Current Pharmaceutical Analysis - Volume 1, Issue 2, 2005

Microdialysis is an excellent sampling technique for continuous monitoring of endogenous and exogenous compounds in the extracellular fluid. This technique has several advantages compared with conventional methods. Accordingly, this technique is extensively applied to study pharmacokinetics and pharmacodynamics both in experimental animals and human. In this mini-review, various topics related to microdialysis for the last five years will be discussed on its benefits. With the development of microdialysis technique and increasing number of applications of microdialysis for human study, this technique seems to play an important role in clinical practice, for example, bedside microdialysis as drug monitoring or diagnostic of disease.

Many important herbal drugs (e.g. ginkgo, black cohosh, soy) contain bioactive compounds possessing no chromophore, thus detection techniques other UV are needed for their identification and standardization. Evaporative light scattering is one of the possible alternatives, but despite the fact that this technique has been developed more than 30 years ago, it is still considered to be an exotic detection alternative, with few applications at hand. Over the last decade ELSD has steadily evolved, so that from today's point of view it can be considered a reliable, economic and versatile mode of detection. In this article the basic principles of ELSD are described and advantages / disadvantages compared to other LC detectors (IR, MS) are discussed. An overview of recent applications in natural products analysis (mainly carbohydrates, lipids, saponins, terpenes) is given. The wide range of possible analytes and matrices should indicate the impact of ELSD in this field so far, and arouse further interest in a novel, yet old detection method.

The field of pharmaceutical analysis calls for rapid, simple, specific and accurate methods of analysis that ensure the quality of the products. The determination of active contents of compounds in pharmaceutical preparations is often achieved by high-performance liquid chromatography (HPLC). On the other hand, multivariate calibration methods are being successfully applied to solve a wide variety of tasks/problems in different fields of analytical chemistry. Several of these methods have been presented in the literature in the last few years. Partial least squares (PLS) has become a routine practice in pharmaceutical analysis. However, there are certain problems that still exists which require more sophisticated models to be solved. We present several situations in which conventional multivariate models have been successfully applied to simultaneously analyze several active principles in tablets, syrups, injections and drops. We also present events in which the presence of non-linearity was taken into account by using artificial neural networks (ANNs). Finally, a new tool that allows one to analyze samples containing non modeled interferences has been discussed, based on the acquisition of matrix-type (second-order) data, and subsequent construction of models presenting the phenomenon known as the “second order advantage”.

Fluoroquinolones antibiotics are more effective towards pathogens resistant to other antibacterials, thus being regularly prescribed drugs in human and veterinary medicine. Their favourable kinetics and broad antibacterial activity account for their therapeutic value in the treatment of several infections. They constitute the second, third and fourth generation of quinolone antibiotics. An extended and comprehensive review on the analytical techniques and methods concerning fluoroquinolone antibiotics in pharmaceutical formulations and biological samples reported in literature is provided in the present article. Emphasis is given on sample preparation, method validation and application to real samples. Results of various published assays are comparatively presented and are criticized.

Estramustine phosphate has been used for over 20 years in the treatment of advanced prostate cancer. Recent reports of promising results from clinical combination studies, and neoadjuvant studies, have caused a renewed interest in this relatively old drug. After oral or intravenous administration, estramustine phosphate is metabolised to four main metabolites: estramustine, estromustine, estradiol and estrone. Due to the potential biological activity of all these estramustine phosphate metabolites, it is necessary to analyse the parent compound and all four metabolites in plasma, tissues and tumours. Consequently, various methods have been developed for the bioanalysis of these compounds. In this review various methods are described for the analysis of estramustine phosphate and its metabolites in biological fluids and tissues. Methods described included RIA, TLC, HPLC, HPLC-MS, GC and GC-MS.

An important part of quality control of herbal drug preparations is the evaluation of the chemical stability of a finished product during the storage period. Measuring chemical stability is very challenging due to the complexity of a plant extract, which may contain thousands of different compounds. Moreover, the presence of enzymes like glycosidases, esterases or oxidases plays an important role in the breakdown of secondary plant metabolites. This is of particular significance for liquid herbal products. Many reports so far have focused on the stability of an isolated secondary metabolite and its decomposition products. However, results from these data do not always accurately reflect the chemical stability of the compound in an extract. Other metabolites, the so-called concomitant compounds, present in the extract, may influence the overall stability. This has been shown for extracts containing organic acids like citric acid or malic acid, which enhance the stability of phenolic compounds present in the same product. The current paper gives an overview of the parameters influencing the stability of herbal extracts, describes analytical approaches to measure chemical stability of dry and liquid plant extracts, and gives a summary of the stability data available on extracts of some of the important medicinal plants.