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Alkaloids from Melodinus suaveolens
Phyrochemistry. Vol. 30, No. 9. pp. 3168 3170, 1991 Printed in Great Britain.
ALKALOIDS JIAN Shanghai
Institute
of Materia
HUA
003 I -9422/91 53.00 + 0.00 Ic;: 1991 Pergamon Press plc
FROM MELODINUS
YE, Yu!+Lr
Medica,
Academia
ZHOU, ZHI HENG HUANG and FRAWOISE Sinica. 319 Yue-Yang
Substances Naturelles (Rewired Key
Word
Index--Me/odinus
SUAVEOLENS
du C.N.R.S..
Road, Shanghai, 200031,
91198, Gif-sur-Yvette.
in revised firm
.suat~o/ens; Apocynaccae;
PICOT*
7 January trunk;
China; *Institut
de Chimie des
France
1991)
indole
alkaloids;
suaveoleninc;
NMR;
mass
spectrometry.
Abstract-Fourteen alkaloids were isolated from the trunk of Melodinus suaveohs. Thirteen of them were identified as A14-vincine, vindolinine, 1 I-methoxytabersonine, vincadifformine, hazuntine, 1I-hydroxytabersonine, 1 l-methoxyvincadifl’ormine, cathovalinine, vincoline. 19R-hydroxytabersonine, 1 I-methoxy-19R_hydroxytabersonine, 11,19R-dihydroxytabersonine and tabersonine. The last one is a new alkaloid, named suaveolenine; its structural elucidation was achieved by means of detailed spectral analysis.
INTRODUCTION
Melodinus suaveolens is used in Chinese folk medicine for the treatment of hernia, infantile malnutrition, dyspepsia and testitis [l]. About 30 years ago, the crude alkaloid mixture was found to exhibit antibiotic properties [2], but no detailed reports of its chemical composition have appeared so far. RESULTS AND DlSCUSSlON
The crude alkaloid mixture obtained from the ethanol extract of the trunk of Melodinus suaveolens was subjected to pH fractionation followed by repeated column chromatography and preparative TLC over silica gel. Thirteen alkaloids were isolated and identified as A14vincine (I), vindolinine (2), 1 I-methoxytabersonine (3), vincadifformine (4), hazuntine (S), I 1-hydroxytabersonine (6). 11-methoxyvincadifformine (7), cathovalinine (8), vincoline (9), 19R-hydroxytabersonine (IO), 1l-methoxy19R-hydroxytabersonine (ll), 11,19R-dihydroxytabersonine (12) and tabersonine (13). A new alkaloid, named suaveolenine, was also isolated and its structure was established as follows. The HR mass spectrum of suaveolenine 14 showed [M’] appeared at m/z 366.1587 which was consistent with the molecular formula Cz,HZ2Nz04; this showed the presence of 12 double bond equivalents. The UV spectrum sho’wing absorptions at 226 (loge 4.56), 288 (log& 3.98) and 295 nm (logt; 3.92) typical of an indolic chromophore [3]. The IR spectrum showed absorption bands at 1740 (ester GO), 1690 (amidic GO) and 1055 cm - ’ (C-O-C). The failure of attempted acetylation and methylation supported the presence of an oxygen atom as an ether linkage. From biogenetic considerations combined with spectroscopic data, the structure 14 was proposed for suaveolenine. This seems plausible since it only differs from vincoline by the lack of a hydroxy group and a C-7/C-21 bond instead of an amidic carbonyl. The ‘H NMR spectrum exhibited 1 H signals at 67.45, 7.28, 7.15 and 7.05,
which were assigned to the aromatic protons at C-9, C-10, C-l I and C-12, respectively. Methoxy protons appeared at b3.70 (3H, s) and a NH proton at 68.37 (s). The C-18 methyl protons showed a doublet at 61.62 (3H, d, J = 6.9 Hz), the C-19 proton was observed as a split quartet at 64.32 (1 H, q, J = 6.7 Hz) and a pair of non-equivalent methylene protons showing a doublet at 6 2.28 (1 H, d, J = 13.5) and 63.56 (1 H, d, J = 13.5 Hz) was assigned to the C-5 protons. The low field two protons of C-3 were observedat~3.82(1H,dd,J=5.5,17.4Hz)and64.17(1H, hr d, J = 17.3 HL). The C-14/C-l 5 olefinic protons were observed at 65.91 and 6.06. Further support for structure 14 was provided by DEPT “C NMR experiments. These indicated the presence of seven methine, four methylene, one methyl and eight quaternary carbon atoms in addition to an ester group (Table 1). This is the first time that a structure with a lactam ring and an additional five-membered ring containing an oxygen atom has been found. The stereochemical structure of 14 has been verified by X-ray crystal structural analysis (Fig. 1).
