Department of Plant Physiology, Genetics and Biotechnology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 1A, 10-718 Olsztyn, Poland.
Department of Physics and Biophysics, Faculty of Food Science, University of Warmia and Mazury in Olsztyn, Oczapowskiego 4, 10-719 Olsztyn, Poland.
Molecules. 2022 Dec 2;27(23):8498. doi: 10.3390/molecules27238498.
Iron ions can be used to degrade tetracycline dispersed in nature. Studies of absorption and fluorescence spectra and quantum chemistry calculations showed that iron is more readily released from Fe(III)-citrate than from Fe(III)-EDTA, so Fe(III)-citrate (Fe(III)-Cit) is more suitable for tetracycline (TC) degradation. At 30 °C, a severe degradation of TC by Fe(III)-Cit occurred as early as after 3 days of incubation in the light, and after 5 days in the dark. In contrast, the degradation of TC by Fe(III)-EDTA proceeded very slowly in the dark. By the fifth day of incubation of TC with Fe(III)-Cit in darkness, the concentrations of the former compound dropped by 55% and 75%, at 20 °C and 30 °C, respectively. The decrease in tetracycline concentrations caused by Fe(III)-EDTA in darkness at the same temperatures was only 2% and 6%, respectively. Light increased the degradation rates of TC by Fe(III)-EDTA to 20% and 56% at 20 °C and 30 °C, respectively. The key role of the light in the degradation of tetracycline by Fe(III)-EDTA was thus demonstrated. The TC degradation reaction showed a second-order kinetics. The rate constants of Fe(III)-Cit-induced TC degradation at 20 °C and 30 °C in darkness were = 4238 Mday and = 11,330 Mday, respectively, while for Fe(III)-EDTA were 55 Mday and 226 Mday. In light, these constants were = 15,440 Mday and = 40,270 Mday for Fe(III)-Cit and = 1012 Mday and 2050 Mday at 20 °C and 30 °C; respectively. A possible reason for the higher TC degradation rate caused by Fe(III)-Cit can be the result of its lower thermodynamical stability compared with Fe(III)-EDTA, which we confirmed with our quantum chemistry calculations. Two quantum chemistry calculations showed that the iron complex with EDTA is more stable (the free energy of the ensemble is 15.8 kcal/mol lower) than the iron complex with Cit; hence, Fe release from Fe(III)-EDTA is less effective.
铁离子可用于降解自然界中分散的四环素。吸收和荧光光谱研究以及量子化学计算表明，柠檬酸铁（III）（Fe（III）-Cit）比乙二胺四乙酸铁（III）（Fe（III）-EDTA）更容易释放铁，因此更适合用于四环素（TC）降解。在 30°C 下，在光照下孵育 3 天后，TC 即可被 Fe（III）-Cit 严重降解，而在黑暗中则需 5 天。相比之下，在黑暗中，TC 与 Fe（III）-EDTA 的降解速度非常缓慢。在黑暗中用 Fe（III）-Cit 孵育 TC 5 天后，在 20°C 和 30°C 下，前者的浓度分别下降了 55%和 75%。在相同温度下，Fe（III）-EDTA 导致的四环素浓度下降仅分别为 2%和 6%。光照分别将 Fe（III）-EDTA 对 TC 的降解率提高到 20°C 和 30°C 时的 20%和 56%。由此证明了光在 Fe（III）-EDTA 降解四环素中的关键作用。TC 降解反应呈二级动力学。在黑暗中，20°C 和 30°C 下 Fe（III）-Cit 诱导的 TC 降解的速率常数分别为 = 4238 M·day 和 = 11,330 M·day，而 Fe（III）-EDTA 分别为 55 M·day 和 226 M·day。在光照下，20°C 和 30°C 下 Fe（III）-Cit 的这些常数分别为 = 15,440 M·day 和 = 40,270 M·day，而 Fe（III）-EDTA 则分别为 1012 M·day 和 2050 M·day。Fe（III）-Cit 导致 TC 降解率更高的一个可能原因是与 Fe（III）-EDTA 相比，其热力学稳定性较低，我们的量子化学计算证实了这一点。两项量子化学计算表明，EDTA 与铁形成的配合物更稳定（配合物的总自由能低 15.8 kcal/mol），因此，从 Fe（III）-EDTA 中释放铁的效果较差。
