（Department of Chemistry, Huaqiao University, Quanzhou, Fujian 362011）

Yang Chongren

（Kunming Institute of Botany, Chinese Academy of Sciences, Kunming）

Wang Hanqing

（Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou）

AbstractSix new oleanane-type saponins, arilloside A-F (Ⅰ～Ⅵ), along with a known saponin, polygalasaponin ⅩⅩⅩⅤ(Ⅶ), were isolated from the root of Polygala arillata Buch.-Ham.. The structures of these new compounds were elucidated as 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-(3, 4-di-O-acetyl)-β-D-fucopyranoside(Ⅰ); 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→3)-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-β-D-fucopyranoside(Ⅱ); 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→3)-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-(3,4-di-O-acetyl)-β-D-fucopyranoside(Ⅲ); 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→3)-［β-D-galactopyranosyl (1→4)］-β-D-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-β-D-fucopyranoside(Ⅳ); 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→3)-［β-D-galactopyranosyl (1→4)］-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-(3-O-acetyl)-β-D-fucopyranoside(Ⅴ) and 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→3)-［β-D-galactopyranosyl (1→4)］-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-(3,4-di-O-acetyl)-β-D-fucopyranoside(Ⅵ) on the basis of spectroscopic and chemical methods.

Key wordsPolygala arillata Buch.-Ham.Polygalaceaetriterpenoid presenegeninoleananetype saponin

摘要中药黄花远志 Polygala arillata Buch.-Ham. 远志科远志属植物，为落叶灌木或小乔木，分布于西南、华东、陕西、湖北等地。其根具有祛风除湿，补虚消肿，调经活血等功效。我们对采自云南省文山县黄花远志的皂苷成分进行了研究，从甲醇提取物中分得7个单体三萜皂苷，经波谱和文献分析确定了它们的结构，其中有6个新三萜皂苷并命名为arilloside A～F。

关键词黄花远志三萜皂苷arilloside A～F

Introduction

Polygala arillata Buch.-Ham.is a Chinese medicinal plant, the root of which was used as a tonic, anticoagulant or for the treatment of hepatitis^〔1，2〕. Six new triterpenoid saponins christened as arilloside A～F(Ⅰ～Ⅵ)and one known saponin, polygalasaponin ⅩⅩⅩⅤ(Ⅶ) were isolated from its root. The last of which,Ⅶ has been previously isolated from P.fallax Hemsl.^〔3〕. In this paper, we wish to present the structure elucidation of arilloside A～F(Ⅰ～Ⅵ).

Results and Discussion

A crude saponin fraction of the metha-nol extract of the root of P.arillata Buch.-Ham.was subjected to pass through a porous polymer gel (D₁₀₁) column and the adsorbed materials were eluted successively with 30% aq. MeOH and MeOH. The methanol eluate was repeatedly chromatographed on silica gel RP-8 to give saponins (Ⅰ～Ⅶ). On alkaline hydrolysis, saponins Ⅰ～Ⅶ afforded tenuifolin (Ⅰ_a)^〔4〕，the 3-O-β-D-glucopyranoside of presenegenin. Therefore, it was justifiable to claim that these saponins Ⅰ～Ⅶ(Fig.1) were analogs of presenegenin glycosides.

Fig 1Chemical structure of Ⅰ～Ⅶ, I_a and HMBC Correlation of Arilloside E (Ⅴ)

