Spectroscopic characteristic (FT-IR, FT-Raman, UV, 1H and 13C NMR), theoretical calculations and biological activity of alkali metal homovanillates
Introduction
Following the increase in bacterial resistance to previously used preservatives, disinfectants or drugs the scientists are forced to search new antimicrobial substances that are safe human and environment. The new substances especially natural origin with predictable biological activity are searched [1], [2]. Therefore, relationship between molecular structure and biological activity of chemical compound was intensively studied [3], [4]. Kalinowska et al. [3] investigated relationship between molecular structure of alkali metal o-, m-, p-anisate molecules and their antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris. They performed the statistical analysis (multidimensional regression and principal component) for selected wavenumbers from FT-IR spectra and parameters that describe microbial activity to evaluate the dependency between chemical structure and biological activity of alkali metal anisates. They showed that the FT-IR spectra can be a rapid and reliable analytical tool and a good source of information for the quantitative analysis of the relationship between the molecular structure of the compound and its biological activity.
Metal cations play very important role in various biological systems. They may modify biological properties of organic ligands and affect the therapeutic properties of some compounds which are used as drugs [5]. It has been showed in several studies [3], [6], [7] that the biological activity of many important biological ligands is enhanced following the formation of salts or complexes with the metal atom.
In our previous paper [8] experimental and theoretical FT-IR, FT-Raman, 1H and 13C NMR spectra of homovanilic acid and its sodium salt were registered and analyzed. In this paper lithium, potassium, rubidium and cesium homovanillates were taken into consideration so as to be able to analyze the impact of the whole I group of the periodic table on the electronic system of homovanillic acid molecule. Alkali metals may be considered as a logical series, because they have the same degree of oxidation but different atomic radius. To select them to this study the following criteria were taken into account: (a) as small as possible harmfulness of the human body and the natural environment; (b) the possibility of the practical application because of good solubility of alkali metal compounds in polar solvents and water; (c) the availability; (d) the ease of the preparation and (e) the stability. The experimentally observed spectral data (FT-IR, FT-Raman, 1H and 13C NMR) of the title compounds were compared with the spectral data obtained by DFT/B3LYP method using 6-311++G** basis set and the results were discussed. Microbiological analysis studied compounds was performed with respect to: gram-negative bacteria such as P. aeruginosa and E. coli; gram-positive: Bacillus subtilis and Staphylococcus aureus as well as fungi Candida albicans. Biological activity of alkali metal homovanillates was studied in comparison with homovanillic acid. The relationship between spectroscopic parameters of studied compounds in regard to their activity was also analyzed. The question is, whether statistically significant correlation between molecular structure and microbial activity of tested compounds may be observed.
Section snippets
Materials and methods
Homovanillic (4-hydroxy-3-methoxyphenylacetic) acid was purchased from Acros Organic with a stated purity 98% and it was used without further purification. Lithium, sodium, potassium, rubidium and cesium homovanillates were prepared by dissolving the powder of homovanillic acid in the water solution of the appropriate alkali metal hydroxide in a stoichiometric ratio of 1:1. The mixed solution was slowly condensed at 70 °C. Then, the remaining solvent was removed by drying at 105 °C. Elementary
Vibrational spectra (FT-IR and FT-Raman)
The wavenumbers, intensities and assignments of bands occurring in the FT-IR and FT-Raman spectra of the synthesized lithium, sodium, potassium, rubidium and cesium homovanillates are presented in Table 1. However sodium homovanillate spectrum was presented in previous article [8], in this paper calculated spectra for this salt is added. All bands have been assigned and placed in comparison with other elements of I group of the periodic table. In this way we can analyze the changes in the
Conclusions
In the present work, the experimental and theoretical spectroscopic analysis of lithium, sodium, potassium rubidium and cesium homovanillates, using FT-IR, FT-Raman, UV and NMR methods were carried out. Tools of density functional theory were also used to calculate the molecular structure and electronic charge distribution in molecules of studied compounds. The calculated parameters were compared to the experimental characteristics of investigated compounds. For example, the linear correlation
Acknowledgments
The work was supported by Bialystok University of Technology (Theme no. S/WBiIŚ/1/2012). The assessment of antibacterial activity of the homovanillic acid and alkali metal salts were tested in Department of Microbiology, University of Bialystok, Poland, leaded by Izabela Święcicka and supported by the fund in the frame of “Specific scientific equipment”, of the Ministry of Science and Higher Education in Poland.
References (20)
- et al.
Food Biosci.
(2015) - et al.
Spectrochim. Acta. Part A
(2011) - et al.
Food Chem.
(2006) - et al.
J. Mol. Struct.
(2011) - et al.
Spectrochim. Acta. Part A
(2014) - et al.
Spectrochim. Acta. Part A
(2013) - et al.
Polyhedron
(2009) Spectrochim. Acta. Part A
(2014)- et al.
Spectrochim. Acta. Part A
(2015) - et al.
Trends food Sci. Tech.
(2015)
Cited by (2)
The study on molecular structure and microbiological activity of alkali metal 3-hydroxyphenylycetates
2017, Journal of Molecular StructureCitation Excerpt :The maxima of bands were similarly located at 198, 228, and 278 nm. However intensities of the bands were different and increased in the order CsHV → LiHV → RbHV → HV → KHV → NaHV [14]. The antimicrobial activity of 3-hydroxyphenylacetic acid and its sodium and potassium salts against several bacterial strains, such as Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli and Klebsiella oxytoca was analyzed.