Predominant Degradation Product Research Articles

Promoted dissipation and detoxification of atrazine by graphene oxide coexisting in water.

The herbicide atrazine (ATZ) has a detrimental effect on the health of aquatic ecosystems and has become a global concern in recent years. But the understanding of its persistence and potential toxicity under combined pollution, especially in the coexistence of other emerging pollutants, remains limited. In this work, the dissipation and transformation of ATZ in combination with graphene oxide (GO) in water were investigated. Results showed that dissipation rates of ATZ dramatically increased by 15-95% with half-lives shortened by 15-40% depending on initial concentrations of ATZ, and the products were mainly toxic chloro-dealkylated intermediates (deethylatrazine (DEA) and deisopropylatrazine (DIA)), but their contents were significantly lower under the coexistence of GO compared to ATZ alone. In the presence of GO, the nontoxic dechlorinated metabolite hydroxyatrazine (HYA) was detected earlier than 2-9days, and ATZ transformation into HYA was increased by 6-18% during 21-day incubation periods. This study indicated that the coexistence of GO enhanced the dissipation and detoxification of ATZ. From a remediation standpoint, GO-induced hydrolytic dechlorination of ATZ can reduce its ecological toxicity. But the environmental risks of ATZ for aquatic ecosystem under the coexistence of GO should still be given the necessary prominence due to the potential hazard of ATZ adsorbed on GO and the predominant degradation products (DEA and DIA).

Radiolytic evaluation of acetohydroxamic acid (AHA) under biphasic (HNO3:n-dodecane and TBP/DEHBA/DEHiBA) used nuclear fuel reprocessing conditions

Acetohydroxamic acid (AHA) has been proposed as a substitute for hydrazine-stabilized reductants for the selective separation of plutonium and neptunium from co-extracted uranium during the reprocessing of used nuclear fuel. However, limited information exists for the chemical behavior of AHA in ionizing radiation fields, especially under representative biphasic reprocessing solvent system conditions. Here we present a systematic gamma irradiation study on the radiolytic integrity of AHA in aqueous nitric acid solutions (0.2 M HNO3) in contact with an organic phase, comprising current (tri-butyl phosphate) and next generation (N,N-di-(2-ethylhexyl)butyramide and N,N-di-(2-ethylhexyl)isobutyramide) reprocessing ligands dissolved in n-dodecane diluent. Biphasic AHA irradiations exhibited negligible effect of the organic phase on the rate of AHA radiolysis—affording an average pseudo dose constant of d' = (−58.66 ± 6.10) × 10−4 kGy−1—and subsequent formation of the predominant degradation products (hydroxylamine and acetic acid), relative to complementary single-phase systems. The radiolysis of AHA was found to have negligible impact on ligand degradation rates: G(TBP) = −0.038 ± 0.002 μmol J−1, G(DEHBA) = −0.117 ± 0.004 μmol J−1, and G(DEHiBA) = −0.102 ± 0.003 μmol J−1. These observations demonstrate that the radiolytic transients and steady-state degradation products generated in either phase have limited capacity for migrating across the aqueous-organic interface to undergo subsequent chemistry within the investigated dose range (≤110 kGy). These findings support the substitution of AHA into advanced reprocessing flowsheets.

Radiolytic evaluation of select sulfur chlorides (S2Cl2 and SOCl2) for advanced low temperature chlorination of zirconium-based used nuclear fuel cladding

New sulfur chloride compounds—sulfur monochloride (S2Cl2) and thionyl chloride (SOCl2)—have been proposed as alternative chlorinating agents for the chemical decladding of zirconium-based used nuclear fuel cladding materials. However, the radiation stability of these compounds has not been thoroughly evaluated, despite envisioned process conditions involving intense, multi-component radiation fields. Knowledge of the radiation chemistry of these sulfur chlorides is essential for the development and optimization of alternative chlorination technologies. To this end, we present preliminary findings on the gamma radiolysis of neat S2Cl2 and SOCl2 at ambient temperature up to ∼ 34 MGy. In this study, Raman spectroscopy and density functional theory calculations were used to identify the Raman-active degradation products from S2Cl2 and SOCl2 radiolysis. Both sulfur chloride compounds exhibited significant radiation resistance, with respect to changes in the Raman signatures of the parent compounds and the ingrowth of Raman-active degradation products. For S2Cl2, molecular chlorine (Cl2) was directly identified as the predominant degradation product, which was completely consumed at higher absorbed doses (> 9 MGy). Similarly, the main degradation product from SOCl2 radiolysis was also Cl2, although in this system it continued to grow in with dose over the entire dose range. An “SO” containing degradation product(s) was also identified as a compliment to Cl2. Overall, the perceived radiation resistance of these sulfur chloride compounds makes them suitable for inclusion in a used nuclear fuel chemical decladding process, especially as radiolytically formed Cl2 can be used to reform the parent compounds, thereby increasing the longevity of the solvents used.

