Withanolides from the leaves of Datura metel L.

Twelve previously undescribed withanolides, including three uncommon chemotypes of aglycones, daturafolisides (J-L), and six common structures, daturafolisides (M-U), as well as one known withanolide were isolated from the leaves of Datura metel L. Their structures were elucidated by interpretation of spectroscopic data (1D, 2D NMR and CD), HRESIMS experiments and comparison with published data for similar compounds. These isolated compounds were evaluated for their inhibitory activities on nitric oxide production. The IC50 values of daturafoliside L, daturafoliside M, and daturafoliside T were between 9.37 and 18.64 μM, while daturafoliside K, daturafoliside R, and daturametelin A had IC50 values of 22.83-33.36 μM. Herein, three proposed biosynthetic pathways for uncommon structures daturafolisides J-L were discussed. These constituents found in the leaves of Datura metel L. may be a good source of bioactive substances, making contributions to the sustainable utilization of this plant resources.