Abstract: 3/4/5-O-Feruloylquinic acids (3/4/5-O-FQA) have antioxidant activity, which is beneficial to disease prevention and human health maintenance, however, their exact 3D structures are still unknown. In the present work, the structures of 3/4/5-O-FQA in gas phase, D₂O solution and DMSO-d₆ solution are investigated respectively using ¹H nuclear magnetic resonance (NMR) spectroscopy combined with quantum chemistry calculation. We find a difference of 4.147° in dihedral angle τ (H3C3O1C9) for 3-O-FQA in D₂O and DMSO-d₆ solutions, which can explain the ¹H NMR spectra of 3-O-FQA in the two solutions. This work provides the 3D structures of 3/4/5-O-FQA, which are helpful for further studies on their properties and potential applications.

Key words: 3D structure, NMR, Quantum chemistry calculation, Chemical shift, 3/4/5-O-feruloylquinic acid