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Two catecholamines (epinephrine and isoprenaline) were studied by cyclic (CV) and square-wave voltammetry (SWV) at bare graphite (G) and Pt nanoparticles (Pt-NP) - chitosan modified graphite electrodes (G/Pt-NPChitosan). The obtained results shown similarly redox behavior for both investigated compounds by mentioned electrochemical techniques at the investigated electrodes, consisting in two pairs of peaks (peak I and II) corresponding to a quasi-reversible processes. The difference between the structures of compounds doesn’t influence the electrochemical parameters values. As expected, the presence of the Pt nanoparticles acts as a diffusion barrier on the electrode surface leading to a decrease of the current intensities values, when electrodes were investigated by CV and SWV. The G/Pt-NPChitosan nanocomposites matrix can be satisfactorily used for detecting catecholamines.

Electrochemical measurements of the oxidation of organic compounds can be helpful to understand how these compounds are metabolized by living organisms. Cyclic and square-wave voltammetry were used in view to estimate the electrochemical parameters of redox processes involving catecholamines compounds (isoprenaline, epinephrine, levonordefrin, norepinephrine, dopamine, d-DOPA and carbidopa). Redox processes related to catecholamines are quasi-reversible diffusion controlled reactions at a graphite electrode. According to the decreasing of the oxidation potential, the capacity to act as antioxidant of different catecholamines increases in the order: norepinephrine < levonordefrin < epinephrine < isoprenaline or carbidopa < d-DOPA < dopamine. Both series are influenced by the position of –OH and – NH2 in para-alkyl substituents.

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A sensitive and convenient method for acidic catecholamine metabolites (including homovanillic acid, vanillylmandelic acid, 3,4-dihydroxymandelic acid, and 3,4- dihydroxyphenylacetic acid) determination was developed based on thin-layer chromatography and image-processing analysis. The metabolites were separated without a prederivatization step using reversed phase RP-18W high-performance plates. The mobile phase composition, detection, and quantification conditions were systematically investigated through several trials. The reaction with 2,2-diphenyl-1-picrylhydrazyl radical allowed specific detection of acidic catecholamine metabolites with a high sensitivity and a wide linear range. The limit of detection and the limit of quantification were in the range of 13–103 and 18–120 ng/spot, respectively, in all cases. Mean recoveries determined were in the range 95–106% for all of the investigated compounds. The proposed method allowed rapid simultaneous determination of acidic catecholamine metabolites from spiked human urine sample.

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The increased excretion of normetanephrine, metanephrine and 3-methoxytyramine in urine is indicative of the presence of pheochromocytoma, neuroblastoma or paragangliomas, therefore the development of new methods has appeared to be of great importance in the early screening of these diseases. Consequently, measurement of these catecholamine metabolites in spiked urine specimens, has been carried out by applying a rapid and convenient thin-layer chromatography method with DPPH• radical detection and specialized software for quantitative TLC analysis. The obtained results showed recovery rates between 97.96% and 103.48% for all of the investigated compounds, thus making this method suitable for routine screening of adrenal tumors associated with over-production of catecholamines and hyper-excretion of their metabolites.

The lipophilicity of some drugs with tricyclic structure (antidepressants and phenothiazines) was investigated by thin-layer chromatography, on three stationary phases of RP-18, RP-8, and CN. The mobile phases were based on ethanol and different pH buffers (2, 4, 6, 7, 8, 10 and 12). The investigated lipophilicity indices were both experimentally (mRM, RM0, b, f0, PC1/RM) and theoretically expressed (Log D and Log P). The effect of pH modification over the chromatographic behaviour has been evaluated. In order to find an objective manner of quantitative comparison of different chemically bonded stationary phases and evaluate the reliability of the obtained results some comparison procedures based on correlation diagrams and matrices were performed. The results indicated that all the stationary phases were useful for the lipophilicity investigation and that the chromatographic behaviour is highly dependent by the ionization state of the investigated compounds. This is also confirmed through the significant correlations obtained between pKa values and experimental lipophilicity indices.

