DEVELOPMENT OF HPLC–UV TECHNIQUES FOR QUANTITATIVE ANALYSIS OF 4-HYDROXYBENZOIC ACID ESTERS (PARABENS) IN FOODSTUFFS, COSMETICS AND PHARMACEUTICAL PRODUCTS

Four methods have been proposed for the determination of methyl-, ethyl- and propyl- esters of 4-hydroxybenzoic acid (parabens) in foodstuff, cosmetic products and pharmaceutical formulations by RF-HPLC. Electronic spectra parameters of parabens have been determined. It was found that in neutral solutions the absorption maximums were 195 and 254 nm for all analytes. Signal ratios have been calculated (S254/S230). Signal ratios were used as an additional criterion for identification. The conditions of chromatographic separation were common for all types of samples. A precolumn and an Acclaim (Thermo) column with a C-18 sorbent without any additional modifications (both structural and dynamic), a gradient elution mode with water-acetonitrile mixtures and a spectrophotometric method of detection at two wavelengths were used. The total time of chromatographic analysis was 45 min, including the stage of conditioning the system with a starting eluent (15 min). The retention times of parabens in the reversed-phase variant of separation increased with the increase in alkyl groups in the structure of molecules. The effectiveness of the removal of surfactants from cosmetics by the column chromatography method with silica gel as a polar sorbent and using ethylacetate (an ethylacetate extract of the sample) as an eluent has been shown. The necessity of applying gradient elution mode for reducing analysis time and increasing the amplitude of analytes signals was established. The calculated validation parameters (detection limit, limit of quantitation, limit of repeatability, recovery) show the compliance of the methods with the current regulatory documents (SanPiN 2.3.2.1293-03, SanPiN 2.3.2.2364-08).

Plant-Mediated Stereoselective Biotransformation of Phenylglyoxylic Acid Esters

Enantioselective reduction of the carbonyl group of three phenylglyoxylic acid esters (methyl, ethyl, and n-propyl esters, 2 - 4) was conducted using blended plant materials (roots of carrot, beetroot, celeriac and parsley; apple). All used biocatalysts transformed these esters to the corresponding mandelic acid esters with high yield, preferably into the respective R-enantiomer. Butanedione addition improved the enantioselectivity of the reaction.