Clarification of the USP compendial procedure for phenoxybenzamine hydrochloride via updating impurity profiles

The current United States Pharmacopeia–National Formulary (USP–NF) and the British Pharmacopoeia phenoxybenzamine (PBA) hydrochloride drug substance and drug product monographs describe an HPLC procedure for the determination of a specified impurity “tertiary amine phenoxybenzamine” and use the resolution of an “unknown related substance” from PBA as a system suitability criterion; however, neither structural information of the “unknown related substance” is provided nor reference standards of the two impurities are available. The ambiguity in pharmacopeias poses difficulties in implementing the procedure for quality control. To clarify the degradation pathways, and incorporate the impurity profile of PBA into the USP monographs, the degradation of PBA was revisited. PBA undergoes rapid degradation in neutral or basic aqueous solutions to generate the “tertiary amine phenoxybenzamine” as the predominant degradation product, which was confirmed as phenoxybenzamine hydroxide (PBA-OH). In addition, the “unknown related substance” was proposed as the phenoxybenzamine nitrile (PBA-CN) on the basis of LC–MS studies. The identity of PBA-CN was unambiguously verified via chemical synthesis, HPLC and NMR analyses. A stability-indicating method was developed and validated for the determination of PBA and its impurities, and was used to support USP monograph modernization.

Stability of a compounded oral liquid formulation of clopidogrel for infants

AbstractBackgroundClopidogrel is recommended to prevent thrombotic complications in at‐risk infants. No commercial liquid formulation is currently available. Published compounded liquid formulations have not accounted for chiral instability at recommended storage conditions, and studied strengths are problematic in measuring accurate doses for infants.AimThis study examined the stability of a low strength (1 mg/mL) oral liquid formulation of clopidogrel using a chiral chromatographic method to separate active S‐clopidogrel from its predominant degradation product R‐clopidogrel, as well as its acid products.MethodsClopidogrel mixtures (1 mg/mL) prepared using Plavix tablets (Sanofi‐Aventis, Macquarie Park, NSW, Australia) in 1 : 1 Ora‐Plus : Ora‐Sweet (Perrigo, Minneapolis, MN, USA) were stored at room temperature (25°C) and under refrigeration (4°C). Samples stored were assayed periodically for S‐clopidogrel using chiral liquid chromatography to a minimum of 55 days. The percentage of S‐clopidogrel remaining (at least 90% of nominal content) was used to estimate shelf life. Physical and microbiological stability was also assessed.ResultsEstimated shelf lives at room temperature and under refrigeration were 12 and 46 days, respectively. When removed from refrigeration, kept at 25°C for 3 days and then returned to the refrigerator, the shelf life was reduced to 41 days. Physical stability was maintained during these periods, and there was no evidence of microbiological contamination.ConclusionIt is recommended that clopidogrel 1 mg/mL in an oral preparation containing Ora‐Plus : Ora‐Sweet be stored in the refrigerator (4°C) and discarded 6 weeks after compounding. If removed from the refrigerator to room temperature (25°C) for 3 days, so long as the suspension is returned to the refrigerator, it could be used at a reduced shelf life of 1 month.