A set of 38 catecholamine related compounds was submitted to a novel QSAR approach based on weighting and alignment of the molecules over a hypermolecule. Any QSAR approach assumes that a macroscopic property of a chemical compound depends on the molecular structure or the topological indices, which are derived from the molecular topology or geometry. In this study the indices were calculated using TOPOCluj software and these were adjacency, connectivity, detour, distance, IE[CjMax], IE[CjMin], IP[CjMax], IP[CjMin] and Randic. Further, the calculated indices were correlated with the lipophilicity coefficient, logP, using multivariate regression and genetic algorithms.

Lipophilicity of novel potentially anti-inflammatory 1,2,4-triazole derivatives (Schiff and Mannich bases) has been estimated by thin-layer chromatographic method (TLC). The chromatographic retention was measured using phosphate buffer as aqueous component and methanol respectively methanol containing 10% of different upper alcohol (1-butanol and 1-octanol) as the hydrophobic additive of the mobile phase. Different experimental lipophilicity indices (denoted by mRM, RM0 and PC1/RM) were estimated using retention parameters in all cases. Various partition coefficients (log P) values were calculated by means of different software and further correlated with the experimental indices determined using the organic–aqueous eluent system and systems modified with hydrophobic alcohol addition. It was found that values measured in eluent system modified with 1-butanol better correlate with computed lipophilicity parameters. Furthermore, by applying the principal component analysis (PCA) on the experimental values, the similarity and differences of compounds from the lipophilicity point of view were highlighted.

The goal of this study was to develop high statistical significant models for lipophilicity estimation for a group of 60 compounds with increased toxicity, belonging to alkaloids and mycotoxins. The multiple linear regression modelling was made by means of genetic algorithms as a function of 972 molecular descriptors, computed by ChemOffice and Dragon Plus software and completed by internet available module for Log P computation, ALOGPS 2.1. The compounds classification has been realized using principal component analysis and hierarchical cluster analysis. Data evaluation has been realized by various correlation matrices and relevant graphs. The modelling was made on the basis of 26 compounds with known log Pexp values and the results were validated by means of additional models developed for a series of 20 compounds. The other 6 compounds, which were excluded from the modelling process, were used afterwards as test set for prediction and comparison. The most descriptive models were those retaining four descriptors, and in all models were selected at least one computationally expressed log P value (miLogP, KOWWIN and ALOGP most often). All the obtained results are highly suggestive and offer a very pertinent idea regarding the lipophilicity range of natural compounds of increased toxicity. The models were validated considering various statistical parameters and different correlation matrices defined by high statistical significance.

We have studied dietary supplements containing sea-buckthorn (Hippophae rhamnoides), bilberry (Vaccinium myrtillus), and cranberry (Vaccinium vitis-idaea) by use of thin-layer chromatography (TLC), image analysis, and UV–visible spectroscopy. The results were subjected to multivariate techniques, for example cluster analysis (CA), principal-components analysis (PCA), and linear discriminant analysis (LDA). Evaluation of the discriminating power of TLC coupled with digital image analysis for characterization of the supplements was performed by use of chemometrics. Zero-order, first-order, and normalized zero-order UV–visible spectra of extracts of fruit and dietary supplements were digitized and used in the chemometric analysis. To increase the relevance of the study, the dietary supplement extracts were compared with extracts of the natural fruit. Results obtained by application of CA, PCA, and PCA–LDA to the chromatograms suggest the possibility of discrimination among dietary supplements on the basis of the raw material used for their preparation.

A series of 25 phenol derivative compounds having potential antioxidant capacity were studied by cyclic voltammetry and square-wave voltammetry, in order to estimate the electrochemical parameters of the redox process occurring at the graphite electrode. A correlation between the structure of phenol derivatives, the peak potential, the HOMO–LUMO gap and their antioxidant activity lead to a qualitative classification of the studied compounds as a function of the increase of their antioxidant capacity.

A thin-layer chromatographic (TLC) procedure combined with digital image processing analysis was developed for quantitative time-monitoring of the radical- scavenging activity. Reaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH•) with reference antioxidants and selected catecholamine compounds was monitored on RP-18 chromatographic plates using dot-blot technique and different concentrations of standards. Images of the chromatographic plate were recorded after background staining every 5 min for 1 h using

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