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Two new benzopyran derivatives from Gouania leptostachya DC. var. tonkinensis Pitard.
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Chinese Chemical Letters 22 (2011) 175–177 www.elsevier.com/locate/cclet
Two new benzopyran derivatives from Gouania leptostachya DC. var. tonkinensis Pitard. Chong Yao a,b, Shu Jie Zhang c, Zheng Zhong Bai c, Tong Zhou d, Li Jiang Xuan d,* a
Huzhou Central Hospital, Huzhou 313000, China Heilongjiang University of Chinese Medicine, Harbin 150040, China c Heilongjiang Institute for Drug Control, Harbin 150001, China d State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai 201203, China b
Received 27 May 2010
Abstract Two new benzopyran derivatives, 1-[(rel 2S,3R)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone (1), and 1-[(rel 2S,3S)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone (2), along with four known flavonoids, prodelphinidin C, prodelphinidin B3, ()-epi-gallocatechin and (+)-gallocatechin, were isolated from the stems of Gouania leptostachya DC. var. tonkinensis Pitard. Their structures were determined on the basis of spectroscopic methods including HR-ESI-MS, 1D and 2D NMR. Prodelphinidin C exhibited significant inhibitory activity for a-glucosidase. # 2010 Published by Elsevier B.V. on behalf of Chinese Chemical Society. Keywords: Gouania leptostachya DC. var. tonkinensis Pitard.; Benzopyran derivatives; a-Glucosidase inhibitory activity
The genus Gouania (Rhamnaceae) is comprised of 70 species of plants, four of which are found in China. Gouania leptostachya DC. var. tonkinensis Pitard. is the one distributed abundantly in the south of China and has been used as a Chinese folk medicine for the treatment of scald and acroanesthesia [1]. Previous phytochemical studies on the genus plants led to the identification of several triterpenoid saponins and steroids [2,3]. As a part of our ongoing program on the discovery of new bioactive components from terrestrial plants, we found the extract of G. leptostachya exhibited significant a-glucosidase inhibitory activities, in which the aqueous extract showed the important activity. So, the stems of G. leptostachya were studied systematically. This paper describes the isolation and structural elucidation of two new benzopyran derivatives (1 and 2), along with four known compounds, prodelphinidin C [4], prodelphinidin B3 [5], ()-epi-gallocatechin [5] and (+)-gallocatechin [5], and bioactivity detection for a-glucosidase inhibition. The stems of G. leptostachya were collected at Nanning, Guangxi Province, China, in December 2008, and identified by Prof. He Ming Yang. A voucher specimen was deposited at Shanghai Institute of Materia Medica (SIMMGL511). The stems (5 kg) were extracted with 70% acetone (3 15 L, 48 h respectively). After concentration in vacuo to no organic solvent, the hydrophobic fraction was removed by precipitation and filtration. The filtrate was submitted to MCI gel CHP 20P column chromatography eluted with MeOH–H2O gradiently. The aqueous-soluble * Corresponding author. E-mail address: [email protected] (L.J. Xuan). 1001-8417/$ – see front matter # 2010 Published by Elsevier B.V. on behalf of Chinese Chemical Society. doi:10.1016/j.cclet.2010.09.028
176
C. Yao et al. / Chinese Chemical Letters 22 (2011) 175–177
