title: Conformational studies of dammarane-type triterpenoids using computational and NMR spectroscopic methods.
abstract: Natural triterpenoids are of great interest to researchers of various fields as they possess diverse physicochemical and biological properties. In medicinal chemistry, detailed information about the chemical structures of bioactive triterpenoids often helps find new lead compounds. Herein, the low-energy structures of (20S)-protopanaxadiol and (20S)-protopanaxatriol, the aglycones of various triterpenoid saponins found in Panax ginseng, and their (20R)-epimers have been predicted by the geometry optimization of the conformers extracted from molecular dynamics simulations with the self-consistent-charge density functional tight-binding method. By performing quantum mechanical calculations on the low-energy conformers, we have estimated the NMR chemical shifts of the compounds, which display good agreement with the most recently reported experimental values within an expected range of errors. Our results indicate that theoretical estimation of the NMR parameters of a relatively large molecule with a molecular mass of 500 is feasible.
authors.affiliation: College of Pharmacy, Seoul National University, Seoul, 151-742, South Korea.
authors.forename: Byong-Kyu
authors.initials: BK
authors.lastname: Shin
authors.affiliation: Department of Chemical Engineering Education, Chungnam National University, Daejon, 305-764, South Korea.
authors.forename: Jihyung
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering Education, Chungnam National University, Daejon, 305-764, South Korea.
authors.forename: Tae Hoon
authors.initials: TH
authors.lastname: Choi
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D008970:Molecular Weight; D005894:Panax / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D011789:Quantum Theory; D014315:Triterpenes / Q000737:chemistry*; D000097669:Dammaranes
chemical_list: D010936:Plant Extracts; D014315:Triterpenes; D000097669:Dammaranes
keywords: 1H and 13C; NMR; conformer; molecular dynamics; protopanaxadiol; protopanaxatriol; self-consistent-charge density functional tight-binding