Two New C19-Diterpenoid Alkaloids from Aconitum nagarum var. lasiandrum

Further investigation on the phytochemistry of the plant Aconitum nagarum var.lasiandrum led to isolate two C 19 -diterpenoid alkaloids, francheline(1) and lasianine (3).Their structures were established on the basis of the spectral data.The plant Aconitum nagarum var.lasiandrum (Ranuculaceae) growing in the Xuanwei district of Yunna province of China is used for folklore medicine to treat rheumatism and neuralgia. 1 The roots of A. nagarum var.lasiandrum has been reported to contain many diterpenoid alkaloids belong to the aconitine-type, e.g., aconitine, 3-deoxyaconitine, neoline, nagarine, aconifine; 2 14-acetylneoline, 3 flavaconitine, 4 vilmorrianine A, karakoline, sachaconitine, talatizidine, isotalatizidine, chasmanine, and yunaconitine; 5 the lycoctonine-type, e.g., virescenine; 4 the denudatine-type, e.g., denudatine as the major alkaloid, 4 as well as the napelline-type, e.g., songorine 3 and songoramine. 4Considering the contribution of this plant to both local folk medicine and chemotaxonomy, 4 our investigation on its roots led to isolate two additional new alkaloids, francheline (1) and lasianine (3).The present report describes the isolation and structural elucidation of these alkaloids.The new base, francheline (1), was obtained as amorphous powder substance.Its molecular formula, C 24 H 37 NO 6 , was established based on HR-ESI-MS and 2D-NMR.NMR and MS spectra showed that it was the franchetine-type C 19 -diterpenoid alkaloid. 6The NMR spectra showed the presence of an N-ethyl (δ H 0.99, 3H, t, J=7.2 Hz; 2.42, 2.60, each 1H, m; δ C 49.0 t, 13.0, q), and three methoxyls (δ H 3.29, 3.31, 3.42, each 3H, s).Its 1 H-and 13 C-NMR spectra also showed the distinctive N,O-mixed acetal moiety (δ H 4.32, br s, 1H; δ C 92.5, d), and a trisubstituted double bond (δ H 5.71, d, J=5.6 Hz, 1H; δ C 128.7, d, 136.6, s).One-proton wide singlet signal at δ H 4.04 was assigned to be H-14β, indicating the appearance of the hydroxyl group at C-14.Three methoxyl groups could be located at C-1, C-16, and C-18 due to the