The WHIM descriptors

are molecular descriptors based on statistical indices calculated on the projections of the atoms along principal axes. They are built in such a way as to capture relevant molecular 3D information regarding molecular size shape, symmetry, and atom distribution with respect to invariant reference frames (Todeschini et find more al., 2000). In general, the obtained data indicate that hydrophobic and total molecular symmetry properties are important for antitumor activity of acridinones. These observations are in partial agreement with the data obtained by Mazerska (Mazerska et al., 1996), for which antitumor activity of imidazoacridinones is dependent on lipophilicity. However, impact of lipophilicity on the biological activity of these compounds was observed only ARS-1620 in vivo in the case of derivatives with 8-hydroxyl group, which undergo metabolic activation (Mazerska et al., 1999, 2003). Moreover, non-hydroxyl or 9-hydroxyl derivatives also exhibited lipophilic properties, but its effect was not crucial when metabolic

activation did not occur. Relocation of hydroxyl group from position 8 to 9 drastically PX-478 decreases antitumor activity (C-1311 8-hydroxyl, C-1419 9-hydroxyl). In addition, hydrophobic properties of acridinones can play important role in transport and accumulation of these compounds in cells in view of fastening of metabolic activation (Składanowski et al.,

1996). On the other hand, diaminoalkyl side chain has also crucial influence on antitumor activity of acridinones. For compounds without 8-hydroxyl group, the increase in number see more of carbon atoms between nitrogen atoms from two to three or five (C-1415, C-1176, and C-1233 two; C-1212 and C-1296 three; and C-1266 five) generally decreases antitumor activity of imidazo- and triazoloacridinones. In case of derivatives bearing 8-hydroxyl group, the increase in number of carbon atoms (C-1311, C-1263 two, C-1371 three, and C-1492 five) rather do not augment antitumor activity for imidazoacridinones, while good increase in antitumor activity is observed in case of triazoloacridinones (C-1303, C-1410 two, and C-1305 three carbon atoms).