A new iridoid from Incarvillea delavayi

Tao Lu a,c, Wei Dong Zhang a,b, Yue Hu Pei c, Chuan Zhang a,Jin Cheng Li c, Yun Heng Shen a,*

a Department of Phytochemistry, School of Pharmacy, Second Military Medical University, Shanghai 200433, Chinab School of Pharmacy, Shanghai Jiao tong University, Shanghai 200030, China

c Shenyang Pharmaceutical University, Liaoning Province, Shenyang 110016, China

Received 12 July 2007

Abstract

A new iridoid was isolated from the 80% ethanol extract of the whole plant of Incarvillea delavayi. Its structure was defined, and

named incarvillic acid, on the basis of spectral evidences.

# 2007 Yun Heng Shen. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Incarvillea delavayi; Bignoniaceae; Iridoid; Incarvillic acid

Incarvillea delavayi, a member of the genus Incarvillea (Bignoniaceae), is mainly distributed in Yunnan and

Sichuan provinces [1]. It is often treated as ornamental plant because of its beautiful flowers [2]. Recently, the

Incarvillea species have been found to be a rich source of actinidine-type monoterpenoid alkaloids [3–6], and possess

significant antinociceptive activity. It was also reported that some monoterpenoid alkaloids and iridoids have been

isolated from I. delavayi [7,8]. In our search for bioactive constituents from Incarvillea species, a new iridoid was

isolated from the 80% ethanol extract of the whole plant of I. delavayi. In this paper, we present the isolation and

structural characterization of this new iridoid on the basis of the interpretation of spectral data, including 1D and 2D

NMR data.

The whole plants of I. delavayi were collected, in Eryuan county, Yunnan province, China, in July 2006, and were

authenticated by Prof. Li-shan Xie of Kunming Institute of Botany, The Chinese Academy of Sciences. A voucher

specimen (No. 2006071003) is deposited in School of Pharmacy, Second Military Medical University.

The dried whole plants (17 kg) were extracted with 80% EtOH three times under reflux. The EtOH extract was

concentrated under reduced pressure to syrup, which was dissolved in 2% HCl and filtered. The filtrate was adjusted to

pH 9–10 by adding 10% NaOH, and then extracted with CHCl3. The CHCl3 fraction (350 g) was subjected to silica gel

column chromatography with gradient CHCl3–acetone (100:0! 0:100) to afford fractions 1–6. Fraction 1 was

purified by repeated column chromatography over silica gel and Sephadex LH-20 (CHCl3:MeOH, 1:1) to provide 1(7.8 mg).

Compound 1 was obtained as yellow oil with an optical rotation [a]20D + 63 (c 0.25, CH3Cl). The IR spectrum

showed absorption bands for methyl (2961 cm�1, 2876 cm�1), carboxyl (1769cm�1). Its molecule formula was

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Chinese Chemical Letters 18 (2007) 1512–1514

* Corresponding author.

E-mail address: shenyunheng9217018@yahoo.com.cn (Y.H. Shen).

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

doi:10.1016/j.cclet.2007.10.020

deduced as C10H16O4 by positive ESIMS (m/z 239 [M + K]+) as well as the 1H and 13C NMR data (Table 1), and further

confirmed by the HRESIMS (m/z 201.1128 [M + H]+, calcd. for C10H17O4 201.1127).

The 1H NMR spectrum of 1 exhibited an oxygen-bearing proton at dH 5.63 (d, 1H, J = 1.2 Hz) correlated with a

carbon atom at dC 98.4 in the HSQC experiment, a doublet methyl at dH 1.14 (d, 3H, J = 6.6 Hz), together with two

double doublets at dH 4.02 (dd, 1H, J = 8.0, 2.0 Hz) and 3.95 (dd, 1H, J = 8.0, 1.0 Hz). The 13C NMR spectrum gave 10

carbon resonances, including one methyl (dC 14.9), three methylenes (dC 65.6, 30.1, and 32.8), five methines (dC 98.4,

42.5, 40.1, 37.3, and 45.6), and one carboxyl (dC 172.2). The above evidences suggested that 1 possessed an iridoid

skeleton.

In the HMBC spectrum of (Table 1) 1, H-5, H-3, and H-4 exhibited long-range correlations with carboxyl, implying

that the carboxyl was substituted at C-4. Moreover, the observation of the long-range correlations between methyl with

C-7 (dC 32.8), C-8 (dC 37.3), and C-9 (dC 45.6), located the methyl at C-8. The oxygen-bearing methine (dC 98.4) and

methylene (dC 65.6) were assigned as C-1 and C-3, respectively, based on the interpretation of NMR data.

Biogenetically, the 1-OH, H-5, and H-9 of iridoid skeleton are b-orientation. The NOESY cross-peaks of H-4 (dH 2.74)

with H2-3, H2-6, and H-9 revealed that the relative configuration of H-4 was b-orientation. The stereo configuration of

H-8 was determined as b-orientation on the basis of the NOESY correlations of H-8 with H-9 and H-7b. Thus, the

structure of 1 was elucidated as shown in Fig. 1., and named incarvillic acid.

Acknowledgments

This research was partially supported by program for Changjiang Scholars and Innovative Research Team in

University (PCSIRT), the National Natural Science Foundation of China (No. 20402024), and the Scientific

T. Lu et al. / Chinese Chemical Letters 18 (2007) 1512–1514 1513

Table 1

NMR data for 1 (CDCl3, d ppm)

No. dH (mult., J) dC (mult.) HMBC (H! C) NOESY (H$ H)

1 5.63 (d, 1H, J = 1.2 Hz) 98.4 (d) C-3, C-5 Me-10

3a 4.02 (dd, 1H, J = 8.0, 2.0 Hz) 65.6 (t) C-5, C-11 H-4

3b 3.95 (dd, 1H, J = 8.0, 1.0 Hz) C-4, C-5, C-1, C-11 H-4, H-5

4 2.74 (m, 1H) 42.5 (d) C-9, C-11 H2-3, H2-6, H-9

5 2.72 (m, 1H) 40.1 (d) C-11 H-6b, H-3b, H-9

6a 1.72 (m, 1H) 30.1 (t) C-4, C-8, C-9 H-7a, H-5

6b 1.87 (m, 1H) C-4 H-5, H-7a

7a 1.29 (m, 1H) 32.8 (t) C-6, C-8 Me-10, H-6b

7b 1.65 (m, 1H) C-5, C-9 H-6b, H-8

8 2.16 (m, 1H) 37.3 (d) C-1, C-9 H-7b, H-9

9 2.56 (m, 1H) 45.6 (d) C-7 H-5, H-8

10 1.14 (d, 3H, J = 6.6 Hz) 14.9 (q) C-7, C-8, C-9 H-7a, H-1

11 172.2 (s)

Fig. 1. Structure of 1.

Foundation of Shanghai of China (No. 05DZ19733, 06DZ19717, and 06DZ19005). The authors thank Li-shan Xie of

Kunming Institute of Botany, The Chinese Academy of Sciences, for collection and identification of the plant.

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