Quantitation of camptothecin and related compounds

Acceleration of carboxylesterase-mediated activation of irinotecan to SN-38 by serum from patients with end-stage kidney disease

PURPOSE

Pharmacokinetics and pharmacodynamics of irinotecan have been reported to be altered in cancer patients with end-stage kidney disease (ESKD). Carboxylesterase (CES) has an important role in metabolism of irinotecan to its active metabolite, SN-38, in human liver. The purpose of the present study was to investigate whether CES activity was altered in ESKD patients.

METHODS

The present study investigated the effects of uremic serum, uremic toxins, and fatty acids on the hydrolysis of irinotecan and a typical CES substrate, p-nitrophenyl acetate (PNPA), in human liver microsomes. Normal and uremic serum samples were deproteinized by treatment with methanol were used in the present study.

RESULTS

The present study showed that both normal and uremic serum significantly inhibited CES-mediated metabolism of both irinotecan and PNPA. The inhibition by uremic serum was weaker than that by normal serum, suggesting that CES activity may be higher in ESKD patients. Although four uremic toxins did not affect PNPA metabolism, arachidonic acid inhibited it. There was no difference in inhibitory effect of PNPA metabolism between both mixtures of seven fatty acids used at concentrations equivalent to those present in 10% normal or uremic serum. Interestingly, those mixtures had a more pronounced effect than either 10% normal or uremic serum.

CONCLUSIONS

The present study showed that the inhibition of CES activity by uremic serum was weaker than that by normal serum, suggesting that an increase in maximum plasma concentration of SN-38 in cancer patients with ESKD can be attributed to an accelerated CES-mediated irinotecan hydrolysis.

Antineoplastic drugs and their analysis: a state of the art review

We provide an overview of the analytical methods available for the quantification of antineoplastic drugs in pharmaceutical formulations, biological and environmental samples.

New and highly efficient column chromatographic extraction and simple purification of camptothecin from Camptotheca acuminata and Nothapodytes pittosporoides

INTRODUCTION

Camptothecin, a widely used natural anti-cancer drug, is difficult to extract and purify effectively from plants.

OBJECTIVE

To develop new and highly efficient extraction and purification methods for analysis and production of camptothecin from leaves and fruits of Camptotheca acuminata and Nothapodytes pittosporoides roots.

METHODS

Dried materials were loaded in empty columns with fivefold 60% ethanol for leaves or 70% ethanol for fruits of C. acumnata, and sixfold 70% ethanol for N. pittosporoides roots. The columns were eluted with the same solvents at room temperature. Eluent was collected as extraction solution. Extraction solution from leaves and fruits of C. acuminata was vacuum-evaporated to remove ethanol, precipitated at pH 8.0 to remove alkaline insolubles and fractionated with chloroform at pH 3.0, which yields a crude product with 70% purity. Extraction solution from N. pittosporoides roots was concentrated to 1/10 volume and precipitated at pH 3.0, which yields a crude product with 60% purity. All crude products were purified by crystallisation. All steps were monitored by HPLC.

RESULTS

Camptothecin was extracted from the three plant materials at a 98% rate with 15- or 18-fold solvent for content analysis, or at a 97% rate with five- or sixfold solvent for production. All crude products were purified to 98%. The overall recovery rates of camptothecin from plant materials to purified products reached 92% or higher.

CONCLUSION

The new procedures are simple and highly efficient, and have multiple advantages for quantitative analysis and large production of camptothecin from plants.

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

Liquid chromatographic analysis of the anticancer alkaloid luotonin A and some new derivatives in human serum samples

The quantitation of the natural cytotoxic and anti-inflammatory alkaloid luotonin A and five recently synthesized derivatives is described, constituting the first report of a HPLC method for the analysis of these compounds in human serum samples. The conditions for the chromatographic separation were optimized and the method was validated for the analysis of these compounds in biological samples according to international guidelines. An RP-HPLC method with fluorimetric detection and a C(18) stationary phase was applied. Different ACN/water mobile phases were assayed, including 0-4% of a mobile phase modifier such as tetrahydrofuran, dioxane or tert-butyl methyl ether. Isocratic and gradient elution conditions are compared. The influence of pH on the efficiency and resolution of the separation was also considered. The developed method was applied to the determination of luotonins in pooled human serum samples by gradient elution RP-HPLC using a simple cleanup procedure. The proposed chromatographic method exhibits satisfactory analytical figures of merit, with LOD from 1.0 x 10(-10) to 2.0 x 10(-10) M, intraday and interday precision below 6% except for the concentration level closest to LOD, and good agreement between experimental and theoretical concentrations. Therefore, the developed method is suitable, reliable, rapid, and simple.

