Aminodinitrotoluenes

The degradation of aminodinitrotoluenes has been examined, and destruction of the rings... 

Spanggord RJ, CD Yao, T Mill (2000) Oxidation of aminodinitrotoluenes with ozone products and pathways. Environ Sci Technol 34 497-504. 

Johnson GR, BF Smets, JC Spain (2001) Oxidative transformation of aminodinitrotoluene isomers by multi-component dioxygenases. Appl Environ Microbiol 67 5460-5466. 

A similar enzyme (nitroreductase) from the same bacterium was transferred into tobacco by Hannink et al. (2001). This enzyme utilises NAD(P)H to reduce TNT to aminodinitrotoluenes (ADNTs). Transgenic plants showed an enhanced tolerance and detoxification of TNT, although the metabolites could not be identified. 

A production of aminodinitrotoluenes and diaminonitrotoluenes was observed in culture of R. palmatum. The changes of their concentration in media during cultivation is displayed on the Fig. 1. In the cells, the same products as in media were identified at the end of experiment in the same ratio. 

Figure 6. The concentration of TNT and aminodinitrotoluenes (4-ADNT, 2-ADNT) in medium treated by C. gracillis (a), J. glaucus (b), Ph. australis (c), T. latipholia (d) for 10 days.

A.T. Nielsen et al, Reduction and Ammonoly-sis Products Derived from Isomeric Trinitrotoluenes. Synthesis and Chemical Stability of the Aminodinitrotoluenes , NWC-TP-5933, NavalWeapCenter, China Lake (1977)... 

Aminodinitrotoluenes, x,x-Dinitro-x-amino-toluenes, x,x-Dmitro-x-methyl anilines or x,x-Dinitro- (o-, m-, p-) -toluidines). CH3.C6H2-NH2(N02)2, C7H7N304 mw 197.17 N 21.32% OB to C02 —109.55%, V sol in acet fairly sol in RT ethanol, eth and acetic acid si sol in coned hydrochloric acid... 

The principal methods of synthesis of the aminodinitrotoluenes are as follows 1) Am-monolysis of trinitrotoluenes with excess etha-nolic ammonia at reflux or 25° 2) ammonolysis of hydroxy, alkoxy or halodinitrotoluenes ... 

L.R. Johnson, R. Davenport, H. Balbach, D.J. Schaeffer (1994). Near-ultraviolet light-enhancement of Microtox assays of trinitrotoluene and aminodinitrotoluenes. EcotoxicoL Environ. Saf., 27, 23-33. 

Trinitrotoluene is reduced by the aquatic plant Myriophyllum spicatum to aminodinitrotoluenes (Pavlostathis et al. 1998), and in axenic root cultures of Catharanthus roseus the initial metabolites 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dintrotoluene are conjugated probably with C6-units (Bhadra et al. 1999). There are then several important unresolved issues including the phytotoxicity of these metabolitres before phytoremediation can be exploited. 

Note +, produced not produced ND, no data T, toluene NT, nitrotoluene DNT, dinitrotoluene 2A4NT, 2-amino-4-nitrotoluene ADNT, aminodinitrotoluene. 

Alvarez MA et al., Pseudomonas aeruginosa strain MA01 aerobically metabolizes the aminodinitrotoluenes produced by 2,4,6-trinitrotoluene nitro-group reduction, Can. J. Microbiol., 41, 984, 1995. 

Successive reduction of TNT to aminodinitrotoluenes (ADNTs) and diamino-nitrotoluenes (DANTs) leads to a sequential decrease of toxicity to the microalga, Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum) [32] and in the Microtox test [30], Further toxicity decrease occurs in the latter with an additional reduction to triaminotoluene (TAT) [30] (Table 4.2 and Table 4.3). The ADNTs were also less toxic than the parent compound to the freshwater fish Pimephales promelas [19], and embryos of the frog Xenopus laevis [33], The reduction of 2,3,6-TNT to ADNTs promoted decreased toxicity in studies with P. promelas and D. magna... 

It is important to note that the reduced metabolites of TNT bind to the humic fraction of soil in a manner similar to that seen in plants. After 60 d in a growth chamber, up to half of the applied dose of TNT was converted to aminodinitrotoluenes and was bound to soil [64], It is generally recognized that the amino reduction products can be retained by soil in two ways by covalent bonding to reactive centers and by... 

Another extensive paper on the reaction of unsymmetrical trinitrotoluenes with ammonia leading to aminodinitrotoluenes was that by Nielsen. Coon and co-workers [55]. The main purpose of this work was to identify the major com-... 

