A novel method for the study of inhibition of DNA synthesis by hydroxyurea(s) using topological indices and frontier molecular orbital energies:E_homo,E_lumo andE_total is described. The data suggest that the inhibitory activities of urea(s) can be successfully modelled by these molecular descriptors. Excellent results are obtained in multivariate systems as well as upon introducing a dummy parameter.

The paper gives a brief account of the recently introduced Szeged index (Sz). Using this index antitubercular activities of N-2,4-difluorophenyl quinolones are subjected to quantitative structure-activity relationship analysis. The potential of Sz related to the Wiener index (W) is critically discussed. In addition, Huckel molecular orbital energies:E_HOMO,E_LUMO andE_total were also used for comparing and modelling antitubercular activities of the quinolones. The results, based on univariate as well as multivariate regressions, have shown that W, S_Z andE_total give better results and that the correlations improve in multivariate regression analyses.