Potential risk to human skin cells from exposure to dicloran photodegradation products in water

Exposure to sunlight and certain pesticides can induce phototoxic responses. Long- and short-term exposure to the photoactivated pesticides can cause a variety of skin diseases. However, assessment of pesticide phototoxicity on human skin is difficult. In the present study, human skin keratinocytes were cultured in several forms: monolayer cell sheet, three-dimensional culture, and keratinocyte-fibroblast co-culture. A common fungicide, dicloran (DC, 2,6‑dichloro‑4‑nitroaniline), was irradiated with simulated sunlight for 2 (DC-PD-2h) and 4 (DC-PD-4h) hours. Dicloran, and two purified intermediate photodegradation products, 2‑chloro‑1,4‑benzoquinone (CBQ) and 1,4‑benzoquinone (BQ), were applied in toxicity tests independently with the keratinocyte culture models. The cell migration, cell differentiation, pro-inflammatory molecule production, and dermal fibroblast cell activation were all measured in the keratinocytes treated with the chemicals described above. These parameters were used as references for dicloran phototoxicity assessment. Among all tested chemicals, the DC-PD-4h and BQ demonstrated elevated toxicities to the keratinocytes compared to dicloran based on our results. The application of DC-PD-4h or BQ significantly delayed the migration of keratinocytes in monolayer cell sheets, inhibited the keratinocyte differentiation, increased the production of pro-inflammatory molecules by 3D keratinocyte culture, and enhanced the ability of 3D cultured keratinocytes in the activation of co-cultured dermal fibroblast cells. In contrast, dicloran, DC-PD-2h, and CBQ showed minimal effects on the keratinocytes in all assays. The results suggested that the four-hour photodegraded dicloran was likely to induce inflammatory skin diseases in the natural human skin. The 1,4‑benzoquinone, which is the predominant degradation product detected following 4 h of irradiation, was the main factor for this response. Photoactivation increased the risk of skin exposed to dicloran in nature. Our models provided an efficient tool in the assessment of toxicity changes in pesticide following normal use practices under typical environmental conditions.

The Role of Excipients in the Stability of Triamcinolone Acetonide in Ointments

Degradation of triamcinolone acetonide (TCA) in an ointment was investigated. TCA appeared to be concentrated in propylene glycol (PG) which in turn is dispersed in a lanolin-petrolatum mixture. Two predominant degradation products were identified: a 21-aldehyde and a 17-carboxylic acid. The 21-aldehyde is formed after TCA is oxidized by O2, a reaction that is catalyzed by trace metals. Logically, the content of trace metals has a profound effect on the degradation rate. It was shown that trace metals are extracted from lanolin and petrolatum by PG, increasing the concentration in PG. In accordance with these findings, TCA degrades faster in PG that is present in the ointment formulation than in regular PG. The 21-aldehyde was confirmed to be a primary degradation product, while the 17-carboxylic acid was identified as a secondary degradation product. Based on the mechanism of degradation, the ointment can be stabilized by the addition of sodium metabisulfite which was shown to reside also in the PG phase within the ointment.

Fate of the drug chlorpromazine in river water according to laboratory assays. Identification and evolution over time of degradation products. Sorption to sediment

Toxic effects of the non-biodegradable drug chlorpromazine and its degradation products have been reported on microorganisms in aqueous media. Here, chlorpromazine degradation assays in forced and non-forced conditions have been done to know its persistence and degradation products in river water. Sunlight irradiation promotes the complete degradation of chlorpromazine (2 μg L−1) in less than 4 h, but if the exposure to sunlight is limited chlorpromazine is detected during 4 weeks in river water. Sixteen degradation products in surface water are described for first time after solid-phase extraction and analysis by ultra-pressure liquid chromatography/quadrupole time-of-flight/mass spectrometry; their structures are proposed from the molecular formulae of the fragment-ions observed in high-resolution tandem mass spectra. Hydroxylation and oxidation products such as chlorpromazine sulfoxide, 2-hydroxypromazine and 2-hydroxypromazine sulfoxide were predominant degradation products in the early stages; some benzo[1,4]thiazin-6-ol derivatives resulting from the breakdown of the phenothiazine core were the major and relatively stable products after 20 weeks under non-forced conditions. A degradation pathway of chlorpromazine in water is outlined. Moreover, it is shown that chlorpromazine is very strongly adsorbed on sediment while the degradation products that kept the promazine core have a notable capacity of sorption, too; sorption coefficients are calculated. Finally, a prediction about the toxicity of the degradation products in aquatic ecosystems suggests that some of them have toxicities similar, or even higher, than chlorpromazine.

