Nonlinear partial least squares modeling of phenyl alkylamines with the monoamine oxidase inhibitory activities

The nonlinear partial least squares (PLS) method is a nonlinear version of PLS. In this approach, a quadratic inner relation is used instead of the linear inner relation in PLS. Since the quadratic inner relation can be extended to a general form, it is said that the nonlinear PLS method has a high potential for nonlinear modelling. However, few applications of the method have been appeared in quantitative structure--activity relationships (QSAR) studies, because the mathematical descriptions underlying the algorithm were not so clear. In this paper, we have carried out the QSAR analysis of four monoamine oxidase (MAO) inhibitory activities using the nonlinear PLS method. The in vitro and in vivo MAO inhibitory activities were analyzed separately. From the PLS loadings, the structural requirements could be estimated and the utility of the nonlinear PLS method was demonstrated.