Classification of structurally related compounds fromAstragalus extract by correlation of the logk w andS

Summary The linear relationship between logk _w andS derived from molecular interactions and statistical thermodynamics was investigated by four series of different polar probe solutes. For each series of similar polar solutes, structurally related compounds with similar dipolarity/polarizability and hydrogen bonding energy, a linear relationship between logk _w andS was obtained. The more similar the solutes, the greater were the regression coefficients obtained. For two series of solutes with different strong polar groups resulting in different dipolarity/polarizability and hydrogen bonding energy, two parallel lines were observed in the logk _w-S plots. Each line represented one series of compounds and the distance between them indicated the difference in the dipolarity/polarizability and hydrogen bonding energy. Based on the parallel lines implying information on structurally related compounds in the logk _w-S plot, a method of classification of structurally related compounds was put forward and the linear logk _w-S correlation for unknown components in nonaqueous RP-HPLC analysis ofAstragalus extract with isopropanol-methanol mobile phase was studied. Two nearly parallel lines were obtained in the logk _w-S plot and two series of structurally related compounds were classified in this way.