A novel alkenoic acid ester and a new benzophenone

from Ranunculus ternatus

Ying Xiong a, Ke Zhong Deng b, Wen Yuan Gao a,*, Yuan Qiang Guo c,Tie Jun Zhang d

a School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, Chinab Jiangxi University of Traditional Chinese Medicine, Nanchang 330006, China

c Department of Pharmaceutical Sciences, Nankai University, Tianjin 300071, Chinad Tianjin Institute of Pharmaceutical Research, Tianjin 300193, China

Received 4 July 2007

Abstract

A novel alkenoic acid ester, (E)-4-hydroxy-dodec-2-enedioic acid-12-O-methyl ester and a new benzophenone, ethyl (S)-3-[2-

(3,4-dihydroxybenzoyl)-4,5-dihydroxyphenyl]-2-hydroxypropanoate, together with a known compound, (E)-4-hydroxy-dodec-2-

enedioic acids were isolated from the roots of Ranunculus ternatus. Their structures were elucidated by spectroscopic methods.

# 2007 Wen Yuan Gao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Ranunculus ternatus; Alkenoic acid ester; Benzophenone

Ranunculus ternatus Thunb. (Ranunculaceae) has been used as an herbal drug for treatment of tuberculosis,

faucitis, neck scrofula in China. It was previously reported [1–3] that some compounds, such as g-keto-d-

valerolactone, b-sitosterol, palmic acid, ternatoside A and ternatoside B etc. were isolated from the roots of R.

ternatus. In the course of our study on searching biological active components from this plant, a novel alkenoic acid

ester (1) and a new benzophenone (2), together with a known compound (3) were isolated. In this paper, we presented

the structural elucidation of 1 and 2 based on the spectral analysis.

The plant was purchased from Anguo, Hebei province, China and was identified by Prof. Wen Yuan Gao. Avoucher

specimen is deposited in the School of Pharmaceutical Science and Technology, Tianjin University, China. The

ethanol extract of roots of R. ternatus was separated by repeated silica gel column chromatography, Sephadex LH-20

and preparative HPLC to afford compounds 1–3.

Compound 1, amorphous powder, m.p. 67–69 8C, [a]25 D-30.7 (c 0.09, MeOH), had the molecular formula to be

C13H22O5 deduced from quasi-molecular ion peak [M+Na]+ at m/z 281.1365 in HRESI-MS (calcd. 281.1359). The IR

spectrum showed absorption bands of ester carbonyl (1734 cm�1) and a, b-unsaturated acid (1699 and 1651 cm�1).

The 1H NMR, 13C NMR and DEPT spectrum (Table 1) indicated that this compound possesses one carbonyl ester (dC

176.0), one carboxyl (dC 170.0), one trans double bond [dH 6.91 (dd, 1H, J = 4.8 and 15.6 Hz), 5.96 (dd, 1H, J = 1.6

and 15.6 Hz)], one oxygenated methine (dC 71.6), one methoxyl and seven methylene groups. The NMR spectral data

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Chinese Chemical Letters 18 (2007) 1364–1366

* Corresponding author.

E-mail address: pharmgao@tju.edu.cn (W.Y. Gao).

1001-8417/$ – see front matter # 2007 Wen Yuan Gao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

doi:10.1016/j.cclet.2007.09.017

of 1 were similar to those of 3 [4], except for the methoxyl group. In HMBC spectrum, 13C–1H long range correlation

signals (see Fig. 1) were found between C-1 and H-2, H-3; C-4 and H-2, H-3, H-5; C-12 and OCH3. Thus, compound 1

was identified as (E)-4-hydroxy-dodec-2-enedioic acid-12-O-methyl ester.

Compound 2, was obtained as yellowish oil, [a]25 D-35.2 (c 0.08, MeOH). Its HRESI-MS showed [M+Na]+ at m/z

385.0891 (calcd. 385.0899), corresponding to the molecular formula C18H18O8. Its IR spectrum indicated the presence

of hydroxyl (3212 cm�1), ester carbonyl (1721 cm�1), conjugated carbonyl (1657 cm�1) and aromatic rings (1583 and

1517 cm�1). The 1H and 13C NMR spectrum (see Table 2) of compound 2, extensively analyzed with the aid of 1H-1H

COSYand HSQC exhibited one methylene, one methine, one ethyl, two phenyls [three aromatic protons at dH 7.29 (d,

J = 2.0 Hz), 7.17 (dd, J = 8.0 and 2.0 Hz), 6.82 (d, J = 8.0 Hz) as an ABX-type system and two at dH 6.80 (s, 2H)], one

Y. Xiong et al. / Chinese Chemical Letters 18 (2007) 1364–1366 1365

Table 11H (400 MHz) NMR, 13C (100 MHz) NMR and DEPT data of 1 (CD3OD, d ppm, J Hz)

No. dH dC(DEPT) No. dH dC(DEPT)

1 170.0(C) 8 1.33 (br.s, 2H) 30.2(CH2)

2 5.96 (dd, 1H, 15.6, 1.6) 120.9(CH) 9 1.33 (br.s, 2H) 30.1(CH2)

3 6.91 (dd, 1H, 15.6, 4.8) 152.7(CH) 10 1.60 (m, 2H) 26.0(CH2)

4 4.22 (m, 1H) 71.6(CH) 11 2.31 (t, 2H, 7.2) 34.8(CH2)

5 1.54 (m, 2H) 37.6(CH2) 12 176.0(C)

6 1.33 (br.s, 2H) 26.3(CH2) OCH3 3.64 (s, 3H) 51.9(CH3)

7 1.33 (br.s, 2H) 30.4(CH2)

Fig. 1. The key HMBC (H! C) correlations of compounds 1 and 2.

Table 2

(400 MHz) and 13C (100 MHz) NMR data of 2 (CD3OD, d ppm, J Hz)

No. dH dC No. dH dC

1 175.5 40 144.1

2 4.25 (dd, 1H, 6.0) 73.3 50 148.9

3 3.01, 2.93 (dd, 2H, 14.0, 6.0) 38.3 60 6.80 (s, 1H) 119.4

4 4.09 (dd, 2H, 7.0) 62.0 100 131.6

5 1.19 (t, 3H, 7.0) 14.4 200 7.29 (d, 1H, 2.0) 118.3

CO 199.2 300 146.2

10 130.3 400 152.3

20 131.8 500 6.82 (d, 1H, 8.0) 115.6

30 6.80 (s, 1H) 118.5 600 7.17 (dd, 1H, 8.0, 2.0) 125.8

carbonyl ketone and one carbonyl ester groups. In the HMBC spectrum (see Fig. 1), the correlation between H-30, H-

200, H-600 and C O (dC 199.2) displayed that compound 2 possessed a diphenylketone skeleton. Moreover, H-3

correlated with C-1, C-2, C-20 and C-60; H-2 correlated with C-1 and C-10; H-4 correlated with C-1. The absolute

configuration at C-2 was determined as S by CD analysis, which showed a positive Cotton effect at 219 nm (De + 15.5)

[4,5]. Based on the above evidence, the structure of compound 2 was elucidated to be ethyl (S)-3-[2-(3,4-

dihydroxybenzoyl)-4,5-dihydroxyphenyl]-2-hydroxypropanoate.

The structures of one known compound were identified as (E)-4-hydroxy-dodec-2-enedioic acid [6] (3), which was

isolated from the roots of R. ternatus Thunb. for the first time.

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[5] S. Yahara, M. Satoshiro, I. Nishioka, et al. Chem. Pharm. Bull. 33 (2) (1985) 527.

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