3168
Table
I.
“CNMR
spectral data of compound c
C 2
135.99
13
133.19
3
51.62
14
127.65
5
48.49
15
127.28
6
24.21
16
81.33
7
111.78
17
40.15
8
128.35
18
14.12
9
122.92
19
82.20
IO
118.43
20
54.07
I1
119.39
21
172.27
12
I 1 I .26
(70,Me
174.2
I
14
3169
Short Reports
13 3 6 11 12 10
R’ H Me0 OH Me0 OH H
R’ H H H OH OH OH
CO*Me
CO,Me
COTMe R’
R2
R’
R4
H H
Me0 H Me0
H H H
‘0’ H
H
/O\
Fig. 1. Structure of alkaloid 14 as deduced from X-ray analysis. EXPERIMENTAL
General. Mps: uncorr. IR spectra were recorded in KBr and UV spectra in MeOH. NMR were recorded in CDCl, using CHCl, and TMS as refs. Pht material. The whole trunk of M. sunceolens Champ. ex Benth. was collected at Shan Yai of Hainan Province, China and identified by Prof. Y. Zhong (Hainan Teacher’s College) where a voucher specimen is deposited. Extraction and isolation. Air-dried, whole trunk was extracted with EtOH; after cOncn under red. pres., a gummy material was obtained which was then dissolved in 5% citric acid, filtered and the soln adjusted to pH 7 and 9 with NH,OH and then extd with CHCI, repeatedly. The CHCI, solns were dried and filtered, then distilled under red. pres. to dryness. Two crude alkaloidal frs I and II were obtained. Fr. I was subjected to CC on silica gel,
9
H OH Et,O, CHCI, and MeOH being used as eluents. According to TLC behaviour, 4 main frs were collected. Fr. 1 eluted with Et,0 was further purified by prep. TLC (silica gel GF254, cyclohexane-EtOAc, 7:s) to give 1I-methoxy tabersonine (3) [4], vincadifformine (4) [S], hazuntine (5) [4] and Il-hydroxytabersonine (6) [4] which were identified separately by comparison with authentic samples. Fr. 2 eluted with Et,0 was subjected to further CC on silica gel. Frs 1 and 2 were obtained by successive elution with petrol-Et,0 (1: 1). After further sepn by prep. TLC, II-methoxyvincadifformine 7 [6] and 19Rhydroxytabersonine 10 [7] were obtained from fr. 1. llMethoxy-19R-hydroxy tabersonine (11) and 11,19Rdihydroxy tabersonine (12) were obtained from fr. 2. They were all identified by comparison with authentic samples. Fr. 3 eluted with CHCl,-MeOH (99: 1) was subjected to further CC on silica gel. Cathovalinine (8) and vincoline (9) were obtained by successive elution with CH,CI,-Me&O (9: 1) and CH,CI,-MeOH (4: 1). They were identified by comparison of the mps, UV, IR, MS and NMR with the lit. [8,9]. Fr. 4 eluted by CHCl,-MeOH (19: 1) gave vindolinine (2) identified by comparison with an authentic sample [4]. The mother liquors were subjected to further CC on silica gel. Fr. 1 eluted with CHICI, was purified by prep. TLC (cyclohexane_EtOAc, 7: 5). Alkaloid 13 was obtained and identified as tabersonine 13 [7] by comparison with an authentic sample. Fr. 2 eluted with CHJl,-MeOH (4: 1) provided the new alkaloid 14, mp 205”. UV I,,, nm: (loge) 226 (4.56), 288 (3.98). 295 (3.92). IR #a’ cm- ‘: 3380,1740,1690,1055. MS(EI)m/z 366, 307,292,279,263,250,227,225,216,214,206,195,188,186,170, 167, 156, 144, 136, 122, 108. ‘HNMR (CD&) 61.62 (3H, d, J =6.5 Hz), 62.28 (lH, d, J= 13.4 Hz), 63.05-3.20 (3H, m), 63.56 (lH, d, J= 13.6 Hz), S3.70 (3H, s), 63.82 (lH, dd, J= 17.6 Hz), 64.17 (lH, br d, J= 17.3 Hz), 64.32 (lH, q, J=6.5 Hz), 4.31 (lH, m), 65.90 (lH, dd, 5=3.2, 9.3 Hz), 66.06 (lH, qd, 5=1.2, 5.5, 9.3 Hz), 67.05 (lH, t, J=7.3 Hz), 67.15 (lH, 1, J=7.3 Hz), 7.28 (lH, d, 5=8.0 Hz), 67.45 (lH, d, J=8.2 Hz), 68.37 (lH, s). “CNMR see Table 1.
