- Email: [email protected]
Two new amide alkaloids from the flower of Datura metel L.
Fitoterapia 81 (2010) 1003–1005
Contents lists available at ScienceDirect
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
Two new amide alkaloids from the flower of Datura metel L. Bing-You Yang a, Yong-Gang Xia a, Qiu-Hong Wang a, De-Qiang Dou b, Hai-Xue Kuang a,⁎ a b
Heilongjiang University of Chinese Medicine, Harbin 150040, China Liaoning University of Traditional Chinese Medicine, Dalian 116600, China
a r t i c l e
i n f o
Article history: Received 25 March 2010 Received in revised form 10 June 2010 Accepted 19 June 2010 Available online 28 June 2010 Keywords: Datura metel L. Amide alkaloids Baimantuoluoamides A and B
a b s t r a c t Two new amide alkaloids were isolated from the alkaloidal fraction of Datura metel L. Their structures were elucidated as (E)-methyl 4-(3-(4-hydroxyphenyl)-N-methylacrylamido) butanoate and 6,7-dimethyl-1-D-ribityl-quinoxaline-2,3(1H,4H)-dione-5′-O-β-Dglucopyranoside on the basis of spectroscopic methods including HRESIMS, 1D and 2D NMR. Tropane alkaloids have for a long time been considered as characteristic ingredients of D. metel. However, the presence of amide alkaloids in D. metel was reported for the first time in this study. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved.
1. Introduction Datura metel L. (baimantuoluo in Chinese) is an annual herb, belonging to the family Solanaceae [1]. The flower of D. metel, named “yangjinhua” in Chinese, is a famous traditional Chinese medicine for centuries. It has been used for the treatment of asthma, cough, convulsion and insanity in China, and also has been long listed in Chinese Pharmacopoeia [2]. D. metel is rich in tropane alkaloids, important characteristic components of Solanaceae family [2]. So far, many tropane alkaloids have been isolated from the flower of D. metel including hyoscyamine, scopolamines, anisodamine, and atropine [2]. Recently “yangjinhua” has been clinically used for the treatment of psoriasis in China [3,4]. The effective part for psoriasis, non-alkaloid water-soluble fraction of yangjinhua, has been demonstrated that it had anti-inflammatory, anti-titillation of skin and anti-anaphylaxis actions by detailed pharmacological experiments [3,4]. Previously, a series of flavanoids and with anolides compounds had been isolated, including kaempferol, kaempferol7-O-α-L-rhamnopyranoside, baimantuoluosines A–F, and baimantuoluosides A–C [5–9]. It might contain some other trace alkaloids other than tropanes in the alkaloidal fraction ⁎ Corresponding author. Tel.: + 86 45182193001; fax: + 86 45182110803. E-mail address: [email protected] (H.-X. Kuang).
of yangjinhua. In order to screen interesting constituents, we have investigated the alkaloidal fraction of yangjinhua, which resulted in the discovery of two new amide alkaloids (Fig. 1). This paper deals with the structural elucidation of the new amide alkaloids by analysis of physicochemical evidences.
2. Experimental 2.1. General The melting points were measured on Kofler micromelting point apparatus (uncorrected). The NMR spectra were recorded on Bruker DPX 400 (400 MHz for 1H NMR and 100 MHz for 13C NMR), respectively. Chemical shifts are given as δ values with reference to tetramethylsilane (TMS) as an internal standard, and coupling constants are given in Hz. The HRESIMS analyses were conducted on IonSpec Ultima 7.0 T FTICR; ESIMS were carried out on Finnigan MAT LCQ mass spectrometer. Preparative HPLC (Waters, Delta 600-2487) was performed on Pegasil ODS II (5 μm, 10 × 250 mm, Senshu Pak, Japan). Ion exchange resin, macroporous absorption resin (Styrene-DVB 001 × 7 and AB-8 Crosslinked Polystyrene, Nan Kai, Tian Jin, China) and alumina (Neutral, 100–160 mesh, Gangyu, Shanghai, China) were employed for column chromatography ODS-A (120 A, 50 μm) was obtained from YMC Co..
