolic extracts of plant material using dilute aqueous acid. The subsequent integration of solid-phase extraction (with a strong cation exchanger) of the alkaloids and N-oxides from the aqueous acid solution, together with analysis using HPLC-ESI/MS, provides a method for the simultaneous profiling of the pyrrolizidine alkaloids and their N-oxides in plant samples and the collection of useful structural data as an aid in their identification. The N-oxide character of the analytes may be confirmed by treating analytical samples with a redox resin and observing the formation of the corresponding parent pyrrolizidine alkaloids. The present case study of Echium plantagineum highlighted a higher ratio of N-oxides to the parent tertiary bases than has been previously reported. Furthermore, a higher proportion of acetylated pyrrolizidine-N-oxides was observed in the flower heads relative to the leaves. Six pyrrolizidine alkaloids or pyrrolizidine-N-oxides, not previously reported from E. plantagineum, were tentatively identified on the basis of MS and biogenetic considerations. Three of these, 3'-O-acetylintermedine/lycopsamine, leptanthine-N-oxide and 9-O-angelylretronecine-N-oxide, have been reported elsewhere, whilst three others, 3'-O-acetylechiumine-N-oxide, echimiplatine-N-oxide and echiuplatine-N-oxide, appear unreported from any other source.

Pyrrolizidine alkaloids of Echium vulgare honey found in pure pollen

The pyrrolizidine alkaloids previously identified in floral honey attributed to Echium vulgare (Boraginaceae) have been detected (8000-14 000 ppm) in pure pollen collected from the anthers of Echium vulgare. Pyrrolizidine alkaloids and/or their N-oxides were isolated from the aqueous acid extracts of pollen by use of strong cation-exchange, solid-phase extraction and identified by liquid chromatographic/mass spectrometric (LCMS) analysis. The pyrrolizidine alkaloids in the pollen are present mainly as the N-oxides. In addition to seven previously described pyrrolizidine alkaloids and/or their N-oxides (echimidine, acetylechimidine, uplandicine, 9-O-angelylretronecine, echiuplatine, leptanthine, and echimiplatine), one unidentified (echivulgarine), but previously found in honey, and two previously undescribed (vulgarine and 7-O-acetylvulgarine) pyrrolizidine alkaloids and/or their N-oxides were identified in the pollen. Tentative structures for these unidentified pyrrolizidine alkaloids are proposed on the basis of the mass spectrometric data and biogenetic considerations. The implications of these results for identifying the source and subsequent concentrations of pyrrolizidine alkaloids in honeys and commercial bee pollen are briefly discussed.

Solid-phase extraction and LC-MS analysis of pyrrolizidine alkaloids in honeys

Strong-cation-exchange, solid-phase extraction of pyrrolizidine alkaloids and their N-oxides from honey samples was followed by reduction of the N-oxides and subsequent analysis of total pyrrolizidine alkaloids using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry. A limited survey of 63 preprocessing samples of honey, purposefully biased toward honeys attributed to floral sources known to produce pyrrolizidine alkaloids, demonstrated levels of pyrrolizidine alkaloids up to approximately 2000 parts per billion (ppb) in a sample attributed to Echium plantagineum. Up to 800 ppb pyrrolizidine alkaloids was detected in some honeys not attributed by the collector to any pyrrolizidine alkaloid-producing floral source. No pyrrolizidine alkaloids were detected in approximately 30% of the samples in this limited study, while some honeys showed the copresence of pyrrolizidine alkaloids from multiple floral sources such as E. plantagineum and Heliotropium europaeum. In addition, retail samples of blended honeys (with no labeling to suggest that pyrrolizidine alkaloid-producing floral sources were used in the blends) have been shown to contain up to approximately 250 ppb pyrrolizidine alkaloids.