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O2 Batteries during the 1st Cycle

The surface chemistry of the commonly employed positive electrode substrate Super C65 carbon was investigated during the 1st cycle of a Li-O2 battery with a typical ether electrolyte (0.2 M LiTFSI in Diglyme) by performing in situ online electrochemical mass spectrometry (OEMS), ex situ scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). During discharge, a nanometer-thin (< 5 nm) layer of Li2O2 forms homogeneously throughout the electrode before it is passivated at a final specific charge of ∼365 mAh/g. Higher discharge charge rates lead to thinner and more densely packed layers of Li2O2. Electrolyte decomposition also occurs in parallel, as evidenced by the continuous increase of LiF and sulfur containing species of the degraded LiTFSI salt. On charge, O2 evolves initially according to a 2e−/O2 rate, but as the cell over-potentials increase, O2 evolution rate approaches 4e−/O2, thus demonstrating a significant extent of parasitic side-reactions. Unlike the discharge, the charge leads to inhomogeneous electrode reactions causing a continuous removal of Li2O2 with no indication of LiO2 or Li2O intermediates. The decomposition side-products formed during discharge are also removed and the spectra of the pristine electrode are nearly retained at a full charge. Our results show that the analysis of Li-O2 battery chemistry requires broad approach based on the combination of various electrode surface sensitive techniques, such as XPS and OEMS, in order to provide further fundamental understanding of the mechanisms behind the complex electrochemistry involving the Li and O2 as well as several other predominant degradation products of the electrode and electrolyte.

Evaluation of thermal stability of enalapril maleate tablets using thermogravimetry and differential scanning calorimetry

Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in order to evaluate the thermal stability of an enalapril maleate formulation packaged in two types of packaging, polyvinyl chloride/aluminum blister and aluminum strip. Enalapril and the excipients employed in the formulation were also evaluated by TG and DSC. Tablets were analyzed before and after storage in an acclimatized room at 40 °C and relative humidity of 75 % for 90 days. The DSC and TG results were compared with the results of dosage of enalapril and related compounds obtained by high-performance liquid chromatography. These results indicate an occurrence of chemical interaction between enalapril maleate and the excipients during its storage. After storage, it was observed that the enalapril content reduced and the predominant degradation product was diketopiperazine for both types of packaging. The predominance of diketopiperazine could be related to the absence of sodium bicarbonate in the tablets, alkalinizing agent employed in the thermal stabilization of the drug.

Mechanism and Related Kinetics of 5-Methyltetrahydrofolic Acid Degradation during Combined High Hydrostatic Pressure−Thermal Treatments

The mechanism and kinetics of the degradation of 5-methyltetrahydrofolic acid during thermal and combined high pressure-thermal treatments in an aqueous solution were investigated. In a first approach the degradation was described by a first-order kinetic model using single-response modeling, and the combined pressure-temperature dependence of the resulting degradation rate constants was empirically described. To obtain a mechanistic insight, degradation products were purified and identified by LC-MS and NMR. Quantification of an s-triazine derivative, 5-methyldihydrofolic acid, and p-aminobenzoyl-l-glutamate as predominant degradation products at atmospheric pressure resulted in elucidation and kinetic characterization of the folate degradation mechanism by Bayesian multiresponse modeling. The postulated mechanism was evaluated at elevated hydrostatic pressure. On the basis of the pressure and temperature dependence of the reaction rates, some degradation reactions were either accelerated or decelerated upon application of pressure. Multiresponse kinetics can be a valuable tool to assess the impact of high hydrostatic pressure and other processing techniques on nutrients, and incorporating mechanistic insights can advance the current kinetic approach for process optimization.

Mass Spectrometry Reveals the Missing Links in the Assembly Pathway of the Bacterial 20 S Proteasome

The 20 S proteasome is an essential proteolytic particle, responsible for degrading short-lived and abnormal intracellular proteins. The 700-kDa assembly is comprised of 14 alpha-type and 14 beta-type subunits, which form a cylindrical architecture composed of four stacked heptameric rings (alpha7beta7beta7alpha7). The formation of the 20 S proteasome is a complex process that involves a cascade of folding, assembly, and processing events. To date, the understanding of the assembly pathway is incomplete due to the experimental challenges of capturing short-lived intermediates. In this study, we have applied a real-time mass spectrometry approach to capture transient species along the assembly pathway of the 20 S proteasome from Rhodococcus erythropolis. In the course of assembly, we observed formation of an early alpha/beta-heterodimer as well as an unprocessed half-proteasome particle. Formation of mature holoproteasomes occurred in concert with the disappearance of half-proteasomes. We also analyzed the beta-subunits before and during assembly and reveal that those with longer propeptides are incorporated into half- and full proteasomes more rapidly than those that are heavily truncated. To characterize the preholoproteasome, formed by docking of two unprocessed half-proteasomes and not observed during assembly of wild type subunits, we trapped this intermediate using a beta-subunit mutational variant. In summary, this study provides evidence for transient intermediates in the assembly pathway and reveals detailed insight into the cleavage sites of the propeptide.

