SYNTHESIS AND APPLICATIONS OF FLAVINS AND THEIR ANALOGUES

Abstract

Flavoenzymes are colourful oxidoreductases occurring widely in living systems. The flavin cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are involved in the catalysis of a wide variety of biological redox reactions. To understand the molecular mechanism of the flavoenzymes and their applications, the quantitative amount of these cofactors and their analogues are essential. Hence, the synthesis of flavins has been the focus of research due to its paucity in the natural systems. Chapter 1 deals with the solid and solution phase synthesis of flavin and their analogues. The traditional solution phase synthesis suffers from a number of limitations and hence a better and more environmental friendly synthesis is achieved in this chapter using the Merrifield resin as polymer support. The polymer-supported synthesis was found to be advantageous over solution phase synthesis. Chapter 2 describes the application of flavin as catalyst for the Baeyer-Villiger (BV) Oxidation. The Baeyer Villiger (BV) oxidation is the basic reaction for the synthesis of lactones. In this chapter, different flavin derivatives have been utilized as catalyst in hydroperxy form for the transformations of cyclic ketones to corresponding lactones. The reactions have been performed to validate biomimetic reaction for BVMOs. Also, the developed catalyst served as metal free organocatalyst. Further, this chapter discussed the effect of chain length at N-10 position on BV reactions. Chapter 3 explains about the application of flavin as catalyst for remediation of selected halogenated compounds. Halogenated organic compounds (HOCs) are considered as a major pollutant for any ecosystem due to their persistent, lipophilic and toxic nature. we have mimicked the reactions of cholorophenol monoxygenases. Under the present newly designed biomimetic experimental conditions, we confirmed the removal of chlorine in 4-halophenols using synthetic cofactor of flavoenzymes. Chapter 4 explains the electrochemical study of flavin derivatives. In this context, we report the electrochemical oxidation-reduction process of riboflavin in buffered aqueous solution at varying pH using cyclic voltammetry (CV) techniques. The CV results indicate that the redox voltammetry behavior of riboflavin (Rf) at the sensor was reversible as well as quasi-reversible involving two anodic and cathodic peaks. Electrochemical kinetic parameters for Rf at different pH values in buffered aqueous solution have been calculated, which indicates the structural changes/ behavior of Rf at different pH conditions and provides insight into the one or two electron transfer reaction. Chapter 5 deals with the studies of Bombax ceiba flower extract and their secondary metabolite conjugate with flavin. In this chapter; we have utilized the crude and semi crude extract of B. ceiba for identification of group of compound present in it using chemical test method. Further, the extract has been evaluated for antioxidant properties. An secondary metabolite, vanillic acid has also been conjugated with riboflavin tetracetate and evaluated for their antioxidant properties.