Marginols A-H, unprecedented pimarane diterpenoids from Kaempferia marginata and their NO inhibitory activities

Kaempferia marginata rhizomes are used as an herb in food and as traditional medicine for the treatment of inflammatory-related diseases in Asian countries. In contrast to the previously reported phytochemical investigation of Thai and Chinese K. marginata rhizomes, which demonstrated the presence of sandaracopimaradiene and ent-sandaracopimaradiene, our first investigation of Vietnamese K. marginata rhizomes led to the isolation of eight undescribed pimarane diterpenoids, marginols A-H, along with 18 known pimarane diterpenoids. The structures of these compounds were elucidated by spectroscopic techniques, including 1D and 2D NMR, HRESIMS, and CD spectroscopy and/or by comparisons of their NMR data with previously reported data. Furthermore, evaluations of the NO production inhibitory activity against LPS-stimulated RAW264.7 cells revealed that the undescribed compounds, marginols B and D-G, and the known compounds, sandaracopimaradien-6 beta,9 alpha-diol-1-one and 6-acetoxysandaracopimardien-9-ol-1-one, showed potent activities. These results provide insights into the chemodiversity of Vietnamese K. marginata rhizomes as well as their traditional usage from the viewpoint of their chemical constituents.