Separation of cyclosporins by high-performance liquid chromatography and mass spectrometric study of cyclosporin metabolites

Development of an automatic solid phase extraction and liquid chromatography mass spectrometry method by using a monolithic column for the analysis of Cyclosporin A in human plasma

A sensitive and specific and automated liquid chromatography-electrospray mass spectrometric (LC-ESI-MS) assay for the quantification of Cyclosporin A in human plasma was developed. Following a simple protein precipitation step, the supernatant was extracted on-line and directly injected into the system LC-ESI-MS. A relatively new type of monolithic column consisting of a silica rod with bimodal pore structure was used to achieve a retention time of 2.4 min with a very low backpressure at a flow rate of 1 ml/min. The assay was linear from 0.050 to 1.000 microg/ml. The mean recovery was 91%. The mean inter-day and intra-day precisions were 1.85% and 2.83%, respectively. The combination of the automated solid phase extraction and the low retention time achieved with this columns increase the throughput and decrease the time of analysis of each sample. This technology is useful in order to improve the efficiency of the bioanalytical studies.

Development and validation of HPLC method for the determination of Cyclosporin A and its impurities in Neoral capsules and its generic versions

Cyclosporin A (CyA) is a cornerstone immunosuppressant for the prophylaxis against allograft rejection after organ transplantation. The most widely prescribed CyA formulation is Neoral soft gelatine capsules (Novartis Pharmaceuticals, Basel, Switzerland). After Novartis patent expiration, several generic formulations have been developed. In this paper, a simple and reliable HPLC method was developed and validated for the evaluation of four CyA degradation products (ID-005-95, CyH, IsoCyH and IsoCyA) and two related compounds (CyB and CyG) aimed for the quality control of Neoral capsules and its generic formulations. In a second step, the validated method was then compared to the USP assay method for capsules, where some of the mentioned impurities were not adequately resolved from the CyA peak. Isocratic elution at a flow rate of 1.0mLmin(-1) was employed on a Lichrospher RP-18 (4mmx250mm; 5microm) analytical column maintained at 75 degrees C with a tetrahydrofuran:phosphoric acid (0.05M) (44:56, v/v) as mobile phase. The chromatograms were recorded using a Hewlett Packard 1100 chromatographic system. The UV detection wavelength was performed at 220nm and 10microL of sample was injected. The developed method was validated in terms of selectivity, linearity, precision, accuracy, limit of detection and limit of quantitation. The validate method was successfully applied to commercial capsules, Neoral and generic versions. Therefore, the proposed method is suitable for the simultaneous determination of CyA as well as its major impurities.

Spontaneous N --> O acyl shift in the [M + H](+) ions of [MeBmt1]-cyclosporins in an ion trap

In an ion trap the protonated molecules of the cyclic undecapeptides cyclosporins having 3-hydroxy-4-methyl-2-methylamino-6-octenoic acid (MeBmt) in their backbone undergo an N --> O peptidyl shift into the corresponding [M + H](+) ions of isocyclosporins. This rearrangement does not take place in cyclosporins [Bmt1]Cs and [3'-deoxy-MeBmt1]Cs. In cyclosporin [Thr2]Cs having two threonines in the molecule, only one of them participates in the N,O-acyl transfer. It can be concluded that the presence of the basic N-methylamino group of MeBmt, which can serve as the primary site of protonation, is necessary for isocyclosporin formation. A dominating ion series originating from the primary cleavage between MeBmt (first position in the cyclosporin ring) and amino acid residue at the neighbouring eleventh position is then observed in collision-induced dissociation spectra of protonated molecules of cyclosporins. This 'isocyclosporin' ion series can effectively be used for easy and complete cyclosporin sequencing using a tandem mass spectrometric (MS3) experiment in an ion trap. The paper further introduces an improved Gross mass spectral nomenclature for cyclic peptide sequencing and several techniques for the generation of protonated molecules of cyclosporins. Their preparation represents the fundamental requirement for smooth sequencing of cyclosporins by tandem mass spectral techniques.