0367-326X/$ – see front matter. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fitote.2010.06.017
1004
B.-Y. Yang et al. / Fitoterapia 81 (2010) 1003–1005
2.2. Plant materials The dry flowers of D. metel were collected in Nanjing city of Jiangsu Province of China in September 2002, and identified by prof. Zhenyue Wang. A voucher specimen (No. 2002035) was deposited at the Herbarium of Heilongjiang University of Chinese Medicine, China. 2.3. Extraction and isolation The dried flowers (15 kg) of D. metel L. were extracted with 70% EtOH under reflux (2 × 50 L) for 2.5 h (each), and the combined solution was filtered and evaporated under vacuum to a syrup, followed by suspension in H2O. The suspension was acidified with 0.1% HCl, and then filtered and exchange for Styrene-DVB (001 × 7). Styrene-DVB (10 kg) were air-dried and alkalized with ammonia and then extracted with CHCl3 under reflux for 5 h, and the combined solution was filtered and evaporated under vacuum to afford the alkaloidal fraction of the flower of D. metel (87 g). This crude residue (87 g) was subjected to alumina column chromatography and eluted successively with CHCl3/MeOH (10:1 → 1:1) gradient to give 9 fractions (Fr. 1–9). Fr. 8 (4.5 g) was subjected to alumina column chromatography eluted with CHCl3/MeOH (5:1 → 1:1) to afford a number of subfractions A1–A10. Compound 1 (23 mg) was obtained by repeated Prep. HPLC chromatography of the sub-fraction A3 (0.8 g) with MeOH/H2O (3:7). Compound 2 (15 mg) was obtained by repeated Prep. HPLC chromatography of the subfraction A4 (0.6 g) with MeOH/H2O (2:3).
Table 1 1 H and 13C NMR data for compounds 1 and 2 at 400 MHz for protons and 100 MHz for carbons. 1a No.
δC
δH (J in Hz)
δC
δH (J in Hz)
1 2 3 4 5 6 7 8 9 10 1′
128.1 131.1 116.4 159.3 116.4 131.1 135.0 120.5 172.0 – 174.8
– 7.19(d,8.8) 6.72(d,8.8) – 6.72(d,8.8) 7.19(d,8.8) 6.58(d,12.8) 5.91(d,12.8) – – –
– 155.6 153.7 – 116.5 131.2 130.8 115.9 124.8 123.2 44.5
– – – –
2′ 3′ 4′ 5′
31.5 24.2 50.9 –
2.21(t,7.2) 1.72(qui,7.2) 3.34(t, 7.0) –
67.7 73.6 70.6 72.0
1″ 2″ 3″ 4″ 5″ 6″
– – – – – –
– – – – – –
103.6 73.6 76.2 69.8 76.8 60.8
3.61(s) 2.96(s) – – –
– – 21.2 20.6 –
O–CH3 N–CH3 6–CH3 7–CH3 NH a b
ðEÞ−methyl 4−ð3−ð4−hydroxyphenylÞ−N−methylacrylamidoÞ butanoate:
ð1Þ White powder, HRESIMS (positive ion mode) m/z: 278.1382 [M+H]+ (calc. for C15H20O4N 278.13923), 300.12009 [M+Na]+ (calc. for C15H19NO4Na 300.12118), 316.09400 [M+K]+ (calc. for C15H19NO4K 316.09512); 1H and 13C NMR: see Table 1.
2b
52.1 32.7 – – –
7.32(s) – – 6.93(s) – – 4.02–4.06(m) 4.46–4.52(m) 4.02–4.06(m) 3.56–3.60(m) 3.76–3.78(m) 3.41–3.47(m) 4.02–4.06(m) 4.17(d,7.6) 3.00(t,8.4) 3.06–3.19(m) 3.06–3.19(m) 3.06–3.19(m) 3.43(dd,11.2,2.2) 3.67(dd,11.2,5.2) – – 2.23(s) 2.19(s) 11.80(brs)
In CD3OD. In DMSO-d6.
