A simple and cost-effective two-tier drug screening procedure comprises a 'dedicated' NIR spectral database of common medicines and a 'unified' database was developed to detect the sildenafil analogue in Eurycoma longifolia products. Diffuse reflectance spectra of ten commercial herbal products containing E. longifolia were obtained over the wavelength range of 1100-2500 nm. The spectral search of two products purchased via the internet against a dedicated database of reputable E. longifolia products have resulted in the similarity index of more than 0.1 which indicated significantly different spectra. Further searches against the unified database showed a close match to the spectra of drug containing sildenafil citrate suggesting the presence of a sildenafil analogue. This finding was supported by clustering of these spectra in the PCA score plot within 5% significance level. This approach has alleviated the use of reference product or standard active for direct comparison and has a potential to be used for adulterated food and drugs detection.
The influx of medicines from different sources into healthcare systems of developing countries presents a challenge to monitor their origin and quality. The absence of a repository of reference samples or spectra prevents the analysis of tablets by direct comparison. A set of paracetamol tablets purchased in Malaysian pharmacies were compared to a similar set of sample purchased in the UK using near-infrared spectroscopy (NIRS). Additional samples of products containing ibuprofen or paracetamol in combination with other actives were added to the study as negative controls. NIR spectra of the samples were acquired and compared by using multivariate modeling and classification algorithms (PCA/SIMCA) and stored in a spectral database. All analysed paracetamol samples contained the purported active ingredient with only 1 out of 20 batches excluded from the 95% confidence interval, while the negative controls were clearly classified as outliers of the set. Although the substandard products were not detected in the purchased sample set, our results indicated variability in the quality of the Malaysian tablets. A database of spectra was created and search methods were evaluated for correct identification of tablets. The approach presented here can be further developed as a method for identifying substandard pharmaceutical products.
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