Pulmonary targeting microparticulate camptothecin delivery system: anticancer evaluation in a rat orthotopic lung cancer model

Large (>6 microm) rigid microparticles (MPs) become passively entrapped within the lungs after intravenous (i.v.) injection making them an attractive and highly efficient alternative to inhalation for pulmonary delivery. In this study, PEGylated 6 microm polystyrene MPs with multiple copies of the norvaline (Nva) alpha-amino acid prodrug of camptothecin (CPT) were prepared. Surface morphology was characterized using a scanning electron microscope. CPT was released from the CPT-Nva-MPs over 24 h in rat plasma at 37 degrees C. In-vivo CPT plasma concentrations were low (approximately 1 ng/ml or less) and constant over a period of 4 days after a single i.v. injection of CPT-Nva-MPs as compared with high but short-lived systemic exposures after an i.v. injection of free CPT. This suggests that sustained local CPT concentrations were achieved in the lung after administration of the MP delivery system. Anticancer efficacy was evaluated in an orthotopic lung cancer animal model and compared with a bolus injection of CPT. Animals receiving free CPT (2 mg/kg) and CPT-Nva-MPs (0.22 mg/kg CPT and 100 mg/kg MPs) were found to have statistically significant smaller areas of lung cancer (P<0.05 and 0.01, respectively) than untreated animals. In addition, 40% of the animals receiving CPT-Nva-MPs were found to be free of cancer. The CPT dose using targeted MPs was 10 times lower than after i.v. injection of free CPT, but was more effective in reducing the amount of cancerous areas. In conclusion, CPT-Nva-MPs were able to achieve effective local lung and low systemic CPT concentrations at a dose that was 10 times lower than systemically administered CPT resulting in a significant improvement in anticancer efficacy in an orthotopic rat model of lung cancer.

A series of alpha-amino acid ester prodrugs of camptothecin: in vitro hydrolysis and A549 human lung carcinoma cell cytotoxicity

The objective of the present study was to identify a camptothecin (CPT) prodrug with optimal release and cytotoxicity properties for immobilization on a passively targeted microparticle delivery system. A series of alpha-amino acid ester prodrugs of CPT were synthesized, characterized, and evaluated. Four CPT prodrugs were synthesized with increasing aliphatic chain length (glycine (Gly) (2a), alanine (Ala) (2b), aminobutyric acid (Abu) (2c), and norvaline (Nva) (2d)). Prodrug reconversion was studied at pH 6.6, 7.0, and 7.4 corresponding to tumor, lung, and extracellular/physiological pH, respectively. Cytotoxicity was evaluated in A549 human lung carcinoma cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The hydrolytic reconversion rate to parent CPT increased with decreasing side chain length as well as increasing pH. The Hill slope of 2d was significantly less than CPT and the other prodrugs tested, indicating a higher cell death rate at lower concentrations. These results suggest that 2d is the best candidate for a passively targeted sustained release lung delivery system.

Determination of camptothecins in DMSO extracts of Nothapodytes foetida by direct injection capillary electrophoresis

A rapid capillary electrophoresis procedure was developed for determining the anti-cancer components, camptothecins, in Nothapodytes foetida. The hydrophobic compound was extracted from plant tissue (ca. 1 mL of DMSO for 100 mg of dried plant tissue) with a water-miscible organic solvent, DMSO, at elevated temperature (60 degrees C). The extract was directly injected into the separation capillary (untreated fused silica, 34 cm in length, 75 microm i.d.) and analysed in MEKC mode (369 nm). Within 5 min of migration, camptothecins were successfully separated and quantified by adding organic modifiers to the running buffer (20% DMSO, 90 mm SDS in 10 mm borate buffer, pH 8.60). The linear dynamic range for camptothecin was from 5 to 400 microg/mL. This method was proven to be very suitable for monitoring the amount of camptothecins during the cultivation of the medicinal plant.

Liquid chromatography-mass spectrometry for the quantitative bioanalysis of anticancer drugs

The monitoring of anticancer drugs in biological fluids and tissues is important during both pre-clinical and clinical development and often in routine clinical use. Traditionally, liquid chromatography (LC) in combination with ultraviolet (UV), fluorescence, or electrochemical detection is employed for this purpose. The successful hyphenation of LC and mass spectrometry (MS), however, has dramatically changed this. MS detection provides better sensitivity and selectivity than UV detection and, in addition, is applicable to a significantly larger group of compounds than fluorescence or electrochemical detection. Therefore, LC-MS has now become the method of first choice for the quantitative bioanalysis of many anticancer agents. There are still, however, a lot of new developments to be expected in this area, such as the introduction of more sensitive and robust mass spectrometers, high-throughput analyses, and further optimization of the coupled LC systems. Many articles have appeared in this field in recent years and are reviewed here. We conclude that LC-MS is an extremely powerful tool for the quantitative analysis of anticancer drugs in biological samples.

Determination of irinotecan (CPT-11) and SN-38 in human whole blood and red blood cells by liquid chromatography with fluorescence detection

An analytical method was developed for the anticancer agent irinotecan (CPT-11) and its main metabolite SN-38 in human whole blood and in red blood cells (RBCs). Sample pretreatment involved deproteinization of whole blood or plasma-diluted RBCs isolated by MESED instruments, with a mixture of aqueous perchloric acid and methanol (1:1, v/v). Separation was carried out using isocratic elution on a Hypersil ODS stationary phase, with detection at excitation and emission wavelengths of 355 and 515 nm, respectively. The lower limit of quantitation (LLQ) in blood was established at 5.00 ng/ml for both compounds, with values for within-run precision (WRP) and between-run precision (BRP) of less than 10%. The method is currently being applied to investigate the blood distribution of CPT-11 and SN-38 in cancer patients.