Yellow amorphous powder, HRESIMS (positive ion mode) m/z: 487.19103 [M + H]+ (calc. for C21H31N2O11 487.19287), 509.17352 [M + Na]+ (calc. for C21H30N2O11Na 509.17473), 525.14609 (calc. for C21H30N2O11K 525.14867); 1H and 13C NMR: see Table 1. 3. Results and discussion
6; 7−dimethyl−1−D−ribityl−quinoxaline−2; 3ð1H; 4HÞ −dione−5′−O−β−D−glucopyranoside:
ð2Þ
Compound 1, named baimantuoluoamide A, was obtained as yellow amorphous powder. The molecular formula was
Fig. 1. Structures of compounds 1 and 2.
B.-Y. Yang et al. / Fitoterapia 81 (2010) 1003–1005
determined by positive HRESIMS as C15H19NO4 from the [M + H]+, [M + Na]+ and [M+ K]+ signals at m/z 278.1382 (calc. for C 15 H20 O4 N [M + H] + 278.13923), 300.12009 (calc. for C15H19NO4Na [M+ Na]+ 300.12118), and 316.09400 (calc. for C15H19NO4K [M+ K]+ 316.09512), indicating seven degree of unsaturation. The 1H NMR signals at δH 7.19 (d, J = 8.8 Hz) and 6.72 (d, J = 8.8 Hz) indicated the presence of a 1,4-disubstituted benzene ring. Signals at δH 6.58 (d, J= 12.8 Hz) and 5.91 (d, J=12.8 Hz) indicated the presence of a trans-double. Signals at δH 2.21 (t, J = 7.2 Hz), 1.72 (qui, J = 7.2 Hz) and 3.34 (t, J =7.0 Hz) indicated the presence of a –CH2–CH2–CH2– structure fragment according to 1H NMR and 1H–1H COSY spectra. The singlet signal at δH 2.96 (3H, s) was characteristic of N-methyl proton signal. At the same time, a methoxy proton signal can be seen at δH 3.61 (3H, s). The 13C NMR (DEPT) spectra of 1 (Table 1) also revealed the presence of an aromatic ring, a trans-double bonds, two carbonyl groups, a methoxy group, and a N-methyl in 1. The HMBC spectra was used to elucidate the connection of different structural fragments, as well as to confirm the above assignments. In the HMBC spectra (Fig. 2), some key longrange correlations were observed between the N-methyl proton signal and the C-9 and C-4′, between N–CH2 proton signal (H-4′) and C-2′, C-3′, C-9 and N-methyl carbon, and between methoxy proton signal and C-1′. On the basis of the above data, 1 was elucidated as (E)-methyl 4-(3-(4-hydroxyphenyl)-N-methylacrylamido) butanoate. Compound 2, named baimantuoluoamide B, was obtained as yellow amorphous powder. The molecular formula was determined by positive HRESIMS as C21H30N2O11 from the [M+H]+, [M+Na]+ and [M+K]+ signals at m/z 487.19103 (calc. for C21H31N2O11 [M + H]+ 487.19287), 509.17352 (calc. for C21H30N2O11Na [M+ Na]+ 509.17473), and 525.14609 (calc. for C21H30N2O11K [M+ K]+ 525.14867), indicating eight degree of unsaturation. The 1H NMR spectra showed some typical proton signals, including two para orientation benzene ring proton signals [δH 7.32 (s) and 6.93 (s)], two methyl proton signals in benzene ring [δH 2.23 (s) and 2.19 (s)], a N proton signal [δH 11.80 (brs)], and an anomeric proton of β-glucopyranosyl [δH 4.17 (d, J=7.6 Hz)].
