Hydrolysis and photolysis of oxytetracycline in aqueous solution

Abstract

Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 +/- 0.001 to 0.106 +/- 0.003 day(-1) were obtained at different initial concentration ranging from 10 to 230 microM. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 x 10(2) to 0.15 day with the increasing temperature from 4 +/- 0.8 to 60 +/- 1 degrees C. The presence of Ca(2+) made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 +/- 0.06 day(-1), which is comparable to that of hydrolysis at 60 degrees C. The presence of Ca(2+) accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca(2+). The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment.

RETRACTED: Stabilization of vaccines and antibiotics in silk and eliminating the cold chain

“…Dating back to Fleming's original 1929 paper on penicillin (26), penicillin is unstable in solution, breaking down within weeks at 25°C and within 24 h at 37°C (27). Tetracycline possesses broad specificity and low cost, but undergoes rapid photolysis and hydrolysis in solution (28,29).…”

Beta-blockers in the environment: Part I. Mobility and hydrolysis study

“…However, it must be highlighted that, even though the chemical structure of some compounds may indicate their hydrolytic stability in an aqueous environment, there are known cases in the literature in which hydrolysis occurred elsewhere in the molecule than could have been expected (Xuan et al, 2010).…”

Establishment of a pretreatment method for tetracycline production wastewater using enhanced hydrolysis

“…Many antibiotics, such as tetracyclines, penicillins, erythromycins and sulfonamides, have poor stability in aqueous solutions, and are susceptible to hydrolysis to form epimers and dehydrated products [9][10][11]. Although numerous studies have been carried out on the antibiotic hydrolysis process because hydrolysis is a major degradation route for antibiotics in water environments [12], few reports are available regarding APW treatment using hydrolysis technology. This is probably because the hydrolysis half-lives of antibiotics range from days to weeks under normal conditions [10], which is too long for practical application with large volume of APW in limited space of reactors.…”

“…However, no radicals are available during the hydrolysis reaction. So we speculate that this product might be formed from an intermediate with an m/z value of 443.This product might be a-apo-oxytetracycline [12] ) became the major compounds, while ATC and EATC disappeared. At the same time, many small peaks appeared that were difficult to identify.…”