Preparative isolation of swainsonine from locoweed: extraction and purification procedures

The trihydroxy indolizidine alkaloid swainsonine, a plant toxin with potent alpha-mannosidase-inhibitory activity and chemotherapeutic potential, was isolated in gram quantities from locoweed (Astragalus lentiginosus). The key isolation and purification step was a continuous liquid/liquid extraction procedure using dichloromethane to extract a basified aqueous methanol solution obtained after isolation of the polar base fraction by ion-exchange. The concentration of swainsonine was increased from ca. 7% in the polar base material to 68% using the liquid/liquid extraction procedure. Pure swainsonine was then obtained by recrystallisation from ammonia-saturated chloroform or by sublimation. Small samples of swainsonine were also purified by formation of the chloroform-soluble methylboronate derivative, from which the alkaloid could be regenerated easily by hydrolysis.

Poisoning of livestock in oregon in the 1940s to 1960s attributed to corynetoxins produced by Rathayibacter in nematode galls in chewings fescue (Festuca nigrescens)

Tunicaminyluracil antibiotics, similar to the corynetoxins produced by Rathayibacter toxicus in Australia and South Africa, were found in old nematode seed-galls from Festuca nigrescens from New Jersey (USA) and New Zealand (NZ). The toxin profiles from the NZ and USA galls were similar to each other, but differed from those produced by R toxicus from Australia and South Africa, suggesting that a geographical variant of R toxicus or closely related species may be involved. The NZ galls gave a positive response to a R toxicus-specific monoclonal antibody assay, albeit a considerably weaker response than that seen with Australian R toxicus galls, but the older USA galls were negative, possibly due to deterioration of the antigen. From these findings, it is postulated that livestock deaths associated with the feeding of nematode and bacterial infected screenings of F nigrescens in Oregon, USA, in the 1940s to 1960s were caused by corynetoxin-like toxins produced by the bacterium.

Toxic effects of a single parenteral dose of tunicamycin in late stage pregnancy in rats

Tunicamycin (TM) was given as a single parenteral dose at 3 levels to female rats at gestation day 15 (GD 15) and also to non-pregnant rats. At 16 h post-dosing all pregnant rats had moderate to extensive vaginal bleeding and 1/4 at each of the 2 higher doses died. The other severely affected rats, euthanized after 26-28 h, had free blood in the uterus and large decreases in red cell count (RCC), hemoglobin (Hb) and packed cell volume (PCV). The amnion of the fetuses was very easily detached from the maternal placenta by gentle manipulation. Histologically, hemorrhage, venous thrombosis and ischemic necrosis, particularly in the maternal placenta, were consistent with the gross appearance. There was no hemorrhage in any control pregnant rats. In the remaining TM-treated pregnant rats, euthanized at GD 17, there were lesser dose-related decreases in RCC, Hb and PCV, but there was no evidence of bleeding or changes in red blood cell parameters in non-pregnant rats. There was a dose-related decrease in cholesterol and GlcNAc-1-P transferase (GPT) activity and a treatment-related decrease in serum proteins in all rats. Maternal toxicity was demonstrated in pregnant rats at TM doses < 10% of a TM lethal dose in non-pregnant rats.

Honey from plants containing pyrrolizidine alkaloids: a potential threat to health

Following scientific risk assessments, several countries have imposed strict regulations on herbal medicines containing 1,2-dehydro-pyrrolizidine alkaloids. Using published data on the plants used in honey production, pyrrolizidine alkaloid-containing plants are shown in this review to represent a significant source of honey worldwide. This observation, honey consumption data, reported levels of pyrrolizidine alkaloids in honeys, and consideration of tolerable exposure levels determined for pyrrolizidine alkaloids in herbal medicines, leads to the conclusion that some honey is a potential threat to health, especially for infants and fetuses, and further investigation is warranted.