fraction was submitted to column chromatography on Sephadex LH-20, MCI gel CHP 20P, Chromatorex C18 and Toyopearl HW-40 F, respectively, to give six compounds. Compound 1 was obtained as a white amorphous powder, ½a20 D 15:6 (c 0.34, MeOH). Its molecular formula was deduced as C11H12O5 from the ion peak at m/z 247.0575 ([M+Na]+, calcd. 247.0582) in HR-ESI-MS spectrum. IR (KBr, cm1)nmax: 3354 (OH), 1701 (C O), 1624 and 1522 (phenyl ring). The 1H and 13C NMR spectral data of 1 (Table 1) were similar to the known ()-epi-gallocatechin [5], except for the substituent in C-2. The 1H NMR (400 MHz, CD3OD) and 13C NMR (100 MHz, CD3OD) spectrum indicated that the aromatic protons and carbons at dH 5.94 (s, 2H) and dC 158.3, 96.5, 158.0, 97.4, 156.2, 100.4 were attributed to a meta-trihydroxy benzene. The partial structure of CH(O)(C-2)CH(O)(C-3)CH2(C-4) can be elucidated by analyzing the HMQC and 1H-1H COSY spectra. The HMBC correlation from the proton at dH 2.60 (dd, 2H, J = 4.5 Hz, 17.3 Hz, H-4) to the carbons at dC 100.4 (C-10), 158.3 (C-5), and 156.2 (C-9) indicated the partial structure of CH(O)CH(O)CH2 was assigned to C-10. The 13C NMR spectrum also indicated the presence of an acetyl group based on the methyl (dC 28.2, C-20 ) and ketonic (dC 210.9, C-10 ) carbon signals. In addition, the HMBC spectrum showed the correlations of the proton signals of H-20 and H-2 with C-10 , indicating the presence of an acetyl group at C-2. From the molecular formula alone, the degree of unsaturation was deduced as six in the molecule. The degree of unsaturation gave evidence for the presence of a pyran ring in which C-2 and C-9 bonded by an ether linkage. Consequently, full assignments of 1H and 13C NMR chemical shifts were accomplished with the aid of DEPT, HMQC, HMBC and 1H-1H COSY experiments shown in Fig. 2. Compound 2 was obtained as a white amorphous powder, ½a20 D 15:4 (c 0.30, MeOH). Its molecular formula was deduced as C11H12O5 from the ion peak at m/z 247.0600 ([M+Na]+, calcd. 247.0582) in HR-ESI-MS spectrum. The 1H and 13C NMR spectrum showed the benzene-ring and acetyl group in 2 (Table 1) were still unchanged from those in 1. The only different between compounds 1 and 2 was the coupling mode of H-2 and H-3. The configuration of C-2 and C-3 of compounds 1 and 2 can be elucidated from the coupling mode between H-2 and H-3 [6]. If H-2 and H-3 were singlets in 1H NMR spectrum, the configuration between H-2 and H-3 was cis. If H-2 and H-3 had a bigger coupling constant in 1H NMR spectrum, the configuration between H-2 and H-3 was trans [6]. So, the configuration of C-2 and C-3 of compound 1 was cis and the configuration of C-2 and C-3 of compound 2 was trans. Based on the data above, the structure of compounds 1 and 2 were elucidated as 1-[(rel 2S,3R)3,5,7-trihydroxy-3,4dihydro-2H-chromen-2-yl]ethanone and 1-[(rel 2S,3S)3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone respectively shown in Fig. 1. The a-glucosidase inhibitory activity of the compounds 1 and 2, ()-epi-gallocatechin, (+)-gallocatechin, prodelphinidin C, prodelphinidin B3, total extract, BuOH extract and H2O extract were tested. Compounds 1 and 2 and ()-epi-gallocatechin were lack of bioactivity, (+)-gallocatechin and prodelphinidin B3 showed weak inhibitory activity for a-glucosidase, other extracts and compounds have good inhibitory activity for a-glucosidase. In particular, the prodelphinidin C at concentration of 10 mmol/L reduced significantly the activity of a-glucosidase with inhibitory rates of 66.26% (IC50 = 5.52 0.24 mmol/L, acarbose as a positive control, IC50 = 73.6 4.1 mmol/L, acarbose
Table 1 1 H NMR (400 MHz) and
13
Position
1
C NMR (100 MHz) data of 1 and 2 (CD3OD, d). 2
dC 2 3 4 5 6 7 8 9 10 10 20
83.9 65.7 29.6 158.3 96.5 158.0 97.4 156.2 100.4 210.9 28.2
(d) (d) (t) (s) (d) (s) (d) (s) (s) (s) (q)
dH (multility, J in Hz)
dC
4.28 (br s) 4.48–4.49 (m) 2.60 (dd, 4.5, 17.3)
85.1 65.3 27.4 158.4 96.0 158.2 97.1 155.6 100.2 210.0 27.3
5.94 (s) 5.94 (s)
2.31 (s)
dH (multility, J in Hz) (d) (d) (t) (s) (d) (s) (d) (s) (s) (s) (q)
4.21 (d, 5.3) 4.31 (d, 5.5) 2.47 (dd, 5.1, 16.4) 5.95 (s) 5.98 (s)
2.30 (s)
[()TD$FIG]
C. Yao et al. / Chinese Chemical Letters 22 (2011) 175–177
O HO
7 8 6 5
9
O
10 4
2 3
177
O
2' 1' CH3
HO
O
CH3
OH
OH
OH
OH 1
2
Fig. 1. The structure of compounds 1 and 2.
