Alisol C 23-acetate from the rhizome of Alisma orientale

Zha-Jun Zhan; Hong-Ling Bian; Wei-Guang Shan

doi:10.1107/S1600536808032959

. 2008 Oct 31;64(Pt 11):o2231. doi: 10.1107/S1600536808032959

Alisol C 23-acetate from the rhizome of Alisma orientale

Zha-Jun Zhan ^a, Hong-Ling Bian ^a, Wei-Guang Shan ^a,^*

PMCID: PMC2959672 PMID: 21581085

Abstract

The title compound [systematic name: 11β-hydroxy-24,25-epoxy-3,16-oxo-protost-13 (17)-en-23-yl acetate], C₃₂H₄₈O₆, a protostane-type triterpenoid, was isolated from the Chinese herbal medicine alismatis rhizoma (the rhizome of Alisma orientalis Juzep). The molecule contains four trans-fused rings, viz. three six-membered and one five-membered ring. Two of the six-membered rings have slightly distorted half-chair conformations, while the third exhibits a chair conformation. The five-membered ring is almost planar. An intermolecular O—H⋯O hydrogen bond between the hydroxy and epoxy groups and intra- and intermolecular C—H⋯O hydrogen bonds are observed.

Related literature

For related literature, see: Nakajima et al. (1994 ▶); Yoshikawa et al. (1993 ▶, 1997 ▶).

Experimental

Crystal data

C₃₂H₄₈O₆
M _r = 528.73
Orthorhombic,
a = 7.6879 (3) Å
b = 14.6555 (6) Å
c = 26.9557 (10) Å
V = 3037.1 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 296 (1) K
0.55 × 0.38 × 0.27 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.938, T _max = 0.979
28664 measured reflections
3894 independent reflections
2600 reflections with F ² > 2σ(F ²)
R _int = 0.049

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.075
S = 1.00
3894 reflections
345 parameters
H-atom parameters constrained
Δρ_max = 0.15 e Å⁻³
Δρ_min = −0.16 e Å⁻³

Data collection: PROCESS-AUTO (Rigaku/MSC, 2004 ▶); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2004 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶); software used to prepare material for publication: CrystalStructure.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808032959/is2332sup1.cif

e-64-o2231-sup1.cif^{(28.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808032959/is2332Isup2.hkl

e-64-o2231-Isup2.hkl^{(190.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H101⋯O4ⁱ	0.82	2.05	2.869 (2)	174
C19—H193⋯O1	0.96	2.45	3.127 (3)	127
C22—H222⋯O3	0.97	2.53	3.181 (3)	124
C32—H323⋯O1ⁱⁱ	0.96	2.59	3.363 (5)	137

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

The Financial support of the Natural Science Foundation of Zhejiang Province, P. R. China (Y206825) is gratefully acknowledged.

supplementary crystallographic information

Comment

Dry rhizome of Alisma orientale (Sam) Juzep (Alismataceae) is a traditional Chinese medicine, which was used as a diuretic in the treatment of oliguresis and edema. Phytochemical investigations of the species resulted in the isolation of a series of protostane-type triterpenes with a side chain connected to C-17, and oxygenated at C-3, 11, 16, 23, 24 and 25 (Yoshikawa et al., 1993; Nakajima et al., 1994). Some triterpenes from this plant showed a relaxant effect on the contraction of isolated aortic or bladder smooth muscles (Yoshikawa et al., 1997). To investigate the bioactive natural products from this plant, we investigated its triterpene constituents, which led to the isolation of the title compound, alisol C 23-acetate, (I). Its structure was elucidated by spectroscopic analysis, and confirmed by a single-crystal X-ray diffraction analysis.

The relative stereochemistry of (I) has been determined (Fig. 1). The molecule contains three six-membered rings and one five-membered ring. Rings A (C1—C5/C10) and B (C5—C9/C10) adopt slightly distorted half-chair conformations owing to the ketone group at C3, and ring C (C8/C9/C11–14) exhibits a chair conformation. Ring D (C13—C17) adopts a plane conformation owing to the presence of the ketone group at C16. All rings are trans-fused. There is an intermolecular hydrogen bond between the hydroxy and epoxy groups.

Experimental

Dried powder (5.0 kg) of the rhizone of Alisma orientale was extracted three times with 95% EtOH at room temperature. The solvent was removed by evaporation at reduced pressure and the residue was fractioned with chloroform. The residue of the chloroform fraction was subjected to column chromatography on silica gel, and eluted with petroleum ether-EtOH mixture. The crude compound was purified by column chromatography on silica gel with an petroleum ether-acetone mixture and recrystallized from petroleum ether-acetone (2:1) to afford 140 mg of the pure title compound, (I). Crystals suitable for X-ray structure analysis were obtained by slow evaporation of a petroleum ether-acetone (2:1) solution at room temperature (m.p. 505–507 K). ¹³C NMR (100 MHz, CDCl₃): δ 31.1(C1), 33.7(C2), 218.6(C3), 47.1(C4) 48.6(C5), 20.2(C6), 35.0(C7), 40.3(C8), 49.0(C9), 37.1(C10), 69.8(C11) 35.8(C12), 176.3(C13), 49.7(C14), 45.9(C15), 207.2(C16), 138.2(C17), 23.2(C18), 25.7(C19), 26.9(C20), 20.3(C21) 35.3(C22), 71.9(C23), 64.9(C24), 58.7(C25), 20.0(C26), 24.8(C27), 29.7(C28), 19.5(C29), 23.2(C30), 169.6(C31), 21.5(C32).