Fitoterapia 81 (2010) 849–851
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Fitoterapia j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / f i t o t e
A new natural azulene-type pigment from Oreocnide frutescens Changhao Zhang a,b, Hong Liang a,b,⁎, Guangzhong Tu c,⁎, Yuying Zhao a,b a b c
State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, PR China Department of Natural Medicines, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191, PR China Beijing Institute of Microchemistry, Beijing 100091, PR China
a r t i c l e
i n f o
Article history: Received 21 December 2009 Accepted in revised form 13 May 2010 Available online 21 May 2010 Keywords: Oreocnide frutescens Azulene-type pigment Oreolactone Spectroscopic methods
a b s t r a c t A new natural red-purple azulene-type pigment, 1,1,6-trimethylazuleno[1,8-cd]pyran-3(1H)one, named oreolactone (1), together with nine known compounds, scopoletin (2), pomolic acid (3), friedelin (4), 3β-friedelinol (5), 3α-friedelinol (6), stigmast-4-en-3-one (7), stigmast-4, 22-dien-3-one (8), β-sitosterol (9), and daucosterol (10), was isolated from the rhizomes of Oreocnide frutescens. The structures were elucidated on the basis of spectroscopic analysis. © 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
Oreocnide frutescens (Thunb.) Miq (Urticaceae) is a shrub or small tree that grows in South of China and West of China. The fibers are used to make ropes, nets, and coarse cloth and the roots, stems and leaves are used by the folks for the treatment of pain, inflammation, menstrual disturbance, alopecia and promoting hair growth [1,2]. Previous investigations of the other Oreocnide species revealed the genus Oreocnide to be a rich source of flavonoids, ionone-related compounds, tannins, and polysaccharides [3,4]. However, no chemical and bioactive studies on the plant have been reported so far. Our chemical studies on the plant led to the isolation of a new natural azulene-type pigment and nine known compounds (Fig. 1) by column chromatography. This paper presents the details of isolation and structure elucidation of new compounds.
2.1. Generals UV: Jasco MD-1501. HR-ESI-MS: Bruker APEX IV FT-MS (7.0 T). NMR: Bruker AM-500. 2.2. Plant The rhizomes of O. frutescens were collected in Chongqing, China, in June 2006, and were taxonomically identified by Prof. Sirong Yi of the Institute of Medicinal Plantation of Chongqing. A voucher specimen is deposited in the Department of Natural Medicines, School of Pharmaceutical Sciences, Peking University Health Science Center, PR China. 2.3. Extraction and isolation
⁎ Corresponding authors. Hong Liang is to be contacted at Department of Natural Medicines, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191, PR China. Tel.: + 86 10 82801592. Guangzhong Tu, Beijing Institute of microchemistry, Beijing 100091, PR China. Tel.: + 86 10 82693596. E-mail addresses:
[email protected] (H. Liang),
[email protected] (GZ. Tu). 0367-326X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.fitote.2010.05.008
Air-dried powdered rhizomes of O. frutescens (8.3 kg) were extracted consecutively with EtOH at room temperature by percolation. The combined extracts were concentrated in vacuo to yield a dark residue which was suspended in water and partitioned successively with EtOAc and n-BuOH, respectively. The EtOAc extract (40.0 g) was subjected to silica gel column chromatography and eluted with CHCl3–CH3OH–H2O (65:35:10,
850
CH. Zhang et al. / Fitoterapia 81 (2010) 849–851
Fig. 1. The structure, key HMBC, 1H–1H COSY and NOESY correlations of compound 1.
v/v) to give 9 fractions (Fr.1–Fr.9). Fr.2 was recrystallized with acetone to yield compound 4 (4.0 mg). Fr.3 was recrystallized with acetone to yield compound 5 (33.0 mg). Fr.4 (9.8 g) was chromatographed on a silica gel column eluting with gradient mixture of CHCl3–MeOH (30:1 to 10:1) to give 36 subfractions. Subfraction 2 was recrystallized with acetone to give compound 6 (5.0 mg). Subfraction 5 was recrystallized with acetone to give compound 9 (15.0 mg). Subfraction 6 was separated on RP-18 and Sephadex LH-20 column chromatography eluting with MeOH–H2O (1:1) and MeOH–H2O (8:2), respectively, to give compound 1 (5.0 mg), 2 (11.0 mg), and 3 (79.0 mg). Subfraction 15 was separated on Sephadex LH-20 column chromatography eluting with MeOH–H2O (8:2) to give compounds 7 and 8 (6.0 mg). Subfraction 33 was recrystallized with MeOH to give compound 10 (37.0 mg). Compound 1 (Fig. 1) 1,1,6-trimethylazuleno[1,8-cd]pyran3(1H)-one (oreolactone), red-purple needle. UV λmax (MeOH) nm: 237.5, 304.0, 365.0; positive HR-ESI-MS m/z: 227.10619 [M+H]+ (calcd for C15H14O2: 227.10666).1H and 13C NMR data see Table 1. 3. Results and discussion Compound 1 was obtained as red-purple needles. The molecular formula was deduced as C15H14O2 by the HR-ESI-MS at m/z 227.10619 [M+H]+ (calcd for C15H14O2 227.10666),
Table 1 NMR data of compound 1 (in DMSO-d6). No.