1005
The 13C NMR (DEPT) spectra of 2 (Table 1) revealed the presence of six carbon signals of benzene ring (δC 116.5, 131.2, 130.8, 115.9, 124.8 and 123.2), two amide carbonyl groups (δC 155.6 and 153.7), two methyl carbon signals (δC 21.2 and 20.6), a ribityl group (δC 44.5, 67.7, 73.6, 70.6 and 72.0) and a glucopyranosyl group (δC 103.6, 73.6, 76.2, 69.8, 76.8 and 60.8). By the comparison of 13C NMR data of 2 with 6,7-dimethyl-1-Dribityl-quinoxaline-2,3(1H,4H)-dione [10], it showed that chemical shifts are striking resemblance except for the hydrogen and carbon signals of a glucopyranosyl group in 2. The connection position of the glucopyranosyl group was established unambiguously by a HMBC experiment in which long-range correlations between H-1″ of the glucopyranosyl group and C-5′ (Fig. 2). On the basis of the above data, 2 was elucidated as 6,7-dimethyl-1-D-ribityl-quinoxaline-2,3 (1H,4H)-dione-5′-O-β-D-glucopyranoside. Acknowledgements Our work was supported by the Major State Basic Research Development Program of China (973 Program 2006CB504708), the National Natural Science Foundation of China (Nos. 30371736 and 30672633) and Special Fund Project of National Excellent Doctoral Dissertation of China (200980). References [1] Jiangsu New Medical college. Zhong Yao Da Ci Dian, Vol. 2. Shanghai: Science and Technology Press; 1986. p. 1719–1722. [2] National Committee of Chinese Pharmacopoeia. Pharmacopoeia of P. R. China, Vol. 1. Beijing: Chemical Industry Press; 2005. p. 188. [3] Wang QH, Xiao HB, Yang BY, Yao FY, Kuang HX. Chin Exp Tradit Med Form 2008;14:48–50. [4] Wang QH, Xiao HB, Yang BY, Yao FY, Xia YG, Kuang HX. Chin Exp Tradit Med Form 2008;14:32–4. [5] Yang BY, Wang QH, Xia YG, Feng WS, Kuang HX. Helv Chim Acta 2007;90:1522–8. [6] Yang BY, Wang QH, Xia YG, Feng WS, Kuang HX. Helv Chim Acta 2008;91:964–71. [7] Kuang HX, Yang BY, Xia YG, Feng WS. Arch Pharm Res 2008;31:1094–7. [8] Kuang HX, Yang BY, Tang L, Xia YG, Dou DQ. Helv Chim Acta 2009;92: 1315–23. [9] Yang BY, Tang L, Tai CM, Liu YJ, Kuang HX. Chin Tradit Herbal Drugs 2006;37:1147–9. [10] Wu J, Tu PF, Zhao YY. Chin Tradit Herbal Drugs 2005;36:965–8.
Fig. 2. Key 1H–1H COSY and HMBC correlations of compounds 1 and 2.
Contents lists available at ScienceDirect
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
Two new amide alkaloids from the flower of Datura metel L. Bing-You Yang a, Yong-Gang Xia a, Qiu-Hong Wang a, De-Qiang Dou b, Hai-Xue Kuang a,⁎ a b
Heilongjiang University of Chinese Medicine, Harbin 150040, China Liaoning University of Traditional Chinese Medicine, Dalian 116600, China
a r t i c l e
i n f o
Article history: Received 25 March 2010 Received in revised form 10 June 2010 Accepted 19 June 2010 Available online 28 June 2010 Keywords: Datura metel L. Amide alkaloids Baimantuoluoamides A and B
a b s t r a c t Two new amide alkaloids were isolated from the alkaloidal fraction of Datura metel L. Their structures were elucidated as (E)-methyl 4-(3-(4-hydroxyphenyl)-N-methylacrylamido) butanoate and 6,7-dimethyl-1-D-ribityl-quinoxaline-2,3(1H,4H)-dione-5′-O-β-Dglucopyranoside on the basis of spectroscopic methods including HRESIMS, 1D and 2D NMR. Tropane alkaloids have for a long time been considered as characteristic ingredients of D. metel. However, the presence of amide alkaloids in D. metel was reported for the first time in this study. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved.
1. Introduction Datura metel L. (baimantuoluo in Chinese) is an annual herb, belonging to the family Solanaceae [1]. The flower of D. metel, named “yangjinhua” in Chinese, is a famous traditional Chinese medicine for centuries. It has been used for the treatment of asthma, cough, convulsion and insanity in China, and also has been long listed in Chinese Pharmacopoeia [2]. D. metel is rich in tropane alkaloids, important characteristic components of Solanaceae family [2]. So far, many tropane alkaloids have been isolated from the flower of D. metel including hyoscyamine, scopolamines, anisodamine, and atropine [2]. Recently “yangjinhua” has been clinically used for the treatment of psoriasis in China [3,4]. The effective part for psoriasis, non-alkaloid water-soluble fraction of yangjinhua, has been demonstrated that it had anti-inflammatory, anti-titillation of skin and anti-anaphylaxis actions by detailed pharmacological experiments [3,4]. Previously, a series of flavanoids and with anolides compounds had been isolated, including kaempferol, kaempferol7-O-α-L-rhamnopyranoside, baimantuoluosines A–F, and baimantuoluosides A–C [5–9]. It might contain some other trace alkaloids other than tropanes in the alkaloidal fraction ⁎ Corresponding author. Tel.: + 86 45182193001; fax: + 86 45182110803. E-mail address: [email protected] (H.-X. Kuang).
