Studies on the molecular structure of pterocaronol: A new biologically relevant nor-triterpenoid from Peltophorum pterocarpum (Fabaceae)

Abstract

A naturally-occurring new nor-triterpenoid compound (pterocaronol; 1) has been isolated from the barks of Peltophorum pterocarpum (DC.) Backer ex K. Heyne (Fabaceae) based on its detailed spectral and single-crystal X-ray analyses. The compound crystallizes in the orthorhombic space group P 212,121 with the following unit-cell parameters: a = 10.5816(19), b = 13.971(2), c = 17.275(3)Å, α = 90°, β = 90°, γ = 90° and Z = 4. The crystal structure was solved by direct methods using single-crystal X-ray diffraction data collected at 296 K and refined by full-matrix least-squares procedures to a final R-value of 0.0710 for 5007 observed reflections. Exhaustive theoretical studies on the molecular structure, vibrational spectra, reactivity descriptor, and molecular docking of this plant-derived hitherto unknown natural molecule have also been performed. Several stable conformers were optimized in the pterocaronol molecule using MP2 ab initio and Density Functional methods (DFT). The dimer form was also optimized, as reported by X-ray. Large deviations of the planarity were observed in the six-carbon atom rings, with the methyl groups out of these ring planes. The reactivity of the molecule appears in the head and end of the molecule, with the largest positive and negative charges on the atoms. To improve the computed wavenumbers was used one of the best procedures of scaling. Therefore, all the bands of the infrared spectra were accurately assigned. In molecular docking studies, the interactions of pterocaronol with the amino acids corresponding to cyclin-dependant protein kinase 2 (CDK2) and to β-site amyloid precursor protein cleaving enzyme 1 (BACE1) were determined.