Short
3170
REFERENCES 1. Delectis Florae Republicae Popularis Sinicae Agendae Academiae sinicae Edita (1977) Flora Repuhlicae Popularis Sinicae Vol. 63. p. 22. 2. Au, K. S. and Gray, D. E. (1969) Biochemical Pharmacology 18, 2673. 3. Kompis, 1. and Mokry, J. (1968) Coil. Czech. Chem. Commun. 33, 4328. 4. Zhou, Y. L., Ye. J. H.. Li, Z. M. and Huang, Z. H. (1988) Planra Med. 54. 3 15.
Reports
5. Plat, M., Le Men, J., Janot, M. M., Budzikeewicz, H., Wilson, J. M., Durham, L. J. and Djerassi, C. (1962) Bull. Sot. Chim. Fr. 2237. 6. Dopke, M. (1968) Phurmuzie 23, 521. 7. Rabaron, A., Mehri, M. H., Sevenet, T. and Plat, M. M. (I 978) Phytochemistry 17. 1452. 8. Chiaroni, A., Riche. C., Diatta, L., Andriamialisoa, R. Z., Langlois, N. and Pofier. P. (1976) Terrahedron 32, 1988. 9. Aynilian, G. H., Weiss, S. G., Cordell, G. A., Abraham, D. J.. Crane, F. A. and Farnsworth, N. R. (1974) J. Phorm. Sci. 63. 536.
ALKALOIDS JIAN Shanghai
Institute
of Materia
HUA
003 I -9422/91 53.00 + 0.00 Ic;: 1991 Pergamon Press plc
FROM MELODINUS
YE, Yu!+Lr
Medica,
Academia
ZHOU, ZHI HENG HUANG and FRAWOISE Sinica. 319 Yue-Yang
Substances Naturelles (Rewired Key
Word
Index--Me/odinus
SUAVEOLENS
du C.N.R.S..
Road, Shanghai, 200031,
91198, Gif-sur-Yvette.
in revised firm
.suat~o/ens; Apocynaccae;
PICOT*
7 January trunk;
China; *Institut
de Chimie des
France
1991)
indole
alkaloids;
suaveoleninc;
NMR;
mass
spectrometry.
Abstract-Fourteen alkaloids were isolated from the trunk of Melodinus suaveohs. Thirteen of them were identified as A14-vincine, vindolinine, 1 I-methoxytabersonine, vincadifformine, hazuntine, 1I-hydroxytabersonine, 1 l-methoxyvincadifl’ormine, cathovalinine, vincoline. 19R-hydroxytabersonine, 1 I-methoxy-19R_hydroxytabersonine, 11,19R-dihydroxytabersonine and tabersonine. The last one is a new alkaloid, named suaveolenine; its structural elucidation was achieved by means of detailed spectral analysis.
INTRODUCTION
Melodinus suaveolens is used in Chinese folk medicine for the treatment of hernia, infantile malnutrition, dyspepsia and testitis [l]. About 30 years ago, the crude alkaloid mixture was found to exhibit antibiotic properties [2], but no detailed reports of its chemical composition have appeared so far. RESULTS AND DlSCUSSlON
The crude alkaloid mixture obtained from the ethanol extract of the trunk of Melodinus suaveolens was subjected to pH fractionation followed by repeated column chromatography and preparative TLC over silica gel. Thirteen alkaloids were isolated and identified as A14vincine (I), vindolinine (2), 1 I-methoxytabersonine (3), vincadifformine (4), hazuntine (S), I 1-hydroxytabersonine (6). 11-methoxyvincadifformine (7), cathovalinine (8), vincoline (9), 19R-hydroxytabersonine (IO), 1l-methoxy19R-hydroxytabersonine (ll), 11,19R-dihydroxytabersonine (12) and tabersonine (13). A new alkaloid, named suaveolenine, was also isolated and its structure was established as follows. The HR mass spectrum of suaveolenine 14 showed [M’] appeared at m/z 366.1587 which was consistent with the molecular formula Cz,HZ2Nz04; this showed the presence of 12 double bond equivalents. The UV spectrum sho’wing absorptions at 226 (loge 4.56), 288 (log& 3.98) and 295 nm (logt; 3.92) typical of an indolic chromophore [3]. The IR spectrum showed absorption bands at 1740 (ester GO), 1690 (amidic GO) and 1055 cm - ’ (C-O-C). The failure of attempted acetylation and methylation supported the presence of an oxygen atom as an ether linkage. From biogenetic considerations combined with spectroscopic data, the structure 14 was proposed for suaveolenine. This seems plausible since it only differs from vincoline by the lack of a hydroxy group and a C-7/C-21 bond instead of an amidic carbonyl. The ‘H NMR spectrum exhibited 1 H signals at 67.45, 7.28, 7.15 and 7.05,
which were assigned to the aromatic protons at C-9, C-10, C-l I and C-12, respectively. Methoxy protons appeared at b3.70 (3H, s) and a NH proton at 68.37 (s). The C-18 methyl protons showed a doublet at 61.62 (3H, d, J = 6.9 Hz), the C-19 proton was observed as a split quartet at 64.32 (1 H, q, J = 6.7 Hz) and a pair of non-equivalent methylene protons showing a doublet at 6 2.28 (1 H, d, J = 13.5) and 63.56 (1 H, d, J = 13.5 Hz) was assigned to the C-5 protons. The low field two protons of C-3 were observedat~3.82(1H,dd,J=5.5,17.4Hz)and64.17(1H, hr d, J = 17.3 HL). The C-14/C-l 5 olefinic protons were observed at 65.91 and 6.06. Further support for structure 14 was provided by DEPT “C NMR experiments. These indicated the presence of seven methine, four methylene, one methyl and eight quaternary carbon atoms in addition to an ester group (Table 1). This is the first time that a structure with a lactam ring and an additional five-membered ring containing an oxygen atom has been found. The stereochemical structure of 14 has been verified by X-ray crystal structural analysis (Fig. 1).
