senecionine and retrorsine

1,2-unsaturated pyrrolizidine alkaloids (PAs) are secondary plant metabolites that are found in many plant species throughout the world. They are of concern for risk assessment as consumption of contaminated foodstuff can cause severe liver damage. Of late, transporter-mediated uptake and transport has advanced as a vital determinant of PA toxicity. In this study, the authors investigate a transporter-mediated uptake of PAs and its implications in PA toxicity.. Our results confirm previous findings of active transport mechanisms of PAs into hepatocytes and highlight the importance of toxicokinetic studies for the risk assessment of PAs.

Topics: Cations; Chemical and Drug Induced Liver Injury; Hepatocytes; Humans; Peptides; Pyrrolizidine Alkaloids; Taurocholic Acid

Plant specialised metabolites (SMs) are very diverse in terms of both their number and chemical structures with more than 200,000 estimated compounds. This chemical diversity occurs not only among different groups of compounds but also within the groups themselves. In the context of plant-insect interactions, the chemical diversity within a class of structurally related metabolites is generally also related to their bioactivity. In this study, we tested firstly whether individual SMs within the group of pyrrolizidine alkaloids (PAs) differ in their effects on insect herbivores (western flower thrips, Frankliniella occidentalis). Secondly, we tested combinations of PA N-oxides to determine whether they are more active than their individual components. We also evaluated the bioactivity of six PA free bases and their corresponding N-oxides. At concentrations similar to that in plants, several PAs reduced thrip's survival but the effect also differed strongly among PAs. In general, PA free bases caused a lower survival than their corresponding N-oxides. Among the tested PA free bases, we found jacobine and retrorsine to be the most active against second instar larvae of thrips, followed by erucifoline and seneciphylline, while senecionine and monocrotaline did not exhibit significant dose-dependent effects on thrip's survival. In the case of PA N-oxides, we found that only senecionine N-oxide and jacobine N-oxide reduced thrip's survival, although the effect of senecionine N-oxide was weak. Combinations of PA N-oxides showed no synergistic effects. These findings indicate the differences observed in the effect of structurally related SMs on insect herbivores. It is of limited value to study the bioactivity of combined groups, such as PAs, without taking their composition into account.

Topics: Animals; Herbivory; Larva; Molecular Structure; Pyrrolizidine Alkaloids; Thysanoptera

Pyrrolizidine alkaloids (PAs) are feeding deterrents and toxic compounds to generalist herbivores. Among the PAs of Jacobaea vulgaris Gaertn, jacobine and erucifoline are the most effective against insect herbivores as indicated by correlative studies. Because little is known about the effect of jacobine and erucifoline as individual PAs, we isolated these compounds from their respective Jacobaea chemotypes. These PAs and other commercially available senecionine-like PAs, including senecionine, seneciphylline, retrorsine, and senkirkine, were tested as free base and N-oxide forms at a range of 0-70 ppm. Feeding bioassays using live insects are closer to the natural pattern but require relatively large amounts of test compounds. We, therefore, compared the toxicity of PAs using both Spodoptera exigua cell line and larval injection bioassays. Both bioassays led to similar results in the order of PA toxicity, indicating that the cell lines are a valuable tool for a first toxicity screen. Testing individual PAs, jacobine and erucifoline were the most toxic PAs, suggesting their major role in plant defense against generalist herbivores. Senkirkine and seneciphylline were less toxic than jacobine and erucifoline but more toxic than retrorsine. Senecionine was not toxic at the tested concentrations. For all toxic PAs, the free base form was more toxic than the N-oxide form. Our results demonstrate that structural variation of PAs influences their effectiveness in plant defense.

Topics: Animals; Biological Assay; Cell Line; Drug Evaluation, Preclinical; Herbivory; Larva; Oxides; Pyrrolizidine Alkaloids; Spodoptera; Structure-Activity Relationship

This study was designed to confirm the toxicity of a plant implicated in an outbreak of poisoning of stock in Frankfort, Free State Province, South Africa. Cows died acutely after being introduced into a camp, where an abundant, green shrublet was noted to be heavily grazed. This plant was subsequently identified as Senecio inaequidens DC. (Asteraceae) by the South African National Biodiversity Institute (SANBI). Extraction and chemical analyses for pyrrolizidine alkaloids (PAs) in Senecio inaequidens revealed the presence of 4 different compounds, namely retrorsine and senecionine (known to be hepatotoxic) and 2 unidentified compounds. The average total PA (free base plus N-oxide) concentration in plant parts of S. inaequidens collected at Frankfort during the outbreak was 0.81%, compared with the total alkaloid content in the dried, milled S. inaequidens plant material, collected 7 weeks after the outbreak, of only 0.18%. Male Sprague-Dawley rats (n = 4), aged 8-9 weeks, were dosed per os. Each rat received a different dose of the crude Senecio inaequidens extract, ranging from 0.049 mg/g body weight (b.w.) to 0.25 mg/g b.w. No clinical signs were observed in the rat receiving the lowest dose. Rats receiving higher doses showed depression, an unsteady gait, pilo-erection and jaundice, which was particularly noticeable in the ears. Clinical chemistry evaluation revealed an increase in the activities of ALP (except Rat 4), AST and GGT in all animals. Total serum bilirubin, creatinine and urea concentrations were also elevated. All rats had low serum globulin concentrations with an A/G ratio above 1.2. Post mortem examination of the rats revealed marked hepatic lesions. Histopathologically, these changes were characterised by necrosis (variable in extent) of the centrilobular and midzonal hepatocytes (but sparing the portal hepatocytes), with extensive haemorrhage and congestion. Proliferation of the bile ducts, fibrosis and oedema were also present. Ultrastructural changes in affected rats were characterised by margination of chromatin, the presence of numerous autolysosomes in necrotic hepatocytes, intramitochondrial woolly inclusions and changes in the endoplasmic reticulum. A sheep, also dosed with the crude extract, failed to exhibit clinical signs, clinical chemistry aberrations or macroscopic lesions; however, examination of the liver of this sheep revealed histopathological and ultrastructural changes similar, though milder, to those displayed by t

