Hydrophobicity and chromatographic behaviour of aromatic acids found in urine

Structural characterization and evaluation of antimicrobial and cytotoxic activity of six plant phenolic acids

Phenolic acids still gain significant attention due to their potential antimicrobial and cytotoxic properties. In this study, we have investigated the antimicrobial of six phenolic acids, namely chlorogenic, caffeic, p-coumaric, rosmarinic, gallic and tannic acids in the concentration range 0.5-500 μM, against Escherichia coli and Lactobacillus rhamnosus. The antimicrobial activity was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. Additionally, the cytotoxic effects of these phenolic acids on two cancer cell lines, the colorectal adenocarcinoma Caco-2 cell line and Dukes' type C colorectal adenocarcinoma DLD-1 cell line was examined. To further understand the molecular properties of these phenolic acids, quantum chemical calculations were performed using the Gaussian 09W program. Parameters such as ionization potential, electron affinity, electronegativity, chemical hardness, chemical softness, dipole moment, and electrophilicity index were obtained. The lipophilicity properties represented by logP parameter was also discussed. This study provides a comprehensive evaluation of the antimicrobial and cytotoxic activity of six phenolic acids, compounds deliberately selected due to their chemical structure. They are derivatives of benzoic or cinnamic acids with the increasing number of hydroxyl groups in the aromatic ring. The integration of experimental and computational methodologies provides a knowledge of the molecular characteristics of bioactive compounds and partial explanation of the relationship between the molecular structure and biological properties. This knowledge aids in guiding the development of bioactive components for use in dietary supplements, functional foods and pharmaceutical drugs.

Biologically Active Compounds of Plants: Structure-Related Antioxidant, Microbiological and Cytotoxic Activity of Selected Carboxylic Acids

Natural carboxylic acids are plant-derived compounds that are known to possess biological activity. The aim of this review was to compare the effect of structural differences of the selected carboxylic acids (benzoic acid (BA), cinnamic acid (CinA), p-coumaric acid (p-CA), caffeic acid (CFA), rosmarinic acid (RA), and chicoric acid (ChA)) on the antioxidant, antimicrobial, and cytotoxic activity. The studied compounds were arranged in a logic sequence of increasing number of hydroxyl groups and conjugated bonds in order to investigate the correlations between the structure and bioactivity. A review of the literature revealed that RA exhibited the highest antioxidant activity and this property decreased in the following order: RA > CFA ~ ChA > p-CA > CinA > BA. In the case of antimicrobial properties, structure-activity relationships were not easy to observe as they depended on the microbial strain and the experimental conditions. The highest antimicrobial activity was found for CFA and CinA, while the lowest for RA. Taking into account anti-cancer properties of studied NCA, it seems that the presence of hydroxyl groups had an influence on intermolecular interactions and the cytotoxic potential of the molecules, whereas the carboxyl group participated in the chelation of endogenous transition metal ions.

Automatic determination of urinary 4-hydroxy-3-methoxymandelic (vanillylmandelic) acid by liquid chromatography with electrochemical detection

An automated liquid chromatographic method for the determination of urinary concentrations of 4-hydroxy-3-methoxymandelic acid (VMA) is described. Urine samples are purified by solid-phase extraction on an anion-exchange cartridge and automated on-line chromatographic elution is carried out using a Varian AASP (advanced automated sample processor) system. The column effluent is monitored with an electrochemical detector using a glassy carbon working electrode. The method allows the determination of VMA in 0.05 ml of normal urine with a relative standard deviation of less than 3%. The analysis time can be shortened by use of back-flushing technique, and the correlation with a classical (but non-automated) VMA analysis method is excellent.

Correlation between n-octanol/water partition coefficient and liquid chromatographic retention for caffeine and its metabolites, and some structure-pharmacokinetic considerations

A method to establish the correlation between the reverse phase high performance liquid chromatographic retention of caffeine and its metabolites and their n-octanol/water partition coefficients is described. The log (P) values were always below zero, ranging from -0.02 to -2.03. The capacity factor quadratically back-extrapolated to 100% water eluent (k'w) was used as the index of lipophilicity. The compounds examined gave a good correlation (r greater than 0.99) with log (k'w) if considered in separate series, depending on the substituent position. For a structure-pharmacokinetic relationship study, correlations were found between the partition coefficient and some pharmacokinetic parameters, suggesting that for drugs that are widely metabolized, any predictions of their disposition from physicochemical characteristics are hazardous.

Determination of hydrophobic parameters by reversed-phase liquid chromatography: theory, experimental techniques, and application in studies on quantitative structure-activity relationships

The use of RPLC retention parameters as descriptors of the hydrophobic nature of bioactive compounds has been evaluated. The relationship between the capacity factor, measured on n-alkyl-bonded stationary phases using binary eluents, and the n-octanol-water partition coefficient has been illustrated experimentally and theoretically. It is suggested that retention parameters, in particular the capacity factor (log kw) obtained by extrapolation of retention data from binary eluents to 100% water, could successfully replace the n-octanol-water partition coefficient in studies on quantitative structure-activity relationship, and that their use may result in a better correlation with biological data.

Determination of partition coefficients of glucocorticosteroids by high-performance liquid chromatography

Two high-performance liquid chromatographic (HPLC) techniques have been used for the determination of the lipophilicity of 50 glucocorticosteroids. For a log P range of 1 to 3, we used a persilylated octadecylsilane phase saturated with 1-octanol, which was eluted with 1-octanol saturated phosphate buffer (pH = 7). For log P values greater than or equal to 3.00, the same phase was used without 1-octanol saturation and was eluted with different methanol-buffer mixtures. These two procedures allowed the determination of log P values ranging from 1.00 to greater than 5.00. Good agreement was found between these procedures and others described in the literature. The effect of different structural changes in the glucocorticosteroid molecule on the lipophilicity is discussed.

Accurate, wide-range, automated, high-performance liquid chromatographic method for the estimation of octanol/water partition coefficients II: Equilibrium in partition coefficient measurements, additivity of substituent constants, and correlation of biological data

Occasionally, results from the highly reproducible automated log P(o/w) measurement (ALPM) differ from those determined by shake-flask methods. Several specific examples affording different values are presented. One source of these differences may be curvilinearity in plots of log (t - t0) versus percent methanol, which complicate accurate intercept determinations and, thus, estimates of log P(o/w). Other sources of these differences are presented and discussed, although their cause remains unclear. Equilibrium ALPM log P(o/w) measurements of various phenyl-, methyl-, fluoro-, chloro-, and bromobenzenes, suggest substituent constants are not strictly additive. Moreover, the higher values indicate that calculated values may not be accurate for those compounds having multiple substituents or high log P(o/w) values. ALPM gives better predictability of the in vivo concentration process of 8 or 12 toxicants in fish than the shake-flask method, another HPLC method, or even calculated log P(o/w) values. However, it equally correlates the binding to bovine serum albumin by 34 chemicals as predicted by a combination of shake-flask and calculated log P(o/w) values reported elsewhere.