Vibrational spectra and theoretical calculations of a natural pentacyclic triterpene alcool isolated from Mucuna pruriens

Abstract

Nematode control is a significant problem in agriculture industry all over the world. The control is often made with the use of toxic chemicals which can bring detrimental effect to humans, animals, and the environment. Therefore, developing an alternative method of control has become an area of interest such as use of antagonistic plant. Among the variety of antagonist plant species, Mucuna genus are most commonly used. We have carried out a study of the secondary metabolites present on the aerial parts of Mucuna pruriens var. utilis, from which it was isolated and purified a pentacyclic triterpene alcohol, named glutinol. This is the first time the isolation of glutinol is described from this plant species. Identification of this natural product was carried out using infrared, Raman, and NMR spectroscopies. The assignment of the vibrational frequencies was assisted by theoretical calculations using two functionals (HF and B3LYP). Raman optical activity (ROA) frequencies were calculated to assist in te detailed identification of the broad band observed at 2926 cm−1 in the experimental Raman spectrum. The calculated ROA spectra for glutinol (S configuration for the carbon bonded to the hydroxyl group) and R-glutinol (R configuration for the carbon bonded to the hydroxyl group) are discussed to show the potential of this technique to determine the absolute configuration of natural products.