Characterization of an unknown component in Noscapine using liquid chromatography-mass spectrometry and proton nuclear magnetic resonance spectroscopy

Fragmentation study of noscapine derivatives under electrospray conditions

RATIONALE

Noscapine is a biologically active molecule with anticancer activity among other things. Therefore, from an analytical point of view, knowledge of the mass spectrometric properties of noscapine and its derivatives is essential. The goal of the present study is to describe the collision-induced dissociation behavior of noscapine and its seven derivatives ionized by protons and lithium and sodium ions.

METHODS

Protonated noscapines were produced using electrospray ionization (ESI) mass spectrometry (MS). For the tandem mass spectrometry (MS/MS) experiments nitrogen was used as the collision gas and the collision energies were varied in the range of 1-53 eV (in the laboratory frame).

RESULTS

The ESI-MS/MS measurements showed that the MS/MS spectra of the protonated noscapines were more informative than the lithiated and sodiated ones. Based on the MS/MS studies, the main fragmentation channels of the protonated noscapines were found to be the loss of water and the loss of a meconine moiety from the precursor ion; furthermore, methyl transfer was also observed in the MS/MS spectra.

CONCLUSIONS

The MS/MS study of the protonated noscapines gives more structural information than that of lithiated and sodiated noscapines. However, the most important fragmentation channel, which leads to the formation of the most intensive product ion in the MS/MS spectra, is independent of the ionization agent.

A Simple and Rapid Flow-Injection Chemiluminescence Method for the Determination of Noscapine with Ru(phen)32+-Ce(IV) System

A new flow injection chemiluminescence (CL) system was used for the determination of noscapine. This technique is based on the reduction effect of noscapine on the Ru(phen)3(3+), which is produced by reaction between Ru(phen)3(2+) and acidic Ce(IV) solutions, and this rapid reduction produces strong CL. Calibration plots were linear over the range of 3.0 x 10(-7) - 2.0 x 10(-6) mol L(-1) and 2.0 x 10(-6) - 2.0 x 10(-4) mol L(-1). The CL intensity was so high, that it is able to produce a detection limit of 6.6 x 10(-8) M noscapine (3sigma). The relative standard deviation of 2.0 x 10(-6) M noscapine was 1.0% (n=10). The proposed method was successfully applied for the flow injection determination of noscapine in cough and Tonin syrup samples. The results of real sample analyses show good recovery percentages (97.3-102.4%). The minimum sampling rate was 100 samples per hour.

Atmospheric pressure ionisation mass spectrometric fragmentation pathways of noscapine and papaverine revealed by multistage mass spectrometry and in-source deuterium labelling

Two opium alkaloids, noscapine and papaverine, show good response as [M+H]+ ions in positive ion electrospray mass spectrometry and atmospheric pressure chemical ionisation mass spectrometry. The two compounds exhibit markedly different fragmentation pathways and behaviour under multistage mass spectrometry (MSn), with papaverine displaying a wealth of ions in MS2 and noscapine providing a single dominant ion at each stage of MSn prior to MS4. Elucidation of the fragmentation pathways using the MSn capability of the ion trap was aided by spraying the analytes in 2H2O to incorporate an isotopic label. Simplex optimisation allowed optimum trapping and fragmentation parameters to be determined, leading to a six-fold improvement in response for one transition and a seven-fold improvement for one transition sequence.

Online hyphenated liquid chromatography-nuclear magnetic resonance spectroscopy-mass spectrometry for drug metabolite and nature product analysis

Screening analysis that aims at rapidly distinguishing new molecules in the presence of a large number of known compounds becomes increasingly important in the fields of drug metabolite profiling and nature product investigation. In the past decade, online-coupled liquid chromatography-nuclear magnetic resonance spectroscopy-mass spectrometry (LC-NMR-MS) has emerged as a powerful tool for the detection and identification of known and, more important, emerging compounds in complex clinical, pharmaceutical samples and nature product extracts, due to the complementary information provided by the two detectors for unambiguous structure elucidation. This review discusses the practical conditions under which LC-NMR-MS is suitable as a routine tool for unknown analysis, as well as the fundamental concepts and their advantage aspects. Particular attention is paid to its major operating parameters that include the instrumental configurations, working modes, NMR probe improvement and LC mobile phase selection. Finally, the recent applications of LC-NMR-MS to clinical metabolite and nature product analysis are summarized which have shown the benefit of this promising hyphenated technique.