Chapter 1 - Background of QSAR and Historical Developments

Abstract

To search for the existence of any correlation among different objects or observations is a natural human tendency. The notion of quantitative structure–activity relationship (QSAR) modeling was evolved from the idea of possible existence of a mathematical correlation between the nature of chemicals and their behavioral manifestation. Following the initial observations, the “chemical nature” was conceptualized and explored in terms of information extractable from the structure and property of chemicals. Properties elicited by chemicals are significantly influenced by the nature of their chemical structure (branching, functional groups, electronegative behavior, stereochemical features, etc.), as well as different physicochemical properties (hydrophobicity, electronic nature, steric influence, etc.). The development of suitable descriptors (predictor variables) possessing a potential diagnostic nature in extracting the chemical attributes can help in exploring the mechanistic basis involved in a chemical–biological process following mathematical model development. Thus, QSAR studies allow a rational explanation for the behavioral manifestation of chemicals accompanied with providing knowledge on the mechanism involved, thereby creating an opportunity to tune the behavior of a chemical. As it provides a good alternative method to laboratory experimentation, at least for initial screening, QSAR is utilized in costly research like the design of drug molecules and assessment of chemical hazards. This chapter provides an account of the background, history, basic components, and application of QSAR techniques.