title: Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations.
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 (13)C 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.
authors.affiliation: Department of Physics, University of Lucknow, Lucknow 226 007, India.
authors.forename: Bhawani Datt
authors.initials: BD
authors.lastname: Joshi
authors.forename: Anubha
authors.initials: A
authors.lastname: Srivastava
authors.forename: Sara Braga
authors.initials: SB
authors.lastname: Honorato
authors.forename: Poonam
authors.initials: P
authors.lastname: Tandon
authors.forename: Otília Deusdênia Loiola
authors.initials: OD
authors.lastname: Pessoa
authors.forename: Pierre Basílio Almeida
authors.initials: PB
authors.lastname: Fechine
authors.forename: Alejandro Pedro
authors.initials: AP
authors.lastname: Ayala
mesh_terms: D000042:Absorption; D000880:Anthraquinones / Q000737:chemistry*; D004583:Electrons; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D017711:Nonlinear Dynamics; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D055672:Static Electricity; D013816:Thermodynamics; D014732:Vibration
chemical_list: D000880:Anthraquinones; C408504:oncocalyxone A
keywords: (13)C NMR; DFT; NBO analysis; Onco A; UV–vis; Vibrational spectroscopy