Theoretical conformational analysis of rutin

Abstract  

The structural properties of rutin were determined by using a computational multistep progression. In the first step a stochastic strategy based on a molecular mechanics calculation was adopted to obtain a preliminary screening of the low-energy rutin conformations. The most stable structures obtained by the random conformational search were used as a starting point for an Austin Model 1 (AM1) semiempirical optimization. After this treatment, 16 structures characterized by a more stable frontal in respect to back disposition of the glycosidic chain of rutin were identified. To validate the results found from the stochastic search a molecular dynamics simulation was carried out. The results evidenced the presence of a global minimum highly stabilized by a hydrogen bond between the hydroxyl in the 3′ position of the B ring and the endocyclic oxygen of the rhamnose unit followed by approximately 8 kJ mol⁻¹ less stable local minima with similar energy values. Finally, the reliability of the molecular model was confirmed by comparing the calculated electronic absorption spectrum with that measured on a methanolic rutin solution.