Arilloside A (Ⅰ) showed a ［M-H］^－ ion peak at m/z 1 187 in the negative FAB-MS and combined with DEPT spectrum to give the molecular formula C₅₇H₇₂O₂₇. On acid hydrolysis, Ⅰ afforded glucose, fucose, rhamnose and xylose as its sugar moieties. On alkaline hydrolysis, Ⅰ gave a presenegenin 3-O-β-D-glucopyranoside, tenuif-olin. The ¹HNMR spectrum exhibited the presence of five single methyl signals (δ 0.76, 0.88, 1.05, 1.51 and 1.89), a tri-substituted olefinic proton ［δ 5.71 (t-like)］in the aglycone moiety and four anomeric protons ［δ 5.00 (d, J＝6.8 Hz), 5.05 (d, J＝7.1 Hz), 5.68 (br s) and 6.13 (d, J＝8.0 Hz)］. The ¹³CNMR spectrum suggested the presence of a carboxyl signal (δ 182.7), three ester carbonyl signals (δ 170.2, 170.9 and 176.4) and four anomeric carbon signals (δ 94.3, 102.0, 105.2 and 107.2). By comparison of the carbon NMR data of compound Ⅰ with that of polygalasaponin ⅩⅩⅧ^〔5〕, compound Ⅰ was found to contain two acetyl groups than polygalasaponin ⅩⅩⅧ. The ester carbonyl signals at δ 170.2 and 170.9 attaching to the positions C-3 and C-4 of fucose unit showed the HMBC correlation between the ester carbonyl signal (δ 170.2) and H-3 (δ 5.55) of fucose, and the ester carbonyl signal (δ 170.9) and H-4 (δ 5.55) of fucose. The proton signals of H-3, H-4 were overlapped and assigned by its TOCSY and HMQC spectra. Thus, the structure of arilloside A was elucidated as 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl(1→4)-α-L-rhamnopyranosyl(1→2)-(3,4-di-O-acetyl)-β-D-fucopyranoside.

Arilloside B (Ⅱ) showed a ［M-H］^- ion peak at m/z 1235 in the negative FAB-MS, suggesting the molecular formula C₅₈H₇₆O₂₉, combined with the DEPT spectrum. Compound Ⅱ afforded glucose, fucose, rhamnose, xylose as the sugar components on acid hydrolysis. In the NMR spectra, Ⅱ showed five anomeric proton and carbon signals ［δc 94.9/δ_H 6.00(d, J＝7.9 Hz); δ_c 101.1/δ_H 6.45 (br s); δ_c 105.3/δ_H 5.01 (d, J＝7.0 Hz); δ_c 105.9/δ_H 5.12 (d, J＝6.5 Hz) and δ_c 106.8/δ_H 5.02 (d, J＝7.2 Hz)］. The sugar proton and carbon signals in the NMR spectrum were assigned by HMQC, TOCSY, ¹H-¹H COSY and HMBC spectra (see Table 1). In the HMBC spectrum, long range coupling were observed between the anomeric proton signal at δ 5.01 (H-1 of Glc) and the carbon signal at δ 86.4 due to C-3 of the aglycone; between the anomeric proton signal at δ 6.00 (H-1 of Fuc) and the carbon signal at δ 176.7 due to C-28 of the aglycone; between the anomeric proton signal at δ 6.45 (H-1 of Rha) and the carbon signal at δ 73.5 due to C-2 of the fucose; between the anomeric proton signal at δ 5.02 ［H-1 of Xy1 (inn.)］and the carbon signal at δ 85.4 due to C-4 of the rhamnose; between the anomeric proton signal at δ 5.12 ［H-1 of Xyl (ter.)］ and the carbon signal at δ 87.8 due to C-3 of the xylose (inn.). From these evidences, the structure of arilloside B was elucidated as 3-O-β-D-glucopyranosyl presenegenin 28-O-β-D-xylopyranosyl (1→3)-β-D-xylopyranosyl (1→4)-α-L-rhamnopyranosyl (1→2)-β-D-fucopyranoside.

Arilloside C (Ⅲ) showed a ［M-H］^- ion peak at m/z 1319 in the negative FAB-MS, combined with the DEPT spectrum, its molecular formula was deduced to be C₆₂H₈₀O₃₁. The ¹HNMR spectrum suggesting the presence of two acetyl methyl proton signals (δ 2.00 and 2.02) and five anomeric proton signal ［δ 5.05 (d, J＝7.0 Hz); 5.10 (d, J＝7.1 Hz); 5.18 (d, J＝6.7 Hz); 5.69 (br s) and δ 6.17 (d, J＝7.9 Hz)］. On acid hydrolysis, compound Ⅲ afforded glucose, fucose, rhamnose and xylose. The positions of the acetyl groups were that of C-3, C-4 of the fucose moiety by comparing its NMR data with