Study of lipophilicity and application of selected structural descriptors in QSAR analysis of nicotinic acid derivatives. Investigations on RP18WF254 plates. Part II

Nicotinic acid (NAC) and its derivatives methyl nicotinate (MN), ethyl nicotinate (EN), isopropyl nicotinate (IPN), butyl nicotinate (BN), hexyl nicotinate (HN), benzyl nicotinate (BNN), nicotinamide (NAM), and N-methylnicotinamide (MNAM) have been investigated on RP18WF(254) HPTLC plates with methanol-water in different volume proportions as mobile phases. Linear relationships were obtained between R-M values of the compounds and the volume fraction of methanol in the mobile phase. Retention values RM were extrapolated to zero methanol content and the lipophilicity values R MO(RP18WF254) obtained were compared with measured partition coefficients (log P-exp) and with partition coefficients (Alog Ps, IAlog P, Clog P, log P-Kowin, and xlog P) calculated using five different software products. The most significant correlation was found between R MO(RP18WF254) and Alog Ps values. The values of chromatographic lipophilicities R-M0(RP18WF254) and phi(0(RP18WF254)) indicate that lipophilicity of the nicotinic acid derivatives should decrease in the order HN > BN approximate to BNN > IPN > EN > MN > MNAM > NAM > NAC. Chromatographic Rmo values can be used as a measure of the lipophilicity of the nicotinic acid derivatives investigated. Satisfactory linear regression equations were obtained between lipophilicity R-M0(RP18WF254) or partition coefficients (log P-exp, Alog Ps, IAlog P, Clog P, log P-Kowin, xlog P) and some topological indexes (X-0(v), X-1(v), X-2(v), A, B-1, B-2, I-SA, and I-SA) and between lipophilicity phi(0(RP18WF254)) and electrotopological states SaaN and SdO.