Dielectric Spectroscopic and Molecular Simulation Evidence for Aggregation of Surfactant-stabilized Calcium Carbonate Nanocolloids in Organic Media

Dielectric spectroscopy carried out on overbased phenate micelle particles of nominal diameter approximately 2 nm containing calcium carbonate cores in hydrophobic liquids indicates that the micelles are strongly aggregated. Mean cluster sizes in excess of approximately 10(3) individual micelles are typically found in toluene. The level of association is a little higher in dodecane which is chemically closer to engine oil, the usual solvent for these systems. The mean aggregate size increases dramatically with concentration above an effective solids volume fraction of approximately 0.1 on treating the micelles as spheres. Aggregate size also depends on the level of overbasing, with lower levels of overbasing giving more micelles in the cluster. Molecular dynamics simulations of individual micelle particles reveal them to have large dipole moments originating mainly from the amorphous carbonate cores. Dipoles of magnitude approximately 20D are typical for a range of different surfactant types used in the model. The magnitude of the dipole depends somewhat on the chemical composition of the stabilizing surfactant shell. Monte Carlo simulations of two phenate nanocolloids taking into account all atom and charge pair interactions show these particles to have a strong short-range coulombic attraction of typically -25kBT at T = 298 K in the favored "side-by-side" relative arrangement. This attraction could be responsible for the strong level of association inferred from the dielectric spectroscopy experiments. Copyright 1999 Academic Press.

Pyrrolizidine alkaloid plants, metabolism and toxicity

More than 350 PAs have been identified in over 6,000 plants in the Boraginaceae, Compositae, and Leguminosae families (Table 1). About half of the identified PAs are toxic and several have been shown to be carcinogenic in rodents. PA-containing plants have worldwide distribution, and they probably are the most common poisonous plants affecting livestock, wildlife, and humans. In many locations, PA-containing plants are introduced species that are considered invasive, noxious weeds. Both native and introduced PA-containing plants often infest open ranges and fields, replacing nutritious plants. Many are not palatable and livestock avoid eating them if other forages are available. However, as they invade fields or crops, plant parts or seeds can contaminate prepared feeds and grains which are then readily eaten by many animals. Human poisonings most often are a result of food contamination or when PA-containing plants areused for medicinal purposes. This is a review of current information on the diagnosis, pathogenesis, and molecular mechanisms of PA toxicity. Additional discussion includes current and future research objectives with an emphasis on the development of better diagnostics, pyrrole kinetics, and the effects of low dose PA exposure.

Immobilisation of IgG onto gold surfaces and its interaction with anti-IgG studied by surface plasmon resonance

The optical excitation of surface plasmon resonance (SPR) at a metal dielectric interface has been used to study the binding of immunoglobulin G (IgG) to gold and anti-IgG to immobilised IgG layers. In these studies both a monoclonal mouse and polyclonal sheep IgG were used as receptor layers for anti-IgG. The kinetics of binding were investigated by monitoring the reflectivity of light at an angle close to plasmon resonance. Both the initial rate of change and final reflectivity were measured during and after protein binding. The amount of protein bound to the surface was found to be less for the monoclonal mouse IgG compared to the polyclonal sheep IgG, these two IgG nominally being of the same dimensions and molecular weight. Further, anti-IgG binding produced greater changes in reflectivity than the initial IgG layers. By fitting the full angle-dependent reflectivity data to the Fresnel equation the effective protein layer thicknesses of IgG and anti-IgG as a function of concentration were determined. Differences in the effective thickness of the bound layer for the two IgG was observed, the mouse IgG having a thinner effective thickness compared with the sheep IgG. The limitations of direct binding of protein to metal surfaces in SPR biosensor applications are discussed.

Mannitol metabolism in Eimeria tenella

Unsporulated oocysts of Eimeria tenella contain large quantities of carbohydrates, namely amylopectin, mannitol and glucose. Analysis of carbohydrate content of sporulating oocysts revealed that mannitol content increased markedly during early stages of sporogony (first 4-6h) but slowly diminished during the next 40h of sporulation. Accumulation of mannitol was accompanied by a rapid decrease in amylopectin and free glucose, suggesting that mannitol might be synthesized from glucose released from amylopectin. Mannitol was also detected in sporozoite and merozoite extracts. All four mannitol cycle enzymes were detected in oocysts. Sporozoites excysted in vitro had lower activities of all four enzymes. Mannitol-1-phosphatase and mannitol dehydrogenase activity was also detected in merozoites obtained from the second stage schizonts. Sporozoites incubated with 14C-glucose accumulated radioactively labelled precursor continuously for over 12h and some of the 14C-glucose was converted into 14C-mannitol. These results indicate that mannitol plays an important role in the metabolism and development of the intracellular stages of the parasite.

