New C18-Diterpenoid Alkaloids from Delphinium anthriscifolium var. savatieri

Abstract

In the course of comparative research of new activities of alkaloids and evaluation of chemotaxonomy of the diterpenoid alkaloids from the Aconitum and Delphinium species, [1][2][3] we investigated the alkaloids of D. anthriscifolium var. savatieri (FRANCHET) MUNZ. The plant is endemic to China, especially the Sect. Anthriscifolium of Subgen. Delphinium, 4) of which no plants have been phytochemically reported yet, implying that the study is very important value for the chemotaxonomy of genera Delphinium. Our research of the whole herbs of D. anthriscifolium var. calleryi sevealed five new C 18 -diterpenoid alkaloids, anthriscifolcines A, B, C, D, and E, together with a known C 19 -diterpenoid alkaloid delcorine (6). 5) In this paper, we report the isolation and structural elucidation of these alkaloids. Results and DiscussionAnthriscifolcine A (1) was isolated as an amorphous powder, mp 135-137°C. Its molecular formula C 26 H 39 NO 7 , was established based on HR-ESI-MS and 13 C-NMR. The IR (KBr) spectrum of 1 showed absorption bands at 1740 cm Ϫ1 ascribable to carbonyl groups. The NMR data showed the presence of an N-ethyl group (d H 1.03, 3H, t, Jϭ7.2 Hz, 2.73, 2.78, 2H, m; d C 50.3 t, 13.8 q), three methoxyl groups (d H 3.27, 3.34, 3.45, each 3H, s; d C 55.7 q, 56.1 q, 57.7 q), an acetyl group (d H 2.04, 3H, s; d C 170.4 s, 21.6 q), and a methylenedioxyl group (d H 4.91, 2H, s; d C 93.5 t). The single non-oxygenated quaternary carbon signal (d C 49.9 s) suggested that compound 1 was a C 18 -diterpenoid alkaloid from combined NMR data 6) and biogenesis. The three methoxyl groups were attributed to C-1, C-14, and C-16, respectively, based on the long-range correlations (1-OCH 3 /C-1, 14-OCH 3 /C-14, 16-OCH 3 /C-16) in the HMBC spectrum (Fig. 1). The one-proton triplet signal at d H 3.66 (Jϭ4.8 Hz) in the 1 H-NMR spectrum of (1) was assigned to H-14b based on the multiplicity and the coupling constant.7) The only acetoxyl group was located at C-6 due to the HMBC correlation between 6-OAc (d C 170.4 s) and H-6 (d H 5.21 s), and its configuration was determined as b-orientation based on the multiplicity of H-6 (singlet) in the 1 H-NMR spectrum. Finally, the structure of anthriscifolcine A was established as 1 by careful analyses of the 1D-NMR and 2D-NMR ( 1 H-1 H COSY, HMQC and HMBC) spectra.Anthriscifolcine B (2) was a white amorphous powder, mp 75-77°C. The HR-ESI-MS of 2 exhibited a protonated molecular ion peak at m/z 436.2686 (Calcd 436.2694) corresponding to a molecular formula of C 24 H 38 NO 6 (42 mass units lower than that of 1), suggesting that 2 is a hydrolytic derivative of 1, the 13 C-NMR spectra of 2 were similar to those of 1 except for the lack of an acetyl group. Meanwhile, the signal of H-6 in 1 was shifted upfield from d H 5.21 to d H 4.25 in 2 indicting that 6-OAc was substituted for 6-OH. Finally, the structure of 2 was confirmed by NaOH-CH 3 OH treatment of 1 to give the same alkamine with 2 and by full analysis of its NMR data (Table 1). Thus the structure of anthriscifolcine B was deduce...

New C19- and C18-Diterpenoid Alkaloids from Delphinium anthriscifolium var. savatieri

“…As mentioned in our previous report, 6) the configuration of 6-OH in 1 or 6-OAc in 5 and 6 has a b-orientation due to the singlet signal corresponding to H-6a in their 1 H-NMR spectra. 7) The configuration of 16-OCH 3 in compounds 1-3 was also determined to have a b-orientation according to the d values (81-83 ppm) of C-16 in their 13 C-NMR spectra.…”

“…Our earlier chemical investigation of a small batch of specimens of this plant led to the discovery of some new C 18 -diterpenoid alkaloids, which presented a chemotaxonomical advantage for the genus Delphinium. 6) Further investigation of a large batch of recollected samples resulted in the isolation of three new C 19 -diterpenoid alkaloids, anthriscifoldines A-C (1-3), and two new C 18 -diterpenoid alkaloids anthriscifolcines F and G (5, 6), together with five known alkaloids. In this paper, we report the isolation and structural elucidation of these new alkaloids.…”

Norditerpenoid alkaloids from Delphinium anthriscifolium

“…savatieri [3], the characteristic carbon signal of C-11 of compound 1 shifted Figure 2). The two methoxyl groups were connected to C-1 and C-16, respectively, based on the long-range correlations (1-OCH 3 /C-1, 16-OCH 3 /C-16) in the HMBC spectrum ( Figure 2).…”

“…165-1678C. Apart from carbon signals for an isobutyl acyl, a N-ethyl and two methoxys, the remaining 18 carbon signals in 13 C NMR spectrum are characteristic for a lycoctonine skeletoned C-18 norditerpenoid alkaloids [2,3].…”

“…The whole herb can be used as a medicine and has the effects of clearing heat, detoxicating, relieving cough, and resolving phlegm [1]. A series of diterpenoid alkaloids have been isolated from Delphinium genus plants [2][3][4][5][6][7], which exhibited broad activities, including cytotoxic [8]. But the bioactive second metabolities of this plant were hardly reported, except for anthriscifolcine A [2].…”