[()TD$FIG] HO
O
CH3 OH
OH
1
H-1H COSY HMBC (H
C)
Fig. 2. Key HMBC and COSY correlations of 1.
(95%) were obtained from Sigma Corporation). So, prodelphinidin C could be the bioactive compound of the aqueous extract. Acknowledgments The authors gratefully acknowledge grants from the National Science & Technology Major Project ‘‘Key New Drug Creation and Manufacturing Program’’, China (No. 2009ZX09301-001). References [1] [2] [3] [4] [5] [6]
L. Long, J. Ethnomed. Ethnopharm. 18 (2009) 38. E.J. Kennelly, W.H. Lewis, S. Johnson, J. Nat. Prod. 56 (1993) 402. R. Giacomelli Sandro, G. Maldaner, C. Stu¨cker, Planta Med. 73 (2007) 49. L.Y. Foo, L.J. Porter, J. Chem. Soc., Perkin Trans. 1 10 (1978) 1186. L.Y. Foo, Y. Lu, Molan A.L., Phytochemistry 54 (2000) 539. M.H. Abd EL-Razek, Asian J. Chem. 19 (2007) 4867.
Chinese Chemical Letters 22 (2011) 175–177 www.elsevier.com/locate/cclet
Two new benzopyran derivatives from Gouania leptostachya DC. var. tonkinensis Pitard. Chong Yao a,b, Shu Jie Zhang c, Zheng Zhong Bai c, Tong Zhou d, Li Jiang Xuan d,* a
Huzhou Central Hospital, Huzhou 313000, China Heilongjiang University of Chinese Medicine, Harbin 150040, China c Heilongjiang Institute for Drug Control, Harbin 150001, China d State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai 201203, China b
Received 27 May 2010
Abstract Two new benzopyran derivatives, 1-[(rel 2S,3R)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone (1), and 1-[(rel 2S,3S)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone (2), along with four known flavonoids, prodelphinidin C, prodelphinidin B3, ()-epi-gallocatechin and (+)-gallocatechin, were isolated from the stems of Gouania leptostachya DC. var. tonkinensis Pitard. Their structures were determined on the basis of spectroscopic methods including HR-ESI-MS, 1D and 2D NMR. Prodelphinidin C exhibited significant inhibitory activity for a-glucosidase. # 2010 Published by Elsevier B.V. on behalf of Chinese Chemical Society. Keywords: Gouania leptostachya DC. var. tonkinensis Pitard.; Benzopyran derivatives; a-Glucosidase inhibitory activity
The genus Gouania (Rhamnaceae) is comprised of 70 species of plants, four of which are found in China. Gouania leptostachya DC. var. tonkinensis Pitard. is the one distributed abundantly in the south of China and has been used as a Chinese folk medicine for the treatment of scald and acroanesthesia [1]. Previous phytochemical studies on the genus plants led to the identification of several triterpenoid saponins and steroids [2,3]. As a part of our ongoing program on the discovery of new bioactive components from terrestrial plants, we found the extract of G. leptostachya exhibited significant a-glucosidase inhibitory activities, in which the aqueous extract showed the important activity. So, the stems of G. leptostachya were studied systematically. This paper describes the isolation and structural elucidation of two new benzopyran derivatives (1 and 2), along with four known compounds, prodelphinidin C [4], prodelphinidin