Abstract
Regression analysis was carried out in order to predict the effective concentration (EC50) of 34 chemicals for inhibition of the growth of Tetrahymena pyriformis in 24 h. We examined 4 items (n-octanol/water partition coefficient (P), molecular weight (Mr), organic and inorganic characters, and molecular connectivity indices) and their derivatives. The best one-parameter equation was that involing Mr [log EC50=-1.964 (Mr/100)+5.380 (r=-0.821, s=0.603, n=34)], and the second best involved the 3rd order valence molecular connectivity index of path type, 3χvp[log EC50=1.108 3χvp+3.944(r=-0.810, s=0.619, n=34)], while the n-octanol/water partition coefficient was least effective for the prediction of EC50 values [log EC50=-0.735 log P+4.233 (r=-0.780, s=0.660, n=34)]. The best combination for a two-parameter equation was 3χvp and Mr [log EC50=-1.105 (Mr/100)-0.638 3χvp+4.990 (R=0.866, s=0.516, n=34)]. Regression analysis with the same 4 items on median lethal concentration (LC50) of 123 chemicals for Oryzias latipes (red killifish) was refered and the limitations in the application of the parameters and the equations botained are discussed.