Topics: Animal Feed; Animals; Cattle; Cattle Diseases; Dose-Response Relationship, Drug; Female; Male; Plant Poisoning; Pyrrolizidine Alkaloids; Rats; Rats, Sprague-Dawley; Senecio; Toxicity Tests

We developed an immunoassay with antibodies against retrorsine to detect the closely related senecionine, the main alkaloid in various Asteraceae. Sensitivity is about 23 pg (68 fmol) for senecionine. Cross reactivity of monocrotalin, retrorsine N-oxide, senkirkine (< 0.1%), and seneciphylline (3.6-34.5%) was resolved. The alkaloid content in leaves of Petasites hybridus (Asteraceae) was determined to be 3.86 ppm, calculated as senecionine, which was far less than in rhizomes (104.8 ppm). Additionally, we proved specificity by taking immunograms from different parts of Petasites hybridus. The test is a suitable tool for assessing the toxic potential of medicinal plants containing senecionine.

Topics: Animals; Antibodies; Antineoplastic Agents, Phytogenic; Cross Reactions; Immunoenzyme Techniques; Molecular Structure; Plant Leaves; Pyrrolizidine Alkaloids; Rabbits; Sensitivity and Specificity

Topics: Alkaloids; Antineoplastic Agents, Phytogenic; Hong Kong; Medicine, Chinese Traditional; Molecular Structure; Plants, Medicinal; Pyrroles; Pyrrolizidine Alkaloids

A study of the hepatotoxic pyrrolizidine alkaloids (PAs) contained in Packera candidissima (Greene) Weber & Löve (Senecio candidissimus Greene), a Mexican medicinal plant used for the treatment of kidney ailments and noted for its antiseptic properties, is reported. Analysis by TLC and GC-MS have shown the presence in high levels of both PAs and their N-oxides in the root (0.76% dry weight) and the aerial parts (0.36% dry weight) of the plant material. GC-MS analysis showed the presence of senecionine, integerrimine, retrorsine, and usaramine in the aerial parts. The root was found to contain senkirkine as the major component. These results indicate that users of this herb are at high risk of poisoning, especially members of certain cultural groups in Northern Mexico and the Hispanic population in the southwestern United States. In addition, two sesquiterpenes, neoadenostylone and epineoadenostylone were identified from the neutral extracts of this plant material. The 6 alpha-angeloyloxy-9-oxo-delta 10(1)-furanoeremophilane is reported for the first time as a natural product.

Topics: Antineoplastic Agents, Phytogenic; Carcinogens; Chemical Fractionation; Chromatography, Thin Layer; Gas Chromatography-Mass Spectrometry; Humans; Kidney Diseases; Liver; Medicine, Traditional; Mexico; Plant Extracts; Plants, Medicinal; Pyrrolizidine Alkaloids; Sesquiterpenes; Ulcer

Topics: Antineoplastic Agents, Phytogenic; Plants; Pyrrolizidine Alkaloids

An improved method utilizing reverse-phase liquid chromatography on a styrene-divinylbenzene column (PRP-1) and ultraviolet detection was developed for the simultaneous determination of the pyrrolizidine alkaloids (PAs) senecionine, seneciphylline, and retrorsine and their major metabolites produced during in vitro transformation of PAs by microsomal enzyme systems. The procedure employs direct injection of the 46,000g supernatant of the microsomal reaction mixture directly onto the column, and elution with a 0.1 M NH4OH-acetonitrile gradient. The method is very gentle, simple, and fast with excellent precision since no prior extraction, preconcentration, or derivatization steps are required. Using this procedure 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine and the corresponding PA N-oxides were shown to be the major microsomal metabolites of the PAs examined. The detection limit of these metabolites was approximately 1 microM.

Topics: Animals; Biotransformation; Chromatography, High Pressure Liquid; Female; In Vitro Techniques; Male; Mass Spectrometry; Mice; Microsomes, Liver; Pyrrolizidine Alkaloids; Rats; Rats, Inbred Strains; Spectrophotometry, Ultraviolet