Density functional study on the structural conformations and intramolecular charge transfer from the vibrational spectra of the anticancer drug combretastatin-A2

L. Padmaja, C. Ravikumar, D. Sajan, I. Hubert Joe, V. S. Jayakumar, George Pettit, O. Faurskov Nielsen

Research output: Contribution to journalArticlepeer-review

209 Scopus citations

Abstract

Combretastatin-A2 (CA2), a potential anticancer drug in advanced preclinical development, is extracted from the medicinal plant Combretum caffrum. The NIR-FT Raman and FT-IR spectral studies of the molecule were carried out and ab initio calculations performed at the B3LYP/6-31G(d) level to derive the equilibrium geometry as well as the vibrational wavenumbers and intensities of the spectral bands. The vibrational analysis showed that the molecule has a similar geometry as that of cis-stilbene, and has undergone steric repulsion resulting in twisting of the phenyl ring with respect to the ethylenic plane. Vibrational analysiswas used to investigate the lowering of the stretching modes, and enhancement of infraredband intensities of the C-H stretching modes of Me2 may be attributed to the electronic effects caused by back-donation and induction from the oxygen atom. Analysis of phenyl ring modes shows that the CA2 stretching mode 8 and the aromatic C-H in-plane bending mode are equally active as strong bands in both IR and Raman spectra, which can be interpreted as the evidence of intramolecular charge transfer (ICT) between the OH and OCH3groups via conjugated ring path and is responsible for bioactivity of themolecule.

Original languageEnglish (US)
Pages (from-to)419-428
Number of pages10
JournalJournal of Raman Spectroscopy
Volume40
Issue number4
DOIs
StatePublished - Apr 1 2009

Keywords

  • Combretastatin-A2
  • Density functional theory
  • Intramolecular charge transfer
  • NIR fT-raman spectra
  • PES

ASJC Scopus subject areas

  • Materials Science(all)
  • Spectroscopy

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