Chitosan is widely applied in biomedical and cosmetic fields. For this reason, there is a need to modify this biopolymer to achieve new properties of chitosan-based materials. The properties of chitosan can be modified by several cross-linking methods. In this work, we used the chemical cross-linking of chitosan with tannic acid, after which cross-linked chitosan was shaped into a 3D structure by the lyophilisation process. For the material obtained, FTIR-ATR analysis was performed to characterise the structure of cross-linked chitosan. Moreover, mechanical properties and swelling properties were measured for chitosan before and after cross-linking. The results show that several properties of chitosan can be changed after cross-linking by tannic acid. The positions of bands in the FTIR spectra of chitosan were shifted after cross-linking. Mechanical properties were altered for cross-linked chitosan. However, the highest compressive modulus was observed for pure chitosan. The lowest compressive modulus was observed for chitosan cross-linked with 20 wt% of tannic acid. Swelling behaviour also depends on the cross-linking of chitosan. It decreases for chitosan after cross-linking by tannic acid. Overall, the properties of cross-linked chitosan depend on the amount of tannic acid used for modification. This method of cross-linking can be useful for obtaining materials with specific properties.
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The effect of protocatechuic acid, tannic acid and trans-resveratrol on the activity of p-nitrophenol hydroxylase (PNPH), an enzymatic marker of CYP2E1, was examined in liver microsomes from acetone induced mice. trans-Resveratrol was found to be the most potent inhibitor (IC50 = 18.5 ± 0.4 mM) of PNPH, while protocatechuic acid had no effect on the enzyme activity. Tannic acid with IC50 = 29.6 ± 3.3 mM showed mixed- and trans-resveratrol competitive inhibition kinetics (Ki = 1 mM and 2.1 mM, respectively). Moreover, trans-resveratrol produced a NADPH-dependent loss of PNPH activity, suggesting mechanism-based CYP2E1 inactivation. These results indicate that trans-resveratrol and tannic acid may modulate cytochrome P450 2E1 and influence the metabolic activation of xenobiotics mediated by this P450 isoform.
Przedstawiono wpływ kwasów taninowego i fitynowego na zachowanie korozyjne miedzi oraz na zanieczyszczenie wody solami miedzi w wodach naturalnych o podwyższonej agresywności, ze szczególnym uwzględnieniem korozji wżerowej. Na podstawie elektrochemicznego testu korozyjnego określono podstawowe parametry procesu korozji miedzi oraz optymalną zawartość kwasu taninowego w wodzie dla zapewnienia inhibitowania korozji wżerowej.
EN
The influence of tannic and phytic acids on corrosion behaviour of copper and on release of the by-products of copper corrosion in waters with increased the pitting tendency was investigated. Based on electrochemical corrosion test there were determined the basic parameters of copper corrosion process and the optimum concentration of tannic acid for inhibition of copper pitting corrosion.
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Przedstawiono wyniki badań korozyjnych miedzi w wodzie pitnej, zawierającej wybrane naturalne kwasy organiczne: fitynowy, taninowy i L-askorbinowy, otrzymane metodą polaryzacji potencjokinetycznej. Stwierdzono, że wszystkie badane kwasy wykazują właściwości inhibitowania korozji miedzi w zakresie stężeń 0,5-4,0 mg/dm3, przy czym wzrost stężenia powyżej 2 mg/ dm3 powoduje powolny wzrost prądu korozyjnego. Najlepsze właściwości ochronne w stosunku do miedzi wykazuje kwas fitynowy, dla którego przy stężeniu ok. 1,5 mg/dm3 skuteczność ochrony przed korozją osiąga wartość ok. 34%.
EN
The results of potential sweep method corrosion investigations of copper exposed to potable water containing selected natural organic compounds i.e. phytic, tannic and L-ascorbic acids, have been presented. It has been found that all the investigated acids manifest inhibiting properties in the 0.5-4.0 mg/dm3 concentration range; however an increase in the concentration to over 2 mg/dm3 results in the gradual rise of the corrosion current. It has been discovered that phytic acid, when added to water, shows the best copper corrosion protection properties. At a concentration of 1.5 mg/dm3 the corrosion efficiency reaches a value of up to 34%.
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