5^th Annual European Pharma Congress

Biography

Biography: Anna Szemik-Hojniak

Abstract

The spectrum of therapeutic activities of heterocyclic N-oxides and specifically those of pyridine N-oxides is rather broad. Since their discovery about twenty years ago, they were broadly recognized as antibacterial, antihypertensive, anti-inflammatory, ant parasitic, as well as anti-HIV, anti-inflammatory, and neuroprotective agents. The heterocyclic N-oxides form a new class of bio reductive drugs with favourable drug-receptor interactions of the charge transfer (CT) type. Different N-oxides have been detected in animals, plants, and microorganisms, and therefore it is an utmost important issue to recognize their physico-chemical and physiological properties. The former (CT) interactions in N-oxides are strongly enhanced under the light irradiation and the excited electronic CT state results from electron transfer (ET) between electron donor /acceptor (electron-donating/withdrawing) functional groups. When additionally, the N-oxide contains the hydrogen donor and hydrogen acceptor substituents, the compound enhances its reactivity and may exhibit also the proton transfer process that may occur as a concerted or sequential combined Proton Coupled Electron Transfer (PCET) process. The PCET is pivotal both in biological systems and in bioenergetics conversion. Example of the former is the reduction of protons to hydrogen by hydrogenase and for the latter is the energy storage process.rnrnFig.1. Molecular structure of alkylamino nitro pyridine N-oxides rnrnA series of new alkylamino- (NHR-) type hydrogen bonding compounds including 2-aminobuthyl and 2-aminomethyl (4 nitro)-5-or 6 methyl pyridine N-oxides (see Fig.1) were designed and synthesized. This makes feasible the comprehensive spectroscopy and dynamics studies of amino-nitro excited state electron transfer (ET) and excited-state intramolecular proton transfer (ESIPT) along the N-H…O hydrogen bonding in the systems under investigations. In this talk, the PCET process in the electronic excited state of targeted pyridine N-oxides in solution where the normal HB form and the PT form exhibit the CT nature will be discussed both from experimental (absorption, steady state and time-resolved fluorescence) and theoretical [TD DFT B3LYP/6-31G(d,p) calculations] point of view.