The Attenuation of Atrazine and its Major Degradation Products in a Restored Riparian Buffer

The fate and transport of atrazine and three of its major degradation products were studied in a restored forested riparian buffer system in southern Georgia to examine the effectiveness of the system in attenuating the chemicals. Atrazine was applied to a 10 100 m strip immediately upslope from the buffer system, and atrazine, deethylatrazine, deisopropylatrazine, and hydroxyatrazine were monitored in groundwater, soil, and runoff water for 11 months following application. Atrazine removal from groundwater was very effective, with the calculated 3810 mg entering the upslope position being reduced to 174 mg exiting the streamside landscape position. Each of the landscape positions (0, 8, 13, 18, 28, and 38 m from the application strip) in the buffer system contributed significantly to the atrazine concentration reduction in the initial three months following application, when the majority of atrazine was measured. Deethylatrazine is the primary result of biotic degradation and was the predominant degradation product in groundwater, with approximately 10% (379 mg) as much estimated to have entered the upper interface of the buffer system as did the parent atrazine. The riparian buffer system was successful in significantly reducing concentrations of deethylatrazine in groundwater in both the initial three months following application and in the final eight months of the study. Adsorption of the analytes to subsurface soils was minimal in this system. Deethylatrazine was also the predominant degradation product in the runoff water, but hydroxyatrazine was predominant in conjunction with runoff sediments. Removal efficiency of analyte mass loads in surface runoff water ranged from 92% to 100% as the chemicals were transported through the buffer system. While the mass load of atrazine associated with sediment was only 8% of that measured for the water phase, the mass loads of deethylatrazine and deisopropylatrazine (approximately 40%) and particularly hydroxyatrazine (75%) in sediments were proportionally much higher. About 98.6% of measured runoff water and sediment phase transport of atrazine occurred within the first few days following application as a result of an extended rainfall event. In contrast, roughly 45% of the deethylatrazine and deisopropylatrazine and only 16% of the hydroxyatrazine were measured in the first rain event sample. The results of this work indicate that riparian buffer systems can be successfully used to intercept atrazine and the studied degradation products in order to minimize contamination of natural water systems. Riparian buffers can provide year round attenuation, particularly for deethylatrazine. The importance of timing atrazine application to correspond with periods when there is no threat of rainfall is also emphasized.

Aqueous p-nitrotoluene oxidation induced with direct glow discharge plasma

Abstract A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic acid was also observed. The final products of degradation were NH4+, NO3− and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first order reaction hence, a possible reaction pathway was proposed.

Identification of the main oxidation products of 8-methoxy-2′-deoxyguanosine by singlet molecular oxygen

It is now well established that oxidation of 2′-deoxyguanosine (dGuo) in DNA by singlet molecular oxygen [O 2 ( 1Δ g)] produces 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo), whereas the main degradation products of free dGuo in aqueous solution have been identified as the two diastereomers of spiroiminodihydantoin nucleoside. Interestingly, O 2 ( 1Δ g)-mediated oxidation of free 8-oxodGuo gives rise to a pattern of degradation products that is different from that observed when the nucleoside is inserted into DNA. The reasons for these differences and the mechanisms involved in the oxidation reactions are not yet completely understood for either dGuo or 8-oxodGuo, either free or within DNA. In the present work, we report a study of the reaction of O 2 ( 1Δ g) toward a modified nucleoside, 8-methoxy-2′-deoxyguanosine (8-MeOdGuo), either free or incorporated into an oligonucleotide. The reason for the choice of 8-MeOdGuo as a chemical model to study in more detail the oxidation pathways of 8-oxodGuo or, more precisely, of the tautomeric 8-hydroxy-2′-deoxyguanosine was dictated by the fact that only the 7,8-enolic tautomer is present in the molecule. The thermolysis of an endoperoxide of a naphthalene derivative as a clean chemical source of 18O-labeled O 2 ( 1Δ g) was used to oxidize 8-MeOdGuo. The main O 2 ( 1Δ g) oxidation products that were separated and analyzed by HPLC coupled to tandem mass spectrometry were identified as the 2′-deoxyribonucleoside derivatives of 2,2,4-triamino-5-(2 H)oxazolone, 2,5-diamino-4 H-imidazol-4-one together with the methyl-substituted derivatives of spiroiminodihydantoin, oxidized iminoallantoin and urea. On the other hand, O 2 ( 1Δ g) oxidation of 8-MeOdGuo-containing oligonucleotide generated imidazolone as the predominant degradation product. These results provided new mechanistic insights into the reactions of O 2 ( 1Δ g) with purine nucleosides.

