Predominant Degradation Product Research Articles

Fate of 14C-Atrazine in a Silt Loam Soil

Abstract Formation of 14C-atruzine degradation products and their distribution in the top 90 cm of a silt loam soil was determined during 16 months in the field. After 16 months. 68% of the applied 14C was still present in the soil. By 12 months after treatment (MAT). 14C leached to 70–80 cm. Atrazine accounted for 24% of the applied 14C remaining 16 MAT, and was the predominant 14C-compound below 10 cm through 16 MAT. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil comprising 13% of 14C present I MAT and increasing to 24% by 12 MAT. Predominant degradation products at depths greater than 10 cm were HA and deethylatrazine (DEA). Deisopropylatrazine (DIA) accounted for less than 6% of the radioactivity recovered at any soil depth. Deethyldeisopropylatrazine (DEDIA) was detected in soil extracts 2 MAT indicating further degradation of DIA and DEA. The proportion of DEA and DIA increased while the proportion of HA decreased at increasing soil depths indicating that DEA and DIA...

Formation and Movement of14C-Atrazine Degradation Products in a Clay Loam Soil in the Field

Formation of14C-atrazine degradation products and their distribution in the top 90 cm of soil was determined over 16 mo in a Webster clay loam in the field. After 16 mo, 64% of the applied14C could still be accounted for in the 90-cm soil profile. At 1 mo after treatment (MAT),14C moved to the 70- to 80-cm depth. Rapid movement of radioactivity could be attributed in part to preferential movement through vertical macropores. Atrazine accounted for 32% of the14C applied 16 MAT and was the predominant14C-compound in soil below 10 cm through 12 MAT. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil accounting for 9% of the14C present 1 MAT and increasing to 24% within 6 MAT. Deethylatrazine (BEA) was the predominant degradation product at depths greater than 10 cm, accounting for 26% of the14C in the 10- to 20-cm depth 16 MAT. Deisopropylatrazine (DIA) accounted for less than 10% of the14C recovered at any soil depth. Deethyldeisopropylatrazine (DEDIA) and an unidentified product were detected in soil extracts 1 MAT indicating further degradation past primary metabolites. The proportion of DEA and DIA increased while the proportion of HA decreased as soil depth increased indicating that DEA and DIA are more mobile in soil than HA. The large amount of radioactivity remaining in the soil 16 MAT suggests that a large pool of atrazine and its degradation products are present in the soil for a long period of time, having the potential to move deeper in the soil and ultimately contaminate ground water.

Kinetics of acid-catalyzed degradation of cyclosporin A and its analogs in aqueous solution.

The kinetics and mechanism of the degradation of cyclosporin A have been studied under aqueous acidic conditions. The rate of degradation was found to be specific acid-catalyzed over the pH range studied (1-4), with isocyclosporin A as the predominant degradation product. Selective reduction of the olefinic bond of the amino acid 2-N-methyl-(R)-((E)-2-butenyl)-4-methyl-L-threonine (MeBmt) did not affect the overall degradation kinetics and product distribution of cyclosporin A. These observations indicate that the alternative degradation pathway involving intramolecular alkoxy addition to the olefinic bond of amino acid MeBmt apparently does not significantly contribute to the overall degradation kinetics of cyclosporin A in the pH range 1-4. The chemical reactivity of O-acetyl-cyclosporin A was examined to probe the governing mechanism for the isomerization of cyclosporin A. Under identical conditions, O-acetyl-cyclosporin A showed a much greater chemical stability than cyclosporin A, consistent with a mechanism involving the hydroxyoxazolidine intermediate. The chemical stability of cyclosporin C, which contains two beta-hydroxyl groups, was also examined. The rate and product distribution for the degradation of cyclosporin C suggest that under aqueous acidic conditions it undergoes N,O-acyl migration solely at the amino acid residue MeBmt. Additionally, the impact of side-chain bulkiness of amino acid MeBmt was examined by studying the degradation kinetics of a series of cyclosporin A analogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential metabolism of Tyr-MIF-1 and MIF-1 in rat and human plasma

