The production of hydroxamic acid metabolites of nitrosobenzene by Chlorella pyrenoidosa

The ability of the green alga Chlorella pyrenoidosa to convert nitrosobenzene (I), phenylhydroxylamine (VI), aniline, and nitrobenzene to hydroxamic acid metabolites was investigated. Only nitrosobenzene and phenylhydroxylamine were partially converted to N-phenylacetohydroxamic acid (Va) and N-phenylglycolhydroxamic acid (Vb), with the latter compound being the major product. The possible mechanisms for the formation of these hydroxamic acid metabolites are discussed. The most plausible explanation for their production is through the interaction of the nitroso group with certain intermediates of thiamine-dependent enzymes. The conversion of phenylhydroxylamine to the hydroxamic acids probably is the result of initial oxidation to nitrosobenzene. Apparently, C. pyrenoidosa lacks nitroreductase and aniline hydroxylase activities, since no metabolic conversions of aniline or nitrobenzene were observed. The potential environmental significance of hydroxamic acid production from nitrosoaromatics is discussed.