Pyrrolizidine alkaloid composition of three Chinese medicinal herbs, Eupatorium cannabinum, E. japonicum and Crotalaria assamica

The pyrrolizidine alkaloid composition of three Chinese herbs, "pei lan", "cheng gan cao" and "zi xiao rong," identified respectively as Eupatorium cannabinum, Eupatorium japonicum (Compositae) and Crotalaria assamica (Leguminosae), were studied by fast atom bombardment mass spectrometry and gas chromatography-electron impact mass spectrometry. Viridiflorine, cynaustraline, amabiline, supinine, echinatine, rinderine and isomers of these alkaloids were found in the Eupatorium species. Monocrotaline was the only pyrrolizidine alkaloid detected in the Crotalaria species.

Identification of 5 beta-pregnane and 5 beta-androstane derivatives in adrenal venous and peripheral blood plasma of the female possum (Trichosurus vulpecula)

In the possum a marked sex difference has been found in the steroids in adrenal venous plasma. Four 5 beta-pregnane and four 5 alpha (beta) androstane derivatives together with ten 4-ene-3-keto steroids were isolated from the adrenal venous plasma of the female and definitively identified by gas chromatography-mass spectrometry. The major reduced steroids were: 5 beta-pregnane-3 alpha,17 alpha-diol-20-one and 5 beta-pregnane-3 alpha,17 alpha,20 alpha-triol, at concentrations of 52 +/- 12 micrograms/100 ml and 44 +/- 8 micrograms/100 ml mean +/- SEM respectively. The concentration of cortisol was 198 +/- 47 micrograms/100 ml. The concentration of the 2 reduced steroids in peripheral plasma were approx. 100 times less. In contrast the adrenal venous plasma of a male contained 14 steroids of which only three, found in trace amounts, were reduced. The results confirm previous in vitro observations that reduced steroids are produced by the adrenocortical special zone, which is only present in the female. The physiological significance of the presence of reduced steroids of adrenocortical origin in the circulation of the female possum is discussed.

Identification of 5 alpha-androstane-3 alpha,17 alpha-diol in adrenal venous plasma of female possum (Trichosurus vulpecula)

Two hitherto unidentified C19 steroids were isolated from adrenal venous blood plasma of female possum (Trichosurus vulpecula). They were 5 alpha-androstane-3 alpha,17 alpha-diol and its isomer 5 beta-androstane-3 alpha,17 alpha-diol. The compounds were isolated and identified by fractionation on paper chromatograms and HPLC, followed by gas chromatography-mass spectrometry after conversion to trimethylsilyl ethers. In adrenal venous plasma the concentrations of the 5 alpha-isomer ranged from 24-71 micrograms/100 ml, 47.5 +/- 7.7 (mean +/- SEM) and of the 5 beta-isomer 1.5-9.3 micrograms/100 ml, 5.6 +/- 1.6 (mean +/- SEM). In peripheral plasma only the 5 alpha-derivative was detectable, the highest concentration being 0.97 microgram/100 ml. The reduced steroids were not detected in the plasma of a male possum, confirming previous in vitro evidence that reduced steroids are products of the adrenocortical special zone which is found only in the female.