of yangjinhua. In order to screen interesting constituents, we have investigated the alkaloidal fraction of yangjinhua, which resulted in the discovery of two new amide alkaloids (Fig. 1). This paper deals with the structural elucidation of the new amide alkaloids by analysis of physicochemical evidences.
2. Experimental 2.1. General The melting points were measured on Kofler micromelting point apparatus (uncorrected). The NMR spectra were recorded on Bruker DPX 400 (400 MHz for 1H NMR and 100 MHz for 13C NMR), respectively. Chemical shifts are given as δ values with reference to tetramethylsilane (TMS) as an internal standard, and coupling constants are given in Hz. The HRESIMS analyses were conducted on IonSpec Ultima 7.0 T FTICR; ESIMS were carried out on Finnigan MAT LCQ mass spectrometer. Preparative HPLC (Waters, Delta 600-2487) was performed on Pegasil ODS II (5 μm, 10 × 250 mm, Senshu Pak, Japan). Ion exchange resin, macroporous absorption resin (Styrene-DVB 001 × 7 and AB-8 Crosslinked Polystyrene, Nan Kai, Tian Jin, China) and alumina (Neutral, 100–160 mesh, Gangyu, Shanghai, China) were employed for column chromatography ODS-A (120 A, 50 μm) was obtained from YMC Co..
0367-326X/$ – see front matter. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fitote.2010.06.017
1004
B.-Y. Yang et al. / Fitoterapia 81 (2010) 1003–1005
2.2. Plant materials The dry flowers of D. metel were collected in Nanjing city of Jiangsu Province of China in September 2002, and identified by prof. Zhenyue Wang. A voucher specimen (No. 2002035) was deposited at the Herbarium of Heilongjiang University of Chinese Medicine, China. 2.3. Extraction and isolation The dried flowers (15 kg) of D. metel L. were extracted with 70% EtOH under reflux (2 × 50 L) for 2.5 h (each), and the combined solution was filtered and evaporated under vacuum to a syrup, followed by suspension in H2O. The suspension was acidified with 0.1% HCl, and then filtered and exchange for Styrene-DVB (001 × 7). Styrene-DVB (10 kg) were air-dried and alkalized with ammonia and then extracted with CHCl3 under reflux for 5 h, and the combined solution was filtered and evaporated under vacuum to afford the alkaloidal fraction of the flower of D. metel (87 g). This crude residue (87 g) was subjected to alumina column chromatography and eluted successively with CHCl3/MeOH (10:1 → 1:1) gradient to give 9 fractions (Fr. 1–9). Fr. 8 (4.5 g) was subjected to alumina column chromatography eluted with CHCl3/MeOH (5:1 → 1:1) to afford a number of subfractions A1–A10. Compound 1 (23 mg) was obtained by repeated Prep. HPLC chromatography of the sub-fraction A3 (0.8 g) with MeOH/H2O (3:7). Compound 2 (15 mg) was obtained by repeated Prep. HPLC chromatography of the subfraction A4 (0.6 g) with MeOH/H2O (2:3).
Table 1 1 H and 13C NMR data for compounds 1 and 2 at 400 MHz for protons and 100 MHz for carbons. 1a No.