The metabolism of the endogenous brain peptides Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH 2) and MIF-1 (Pro-Leu-Gly-NH 2) was determined by HPLC after incubation of the tritiated peptides in human and rat plasma. Degradation of Tyr-MIF-1 was rapid in the plasma from both species, in contrast to the slightly delayed degradation of MIF-1 in rat plasma and the extremely prolonged persistence of MIF-1 in human plasma. In rat plasma, more than half of the intact Tyr-MIF-1 and MIF-1 was degraded within 5 min, in contrast to the 5 days required for 50% degradation of MIF-1 in human plasma at 37°. To slow the rapid rate of metabolism, studies were then performed at 0°. Incubation of Tyr-MIF-1 in human plasma at 0° for 2 hr resulted in HPLC identification of more Tyr-Pro than Tyr at all times. At 0° in rat plasma, however, more Tyr than Tyr-Pro was formed after the first 5 min of incubation of the Tyr-MIF-1 that was labeled on the Tyr. This raised the possibility that the tetrapeptide Tyr-MIF-1 might be serving as a precursor of the tripeptide MIF-1. Incubation of Tyr-MIF-1 tritiated at the Pro under the same conditions with and without Tyr-MIF-1 tritiated at the Tyr showed that Tyr-Pro, not MIF-1, was the predominant degradation product of Tyr-MIF-1. In addition to the metabolism of Tyr-MIF-1 being slower at lower temperatures, it was also slowed by some enzyme inhibitors. After 10 min of incubation at 37°, EDTA appeared to be more effective than bestatin, p-chloromercuribenzoic acid (PCMB), pepstatin, or aprotinin, but after 30 min, bestatin was more effective. Intravenous injection of the tritiated peptides into rats showed short half-time disappearances; again, MIF-1 persisted in blood longer than Tyr-MIF-1. Thus, the results show the rapid metabolism of Tyr-MIF-1 in human and rat plasma, the slightly slower metabolism of MIF-1 in rat plasma, the predominant formation of Tyr-Pro rather than MIF-1 from Tyr-MIF-1, and the markedly delayed metabolism of MIF-1 in human plasma.

Movement and degradation of [14C]atrazine in undisturbed soil columns

The movement and degradation of [14C]-atrazine were studied in undisturbed soil columns (15 × 60 cm) taken manually from a field with no previous pesticide history. The experiment was conducted indoors under controlled temperature conditions. Three weeks after application of [14C]-atrazine (2.2 kg a.i. per hectare) to the soil surface, the columns were leached at weekly intervals for 12 weeks. Approximately 1.2% of the applied 14C was recovered in the leachate over the 12-week period, which corresponds to an atrazine (plus degradation products) concentration of 7.6 μg/L. On completion of the last leaching event, the columns were cut into 10-cm increments and analyzed for [14C]-atrazine and degradation products. Seventy-seven percent of the 14C applied to soil columns remained in the upper 10 cm and included primarily atrazine (9%) and soil-bound residues (57%). Deethylatrazine was the predominant degradation product in the top 10 cm (3.6%). Other degradation products were found in the top 10 cm at relative concentrations of deisopropylatra-zine > hydroxyatrazine > didealkylatrazine > deethylhydroxyatrazine > deisopropylhydroxyatra-zine. Uncharacterized polar metabolites in the top 10 cm accounted for 6% of the applied 14C. Atrazine, deethylatrazine, and deisopropylatrazine were found at all depths. In addition, didealkylatrazine was detected to the 50-cm depth, hydroxyatrazine to the 30-cm depth, and deethylhydroxyatrazine to the 20-cm depth.

Formation and Movement of14C-Atrazine Degradation Products in a Sandy Loam Soil Under Field Conditions

Formation and distribution of14C-atrazine degradation products in the top 120 cm of soil were determined over 16 mo under field conditions in an Estherville sandy loam. After 16 mo, 78% of applied14C was still present in the soil. By 2 mo after treatment (MAT),14C had moved to the 30- to 40-cm depth; however, movement to depths greater than 40 cm was not observed. Greater than 98% of the14C remaining in the soil profile after 16 mo was in the top 20 cm. Twenty-seven percent of the14C applied was atrazine 16 MAT. Atrazine was the predominant14C-compound in soil below 10 cm. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil. The proportion of14C as HA in the top 10 cm increased from 15% 2 MAT to 37% 16 MAT. Deethylatrazine (DEA) was the predominant degradation product at the 10- to 30-cm depth and accounted for up to 23% of the14C present in the 10- to 20-cm depth. Deisopropylatrazine (DIA) accounted for less than 6% of the radioactivity recovered at any soil depth. The proportion of DEA and DIA increased while the proportion of HA decreased as soil depth increased, indicating that DEA and DIA are more mobile in soil than HA. Detection of HA at depths greater than 10 cm appears to be due to in situ degradation of atrazine previously moved to that soil depth. The large amount of14C remaining in the soil 16 MAT suggests that a large pool of atrazine and its degradation products are present in the soil for an extended period following application and have the potential to contaminate ground water.

