Regioselective Difluoromethane sulfonylation and Triflylation of Resorufin Derivatives

Phenotypic-Based Discovery and Exploration of a Resorufin Scaffold with Activity against Mycobacterium tuberculosis

Tuberculosis remains a leading cause of death by infectious disease. The long treatment regimen and the spread of drug-resistant strains of the causative agent Mycobacterium tuberculosis (Mtb) necessitates the development of new treatment options. In a phenotypic screen, nitrofuran-resorufin conjugate 1 was identified as a potent sub-micromolar inhibitor of whole cell Mtb. Complete loss of activity was observed for this compound in Mtb mutants affected in enzyme cofactor F420 biosynthesis (fbiC), suggesting that 1 undergoes prodrug activation in a manner similar to anti-tuberculosis prodrug pretomanid. Exploration of the structure-activity relationship led to the discovery of novel resorufin analogues that do not rely on the deazaflavin-dependent nitroreductase (Ddn) bioactivation pathway for their antimycobacterial activity. These analogues are of interest as they work through an alternative, currently unknown mechanism that may expand our chemical arsenal towards the treatment of this devastating disease.

Sequential activation strategy of triazinyl resorufin for high selectivity fluorescence GSH detection

The abnormally elevated expression level of glutathione (GSH) has been observed in various human cancer cells and tissue. Thus, effective methods for glutathione detection are of great importance in early diagnosis of cancer. However, many fluorescent probes for GSH detection suffer from the interference of the abundantly existent nucleophilic biomolecules in biological environment. In this work, we propose a sequential activation strategy to overcome this problem by designing and synthesizing a series of 1,3,5-triazinyl resorufin turn-on fluorescent probe (Probes 1-3). As two electrophilic sites are presented in probes, GSH sequentially reacts with the resorufin and the triazine moiety, resulting in significant fluorescence augmentation (up to 165.0-fold). Designed probes possess low limit of detection as low as 1.8 μM). Cellular fluorescent imaging has been successfully applied to selectively detect GSH in several living cells.

Expansion of the Strigolactone Profluorescent Probes Repertory: The Right Probe for the Right Application

Strigolactones (SLs) are intriguing phytohormones that not only regulate plant development and architecture but also interact with other organisms in the rhizosphere as root parasitic plants (Striga, Orobanche, and Phelipanche) and arbuscular mycorrhizal fungi. Starting with a pioneering work in 2003 for the isolation and identification of the SL receptor in parasitic weeds, fluorescence labeling of analogs has proven a major strategy to gain knowledge in SL perception and signaling. Here, we present novel chemical tools for understanding the SL perception based on the enzymatic properties of SL receptors. We designed different profluorescent SL Guillaume Clavé (GC) probes and performed structure-activity relationship studies on pea, Arabidopsis thaliana, and Physcomitrium (formerly Physcomitrella) patens. The binding of the GC probes to PsD14/RMS3, AtD14, and OsD14 proteins was tested. We demonstrated that coumarin-based profluorescent probes were highly bioactive and well-adapted to dissect the enzymatic properties of SL receptors in pea and a resorufin profluorescent probe in moss, contrary to the commercially available fluorescein profluorescent probe, Yoshimulactone Green (YLG). These probes offer novel opportunities for the studies of SL in various plants.