The present invention provides a sensitive fluorimetric indicator for analytes determination in the oxygen-insensitive DT-diaphorase-coupled dehydrogenases assay by omitting NADH, which is generated by reaction in the presence of analytes, which presents to the applicability as a biosensor for future clinical diagnostic. Furthermore, the novel long-wavelength latent fluorimetric indicator is also a user-friendly probe for monitoring DT-diaphorase activity. The fluorescence signal revealed by this process is specific and exhibited in the near red spectrum region.