Biodegradation kinetics of Methylosinus trichosporium OB3b at low concentrations of chloroform in the presence and absence of enzyme competition by methane

The kinetics of chloroform and trichloroethylene (TCE) degradation by the methanotroph, Methylosinus trichosporium OB3b, were measured in batch kinetic experiments. The experiments focused on initial concentrations of around 100 μg/l for chloroform and around 1 mg/l for TCE. The pseudo first-order rate constants ranged from 0.2 to 0.41/mg TSS-day for chloroform and from 0.5 to 3.31/mg TSS-day for TCE in the absence of methane. Comparison of the TCE rate constants to other work indicates that the organisms were producing the soluble form of their methane monooxygenase. The presence of methane caused significant enzyme competition at methane concentrations as low as 0.35 mg/l, resulting in smaller chloroform rate constants. The decreases in the rate constant were consistent with the predictions of an enzyme competitive inhibition model, which indicated a half saturation coefficient for methane in the order of 0.3 mg/l. The predominant degradation products from chloroform was carbon dioxide.

Degradation Kinetics and Mechanisms of Moricizine Hydrochloride in Acidic Medium

AbstractThe degradation kinetics of moricizine hydrochloride (1) were examined over a pH range of 0.6 to 6.0 at an ionic strength of 0.3 and 60°C. The disappearance of intact 1 was followed by a stability‐indicating HPLC assay. The degradation products, which had approximate solubilities of <100 μg/mL, precipitated in aqueous solution. The precipitate was collected for HPLC analysis and identification of degradation products. Degradation of 1 was catalyzed by acetate and phosphate buffers and was pH dependent, with the pH of the minimum rate constant located between 2.8 and 3.2. At pH 0.6‐2.0, 1 degraded via amide hydrolysis to yield first ethyl (10H‐phenothiazin‐2‐yl) carbamate (2), an amide hydrolysis product, which further oxidized in parallel to give ethyl (3‐oxo‐3H‐phenothiazin‐2‐yl) carbamate (3), ethyl (10H‐phenothiazin‐2‐yl) carbamate S‐oxide (4), and diethyl (3, 10′‐bi‐10H‐phenothiazine‐2,2′‐diyl)bis(carbamate) (5), the dimer of the amide hydrolysis product. At pH 2.2‐6.0, 1 degraded via a reverse Mannich reaction, to form the reverse Mannich product ethyl [10‐(1‐oxo‐2‐propenyl)‐10H‐phenothiazin‐2‐yl] carbamate (6), and by parallel reaction via the described amide hydrolysis pathway. The dimer of the amide hydrolysis product was not detectable at pH >2.8. At pH >4.0, the reverse Mannich product was the predominant degradation product. Degradation of 1 was subject to positive and negative kinetic salt effects at pH 1.0 and 4.0, respectively. Arrhenius plots determined at pH 1.0 and 6.0 were linear between 37 and 70°C. Predicted shelf lives at room temperature (22 °C) at pH 1.0 and 6.0 were identical to the shelf lives determined experimentally.

Heat-induced decomposition of disaccharide Amadori compounds in quasi-water-free reaction conditions

The thermally induced decomposition of disaccharide Amadori compounds has been compared to those of monosaccharide ones under almost water-free conditions. The structure of the synthesized maltulosyl compound has been proved to be 4C1-alpha-D-glucopyranosyl- (1----4)-2C5-beta-D-fructopyranosylglycine by 1H- and 13C-NMR spectroscopy. The decomposition of Amadori compounds has been used to study the kinetics of the browning reaction. Compared to fructosylglycine and maltotriulosylglycine, the browning of the disaccharide is faster. Curie point pyrolysis at 300 degrees C and investigation of the pyrolysate by gas chromatography/mass spectrometry have shown that the disaccharide component influences the thermal process. Furanes and furanones have been detected as predominant degradation products, the main one being 2(5H)-furanone. For the first time, we suggest a reaction pathway for the formation of these products via the Maillard reaction which includes 1,6-anhydroglucose.

