Identification of metabolites of adonifoline, a hepatotoxic pyrrolizidine alkaloid, by liquid chromatography/tandem and high-resolution mass spectrometry

Hepatotoxic pyrrolizidine alkaloid (HPA)-containing plants have always been a threat to human and livestock health worldwide. Adonifoline, a main HPA in Senecio scandens Buch.-Ham. ex D. Don (Qianli guang), was used officially as an infusion in cases of oral and pharyngeal infections in China. In this study in vivo metabolism of adonifoline was studied for the first time by identifying the metabolites of adonifoline present in bile, urine and feces of rats using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS(n)) (ion trap) as well as liquid chromatography/electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS) (quadrupole-time of flight). In total 19 metabolites were identified and, among them, retronecine-N-oxides were confirmed by matching their fragmentation patterns with their fully characterized synthetic compounds. These metabolites are all involved in both phase I and phase II metabolic processes and the principal in vivo metabolism pathways of adonifoline were proposed.

Clinical and analytical aspects of pyrrolizidine poisoning caused by South African traditional medicines

In a study carried out in two hospitals in South Africa the authors identified 20 children suffering from hepatic veno-occlusive disease thought to be caused by the administration of traditional remedies. The predominant clinical presentation was ascites of various degrees and hepatomegaly. There was a high morbidity and mortality in the young infants, and in those cases who survived and were followed up the clinical pattern was one of progression to cirrhosis and portal hypertension. Pyrrolizidine alkaloid poisoning is one of the causes of the veno-occlusive disease. Therefore there is a need for objective confirmation of this. In four of our cases an on-admission urine specimen was available and in all of these a simple colorimetric screening test confirmed the presence of pyrrolizidine alkaloids. The other cases were admitted from peripheral hospitals and clinics and urine was not obtained until after 72 h, a time at which the levels of pyrrolizidines in urine were below the limit of sensitivity of the screening test. The screening method is helpful for the detection of acute ingestion of pyrrolizidines in large amounts, but is not sufficiently sensitive for the detection of chronic ingestion of smaller amounts. Nevertheless, in those patients who have hepatomegaly and ascites a positive finding of pyrrolizidines is important and may remove the necessity for expensive and invasive investigative measures.

N-acetylcysteine-conjugated pyrrole identified in rat urine following administration of two pyrrolizidine alkaloids, monocrotaline and senecionine

This report demonstrates that an Ehrlich-reagent-positive metabolite of monocrotaline and senecionine is excreted in the urine of male rats as an N-acetylcysteine conjugate of (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (NAC-DHP). Isolation of the metabolite employed an initial organic extraction followed by HPLC separation of remaining urinary components using a reverse-phase, polymer-based, PRP-1 column. Fast-atom-bombardment tandem mass spectrometry was used to identify the metabolite. This finding suggests that reactive metabolites of pyrrolizidine alkaloids generated in the liver can survive the aqueous environment of the circulatory system as glutathione conjugates or mercapturic acids.

Excretion and blood radioactivity levels following [14C]senecionine administration in the rat

Macrocyclic pyrrolizidine alkaloids (PAs) are a mixed group of phytotoxins with similar chemical structures and varying biological effects. A commonly studied member of this group is senecionine (SEN) which causes hepatotoxicity. We have undertaken metabolism and excretion studies of SEN in rats to provide data for comparison between PAs and to evaluate the potential role of metabolism and excretion in toxicity. Following intravenous administration of [14C]SEN (60 mg/kg, 10 microCi/kg), bile, urine and blood were collected over a 7-h period. Of the total administered radioactivity, 44% and 43% were excreted in the bile and urine, respectively. Using mass spectroscopy, senecionine N-oxide (SENNOX) was identified as the major metabolite in bile (52% of 44%) and urine (30% of 43%). For the total 7 h, less than 5% in bile and 18% in urine was excreted as parent alkaloid. The plasma concentration of Senecionine-equivalents/g (SEN-EQ/g) decreased from 107 to 12 nmol, while red blood cell (RBC) concentrations declined from 109 to 26 nmol/g. Without bile collection, the plasma levels of SEN-EQ were similar, while the final RBC level was almost double (47 vs. 26 nmol/g) and total radioactivity excreted in the urine was increased (59% vs. 43%). Biliary pyrrolic metabolites were estimated to be 1.43 mg, using a dehydroretronectin standard.

