Metabolic map and bioactivation of the anti-tumour drug noscapine.

BACKGROUND AND PURPOSE: Noscapine is a promising anti-tumour agent. The purpose of the present study was to describe the metabolic map and investigate the bioactivation of noscapine. EXPERIMENTAL APPROACH: Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry-based metabolomics was used to analyse the in vitro incubation mixtures, urine and faeces samples from mice treated with noscapine. Recombinant drug-metabolizing enzymes were employed to identify those involved in noscapine metabolism. Hepatic GSH levels and serum biochemistry were also carried out to determine reactive metabolites of noscapine. KEY RESULTS: Several novel phase I metabolites of noscapine were detected after oral gavage of mice, including an N-demethylated metabolite, two hydroxylated metabolites, one metabolite undergoing both demethylation and cleavage of the methylenedioxy group and a bis-demethylated metabolite. Additionally, several novel glucuronides were detected, and their structures were elucidated through MS/MS fragmentology. Recombinant enzymes screening showed the involvement of several cytochromes P450, flavin-containing mono-oxygenase 1 and the UDP-glucuronosyltransferases UGT1A1, UGT1A3, UGT1A9 and UGT2B7, in noscapine metabolism. In vitro glutathione trapping revealed the existence of an ortho-quinone reactive intermediate formed through further oxidation of a catechol metabolite. However, this bioactivation process of noscapine does not occur in vivo. Similar to this result, altered glutathione levels in liver and serum biochemistry revealed no evidence of hepatic damage, thus indicating that, at least in mice, noscapine does not induce hepatotoxicity through bioactivation. CONCLUSIONS AND IMPLICATIONS: A comprehensive metabolic map and bioactivation evaluation provides important information for the development of noscapine as an anti-tumour drug.

General unknown screening procedure for the characterization of human drug metabolites in forensic toxicology: applications and constraints.

LC coupled to single (LC-MS) and tandem (LC-MS/MS) mass spectrometry is recognized as the most powerful analytical tools for metabolic studies in drug discovery. In this article, we describe five cases illustrating the utility of screening xenobiotic metabolites in routine analysis of forensic samples using LC-MS/MS. Analyses were performed using a previously published LC-MS/MS general unknown screening (GUS) procedure developed using a hybrid linear IT-tandem mass spectrometer. In each of the cases presented, the presence of metabolites of xenobiotics was suspected after analyzing urine samples. In two cases, the parent drug was also detected and the metabolites were merely useful to confirm drug intake, but in three other cases, metabolite detection was of actual forensic interest. The presented results indicate that: (i) the GUS procedure developed is useful to detect a large variety of drug metabolites, which would have been hardly detected using targeted methods in the context of clinical or forensic toxicology; (ii) metabolite structure can generally be inferred from their "enhanced" product ion scan spectra; and (iii) structure confirmation can be achieved through in vitro metabolic experiments or through the analysis of urine samples from individuals taking the parent drug.

Validation of meconin as a marker for illicit opiate use.

The detection of markers for illicit opiate misuse is important both in the management of substance misuse and in the postmortem identification of illicit opiate use. In addition to 6-monoacetylmorphine and acetyl codeine, other markers, such as papaverine, noscapine, and their metabolites, have been proposed as markers of illicit opiate use. Urine samples (362) from individuals attending substance misuse services and 26 postmortem cases were analyzed for meconin, a noscapine metabolite by gas chromatography-mass spectrometry. Three hundred of the substance misuse service samples and 14 of the postmortem samples had morphine present as the major opiate. Meconin was detected in 284 (94.7%) of these substance misuse samples and 11 (78%) of the postmortem samples. There was a specificity of 100% in both groups. In the 62 substance misuse cases where morphine was not the major opiate detected and four separate cases in which medicinal diamorphine was known to have been administered, meconin was not detected. The use of meconin as a useful adjunct in detecting illicit opiate use is recommended.

The significance of putative urinary markers of illicit heroin use after consumption of poppy seed products.

