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Table 2 Electronic and structural parameters of cinchona alkaloids in aqueous solvent, based on the common pharmacophores described for (-) mefloquine and quinine and (+) mefloquine and quinidine by Karle & Karle [17]. (*dipole moment calculated for free base).

From: The relationship of physico-chemical properties and structure to the differential antiplasmodial activity of the cinchona alkaloids

drug in water MM+ energy <0.004 dipole moment* proton affinity O12-N1 N1-C5' ring-O12 torsion° O12-N1 torsion° H8-C8-C9-H9 dihedral° H-N1-C9-O12 torsion°
  Kcal/mole Debye Kcal/mole Å Å     
Q 11.9 1.88 208.85 3.14 4.1 157.8 -83.8 -82.6 -123.2
EQ 15.5 2.44 213.36 2.77 4.7 40.6 43.3 174.0 -5.9
QD 18.9 1.66 208.61 3.09 4.2 -161.1 78.2 74.7 104.4
EQD 12.8 2.21 213.84 2.82 4.7 -43.2 -49.1 -175.8 0.6
CD 11.1 1.15 209.38 3.21 4.2 144.9 -91.0 -86.8 -129.6
ECD 13.6 1.54 213.88 2.79 4.6 45.1 46.0 175.0 -5.9
C 10.9 0.96 209.78 3.19 4.1 -156.0 88.9 85.3 118.3
EC 13.5 1.27 213.75 2.85 4.7 -45.4 -50.2 -176.2 -2.5
HQ 10.4 2.08 209.39 3.20 4.1 156.1 -83.6 -82.8 -123.6
HQD 10.7 1.79 209.75 3.23 4.2 -152.7 89.5 88.8 118.6