Absorption and excretion of pyrrolizidine (Senecio) alkaloids and their effects on mineral metabolism in rabbits

A metabolism study was conducted with rabbits to determine the effect of consumption of 5% dietary Senecio jacobaea (SJ) on tissue mineral levels and mineral excretion. Gastro-intestinal (GIT) absorption of pyrrolizidine alkaloids (PA) from SJ was also studied by monitoring excretion into urine and feces and by the use of ligated gut segments in vitro. Inclusion of SJ into a diet containing added Cu (100 ug/g) and Zn (100 ug/g) caused a 2.6-fold increase in liver Cu concentration (P less than .05), decreased total liver Zn (P less than .05), and increased plasma Fe (P less than .05) when compared with rabbits consuming the same diet without SJ. Fecal and urinary excretion of Cu and Zn were not markedly affected by the addition of Cu, Zn and(or) SJ to rabbit diets. Excretion of PA from SJ in the diet was not affected (P greater than .05) by the addition of Cu and Zn to the diet. The PA elimination was much greater in urine than feces (P less than .001). Isolated PA from SJ were found to be readily transferred across the mucosa of isolated everted sacs of jejunum and ileum in vitro against a concentration gradient. These results suggest that the effects of dietary SJ on alterations in mineral metabolism are not due to changes in GIT mineral elimination. In addition, it appears that the resistance of rabbits to dietary SJ intoxication is not caused by low GIT absorption of PA, but rather by efficient urinary elimination.

Pyrrolizidine alkaloids from Symphytum officinale L. and their percutaneous absorption in rats

An analysis of a commercial sample of Symphyti radix originating from Poland with a total alkaloid content of 0.07% revealed the presence of 7 pyrrolizidine alkaloid-N-oxides: 7-acetyl intermedine, 7-acetyl lycopsamine as the main constituents and lycopsamine, intermedine, symphytine and traces of 2 further not yet identified alkaloids. The percutaneous absorption of these alkaloids was investigated in rats, using a crude alcoholic extract of the plant corresponding to a dose of 194 mg alkaloid-N-oxides/kg b.wt. The excretion of N-oxides in the urine during 2 days was in the range of 0.1-0.4% of the dose. The dermally absorbed N-oxides are not or only to a small extent converted to the free alkaloids in the organism. The oral application led to a 20-50 times higher excretion of N-oxides and free alkaloids in the urine.

Metabolic conversion of indicine N-oxide to indicine in rabbits and humans

Indicine N-oxide, a pyrrolizidine alkaloid N-oxide that exhibits antitumor activity without some of the toxic effects associated with other pyrrolizidine alkaloids, is metabolized to indicine in rabbits and humans. Indicine can be detected in the plasma and is excreted in the urine in a dose-dependent manner following the i.v. administration of indicine N-oxide. The p.o. administration of indicine N-oxide leads to an increased plasma concentration and an increased urinary excretion of indicine. The hepatic microsomal fraction and the gut flora both catalyze the anaerobic reduction of indicine N-oxide to indicine in vitro. Whole-animal studies suggest that the gut flora play a major role in the metabolic reduction of indicine N-oxide by the rabbit. Indicine N-oxide is not actively excreted in the bile, and it is probable that indicine N-oxide finds its way into the gut by passive diffusion following i.v. administration. Neomycin and erythromycin, which reduce the number of anaerobic bacteria in the gut, lead to decreased plasma levels and a decreased urinary excretion of indicine.

Determination of indicine N-oxide and indicine in plasma and urine by electron-capture gas-liquid chromatography

A sensitive and specific method is described for the quantitative analysis of indicine N-oxide and indicine in plasma and urine. Indicine N-oxide is reduced to the tertiary amine with zinc--acetic acid (plasma) or zinc--ammonium chloride (urine). The indicine is derivatized with pentafluoropropionic anhydride to provide electron-capture detection. Assay of rabbit and human plasma and urine samples can detect 100 ng/ml (plasma) and 200 ng/ml (urine), and the method was applied to the analysis of indicine N-oxide and indicine in rabbits and one patient following administration of indicine N-oxide.