FT-IR, FT-Raman and UV-visible spectra of motrilin acetogenin isolated from Annona cherimolia

Abstract

Annonaceous acetogenin (ACG), motrilin was experimentally isolated and characterized by using the FT-IR and FT-Raman spectra in the solid state and by UV-visible spectrum in methanol solution. The main bands observed in the vibrational spectra were assigned combining their predicted spectra with hybrid functional B3LYP/6-31G* calculations. The structural, electronic and topological properties were predicted for motrilin in gas phase and in methanol solution. The corrected solvation energy by ZPVE and by total non-electrostatic terms reveals for motrilin in methanol solution a value of −147.54 kJ/mol. The NPA charges have evidenced higher changes on the atoms of motrilin in methanol solution than the values in gas phase while the studies of electrostatic potentials have revealed strongest nucleophilic regions on the two O atoms of lactone ring while electrophilic sites on the H atoms of OH groups. Both NBO and AIM studies support the high stabilities of motrilin, especially in methanol solution probably due to the solute-solvent association phenomenom, as suggested by the expansion of volume in solution and by the H bond formation in this medium predicted by the AIM program. A higher reactivity of motrilin in methanol solution was evidenced by using the frontier orbitals while both electrophilicity and nucleophilicity indexes show values for motrilin similar to those observed in the antimicrobial thione agent. The predicted IR, Raman and UV-visible spectra has evidenced reasonable concordance with the corresponding experimental ones.