After consumption of poppy seeds various substances were detected in urine or blood samples using an immunoassay and a sophisticated liquid chromatographic-tandem mass spectrometric procedure. These compounds are widely considered to be putative markers of heroin (HER) abuse whereas acetylcodeine was regarded as a marker for illicit preparations ("street HER"). Besides positive urinary opiate immunoassay results during a 48 hours monitoring period, peak concentrations of morphine (MOR), codeine and their glucuronides appeared 4 to 8 hours after ingestion of poppy seeds, and concentrations of total MOR higher than 10 microg/mL were observed. Also, in serum samples taken up to 6 hours after consumption, MOR glucuronides were found. Free MOR was only detected in traces (1 to 3 ng/mL) within 2 hours of consumption. In addition, 3 of 6 onsite opiate sweat tests revealed positive results 6.5 hours after ingestion. Furthermore, it was demonstrated that neither noscapine (NOS) nor papaverine (PAP) was detectable in urine or blood samples after the consumption of poppy seeds containing up to 94 microg NOS and up to 3.3 mug PAP. NOS and PAP were rapidly metabolized, whereas desmethylpapaverine and, especially, its glucuronide were found in urine samples of poppy seed consumers even 48 hours after consumption. According to these results PAP metabolites should not be regarded as markers of illicit HER abuse. In conclusion, only acetylcodeine can be regarded as a specific marker but has the problem of a short half-life. Therefore, we suggest that NOS and PAP, but not their metabolites, might be used cautiously as additional markers of illicit HER abuse as they have not been detected after oral intake of poppy seeds in normal doses. But it must be kept in mind that in some cases poppy seeds with an unusually high content of these alkaloids could be available, and that these substances are also agents in some pharmaceuticals.

Gas chromatographic/mass spectrometric detection of narcotine, papaverine, and thebaine in seeds of Papaver somniferum.

In addition to codeine and morphine, three more compounds: narcotine (noscapine), papaverine, and thebaine were found in Indian and Netherlands poppy seeds (Papaver somniferum L). The compounds were detected by a GC/MS technique and the identities were confirmed by comparing retention times and ion ratios with the known references. The concentrations of codeine, morphine, thebaine, papaverine, and narcotine were 44, 167, 41, 67, and 230 micrograms/g in Indian poppy seeds, and were 1.8, 39, 1.0, 0.17, 0.84 micrograms/g in Netherlands poppy seeds, respectively. Because these compounds may be urinary products after poppy seed consumption, the lowest detectable concentrations of codeine, morphine, thebaine, papaverine, and narcotine in urine are of interest and were found to be 4, 4, 5, 0.4, and 4 ng/ml, respectively. The detection of urinary narcotine, papaverine, or thebaine may be utilized to differentiate poppy seed consumption from illicit codeine, morphine, or heroin use.

Metabolic fate of noscapine. III. Further studies on identification and determination of the metabolites.

1. From the urine of rats, rabbits and humans treated with noscapine, two novel metabolites were isolated and identified as 7-hydroxy-6-methoxyphthalide (MA-1) and 6-hydroxy-7-methoxyphthalide (MA-2), mainly by mass spectrometry. 2. MA-2 (free and conjugated) amounted to 8.5% dose in rats (n=2) and 1.7% dose in rabbits (n=2) during the first 48 h. In humans, MA-2 was excreted in amounts of 6.0 to 10.3% dose in the first 24 h urine (three men and a woman), although one woman excreted 52.5% dose as MA-2 during the same period. In all three species MA-2 was excreted 10 times more as conjugates than as the free metabolite. MA-1 was excreted only in trace amounts in the urines of three species. 3. In rabbits, the drug was metabolized also to 1-alpha-methyl-8-methoxy-6,7-dihydroxy-1-(6,7-dimethoxy-3-phthalidyl)-1,2,3,4-tetrahydroisoquinoline (4.6% dose, conjugated only) using g.l.c.-mass spectrometry. This metabolite was excreted conjugated at 0.6 to 5.2% dose in five human subjects, but was not detected in rats. 4. Three 0-demethylated metabolites of noscapine, previously reported, were determined using g.l.c.-mass spectrometry. The total demethylated metabolites (free and conjugated) amounted to 0.2%, 4.0% and 0.1-1.5% dose, respectively, in rats, rabbits and humans (n=5) in the first 24 h urine.

Metabolic fate of noscapine. II. Isolation and identification of novel metabolites produced by C-C bond cleavage.

1. The metabolism of noscapine was studied in rabbits, rats and human. 2. Apart from the O-demethylated metabolites already reported, three metabolites were isolated and identified as meconine, cotarnine and hydrocotamine, respectively. 3. Mass fragmentography (chemical ionization) was used to determine these products simultaneously. 4. Meconine was the major metabolite in all three species, accounting for about 3, 8 and 2% of the dose in the first 24 h urines of rats, rabbits and humans, respectively, although one woman excreted to a very high extent (22%). In rats, cotarnine bases were excreted at almost same level as that of meconine, but at lesser extent in other two species. Hydrocotamine and unchanged noscapine were excreted to less than 1% dose.