Quantum chemical and statistical study of hypocrellin dyes with phototoxicity against tumor cells

A set of molecular properties (variables) of 20 hypocrellin dyes (hypocrellins and their derivatives) with phototoxicity against tumor cells was calculated by the molecular orbital semi-empirical method AM1 and ChemPropStd. Pattern recognition techniques, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to reduce dimensionality and investigate which subset of variables could be more effective for classifying hypocrellins and their derivatives according to their degree of phototoxicities against tumor cells. The PCA and HCA studies showed that μ (dipole moment) and Q3, Q4, Q9 and Q10 (charges on atoms 3, 4, 9 and 10) were the most important variables for the classification between the hypocrellin dyes with higher and lower phototoxicities against tumor cells.