Characterization of cisplatin degradation as affected by pH and light

The stability of cisplatin in 0.9% sodium chloride solution was studied. Cisplatin was reconstituted with sterile water for injection to achieve a concentration of approximately 1 mg/mL in 0.9% sodium chloride solution. The solutions were placed in flexible polyvinyl chloride containers, clear and amber glass flasks, and plastic syringes and stored at 22-25 degrees C in the dark or exposed to measured amounts of light and assayed periodically for up to 96 days. The initial pH of some of the solutions was adjusted. The stability of cisplatin in the solutions was determined by measuring the concentrations of cisplatin, trichloroammineplatinate(II) (TCAP), and trans-dichlorodiammineplatinum(II) (transplatin) with high-performance liquid chromatography and by measuring solution pH. The effect of adding ethylene oxide and other materials was also determined. TCAP was identified as the predominant degradation product of cisplatin in all the solutions. The rate of degradation was dependent on pH: In the dark, about 0.04% and 0.21% of the cisplatin degraded to TCAP per week at pH 4.3 and 6.3, respectively. The presence of ethylene oxide accelerated cisplatin degradation. Degradation also occurred during exposure to short-wavelength (350-490-nm) visible light. Storage in amber glass flasks offered more protection than storage in clear flasks. Isomerization of cisplatin to transplatin was not observed. The major degradation product of cisplatin was trichloroammineplatinate(II). Solution pH was the predominant factor affecting cisplatin stability.

An analytical investigation of the thermal degradation of a cation-exchange resin — part 1

In this first part of a two-part investigation the preliminary results of the thermal degradation at 300 °C in an aqueous milieu of a cation-exchange resin are presented. The resin is a sulphonated copolymer of styrene (92%) and divinylbenzene. The desulphonation and degradation of the resin was followed by the analytical techniques of laser microprobe mass analysis (LAMMA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Sulphuric acid attack on the metallic surface of the pyrolysis crucible was verified and the identification of the resultant inorganic products was performed by LAMMA and Fourier transform infrared spectroscopy. Nuclear magnetic resonance spectroscopy indicated that few or no unsaturated organic degradation products were formed. GC/MS identified a predominant degradation product as 1,3-diphenylpropane. A Py-GC/MS study on resin residues with respect to varying pyrolysis temperatures and times shows that the formation of organic sulphur compounds are favoured at higher temperatures. This implies that some form of reduction occurs during thermal degradation.

Characterization of the Solution Degradation Products of Etintidine, An H2-Receptor Antagonist

The primary solution degradation products of the antiulcer drug etintidine (1, N"-cyano-N-[2-[[(5-methyl-1H-imidazol-4-yl)methyl]thio]ethyl]- N'-2-propynylguanidine) were determined to be the guanyl urea 2, the guanidine 3, the amine 4a, and the cyanoamine 4b. These products resulted from nitrile hydrolysis and/or intramolecular cyclization of the guanidino and propargyl groups. The amine 4a was found to be a predominant degradation product in aqueous media of pH 4-7 at 70 +/- 0.2 degrees C.

Thermal Degradation of Flavor Enhancers, Inosine 5′‐monophosphate, and Guanosine 5′‐monophosphate in Aqueous Solution

ABSTRACTThe mechanism of thermal degradation of inosine 5′‐monophosphate (IMP) and guanosine (GMP) was investigated kinetically in aqueous solution as a function of pH and temperature. The degradation of IMP and GMP followed first order kinetics. The rate constants were considerably affected by pH and temperature. The half‐life times at 100°C were: IMP, 8.7 hr (pH 4.0), 13.1 hr (pH 7.0), 46.2 hr (pH 9.0); GMP, 6.4 hr (pH 4.0), 8.2 hr (pH 7.0), 38.5 hr (pH 9.0). These times were shortened to about one‐third by raising the temperature 10°C. The predominant degradation products were nucleosides and phosphoric acid, indicating that the main reaction of the thermal degradation was the hydrolysis of the phosphoric ester bond in the nucleotides.

Degradation of atrial natriuretic factor by kidney cortex membranes. Isolation and characterization of the primary proteolytic product.

Synthetic rat atrial natriuretic factor (r-ANF, 1-28) was incubated with rat kidney cortex membranes, and a predominant degradation product was identified by reverse-phase high performance liquid chromatography. The degradation product was subjected to amino acid analyses and found to have a composition identical to r-ANF. Amino-terminal sequence analyses identified two distinct amino-terminal residues and suggested that cleavage had occurred between the cysteine-phenylalanine bond (residues 7 and 8) of r-ANF. This degradative process could be inhibited by 1,10-phenanthroline and EDTA, suggesting that the enzyme responsible for proteolysis is a metalloendoprotease. The enzyme exhibits a Michaelis-Menten constant of approximately 10 microM for the metabolism of r-ANF and has a broad pH optimum between 8.5 and 9.5. These findings suggest that ANF may be initially degraded in the kidney at a single cleavage site within the 17-residue ring structure.

Structure elucidation and characterization of daunorubicin degradation products

The thermal degradation of the cytostatic drug, daunorubicin, in aqueous solution was studied. Degradation products were extracted with chloroform from the degradation mixtures and separated by thin-layer chromatography. The predominant degradation products were identified and characterized with several spectroscopic techniques. All identified compounds were aglycones.