A theoretical approach to the solvation of brassinosteroids

The interaction of three different brassinosteroids with water was studied by the Multiple Minima Hypersurface (MMH) procedure to model molecular interactions explicitly. The resulting thermodynamic data give useful information on properties of molecular association with water. This application can serve as a tool for future investigations and modelling concerning interactions of brassinosteroids with receptor proteins in plants. DFT/B3LYP calculations were also made in order to correlate and test the performance of the current AM1 Hamiltonian calculations of these complexes, which are inherent to MMH routine. Diol functionalities located in ring A and lateral chain appears as the sites that show the highest affinity to water. The oxalactone group does not appear to be a key structural requirement in the association with water. Parallel calculations with a “polarizable continuum method” (PCM) agreed with the reported experimental order of biological activities, where Brassinolide exhibited the best solubility features.