Mei Lin GoTong Lan NgiamAgnes Lay Choo TanKunnika KuahaPrapon WilairatNational University of SingaporeMahidol University2018-07-042018-07-041998-01-01European Journal of Pharmaceutical Sciences. Vol.6, No.1 (1998), 19-26092809872-s2.0-0031983679https://repository.li.mahidol.ac.th/handle/20.500.14594/18638The synthesis, physicochemical characterization and in vitro antimalarial activity of a series of indolo[3,2-c]quinolines (9a-f) are described. There is only a poor correlation between the activity and hydrophobicity. In contrast, 33% of the observed variation in antimalarial activity can be attributed to the size of the side chain attached to position 9 of the indoloquinoline ring. An increase in the size of this dibasic side chain generally results in a reduction in activity, suggesting that it is accommodated in a site/cavity of limited size on the receptor. More significantly, the charge on the distal nitrogen (N3) on the side chain, located 10-11 Å from the quinoline N, could account for 75% of the observed variation. Since a large charge on N3 is associated with improved antimalarial activity, it is suggested that N3 is protonated and functions as a H bond donor in the drug-receptor interaction.Mahidol UniversityPharmacology, Toxicology and PharmaceuticsArticleSCOPUS10.1016/S0928-0987(97)00064-X