Spectroscopic and quantum chemical analysis of a natural product – Hayatin hydrochloride

• FT-IR and micro-Raman techniques were employed to study HYHCl.
• A comparison of experimental results was done with theoretical computations.
• The IEF-PCM method along with TD-DFT/6-31G was employed for assignment of electronic excitations.
• Molecular electrostatic potential mapping was used to explain the chemical reactivity.
• NBO analysis was performed to elucidate the charge transfer properties.

Majority of drugs in use today are natural products, natural product mimics or semi synthetic derivatives. Therefore in recent times, focus on plant research has increased all over the world and large body of evidence has been collected to show immense potential of medicinal plants used in various traditional systems. Therefore, in the present communication to aid that research, structural and spectroscopic analysis of a natural product, an alkaloid Hayatin hydrochloride was performed. Both ab initio Hartree–Fock and density functional theory employing B3LYP with complete relaxation in the potential energy surface using 6-311G (d,p) basis set were used for the calculations. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and micro-Raman spectra. The complete assignments were performed on the basis of potential energy distribution. The structure–activity relationship has also been interpreted by mapping electrostatic potential surface, which are valuable information for the quality control of medicines and drug-receptor interactions. Electronic properties have been analysed employing TD-DFT for both gaseous and solvent phase. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

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