The use of fluorescent probes as markers for sheep lymphocyte subpopulations

Sheep blood lymphocytes were labelled with fluorescent probes and examined under the fluorescence microscope and by the fluorescence-activated cell sorter. A novel probe using fluorescamine, coupled to hexylamine, detected 22.9% of cells, apparently of the B-cell series, counted by fluorescence microscopy. Substitution of fluorescein isothiocyanate (FITC) for the fluorescamine did not label the same subpopulation of cells although the lymphocytes could then be examined in the cell sorter. A larger number of cells (38.8%) formed the brighter cluster but did not behave as B cell when separated on nylon-wool columns. Improvement in discrimination of the cell populations was obtained with FITC-hexadecylamine (C16). This probe detected 38% of cells in the smallest cluster, 44% of cells in the intermediate cluster and 19% of cells in the brightest cluster. The proportion of cells in each cluster appeared to parallel closely the "null", erythrocyte (E) rosette-forming T cells and the B cells detected by conventional markers for blood lymphocytes. Other fluorescent probes, formed from FITC and other amines and amino acids, labelled lymphocyte membranes. Probes with a terminal charge labelled the small cluster particularly well, whereas those that were terminally non-polar labelled the larger cells brigthly, but not to the same intensity as the charged probes in the small cells.

Fast atom bombardment mass spectrometry of some anthracycline and bisanthracycline derivatives

Fast atom bombardment (FAB) mass spectra of daunomycin, four of its derivatives, seven bisanthracyclines and three mixed-functional daunomycin-acridine derivatives are reported. These anthracyclines all exhibited their expected [MH]+ ions and peaks corresponding to the fragmentations which are characteristic of the anthracycline moiety, and in addition the spectra showed enhanced [MH + n]+ (n = 1-4) ions which were attributed to reductive processes occurring in the liquid matrix under FAB conditions. Daunomycin was also observed to form a dimeric cluster ion [M2H]+ together with associated reduced ions under FAB conditions. We have found that FAB mass spectrometry is an ideal method for the qualitative analysis of large, non-volatile derivatives of anthracyclines.

Identification of senecionine and senecionine N-oxide as antifertility constituents in Senecio vulgaris

The MeOH extract of Senecio vulgaris L., administered po to rats on Days 1-10 postcoitum, significantly decreased the number of normal fetuses per pregnant rat found at autopsy on Day 16. Additional experiments showed a similar activity for its hepatotoxic constituents senecionine and senecionine N-oxide, suggesting that the latter two compounds were probably responsible for the effect seen with the extract. No antifertility effects were seen in MeOH extract-treated hamsters.

Crotaleschenine, an Alkaloid of Crotalaria leschenaultii

An alkaloid of Crotalaria leschenaultii DC., previously reported as crispatine and now named crotaleschenine, has been re-investigated and shown to be (7β,8α-H,12α,13α,14α)-12β-hydroxy-1,2-didehydrocrotalane-11,15-dione.1 Spectroscopic data are presented and the stereochemistry determined by X-ray crystallography. The esterifying acid of crotaleschenine is identical with that of retusine , which is thereby determined as (1a,7β,8α-H,12α,13α,14α)-12β- hydroxycrotalane-11,15-dione.

Toxic tunicaminyluracil antibiotics identified in water-damaged wheat responsible for the death of pigs

A unique mixture of toxic tunicaininyluracil antibiotics, closely related to the corynetoxins which causc annual ryegrass toxicity and to the tunicamycins, has been identified in rain-damaged, stored wheat implicated in a fatal intoxication of pigs. The toxins, present at a level of approximately 4.5 mg per kg, were isolated by preparative t.1.c. They displayed specific inhibition of uridine diphospho-N-acetylglucosamine : dolichol-phosphate N-acetylglucosamine-1-phosphate transferase and bacterial inhibition consistent with this type of antibiotic, and produced symptoms in rats identical with those associated with the tunicamycin and corynetoxin complexes. Chemical identification, based on t.l.c., h.p.l.c., co-chromatography with authentic toxins and catalytic hydrogenation, was confirmed by fast atom bombardment mass spectrometry. The origin of these toxins is unknown, but the unique mixture of components detected suggests a previously unreported tunicaminyluracil antibiotic-producing microbial source.

