Identification of cholesterol in different media by using the FT-IR, FT-Raman and UV–visible spectra combined with DFT calculations

ROMANO, ELIDA; CATALDO, PABLO G.; IRAMAIN, MAXIMILIANO A.; CASTILLO, MARÍA V.; MANZUR, MARÍA E.; ANTONIA BRANDÁN, SILVIA

JOURNAL OF MOLECULAR LIQUIDS

ELSEVIER SCIENCE BV

Año: 2024 vol. 403

0167-7322

In this investigation, the experimental FT-IR and FT-Raman spectra of cholesterol in the solid phase and inethanol solution have been combined with the B3LYP/6?311++G** calculations and the scaled quantum mechanicalforce field (SQMFF) methodology, normal internal coordinates and transferable scaling factors to obtainthe complete vibrational assignments of 216 vibration modes expected. Hence, complete vibrational assignmentsfor that steroid of greatest biological importance are reported for first time in gas phase and ethanol solutiontogether with its scaled force constants. Changes in the positions of some bands and in force constants values areobserved in the different media due to the predicted intra-molecular interactions between CH3/CH3, CH3/CH2and CH2/CH2 groups by atoms in molecules (AIM) calculations. The 1H- and 13C NMR chemical shifts of normaland deuterated cholesterol in aqueous solution confirm that the H atom of OH group is involved in the formationof H bonds in solution. Studies of experimental electronic spectra of cholesterol in different concentrations ofethanol revealed that the positions of peaks maxima increase conform increase the solution concentration. Thenatural bond orbital (NBO) analyses reveal that the polar OH group and the four fused rings play important rolesin the stability and properties of cholesterol than the large hydrophobic moiety. Frontier orbitals predicted lowreactivity of cholesterol in ethanol probably due to its high ω value in this medium.