Abstract
Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated
from ethanol extract from the heartwood of Auxemma oncocalyx Taub
popularly known as ``pau branco''. Oncocalyxone A (Onco A) has many
pharmaceutical uses such as: antitumor, analgesic, antioxidant and
causative of inhibition of platelet activation. We have performed the
optimized geometry, total energy, conformational study, molecular
electrostatic potential mapping, frontier orbital energy gap and
vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF)
and density functional theory (DFT/B3LYP) method with 6-311++G(d,p)
basis set. Stability of the molecule arising from hyperconjugative
interactions and/or charge delocalization has been analyzed using
natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was
recorded in DMSO and MeOH solvent. The TD-DFT calculations have been
performed to explore the influence of electronic absorption spectra in
the gas phase, as well as in solution environment using IEF-PCM and
6-31G basis set. The C-13 NMR chemical shifts have been calculated with
the B3LYP/6-311++G(d,p) basis set and compared with the experimental
values. These methods have been used as tools for structural
characterization of Onco A. (C) 2013 Elsevier B.V. All rights reserved.
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