A New Flavonoid from Selaginella Tamariscina

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Chinese Chemical Letters 20 (2009) 595–597 www.elsevier.com/locate/cclet

A new ﬂavonoid from Selaginella tamariscina Jian Feng Liu a, Kang Ping Xu a, De Jian Jiang a, Fu Shuang Li a, Jian Shen a, Ying Jun Zhou a, Ping Sheng Xu b, Bin Tan c, Gui Shan Tan a,b,* a School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China b Xiangya Hospital of Central South University, Changsha, Hunan 410008, China c Xiangnan University, Chenzhou, Hunan 423000, China Received 6 October 2008

Abstract 6-(2-Hydroxy-5-acetylphenyl)-apigenin (1), a new ﬂavonoid with a phenyl substituent, was ﬁrst isolated from Selaginella tamariscina. Its structure was elucidated on the basis of 1D and 2D NMR as well as ESI-HR-MS spectroscopic analysis. # 2009 Gui Shan Tan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Selaginella tamariscina; Flavonoids; 6-(2-Hydroxy-5-acetylphenyl)-apigenin

Selaginella tamariscina is a traditional medicine, which was introduced in Chinese Pharmacopeia (2005 Ed) for the effectiveness in promoting blood circulation [1]. Pharmacological investigation of the genus Selaginella revealed its biological activities of anti-oxidant, anti-virus, anti-inflammation and effects on cardiovascular system protection [2–5]. A number of flavones, phenylpropanoids, alkaloids, organic acids, anthraquinones and steroids have been identified from genus Selaginella. As a continuation of our work, we reported hererin the isolation and structural elucidation of a new flavonoid, 6-(2-hydroxy-5-acetylphenyl)-apigenin (1) from the 75% enthanol extract of S. tamariscina, which is shown in Fig. 1. Herbs of S. tamariscina were collected in Jiangxi Province, P.R. China, and were identified by Associate Prof. Li Jinping (Central South University, Changsha, P.R. China). A voucher specimen was deposited in the Department of Pharmacognosy, School of Pharmacy, Central South University (No. JB-003). The whole herb of S. tamariscina. (14.0 kg) was extracted twice with cold 75% EtOH, and extract (1450 g) was obtained under reduced pressure. The extract was chromatographed over D-101 macroporous resin column with EtOH-H2O gradient elution (0%, 30%, 60%, 95%). The 60% EtOH portion was subject to a combination of chromatographies such as silica gel column chromatography, gel permeation chromatography and preparative HPLC to yield compound 1 (19.7 mg). Compound 1 was obtained as amorphous yellow powder. It gave a positive result for the Mg–HCl reaction, + revealing a flavonoid compound. It gave ESI-MS ion peak at m/z 405.0 [M+H] and was deduced as C23H17O7 by ESI- + + HR-MS at m/z 405.09556 [M+H] (calcd. for C23H17O7, 405.09743 [M+H] ), with the degree of unsaturation being

* Corresponding author at: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China. E-mail address: [email protected] (G.S. Tan).

1001-8417/$ – see front matter # 2009 Gui Shan Tan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2009.01.005 596 J.F. Liu et al. / Chinese Chemical Letters 20 (2009) 595–597

H OH H

HO O

H H OH O

H H

CH o 3

Fig. 1. Key HMBC correlations of 1.

16. Its UV spectrum showed the maximum absorption bands at 329 and 270 nm, the IR spectrum showed the presence of hydroxyl (3412 cm1), conjugated carbonyl (1662 cm1), and aromatic ring (1603, 1519 cm1). As evident from the 1H NMR spectrum (Table 1), three phenolic hydroxyl groups were exhibited at d13.11 (s, 1H), d11.22 (s, 2H), d10.92 (s, 1H), and the methyl at d2.49 (s, 3H) linking with the carbonyl (d196.3) to fabricate an acetyl

Table 1 1 13 H (400 MHz) and C NMR (100 MHz) data of compound 1 DMSO-d6 (TMS, JHz).

Position dH dC 2 163.5 3 6.77 (s, 1H) 105.2 4 182.2 5 13.11 (s, 1H, br) 154.7 6 102.7 7 160.7 8 6.28 (s, 1H) 99.7 9 161.2 10 103.3 10 121.7 20/60 7.58 (d, 2H, 8.8) 128.4 30/50 6.75 (d, 2H, 8.8) 116.0 40 161.2 100 120.3 200 162.0 300 7.01 (d, 1H, 8.4) 116.5 400 7.88 (dd, 1H, 8.4, 2.4) 129.8 500 127.9 600 7.93 (d, 1H, 2.4) 134.1 500CO 196.3 00 5 -COCH3 2.49 (s, 3H) 26.5 J.F. Liu et al. / Chinese Chemical Letters 20 (2009) 595–597 597 group. An AMX coupling system was indicated by the signals at d7.93 (d, 1H, J = 2.4 Hz, H-600), d7.88 (dd, 1H, J = 8.4, 2.4 Hz, H-400), d7.01 (d, 1H, J = 8.4 Hz, H-300). The HMBC correlations (Fig. 1) between C-500 (d127.9) and 500- 00 00 00 COCH3 (d26.5), between 5 -CO (d196.3) and H-4 (d7.88), H-6 (d7.93) indicated that the acetyl group was located at C-500, and the HMBC correlations between C-200 (d162.0) and H-400 (d7.88), H-600(d7.93) indicated a hydroxyl group locating at C-200. Hence, the presence of a para-acetylphenol was concluded. Beside the 8 carbon resonances mentioned above, the remaining 15 signals suit a ﬂavonoid skeleton. An AA0XX0 coupling system signals at d7.58 (d, 2H, J = 8.8 Hz, H-20,60) and d6.75 (d, 2H, J = 8.8 Hz, H-30,50) indicated the para-substitution of ring B. The HMBC correlation between H-3 (d6.77) and C-2 (d163.5), C-4 (d182.2), C-10 (d121.7) indicated none-substitution at C-3 of ring C. In the HMBC spectrum, correlations between C-6 (d102.7) and H-300 (d7.01), 5-OH (d13.11), H-8 (d6.28) concluded the linkage of the acetylphenol was located at the C-6 position of the ﬂavonoid moiety. The NMR assignments were based on the combination of 1H–1H COSY, HMQC and HMBC spectrum analysis, and with the comparison of literatured values [6]. Therefore, the structure of 1 was elucidated as 2-[2-(4-hydroxyphenyl)-5,7- dihydroxy-chromen-6-yl]-4-acetylphenol, named 6-(2-hydroxy-5-acetyl)-apigenin.

Acknowledgments

This project was supported by the National Natural Science Foundation of China (No. 30873149) and Precision Equipment and Apparatus Foundation of Central South University (No. ZKJ 2008046).

References

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