Transformation of 1- and 2-methylnaphthalene by Cunninghamella elegans

Abstract

Cunninghamella elegans metabolized 1-and 2-methylnaphthalene primarily at the methyl group to form 1-and 2-hydroxymethylnaphthalene, respectively. Other compounds isolated and identified were 1-and 2naphthoic acids, 5-hydroxy-1-naphthoic acid, 5-hydroxy-2-naphthoic acid, 6-hydroxy-2-naphthoic acid, and phenolic derivatives of 1-and 2-methylnaphthalene. The metabolites were isolated by thin-layer and reverse-phase high-pressure liquid chromatography and characterized by the application of UV-visible absorption, 1H nuclear magnetic resonance, and mass spectral techniques. Experiments with [8-14C]2methylnaphthalene indicated that over a 72-h period, 9.8% of 2-methylnaphthalene was oxidized to metabolic products. The ratio of organic-soluble to water-soluble metabolites at 2 h was 92:8, and at 72 h it was 41:59. Enzymatic treatment of the 48-h aqueous phase with either ,-glucuronidase or arylsulfatase released 60% of the metabolites of 2-methylnaphthalene that were extractable with ethyl acetate. In both cases, the major conjugates released were 5-hydroxy-2-naphthoic acid and 6-hydroxy-2-naphthoic acid. The ratio of the water-soluble glucuronide conjugates to sulfate conjugates was 1:1. Incubation of C. elegans with 2-methylnaphthalene under an 1802 atmosphere and subsequent mass spectral analysis of 2hydroxymethylnaphthalene indicated that hydroxylation of the methyl group is catalyzed by a monooxygenase. Naphthalene and methylnaphthalenes are among the most toxic components in the water-soluble fraction of crude and fuel oils (1, 2, 12, 21). These compounds have also been identified in commercial mosquito repellants (22, 23) and in an aromatic. hydrocarbon solvent, Aerotex 3470 (18). There has been concern about the occurrence, transport, and environmental fate of naphthalene and methyl-substituted naphthalenes because they have been shown to accumulate in vertebrate and invertebrate freshwater and marine organisms (1, 13). The toxic effects of these compounds could be due to the naphthalene and its methyl-substituted derivatives or one or more of their biotransformation products or both. The mechanism of the toxicity of naphthalene and methylsubstituted naphthalenes has not been determined. The metabolism of 1-and 2-methylnaphthalene has been investigated in bacteria, cyanobacteria, rats, and rainbow

Anaerobic degradation of alkylated benzenes in denitrifying laboratory aquifer columns

“…leum-contaminated aquifers (6,7,24,35). We therefore investigated the substrate specificity of the m-xyleneadapted microorganisms towards a number of such aromatic hydrocarbons ( Table 1).…”

Differential developmental toxicity of naphthoic acid isomers in medaka (Oryzias latipes) embryos

“…In this study we have characterized the toxicity of four common PAH metabolites foundin PAH contaminated sediments (Parikha et al, 2004). Compounds of interest are bacterial metabolites of phenanthrene, anthracene, and 2-methyl-naphthalene including: 1-hydroxy-2-naphthoic acid (1H2NA), 2-hydroxy-1naphthoic acid (2H1NA), 2-hydroxy-3-naphthoic acid (2H3NA), and 6-hydroxy-2-naphthoic acid (6H2NA), respectively (Rogoff and Wender, 1957;Cerniglia et al, 1984;Guerin and Jones, 1988;Menn et al, 1993;Machate et al, 1997). These compounds are structural isomers and represent a unique perspective on structure function relationships with regard to observed toxicities.…”

Oxidation of Methyl-Substituted Naphthalenes: Pathways in a Versatile Sphingomonas paucimobilis Strain

“…The profiles obtained are the principal sources of deduced oxygenation-oxidation patterns. Most previous studies on fused ring alkyl aromatic compounds have been concerned with the 1-and 2-methylnaphthalenes and the isomer effects on initial methyl monooxygenation (13,31,39,46) compared with ring dioxygenation (7,8,14,44,46). Pseudomonas putida CSV86, for example, has been reported to convert 1and 2-methylnaphthalenes to the respective methyl catechols by ring dioxygenation or to form naphthoic acids following methyl hydroxylation (31).…”