Investigation on the thermal degradation of poly- n-alkyl acrylates and poly- n-alkyl methacrylates (C 1–C 12)

The thermal degradation of a series of poly- n-alkyl acrylates, from methyl to dodecyl, and poly- n-alkyl methacrylates, from butyl to nonyl, has been studied in isothermal conditions at 400–650 °C using pyrolysis-gas chromatography/mass spectrometry. The type and composition of the pyrolysis products gave useful information about the mechanism of thermal degradation. It was shown that the main thermal degradation processes for poly- n-alkyl acrylates are random main-chain scission with the formation of monomer, dimer, saturated diester, trimer, corresponding acetate and methacrylate, and non-radical side-chain reaction through six-member ring transition state. The most abundant degradation products coming from the alkyl ester decomposition are the corresponding olefin, aldehyde, and alcohol. Poly- n-alkyl methacrylates yield monomer as the predominant degradation product in all investigated pyrolysis conditions. Unlike poly(methyl methacrylate) which gives quantitative yields of monomer, however, the poly- n-alkyl methacrylates with longer alkyl chain produce also significant amounts of olefin and methacrylic acid.

Analysis of the stability of amino acids derivatized with naphthalene-2,3-dicarboxaldehyde using high-performance liquid chromatography and mass spectrometry

The stability of amino acids derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) was investigated using a combination of high-performance liquid chromatography, solid-phase extraction, photodiode array spectrophotometric detection, and mass spectrometric (MS) characterization. The degradation of amino acid derivatives, generated using β-mercaptoethanol as a nucleophile, was characterized under a variety of environmental influences, with a focus on understanding the degradation kinetics and identifying the degradation products. The predominant degradation product observed under most reaction conditions was the nonfluorescent lactam form of the originally fluorescent isoindole derivative. First, the time-dependent degradation of the isoindole derivative l-serine–NDA–β-mercaptoethanol was found to follow pseudo-first order kinetics with a half-life of 2.0 min at pH 9.2 and room temperature. The isoindole derivative was observed to react further with methanol to form a more stable fluorescent methoxy–isoindole, shedding new light on the basis for enhanced stability of these derivatives in methanol. Tandem mass spectrometry (MS/MS) experiments were used to demonstrate unimolecular degradation of the protonated isoindole in the absence of solvent or atmosphere, suggesting an intramolecular reaction mechanism involving the hydroxyethylthio group. Finally, in photobleaching studies, NDA derivatives rapidly degraded into a variety of products within the first 2 min of photobleaching versus timed controls, with the predominant product being the lactam. These results suggest that the degradation pathway for NDA derivatives is similar to the previously reported pathway for o-phthalaldehyde derivatives and clearly identifies the reaction and degradation products under a variety of conditions.

Degradation products of cyanidin glycosides from tart cherries and their bioactivities.