Interaction of phomopsin A and related compounds with purified sheep brain tubulin

Phomopsins comprise a family of peptide mycotoxins containing a 13-membered ring formed by an ether bridge, produced by the fungus Phomopsis leptostromiformis, the causal agent in lupin poisoning (lupinosis). The biochemical actions of two naturally occurring phomopsins, phomopsin A and B, and the chemical derivatives, phomopsinamine A and octahydrophomopsin A, on purified sheep brain tubulin were investigated. All analogues were potent microtubule inhibitors, blocking the polymerization of tubulin at concentrations of less than 1 microM. They inhibited [3H]vinblastine binding to tubulin and, in common with vinblastine and its competitive inhibitor maytansine, enhanced the binding of [3H]colchicine to tubulin. It is postulated that phomopsin A and its analogues exert their action on tubulin by interaction at or near the vinblastine binding site. Two possible mechanisms for the interaction between vinblastine or phomopsins and colchicine binding to tubulin are proposed.

Rapid estimation of corynetoxins in bacterial galls from annual ryegrass (Lolium rigidum Gaudin) by high-performance liquid chromatography

A rapid and sensitive method is described for the extraction, detection and measurement of corynetoxins in ryegrass seed galls colonized by Corynebucterium rathayi. Excised galls are extracted with aqueous methanol and the extract analysed, without further purification, by reversed-phase high-performance liquid chromatography with detection by uItraviolet absorption. The method is applicable down to the level of a single gall or part of a gall with a minimum level of detection of about 0.25 �g using the equipment described. The corynetoxin content of the individual galls examined varied from below the detection limit to 10.6 �g. The highest level of corynetoxin in a single gall was 1.15% of gall weight. The corynetoxin composition of galls collected during outbreaks of annual ryegrass toxicity in South Australia, Western Australia and South Africa during a 19-year period were found to be similar.

Toxicity of Echium plantagineum (Paterson's Curse). 1. Marginal toxic effects in Merino wethers from long-term feeding

Groups of 10 Merino wethers were pen-fed pelleted diets containing 80 or 20% Echium plantagineum, for four periods of 12 weeks alternating with four similar periods on control diet. Mild liver damage, characteristic of pyrrolizidine alkaloid poisoning, aas induced in one wether consuming 80% E. plantagineum. The other animals on the 80% diet showed only a small increase in the size of the hepatocytes, which was not unequivocally due to alkaloids. There were no effects on liver function, serum enzymes, weight gain or wool growth attributable to alkaloids. The 80 and 20% Echium diets contained 0.11-0.15 and 0.032-0.047% alkaloid respectively, indicating that approximately onequarter to one-third of the alkaloid of the fresh plant was lost during diet preparation and storage. Echlum feeding induced a high rate of destruction of pyrrolizidine alkaloids in the sheep rumen. The conversion of the Echium alkaloids into pyrrolic metabolites by microsomal preparations from livers of the experimental sheep taken at necropsy was unaffected by the feeding schedule.

Structure of the corynetoxins, metabolites of Corynebacterium rathayi responsible for toxicity of annual ryegrass (Lolium rigidum) pastures

The corynetoxins, toxic metabolities of Corynebacterium rathayi formed in galled seed-heads of infected annual ryegrass, Lolium rigidum, are shown to be new members of the tunicamycin group of antibiotics. They consist of N-acetylglucosaminyl-tunicaminyl-uracil in amide linkage with fatty acids which differ in certain respects from those present in the tunicamycins. The corynetoxin acids are of slightly longer chain length, C15-C19, occur in a β-hydroxy as well as saturated and α,β-un-saturated series, and have anteiso, iso and normal chain terminations. β-Hydroxy acids have not been observed previously in the tunicamycin group and anteiso chains were reported only recently in the streptovirudin subgroup. Stereochemical identity of the C11-aminosugar in the corynetoxins with the tunicamine part of the tunicamycins is demonstrated by formation of a common hydrolysis product, di(N-trifluoro- acetyl)glucosaminyl-tunicaminyl-uracil. Analysis of the carbon-13 and proton n.m.r. spectra of the main components, corynetoxins H17a and U17a, confirms the stereochemistry proposed for tunicamine except that the glycosidic linkages are changed to α-galactosamine, β-glucosamine.