B3 [5], ()-epi-gallocatechin [5] and (+)-gallocatechin [5], and bioactivity detection for a-glucosidase inhibition. The stems of G. leptostachya were collected at Nanning, Guangxi Province, China, in December 2008, and identified by Prof. He Ming Yang. A voucher specimen was deposited at Shanghai Institute of Materia Medica (SIMMGL511). The stems (5 kg) were extracted with 70% acetone (3 15 L, 48 h respectively). After concentration in vacuo to no organic solvent, the hydrophobic fraction was removed by precipitation and filtration. The filtrate was submitted to MCI gel CHP 20P column chromatography eluted with MeOH–H2O gradiently. The aqueous-soluble * Corresponding author. E-mail address: [email protected] (L.J. Xuan). 1001-8417/$ – see front matter # 2010 Published by Elsevier B.V. on behalf of Chinese Chemical Society. doi:10.1016/j.cclet.2010.09.028
176
C. Yao et al. / Chinese Chemical Letters 22 (2011) 175–177
fraction was submitted to column chromatography on Sephadex LH-20, MCI gel CHP 20P, Chromatorex C18 and Toyopearl HW-40 F, respectively, to give six compounds. Compound 1 was obtained as a white amorphous powder, ½a20 D 15:6 (c 0.34, MeOH). Its molecular formula was deduced as C11H12O5 from the ion peak at m/z 247.0575 ([M+Na]+, calcd. 247.0582) in HR-ESI-MS spectrum. IR (KBr, cm1)nmax: 3354 (OH), 1701 (C O), 1624 and 1522 (phenyl ring). The 1H and 13C NMR spectral data of 1 (Table 1) were similar to the known ()-epi-gallocatechin [5], except for the substituent in C-2. The 1H NMR (400 MHz, CD3OD) and 13C NMR (100 MHz, CD3OD) spectrum indicated that the aromatic protons and carbons at dH 5.94 (s, 2H) and dC 158.3, 96.5, 158.0, 97.4, 156.2, 100.4 were attributed to a meta-trihydroxy benzene. The partial structure of CH(O)(C-2)CH(O)(C-3)CH2(C-4) can be elucidated by analyzing the HMQC and 1H-1H COSY spectra. The HMBC correlation from the proton at dH 2.60 (dd, 2H, J = 4.5 Hz, 17.3 Hz, H-4) to the carbons at dC 100.4 (C-10), 158.3 (C-5), and 156.2 (C-9) indicated the partial structure of CH(O)CH(O)CH2 was assigned to C-10. The 13C NMR spectrum also indicated the presence of an acetyl group based on the methyl (dC 28.2, C-20 ) and ketonic (dC 210.9, C-10 ) carbon signals. In addition, the HMBC spectrum showed the correlations of the proton signals of H-20 and H-2 with C-10 , indicating the presence of an acetyl group at C-2. From the molecular formula alone, the degree of unsaturation was deduced as six in the molecule. The degree of unsaturation gave evidence for the presence of a pyran ring in which C-2 and C-9 bonded by an ether linkage. Consequently, full assignments of 1H and 13C NMR chemical shifts were accomplished with the aid of DEPT, HMQC, HMBC and 1H-1H COSY experiments shown in Fig. 2. Compound 2 was obtained as a white amorphous powder, ½a20 D 15:4 (c 0.30, MeOH). Its molecular formula was deduced as C11H12O5 from the ion peak at m/z 247.0600 ([M+Na]+, calcd. 