Studies of Performance of Graph Theoretical Indices in QSAR Analysis

Comparative studies of performance in exemplary QSAR of the most commonly used structural descriptors derived from molecular graphs were performed. Three diverse series of test compounds were selected for which various property measures existed. One group of compounds were polychlorinated dibenzofurans of determined gas chromatographic retention indices. The second group comprised isomers of general formula C4H8O of known boiling points, refractivity indices and densities. Third set of agents consisted of 2-substituted isonicotinic acid hydrazides of determined antibacterial activity. The following graph theoretical indices were considered: the Kier and Hall [22] generalized molecular connectivity indices, the Balaban distance sum connectivity index calculated after Barysz et al. [23], the indices of molecular shape of Kier [24], the information indices of neighbourhood symmetry of Sarkar et al. [25] and of Basak et al. [26]. Auxiliary structural parameters, e.g., molecular surface area, were also employed. Significant correlation with molecular mass and intercorrelations among the graph theoretical indices were observed excepting the group of information content indices. For the compounds and properties studied the graph theoretical indices considered appeared unable to provide a size-independent, meaningful input to property description.