δC
δH (m, J Hz)
HMBC
NOESY
1 2 3
111.9 133.5 118.0
8.13 (1H, d, 4.5) 7.57 (1H, d, 4.5)
C–1/C–3/C–9/C–10 C–1/C–2/C–4/C–10/ C–11
H–3 H–2/H–12
4 5 6 7
150.8 129.6 138.7 123.5
7.54 (1H, d, 10.5) 7.91 (1H, t, 10.5) 7.62 (1H, d, 10.5)
C–7/C–10/C–12 C–4/C–8 C–5/C–9/C–13
H–6/H–12 H–5/H–7 H–6/H–14/ H–15
8 9 10 11 12 13 14 15
151.1 134.6 138.9 160.5 23.9 85.3 30.9 30.9
2.93 (3H, s)
C–4/C–5/C–10
H–3/H–5
1.81 (3H, s) 1.81 (3H, s)
C–8/C–13/C–15 C–8/C–13/C–14
H–7 H–7
which was supported by the 1H, and 13C NMR data. The UV spectrum of 1 showed absorption maximum at 237.5, 304.0, and 365.0 nm. The 1H NMR spectrum of 1 (Table 1) displayed three methyl proton signals [δ 2.93 (3H, s), 1.81 (6H, s)], and two pairs of coupling system [δ 8.13 (1H, d, J = 4.5 Hz), 7.57 (1H, d, J = 4.5 Hz); δ 7.91 (1H, t, J = 10.5 Hz), 7.62 (1H, d, J = 10.5 Hz), 7.54 (1H, d, J = 10.5 Hz)]. The coupling constants suggested that the two coupling systems were aromatic rings but not benzenes. The 13C NMR spectrum of 1 (Table 1) displayed signals for 15 carbons, including a lactone carbonyl group (δ 160.5), three methyl carbon (δ 23.9, 30.9 × 2), one oxygenated quaternary carbon (δ 85.3), and ten sp2 carbons. The skeleton of 1 was deduced to azulene based on the 1H and 13 C NMR analyses. The protonated carbons and their bonded protons were unambiguously assigned by the HSQC experiment. In the 1H–1H COSY spectrum (Fig. 1), the proton at δ 8.13 (H–2) was coupled with the proton at δ 7.57 (H–3), and the proton at δ 7.91 (H–6) was coupled with the protons at δ 7.54 (H–5) and 7.62 (H–7), respectively. In the HMBC spectrum (Fig. 1), the proton signal at δ 8.13 (H–2) correlated with carbon signals at δ 111.9 (C–1), 118.0 (C–3), 134.6 (C–9), 138.9 (C–10); the proton signal at δ 7.57 (H–3) correlated with carbon signals at δ 111.9 (C–1), 133.5 (C–2), 150.8 (C–4), 138.9 (C–10), 160.5 (C–11); the proton signal at δ 7.54 (H–5) correlated with carbon signals at δ 123.5 (C–7), 138.9 (C–10), 23.9 (C–12); the proton signal at δ 7.91 (H–6) correlated with carbon signals at δ 150.8 (C–4), 151.1 (C–8); the proton signal at δ 7.62 (H–7) correlated with carbon signals at δ 129.6 (C–5), 134.6 (C–9), 85.3 (C–13); the methyl proton signal at δ 2.93 (H–12) correlated with carbon signals at δ 150.8 (C–4), 129.6 (C–5), 138.9 (C–10); the other methyl proton signals at δ 1.81 (H–14 and H–15) correlated with carbon signals at δ 151.1 (C–8), 85.3 (C–13), 30.9 (C–15 and C–14). In the NOESY spectrum, the methyl proton signal at δ 2.93 (H–12) correlated with proton signals at δ 7.57 (H–3) and 7.54 (H–5), the other methyl proton signals at 1.81 (H–14 and H–15) correlated with proton signal at δ 7.62 (H–7). The structure of compound 1 was therefore assigned as 1,1,6-trimethylazuleno[1,8-cd]pyran-3(1H)-one, named oreolactone, might be considered a guaiane derivative where C–11 is oxidized to carboxylic acid, lactonized on the C–13 hydroxyl. The structures of 2–8 were determined to be scopoletin (2) [5], pomolic acid (3) [6], friedelin (4) [7], 3β-friedelinol (5) [8], 3α-friedelinol (6) [8], stigmast-4-en-3-one (7) [9], and stigmast-4, 22-dien-3-one (8) [9], by comparison of spectroscopic data (1H and 13C NMR) with literature. The structures of
CH. Zhang et al. / Fitoterapia 81 (2010) 849–851
9–10 were determined to be β-sitosterol (9) and daucosterol (10) by comparison with authentic samples. References [1] The Editorial Committee of Flora of China. Flora of China 1995;23(2):386. [2] Li TR. Faming Zhuanli Shenqing Gongkai Shuomingshu; 2007. [3] Khan IA, Rali T, Sticher O. Planta Med 1993;59(3):287.
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