247.0582) in HR-ESI-MS spectrum. The 1H and 13C NMR spectrum showed the benzene-ring and acetyl group in 2 (Table 1) were still unchanged from those in 1. The only different between compounds 1 and 2 was the coupling mode of H-2 and H-3. The configuration of C-2 and C-3 of compounds 1 and 2 can be elucidated from the coupling mode between H-2 and H-3 [6]. If H-2 and H-3 were singlets in 1H NMR spectrum, the configuration between H-2 and H-3 was cis. If H-2 and H-3 had a bigger coupling constant in 1H NMR spectrum, the configuration between H-2 and H-3 was trans [6]. So, the configuration of C-2 and C-3 of compound 1 was cis and the configuration of C-2 and C-3 of compound 2 was trans. Based on the data above, the structure of compounds 1 and 2 were elucidated as 1-[(rel 2S,3R)3,5,7-trihydroxy-3,4dihydro-2H-chromen-2-yl]ethanone and 1-[(rel 2S,3S)3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone respectively shown in Fig. 1. The a-glucosidase inhibitory activity of the compounds 1 and 2, ()-epi-gallocatechin, (+)-gallocatechin, prodelphinidin C, prodelphinidin B3, total extract, BuOH extract and H2O extract were tested. Compounds 1 and 2 and ()-epi-gallocatechin were lack of bioactivity, (+)-gallocatechin and prodelphinidin B3 showed weak inhibitory activity for a-glucosidase, other extracts and compounds have good inhibitory activity for a-glucosidase. In particular, the prodelphinidin C at concentration of 10 mmol/L reduced significantly the activity of a-glucosidase with inhibitory rates of 66.26% (IC50 = 5.52 0.24 mmol/L, acarbose as a positive control, IC50 = 73.6 4.1 mmol/L, acarbose
Table 1 1 H NMR (400 MHz) and
13
Position
1
C NMR (100 MHz) data of 1 and 2 (CD3OD, d). 2
dC 2 3 4 5 6 7 8 9 10 10 20
83.9 65.7 29.6 158.3 96.5 158.0 97.4 156.2 100.4 210.9 28.2
(d) (d) (t) (s) (d) (s) (d) (s) (s) (s) (q)
dH (multility, J in Hz)
dC
4.28 (br s) 4.48–4.49 (m) 2.60 (dd, 4.5, 17.3)
85.1 65.3 27.4 158.4 96.0 158.2 97.1 155.6 100.2 210.0 27.3
5.94 (s) 5.94 (s)
2.31 (s)
dH (multility, J in Hz) (d) (d) (t) (s) (d) (s) (d) (s) (s) (s) (q)
4.21 (d, 5.3) 4.31 (d, 5.5) 2.47 (dd, 5.1, 16.4) 5.95 (s) 5.98 (s)
2.30 (s)
[()TD$FIG]
C. Yao et al. / Chinese Chemical Letters 22 (2011) 175–177
O HO
7 8 6 5
9
O
10 4
2 3
177
O
2' 1' CH3
HO
O
CH3
OH
OH
OH
OH 1
2
Fig. 1. The structure of compounds 1 and 2.
[()TD$FIG] HO
O
CH3 OH
OH
1
H-1H COSY HMBC (H
C)
Fig. 2. Key HMBC and COSY correlations of 1.
(95%) were obtained from Sigma Corporation). So, prodelphinidin C could be the bioactive compound of the aqueous extract. Acknowledgments The authors gratefully acknowledge grants from the National Science & Technology Major Project ‘‘Key New Drug Creation and Manufacturing Program’’, China (No. 2009ZX09301-001). References [1] [2] [3] [4] [5] [6]
L. Long, J. Ethnomed. Ethnopharm. 18 (2009) 38. E.J. Kennelly, W.H. Lewis, S. Johnson, J. Nat. Prod. 56 (1993) 402. R. Giacomelli Sandro, G. Maldaner, C. Stu¨cker, Planta Med. 73 (2007) 49. L.Y. Foo, L.J. Porter, J. Chem. Soc., Perkin Trans. 1 10 (1978) 1186. L.Y. Foo, Y. Lu, Molan A.L., Phytochemistry 54 (2000) 539. M.H. Abd EL-Razek, Asian J. Chem. 19 (2007) 4867.