δC
δH (J in Hz)
δC
δH (J in Hz)
1 2 3 4 5 6 7 8 9 10 1′
128.1 131.1 116.4 159.3 116.4 131.1 135.0 120.5 172.0 – 174.8
– 7.19(d,8.8) 6.72(d,8.8) – 6.72(d,8.8) 7.19(d,8.8) 6.58(d,12.8) 5.91(d,12.8) – – –
– 155.6 153.7 – 116.5 131.2 130.8 115.9 124.8 123.2 44.5
– – – –
2′ 3′ 4′ 5′
31.5 24.2 50.9 –
2.21(t,7.2) 1.72(qui,7.2) 3.34(t, 7.0) –
67.7 73.6 70.6 72.0
1″ 2″ 3″ 4″ 5″ 6″
– – – – – –
– – – – – –
103.6 73.6 76.2 69.8 76.8 60.8
3.61(s) 2.96(s) – – –
– – 21.2 20.6 –
O–CH3 N–CH3 6–CH3 7–CH3 NH a b
ðEÞ−methyl 4−ð3−ð4−hydroxyphenylÞ−N−methylacrylamidoÞ butanoate:
ð1Þ White powder, HRESIMS (positive ion mode) m/z: 278.1382 [M+H]+ (calc. for C15H20O4N 278.13923), 300.12009 [M+Na]+ (calc. for C15H19NO4Na 300.12118), 316.09400 [M+K]+ (calc. for C15H19NO4K 316.09512); 1H and 13C NMR: see Table 1.
2b
52.1 32.7 – – –
7.32(s) – – 6.93(s) – – 4.02–4.06(m) 4.46–4.52(m) 4.02–4.06(m) 3.56–3.60(m) 3.76–3.78(m) 3.41–3.47(m) 4.02–4.06(m) 4.17(d,7.6) 3.00(t,8.4) 3.06–3.19(m) 3.06–3.19(m) 3.06–3.19(m) 3.43(dd,11.2,2.2) 3.67(dd,11.2,5.2) – – 2.23(s) 2.19(s) 11.80(brs)
In CD3OD. In DMSO-d6.
Yellow amorphous powder, HRESIMS (positive ion mode) m/z: 487.19103 [M + H]+ (calc. for C21H31N2O11 487.19287), 509.17352 [M + Na]+ (calc. for C21H30N2O11Na 509.17473), 525.14609 (calc. for C21H30N2O11K 525.14867); 1H and 13C NMR: see Table 1. 3. Results and discussion
6; 7−dimethyl−1−D−ribityl−quinoxaline−2; 3ð1H; 4HÞ −dione−5′−O−β−D−glucopyranoside:
ð2Þ
Compound 1, named baimantuoluoamide A, was obtained as yellow amorphous powder. The molecular formula was
Fig. 1. Structures of compounds 1 and 2.
B.-Y. Yang et al. / Fitoterapia 81 (2010) 1003–1005
determined by positive HRESIMS as C15H19NO4 from the [M + H]+, [M + Na]+ and [M+ K]+ signals at m/z 278.1382 (calc. for C 15 H20 O4 N [M + H] + 278.13923), 300.12009 (calc. for C15H19NO4Na [M+ Na]+ 300.12118), and 316.09400 (calc. for C15H19NO4K [M+ K]+ 316.09512), indicating seven degree of unsaturation. The 1H NMR signals at δH 7.19 (d, J = 8.8 Hz) and 6.72 (d, J = 8.8 Hz) indicated the presence of a 1,4-disubstituted benzene ring. Signals at δH 6.58 (d, J= 12.8 Hz) and 5.91 (d, J=12.8 Hz) indicated the presence of a trans-double. Signals at δH 2.21 (t, J = 7.2 Hz), 1.72 (qui, J = 7.2 Hz) and 3.34 (t, J =7.0 Hz) indicated the presence of a –CH2–CH2–CH2– structure fragment according to 1H NMR and 1H–1H COSY spectra. The singlet signal at δH 2.96 (3H, s) was characteristic of N-methyl proton signal. At the same time, a methoxy proton signal can be seen at δH 3.61 (3H, s). The 13C NMR (DEPT) spectra of 1 (Table 1) also revealed the presence of an aromatic ring, a trans-double bonds, two carbonyl groups, a methoxy group, and a N-methyl in 1. The HMBC spectra was used to elucidate the connection of different structural fragments, as well as to confirm the above assignments. In the HMBC spectra (Fig. 2), some key longrange correlations were observed between the N-methyl proton signal and the C-9 and C-4′, between N–CH2 proton signal (H-4′) and C-2′, C-3′, C-9 and N-methyl carbon, and between methoxy proton signal and C-1′. On the basis of the above data, 1 was elucidated as (E)-methyl 4-(3-(4-hydroxyphenyl)-N-methylacrylamido) butanoate. Compound 2, named baimantuoluoamide B, was obtained as yellow amorphous powder. The molecular formula was determined by positive HRESIMS as C21H30N2O11 from the [M+H]+, [M+Na]+ and [M+K]+ signals at m/z 487.19103 (calc. for C21H31N2O11 [M + H]+ 487.19287), 509.17352 (calc. for C21H30N2O11Na [M+ Na]+ 509.17473), and 525.14609 (calc. for C21H30N2O11K [M+ K]+ 525.14867), indicating eight degree of unsaturation. The 1H NMR spectra showed some typical proton signals, including two para orientation benzene ring proton signals [δH 7.32 (s) and 6.93 (s)], two methyl proton signals in benzene ring [δH 2.23 (s) and 2.19 (s)], a N proton signal [δH 11.80 (brs)], and an anomeric proton of β-glucopyranosyl [δH 4.17 (d, J=7.6 Hz)].
