Exploring structural requirements of unconventional Knoevenagel-type indole derivatives as anticancer agents through comparative QSAR modeling approaches

An indole ring system is considered as a versatile scaffold in the pharmaceutical field. In this article, comparative QSAR modeling (2D-QSAR, 3D-QSAR; kNN-MFA and CoMSIA) was performed on some Knoevenagel-type cytotoxic indole derivatives to understand the structural requirements for the cytotoxic property of these compounds. The 2D-QSAR model was statistically significant and imparted high predictive ability (nTrain = 30; R = 0.917; [Formula: see text] = 0.801; [Formula: see text] = 0.757; Q2 = 0.722; nTest = 9; [Formula: see text] = 0.799). A statistically significant 3D-QSAR kNN-MFA model (both with stepwise forward and simulated annealing model selection method) as well as a 3D-QSAR CoMSIA model was developed to identify the key chemical features associated with enhancing the cytotoxic activities of these indoles. The results suggest that the presence of bulky group in R position can cause better cytotoxic activities. Consequently, substitution with cyano group at X portion and cyano/ester/keto/sulphonyl features at Y position is favourable for the cytotoxicity. However, hydrophobic features in R′ region are unfavourable for the biological activity. The chemical and structural features identified from the study may provide important avenues to modulate the structure of these indoles to a desirable biological end point.

Predictive comparative QSAR modelling of (phenylpiperazinyl-alkyl) oxindoles as selective 5-HT1A antagonists by stepwise regression, PCRA, FA-MLR and PLS techniques

5-Hydroxytryptamine, a neurotransmitter released by 5-HT neurons in raphe nuclei and 5-HT(1A) receptors are involved in the pain mechanism of migraine, prevention of postpartum haemorrhage, CNS effects like sleep, anxiety and thermoregulation. Comparative QSAR study was done on thirtytwo (phenylpiperazinyl-alkyl) oxindoles using stepwise regression, PCRA, FA-MLR and PLS techniques to find structurally significant models. ETSA indices at atom numbers 19, 20 and 22, RTSA indices at atom numbers 6, 10 and 20, charge at atom number 19 and presence of chlorine at the atom number 6 may be conducive for the receptor inhibition. Electrophilic attack at atom number 21 may be unfavourable but nucleophilic attack at atom numbers 8 and 14 may be beneficial for % 5-HT(1A) inhibition.