Serotyping of Campylobacter jejuni by slide agglutination based on heat-labile antigenic factors

A serotyping scheme for Campylobacter jejuni was developed based on slide agglutination of live bacteria with whole cell antisera absorbed with homologous heated and heterologous unheated cross-reactive antigens. Among 815 isolates from human and nonhuman sources, 21 serogroups were recognized. Of the 615 isolates from human cases of gastroenteritis, 529 (86%) were typable; 455 strains agglutinated in 20 single antisera, whereas 74 isolates agglutinated in various pairs of antisera, allowing subdivision of some main serogroups into subserogroups. Of the 200 isolates of C. jejuni from nonhuman sources (chicken, swine, etc.), 166 (83%) were typable, 145 cultures agglutinated in various single antisera, and 21 strains agglutinated with different pairs of antisera. Among isolates from all sources, 8 serogroups (1, 2, 4, 5, 7, 8, 9, and 11) were encountered most frequently. Serogroups 1, 2, 4, 5, 7, 9, and 11 were most common among human isolates; the majority of the chicken and all of the swine isolates belonged to the same serogroups identified from human cases. Very good serological correlation was obtained in 20 family outbreaks and 4 community outbreaks.

Isolation of a group of glycolipid toxins from seedheads of annual ryegrass Lolium rigidum Gaud.) infected by Corynebacterium rathayi

A group of highly toxic compounds was isolated from galled seedheads of annual ryegrass (Lolium rigidum Gaud.) containing Corynebacterium rathayi. Purified extracts were resolved by reverse-phase high-performance liquid chromatography into eight main fractions which have been partially characterised and shown to be toxic to nursling rats. A mixture of the toxins also produced clinical signs and brain lesions in lambs consistent with annual ryegrass toxicity. The name 'corynetoxin' is tentatively proposed for the series, individual members being designated according to their order of elution from the high performance liquid chromatography column as corynetoxins 1 to 8. The two main fractions are corynetoxins 3 and 4 of which the former has been crystallised. They appear to be of glycolipid character, 3-hydroxyheptadecanoic acid and a C6 amino sugar being identified among the hydrolysis products of corynetoxin 3, and heptadec-2-enoic acid and a C6 amino sugar from corynetoxin 4.

Structure and toxicity of the alkaloids of Russian comfrey (symphytum x uplandicum Nyman), a medicinal herb and item of human diet

Eight pyrrolizidine alkaloids of hepatotoxic type have been indentified in leaves of Symphytum X uplandicum. The combined alkaloids exhibit chronic hepatotoxicity in rats.

The alkaloids of Heliotropium curassavicum

The main alkaloids of Heliotropium curassavicum Linn. have been identified. They are curassavine(4), an ester of trachelanthamidine with a new acid, curassavic acid [2-hydroxy-2-(1-hydroxyethyl)-3- methylpentanoic acid] (3), coromandaline (1), an ester of trachelanthamidine with (+)-viridifloric acid (previously unknown in nature), and heliovicine (2), an ester of trachelanthamidine with the uncommon (-)-enantiomer of trachelanthic acid.

The alkaloids of Symphytum × uplandicum (Russian comfrey)

Eight pyrrolizidine alkaloids have been identified in the leaves of Symphytum × uplandicum Nyman (Russian comfrey). They are echimidine (1), symphytine (2), lycopsamine (3), intermedine (4) and four new alkaloids, 7-acetyllycopsamine (5), 7-acetylintermedine (6), symlandine (7)(7-angelyl-9-viridiflorylretronecine) and uplandicine (8) (7-acetyl- 9-echimidinylretronecine).