A combined NMR and density functional theory (B3LYP) investigation was crried out on a new alkaloid obtained from huperzia serrata Thunb (Trev.). The theoretical NMR data of 8α-OH phlegmariurine B are in excellent agreement with the experimental results. The configuration was then established through analysis of the vicinal coupling constants and 2D NMR (NOESY and COSY) spectra. This work shows that the quantum chemistry study of NMR can serve as a promising tool in aiding structural assignment of natural products.

Key words: NMR SPECTROMETRY, CHEMICAL SHIFT