Chemometrical evaluation of ropinirole and its impurity's chromatographic behavior

Efficient extraction method using magnetic carbon nanotubes to analyze cocaine and benzoylecgonine in breast milk by GC/MS

Aim: The increasing use of cocaine (COC) during breastfeeding has led to growing concern about exposure of infants. Therefore, to study this exposure, a new method to analyze COC and benzoylecgonine in breast milk was developed. Methodology: A new extraction method was used for the first time to analyze COC and its major metabolite, benzoylecgonine, in breast milk using magnetic carbon nanotubes partially doped with nitrogen. Results: The calibration curves were linear in the range 5.0–180.0 ng ml-1. The limit of quantification was 5.0 ng ml-1. Coefficients of variation were between 3.2 and 13.9%. Recovery was between 89.6 and 99.2%. Conclusion: The proposed method is simple, efficient and suitable to determine analytes in breast milk.

Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design

In this article, a step-by-step optimization procedure for improving analyte response with implementation of experimental design is described. Zwitterionic antiepileptics, namely vigabatrin, pregabalin and gabapentin, were chosen as model compounds to undergo chloroformate-mediated derivatization followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. Application of a planned stepwise optimization procedure allowed responses of analytes, expressed as areas and signal-to-noise ratios, to be improved, enabling achievement of lower limit of detection values. Results from the current study demonstrate that optimization of parameters such as scan time, geometry of ion source, sheath and auxiliary gas pressure, capillary temperature, collision pressure and mobile phase composition can have a positive impact on sensitivity of LC-MS/MS methods. Optimization of LC and MS parameters led to a total increment of 53.9%, 83.3% and 95.7% in areas of derivatized vigabatrin, pregabalin and gabapentin, respectively, while for signal-to-noise values, an improvement of 140.0%, 93.6% and 124.0% was achieved, compared to autotune settings. After defining the final optimal conditions, a time-segmented method was validated for the determination of mentioned drugs in plasma. The method proved to be accurate and precise with excellent linearity for the tested concentration range (40.0 ng ml(-1)-10.0 × 10(3)  ng ml(-1)).

Prioritizing Hits with Appropriate Trade-Offs Between HIV-1 Reverse Transcriptase Inhibitory Efficacy and MT4 Blood Cells Toxicity Through Desirability-Based Multiobjective Optimization and Ranking

Nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) constitute a promising therapeutic option for AIDS. However, the emergence of virus-NNRTIs resistance was found to be a major problem in the field. Toward that goal, a "knock-out" strategy stands out between the several options to circumvent the problem. However the high drug or drug-drug concentrations often used generate additional safety concerns. The need for approaches able to early integrate drug- or lead-likeness, toxicity and bioavailability criteria in the drug discovery phase is an emergent issue. Given that, we propose a combined strategy based on desirability-based multiobjective optimization (MOOP) and ranking for the prioritization of HIV-1 NNRTIs hits with appropriate trade-offs between inhibitory efficacy over the HIV-1 RT and toxic effects over MT4 blood cells. Through the MOOP process, the theoretical levels of the predictive variables required to reach a desirable RT inhibitor candidate with the best possible compromise between efficacy and safety were found. This information is used as a pattern to rank the library of compounds according to a similarity-based structural criterion, providing a ranking quality of 64 %/71 %/73 % in training/validation/test set. A comparative study between the sequential, parallel and multiobjective virtual screening revealed that the multiobjective approach can outperform the other approaches. These results suggest that the identification of NNRTIs hits with appropriate trade-offs between potency and safety, rather than fully optimized hits solely based on potency, can facilitate the hit to lead transition and increase the likelihood of the candidate to evolve into a successful antiretroviral drug.