The bioactive anthocyanins present in tart cherries, Prunus cerasus L. (Rosaceae) cv. Balaton, are cyanidin 3-glucosylrutinoside (1), cyanidin 3-rutinoside (2), and cyanidin 3-glucoside (3). Cyanidin (4) is the major anthocyanidin in tart cherries. In our continued evaluation of the in vivo and in vitro efficacy of these anthocyanins to prevent inflammation and colon cancer, we have added these compounds to McCoy's 5A medium in an effort to identify their degradation products during in vitro cell culture studies. This resulted in the isolation and characterization of protocatechuic acid (5), the predominant degradation product. In addition, 2,4-dihydroxybenzoic acid (6) and 2,4,6-trihydroxybenzoic acid (7) were identified as degradation products. However, these degradation products were not quantified. Compounds 5-7 were also identified as degradation products when anthocyanins were subjected to varying pH and thermal conditions. In cyclooxygenase (COX)-I and -II enzyme inhibitory assays, compounds 5-7 did not show significant activities when compared to the NSAIDs Naproxen, Celebrex, and Vioxx, or Ibuprofen, at 50 microM concentrations. However, at a test concentration of 50 microM, the antioxidant activity of protocatechuic acid (5) was comparable to those of the commercial antioxidants tert-butylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA), and superior to that of vitamin E at 10 microM concentrations.

Accelerated Transformation and Binding of 2,4,6-Trinitrotoluene in Rhizosphere Soil

Enhanced microbial activity and xenobiotic transformations take place in the rhizosphere. Degradation and binding of 2,4,6-trinitrotoluene (TNT) were determined in two rhizosphere soils (RS) and compared to respective unplanted control soils (CS). The rhizosphere soils were obtained after growing corn for 70 d in soils containing 2.8% (Soil A) or 5.9% (Soil B) organic matter. Aerobically agitated soil slurries (3:1, solution/soil) were prepared from RS and CS and amended with 75 mg TNT L−1 (14C-labeled). TNT degraded more rapidly and formed more un-extractable bound residue in RS than in CS. In Soil A, total extractable TNT decreased from 225 to 1.0 mg kg−1 in RS, whereas 11 mg kg−1 remained in CS after 15 d. Unextractable bound 14C residues accounted for 40% of the added 14C-TNT in RS and 28% in CS. The smaller differences in Soil B were attributed partially to the higher organic matter content. The predominant TNT degradation products were monoaminodinitrotoluenes (ADNT), which accumulated and disappeared more rapidly in RS than in CS, and hydroxylaminodinitrotoluenes (HADNT). When sterilized by γ-irradiation, no significant differences between RS and CS were observed in TNT loss or bound residue formation. More rapid TNT degradation and enhanced bound residue formation in the unsterilized RS was attributed to micro-bial-facilitated production and transformation of HADNT and ADNT, which are potential precursors to bound residue formation. If plants can be established on TNT-contaminated soil, these results indicate that the rhizosphere can accelerate reductive transformation of TNT and promote bound residue formation.

Solid-phase extraction and subsequent gas chromatography-mass spectrometry analysis for identification of complex mixtures of degradation products in starch-based polymers

A solid-phase extraction (SPE) method, using silica bonded with aminopropyl groups, was developed to separate highly complex mixtures of degradation products into three fractions. The SPE allowed the subsequent GC-MS identification of nearly 140 thermo-oxidation products of starch-based polymer blends, consisting of 70% starch and either ethylene maleic anhydride (EMA) or ethylene vinyl acetate maleic anhydride (EVAMA). It was thus possible to identify several homologous series of degradation products such as n-alkanes and 1-alkenes, 1-alcohols, 2-ketones, aldehydes, carboxylic acids and dicarboxylic acids. The homologous series of dicarboxylic acids ranged from butanedioic acid (C 4) to nonadecanedionic acid (C 19) and was for the first time identified in thermo-oxidized starch-based blends with polyethylene (PE). Hydrocarbons of even carbon number were formed to a larger extent than those with an uneven carbon number in the starch-EMA blend and the ratio n-alkane to 1-alkene increased (i.e. relatively more alkane is formed) under more severe thermo-oxidation conditions. The same phenomenon was not observed in the starch-EVAMA blend. Formic acid, acetic acid and γ-butyrolactone were the most predominant degradation products in both materials. Typical starch degradation products were difficult to resolve but we identified 2-hexanone, formic acid and acetic acid, which also have been reported previously to be degradation products of starch. The molecular mass measurements showed that the starch-EVAMA blend starts to degrade earlier than the starch-EMA, but on the other hand, at a lower rate. A good correlation between the decrease in M n and the amount of degradation products formed was observed. A higher degree of cross-linking occurred in the starch-EVAMA blend in comparison with the starch-EMA blend and, in parallel, qualitatively and quantitatively more degradation products are formed in the starch-EMA blend.