Figure 4.143 Typical Cl spectra with different amino and nitro substitutions (a) diamino-toluene, (b) aminonitrotoluene, (c) aminodinitrotoluene and (d) diaminonitrotoluene.

The subsequent reduction of the resulting aminodinitrotoluene with almost exclusive formation of 2,4-diamino-6-nitrotoluene is mediated by several mainly facultatively or strictly anaerobic bacteria, as described by Naumova et al. (34) and McCormick et al. (32). Moreover, Naumova et al. (34) observed that the further reduction of aminodinitrotoluene to diaminonitrotoluene was enhanced under conditions of nitrate respiration as compared to aerobic conditions. 

Figure 6. Pathway of complete reduction of trinitrotoluene to triaminotoluene and characteristics of the sequential reduction steps. The reduction rate is indicated in percent of the rate of TNT reduction to the aminodinitrotoluenes.

The reduction rates of the sequential steps catalyzed by cell suspensions of the Desulfovibrio strain differ markedly. Whereas the reduction of the first nitro group proceeds at high rates, yielding both aminodinitrotoluene isomers in almost equal amounts (39), the second reduction step is considerably slower. The reduction of 2,4-diamino-6-nitrotoluene is the rate-limiting step in the overall sequence (Table 2). 

Both aminodinitrotoluene isomers are products of the first reduction step in cell suspensions of Desulfovibrio (39). However, most publications on TNT reduction indicate that the nitro group para to the methyl group is reduced first, with 4-amino-2,6-dinitrotolu-ene being the main reduction product (23, 32, 37). Only Naumova et al. (33) observed the reduction of TNT mainly to 2-amino-4,6-dinitrotoluene by 2i Pseudomonas strain. Figure 6 illustrates the pathway of complete TNT reduction and summarizes the characteristics of the sequential reduction steps. 

TNT was metabolized to amino and diamino metabolites under nonligninolytic conditions, the toxicities of these reduced metabolites were evaluated. The aminodinitrotoluenes (AmDNT) or diaminonitrotoluenes (DAT) exhibited much less toxicity to fungal growth from spores (Fig. 1). No inhibition of respiration was seen below 200 pM. At higher concentrations, the AmDNT were more toxic than the DAT. Respiration was inhibited 50% and 65% by the two isomers of AmDNT at 1250 pM, whereas respiration was actually stimulated 2 to 3-fold by the two DAT isomers. The differences in toxicity between the two AmDNT isomers may represent a difference in the rate of reduction of the ortho vs para nitro-group. 

Remediation of TNT-contaminated soil by R chrysosporium has also been observed (30, 82). In a bench scale (1.0-2.0 kg soil) feasibility study (82), TNT was degraded from 200 and 2,000 mg/kg (Fig. 10) to nondetectable levels within 14 and 100 days, respectively. In another microcosm, the TNT concentration was reduced from 10,000 to 3,500 mg/kg in 100 days. The principal metabolites were the isomeric aminodinitrotoluenes, which reached maximum concentrations of 35, 280 and 2,600 mg/kg on days 14, 35 and 55 for the 200, 2,000 and 10,000 mg/kg microcosms. These metabolites decreased to less than 10 mg/kg by day 28 in the 200 mg/kg microcosms and to 80 and 1,000 mg/kg by day 100 in the 2,000 and 10,000 mg/kg microcosms, respectively. The ultimate fate of the TNT in the microcosms was not explored. Because the microcosms were open systems, no radioactive labeling was possible. However, Fernando et al. (30) observed that in soil contaminated with 10,000 mg/kg TNT approximately 20% of the TNT was converted to CO2 within 90 days. They reported that 11.5% of the radioactivity was bound to a soil-corn cob-fungal matrix. 

Johnson, L. R., R. Davenport, H. Balbach, and D. J. Shaeffer. 1994. Phototoxicology. 3. Comparative toxicity of trinitrotoluene and aminodinitrotoluenes to Daphnia magna, Dugesia dorotocephala, and sheep erythrocytes. Ecotoxicity Environ. Safety 27 34-44. 

TNT can be very easily transformed by successive metabolic reduction of the three nitro groups. Under aerobic conditions aminodinitrotoluene and diaminonitrotoluene are formed (40). 2,4,6-Triaminotoluene additionally appears under anaerobic conditions and a low redox potential (4, 30, 38). TNT is considered to be resistant to oxidative attack by oxygenases (19). 

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