Six New 9,19-Cycloartane Triterpenoids from Cimicifuga foetida L.

Six new 9,19-cycloartane triterpene derivatives, as well as 3 known analogues (7–9), were isolated from the roots of Cimicifuga foetida L. Their structures were established on the basis of extensive spectroscopic analyses (IR, UV, ORD, HRESIMS, 1D and 2D NMR). Electronic supplementary material The online version of this article (doi:10.1007/s13659-016-0097-3) contains supplementary material, which is available to authorized users.


Results and Discussion
Compound 1 had the molecular formula of C 37 H 58 O 10 , which was determined by its HR-EIMS at m/z 662.4414 [M] ? . The IR spectrum showed absorption for hydroxyl group at 3425 cm -1 . The 1 H NMR spectrum (Table 1) showed characteristic cyclopropane methylene signals at d H 0.29 and 0.52 (each 1H, d, J = 3.8 Hz), a secondary methyl at d H 0.86 (d, J = 6.5 Hz), six tertiary methyls at d H 1.01 to 1.52 (each 3H, s), an acetyl group at d H 1.98, and an anomeric proton at d H 4.89 (d, J = 7.6 Hz). The The sugar unit of 1 was further confirmed by comparing its TLC and specific rotation with a standard after acid hydrolysis. Thus, the planar structure of 1 was determined.

), correlations of H-3/H-5 and H-15/H 3 -18 suggested that H-3 and H-15
were aand b-oriented, respectively. Moreover, the configurations of C-23 and C-24 were assigned as R and S, respectively, by comparing the coupling constants of H-23 (9.0 Hz) and H-24 (0 Hz) of 1 with those of known compounds [15].   (Table 2), of which 30 were attributed to a triterpene skeleton and five to a pentose. A DEPT NMR experiment permitted differentiation of the 30 carbon signals into seven methyls, five methylenes, eleven methines (including five oxygenated and two olefinic signals), and seven quaternary carbons (including two oxygenated and two olefinic signals). The diagnostic signals of two oxygenbearing methine carbons at d C 90.6 (C-24) and 70.4 (C-23), and a ketal carbon at d C at 112.7 suggested that 3 was a cimigenol-type triterpene compound. Further inspection of the 1D NMR and HSQC spectra of 3, the characteristic cyclopropane methylene resonances H 2 -19 and two quaternary carbons (C-9 and C-10) were not observed at the characteristic high magnetic field. Besides, comparison the NMR spectra of 3 with those of 12b-hydroxycimigenol-3-O-b-D-xylopyranoside [17], the signals due to C-9, C-10, C-11, and C-19 showed a downfield shift from d C 20.5, 26.1, 40.6, and 30.8 to 140.3, 138.7, 135.9, and 129.6, respectively, in 3. Such evidences indicated that 3 was a 9,10-seco-9,19-cyclolanostane glycoside with two double bonds. And the location of the double bonds (C 10 =C19 and C 9 =C 11 ) could be further deduced. This was further supported by IR, UV and 2D NMR spectra (Fig. 2). Furthermore, the configurations of C-23 and C-24 were assigned as R and S, respectively, by the same way as 1. Ultimately, the structure of 3 was determined as 12b-hydroxy-10,19:9,11-didehydro-9,10-seco-cimigenol-3-O-b-D-xylopyranoside. The molecular of compound 4 was assigned as C 30 H 46 O 6 by HR-EIMS at m/z 502.3294 [M] ? . The 1D NMR data of 4 (Tables 1, 2) showed that 4 was a highly oxygenated 9,19-cycloartane triterpene and resembled that of the aglycone of 7,8-dihydroactaeaepoxide-3-O-b-D-xylopyranoside [18]. However, the signals for the oxymethine at C-3 and the acetoxyl group at C-12 were absent. Instead a carbonyl group signal at d C 215.3 and an upfield oxymethine at d C 72.6 were observed, which indicated that the oxymethine (C-3) and the acetoxyl group (C-12) were replaced by a carbonyl group and a hydroxyl group, respectively. The evidence was established from HMBC correlations (Fig. 2) [19], except for one more acetyl group for the sugar unit, one less substituent methoxy group at C-25, and the presence of two downfield signals at d C 151.3 and 121.7 while the absence of an oxygenbearing quaternary carbon and a methine resonance due to C-16 and C-17, respectively. On the basis of these observations, it was reasonable to deduce that 5 was a 16,17-dehy-  [20]. Therefore, 5 was elucidated as 16,17-didehydro-2 0 ,24-O-diacetyl-hydroshengmanol-3-O-b-D-xylopyranoside.
Compound 6 was isolated as a white powder. Its molecular formula (C 30 H 42 O 6 ) was deduced from HR-EIMS (m/z 498.2991 [M] ? ), corresponding to nine degrees of unsaturation. The 1 H and 13 C NMR spectroscopic data (Tables 1, 2) of 6 showed similarities with those of yunnanterpene A [21], except for the differences of rings A and C, and the chemical shifts of C-22, C-23, and C-24. Two methylene signals due to C-1 at d C 33.3 and C-2 at d C 37.4 appeared in the ring A of yunnanterpene A were absent from the 13 C-DEPT spectrum of 6, respectively. Instead, two olefinic carbon signals at d C 153.5 and 127.2 were observed. Besides, the signal due to C-3 showed an upfield shift from d C 215.0 to 203.4. These evidences suggested the double bond was located at C-1 and C-2, which was further confirmed by the UV, IR (k max 262 nm; 1669 cm -1 ), and the HMBC correlations (Fig. 2) of the olefinic protons at d H 6.65 and 6.12 with the carbonyl carbon signals at d C 204.3 (C-3), The other changes of the ring C was that the methine signal at d C 72.1 (C-12) appeared in yunnanterpene A was absent instead of a quarternary carbonyl carbon signal at d C 210.8 (C-12) in 6. Meanwhile, the 13 C NMR signal due to C-11 showed a downfield shift from d C 40.6 in yunnanterpene A to 46.1 in 6, and the signal due to C-13 exhibited an unfield from d C 50.5 to 46.6, respectively. These observations indicated that the hydroxyl group was attached to C-12 was replaced by the carbonyl group, which was further confirmed by the HMBC correlations (Fig. 2) [19], and cimisterol A (9) [13] were also isolated from this species. Their structures were identified by its 1D NMR spectra as well as comparison with reported data.
Compounds 1-6 isolated in the present study were evaluated for their cytotoxicities against five human cancer cell lines using MTT method, with cisplatin and taxol as the positive control. Unfortunately, none of them showed significant activity [24].

General Experimental Procedures
Optical rotations were measured in MeOH with a Horiba SEAP-300 polarimeter. 1 H and 13 C NMR spectra were recorded in pyridine-d 5 on Bruker Avance III-600 MHz spectrometers (Bruker, Zürich, Switzerland), using TMS as internal standard for chemical shifts. Chemical shifts (d) were expressed in ppm with reference to the TMS resonance. ESIMS, HRTOF-ESIMS and EIMS, HR-EIMS data were obtained using a VG Autospec-3000 and API QSTAR TOF spectrometer, respectively. Infrared spectra were