USE OF PRINCIPAL COMPONENT ANALYSIS AND CLUSTER-ANALYSIS IN QUANTITATIVE STRUCTURE-ACTIVITY-RELATIONSHIPS - A COMPARATIVE-STUDY

The inhibitory effect of some new benzothiazole derivatives on Bacillus subtilis, Aspergillus niger, Helminthosporium sativum and Fusarium graminearum was determined. Hydrophobicity and specific hydrophobic surface area of the pesticides were measured by reversed-phase thin-layer chromatography in neutral, acidic, alkaline and salt-containing environments. To find the relationship between the physicochemical parameters and biological activity, stepwise regression analysis, principal component analysis, nonlinear mapping technique and cluster analysis were applied. Good linear correlations were found between the biological activity, steric parameter and calculated hydrophobicity value of compounds proving the significant impact of the above physicochemical parameters on the inhibitory effect. Nonlinear mapping technique cannot be used on the original data matrix, but it can be successfully applied for the principal component loadings and variables. Cluster analysis requires the lowest computational time and the results are commensurable with those of principal component analysis. Both methods indicate that the pH and salt concentration have a negligible impact on the hydrophobicity and specific hydrophobic surface area of pesticides, whereas the biological activity and the measured physicochemical parameters form two different clusters suggesting the poor correlation between the two groups of variables.