Synthesis and evaluation of halogenated nitrophenoxazinones as nitroreductase substrates for the detection of pathogenic bacteria

Abstract

The synthesis and microbiological evaluation of 7-, 8-and 9-nitro-1,2,4-trihalogenophenoxazin-3-one substrates with potential in the detection of nitroreductaseexpressing pathogenic microorganisms are described. The 7-and 9-nitrotrihalogenophenoxazinone substrates were reduced by most Gram negative microorganisms and were inhibitory to the growth of certain Gram positive bacteria; however, the majority of Gram positive strains that were not inhibited by these agents, along with the two yeast strains evaluated, did not reduce the substrates. These observations suggest there are differences in the active site structures and substrate requirements of the nitroreductase enzymes from different strains; such differences may be exploited in the future for differentiation between pathogenic microorganisms. The absence of reduction of the 8-nitrotrihalogenophenoxazinone substrates is rationalized according to their electronic properties and correlates well with previous findings.

Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganisms

“…The inhibition of Gram-positive bacteria in Columbia agar media has previously been noted with halogenated derivatives of the nitrophenoxazinones 7 . 14 Reducing the substrate concentration to 25 mg L −1 did allow the detection of two additional Gram-positive bacteria ( S. epidermidis and S. pyogenes ), but their associated colour responses were weak at best. Of the two yeast species, only C. albicans colonies produced a trace of colour at low (25 mg L −1 ) substrate concentration.…”

“…1). 14 The 1,2,4-trifluoro derivative of heterocycle 7 produced the most encouraging results with Gram-negative bacteria where 9 out of a panel of 10 reduced this substrate thereby producing red-brown colonies. Most of the 8 Gram-positive bacteria studied were either unable to reduce this substrate or their growth was inhibited by this substrate and hence coloured colonies were not observed.…”

A TCF-based fluorescent probe to determine nitroreductase (NTR) activity for a broad-spectrum of bacterial species

“…7,8 NTR detection can thus improve disease diagnosis, and facilitate the development of selective therapeutics activated by NTR. 9,10 Numerous NTR sensors have been developed with the majority focused on assessing the hypoxic status of tumours. [11][12][13] The high-expression of NTR in bacteria, especially among Escherichia coli (E. coli) provides us an important marker suitable for pathogen-oriented detection.…”

“…7,8 NTR detection can thus improve disease diagnosis, and facilitate the development of selective therapeutics activated by NTR. 9,10 Numerous NTR sensors have been developed with the majority focused on assessing the hypoxic status of tumours. 11–13…”