Synthesis and evaluation of small molecule generators of redox active reactive species

Abstract

Chemically reactive species derived from oxygen nitrogen and sulfur are produced in nearly all living cells and play important roles in numerous physiological processes Recently several studies have demonstrated that reactive oxygen species ROS reactive nitrogen species RNS which includes peroxynitrite ONOO and hydrogen sulfide H2S are involved in host pathogen interaction and antibiotic action However the precise role of these redox active reactive species in bacteria remains poorly characterized This is in part due to transient nature of these reactive species In order to study the precise role of these reactive species in bacteria their reliable sources would be useful Although numerous methodologies for generating ROS ONOO and H2S have been reported they are typically associated with various limitations such as poor cell permeability and lack of specificity Here we propose to design and develop small molecules that can reliably generate each of these reactive species independently within cells and study their roles in bacterial growth inhibition and antibiotic resistance First in order to generate ROS within bacteria a series of natural product inspired benzo b phenanthridine 5 7 12 triones were synthesized and studied These compounds were found to generate ROS only in the presence of a bioreductive enzyme and were capable of enhancing ROS in Staphylococcus aureus S aureus Several ROS generators from this series showed moderate to potent inhibitory activity against drug resistant strain of S aureus suggesting that antibiotic resistance in certain bacteria can be targeted by perturbing bacterial redox homeostasis Next we designed and synthesized a bioreductively activated ONOO generator in which a superoxide generating 1 4 naphthoquinone scaffold is strategically linked to a diazeniumdiolate based nitric oxide donor Using an array of experiments the ability of this small molecule to generate ONOO upon reaction with a bioreductive enzyme was demonstrated The superiority of this compound t newline newline