1005
The 13C NMR (DEPT) spectra of 2 (Table 1) revealed the presence of six carbon signals of benzene ring (δC 116.5, 131.2, 130.8, 115.9, 124.8 and 123.2), two amide carbonyl groups (δC 155.6 and 153.7), two methyl carbon signals (δC 21.2 and 20.6), a ribityl group (δC 44.5, 67.7, 73.6, 70.6 and 72.0) and a glucopyranosyl group (δC 103.6, 73.6, 76.2, 69.8, 76.8 and 60.8). By the comparison of 13C NMR data of 2 with 6,7-dimethyl-1-Dribityl-quinoxaline-2,3(1H,4H)-dione [10], it showed that chemical shifts are striking resemblance except for the hydrogen and carbon signals of a glucopyranosyl group in 2. The connection position of the glucopyranosyl group was established unambiguously by a HMBC experiment in which long-range correlations between H-1″ of the glucopyranosyl group and C-5′ (Fig. 2). On the basis of the above data, 2 was elucidated as 6,7-dimethyl-1-D-ribityl-quinoxaline-2,3 (1H,4H)-dione-5′-O-β-D-glucopyranoside. Acknowledgements Our work was supported by the Major State Basic Research Development Program of China (973 Program 2006CB504708), the National Natural Science Foundation of China (Nos. 30371736 and 30672633) and Special Fund Project of National Excellent Doctoral Dissertation of China (200980). References [1] Jiangsu New Medical college. Zhong Yao Da Ci Dian, Vol. 2. Shanghai: Science and Technology Press; 1986. p. 1719–1722. [2] National Committee of Chinese Pharmacopoeia. Pharmacopoeia of P. R. China, Vol. 1. Beijing: Chemical Industry Press; 2005. p. 188. [3] Wang QH, Xiao HB, Yang BY, Yao FY, Kuang HX. Chin Exp Tradit Med Form 2008;14:48–50. [4] Wang QH, Xiao HB, Yang BY, Yao FY, Xia YG, Kuang HX. Chin Exp Tradit Med Form 2008;14:32–4. [5] Yang BY, Wang QH, Xia YG, Feng WS, Kuang HX. Helv Chim Acta 2007;90:1522–8. [6] Yang BY, Wang QH, Xia YG, Feng WS, Kuang HX. Helv Chim Acta 2008;91:964–71. [7] Kuang HX, Yang BY, Xia YG, Feng WS. Arch Pharm Res 2008;31:1094–7. [8] Kuang HX, Yang BY, Tang L, Xia YG, Dou DQ. Helv Chim Acta 2009;92: 1315–23. [9] Yang BY, Tang L, Tai CM, Liu YJ, Kuang HX. Chin Tradit Herbal Drugs 2006;37:1147–9. [10] Wu J, Tu PF, Zhao YY. Chin Tradit Herbal Drugs 2005;36:965–8.
Fig. 2. Key 1H–1H COSY and HMBC correlations of compounds 1 and 2.