3168
Table
I.
“CNMR
spectral data of compound c
C 2
135.99
13
133.19
3
51.62
14
127.65
5
48.49
15
127.28
6
24.21
16
81.33
7
111.78
17
40.15
8
128.35
18
14.12
9
122.92
19
82.20
IO
118.43
20
54.07
I1
119.39
21
172.27
12
I 1 I .26
(70,Me
174.2
I
14
3169
Short Reports
13 3 6 11 12 10
R’ H Me0 OH Me0 OH H
R’ H H H OH OH OH
CO*Me
CO,Me
COTMe R’
R2
R’
R4
H H
Me0 H Me0
H H H
‘0’ H
H
/O\
Fig. 1. Structure of alkaloid 14 as deduced from X-ray analysis. EXPERIMENTAL
General. Mps: uncorr. IR spectra were recorded in KBr and UV spectra in MeOH. NMR were recorded in CDCl, using CHCl, and TMS as refs. Pht material. The whole trunk of M. sunceolens Champ. ex Benth. was collected at Shan Yai of Hainan Province, China and identified by Prof. Y. Zhong (Hainan Teacher’s College) where a voucher specimen is deposited. Extraction and isolation. Air-dried, whole trunk was extracted with EtOH; after cOncn under red. pres., a gummy material was obtained which was then dissolved in 5% citric acid, filtered and the soln adjusted to pH 7 and 9 with NH,OH and then extd with CHCI, repeatedly. The CHCI, solns were dried and filtered, then distilled under red. pres. to dryness. Two crude alkaloidal frs I and II were obtained. Fr. I was subjected to CC on silica gel,
9
H OH Et,O, CHCI, and MeOH being used as eluents. According to TLC behaviour, 4 main frs were collected. Fr. 1 eluted with Et,0 was further purified by prep. TLC (silica gel GF254, cyclohexane-EtOAc, 7:s) to give 1I-methoxy tabersonine (3) [4], vincadifformine (4) [S], hazuntine (5) [4] and Il-hydroxytabersonine (6) [4] which were identified separately by comparison with authentic samples. Fr. 2 eluted with Et,0 was subjected to further CC on silica gel. Frs 1 and 2 were obtained by successive elution with petrol-Et,0 (1: 1). After further sepn by prep. TLC, II-methoxyvincadifformine 7 [6] and 19Rhydroxytabersonine 10 [7] were obtained from fr. 1. llMethoxy-19R-hydroxy tabersonine (11) and 11,19Rdihydroxy tabersonine (12) were obtained from fr. 2. They were all identified by comparison with authentic samples. Fr. 3 eluted with CHCl,-MeOH (99: 1) was subjected to further CC on silica gel. Cathovalinine (8) and vincoline (9) were obtained by successive elution with CH,CI,-Me&O (9: 1) and CH,CI,-MeOH (4: 1). They were identified by comparison of the mps, UV, IR, MS and NMR with the lit. [8,9]. Fr. 4 eluted by CHCl,-MeOH (19: 1) gave vindolinine (2) identified by comparison with an authentic sample [4]. The mother liquors were subjected to further CC on silica gel. Fr. 1 eluted with CHICI, was purified by prep. TLC (cyclohexane_EtOAc, 7: 5). Alkaloid 13 was obtained and identified as tabersonine 13 [7] by comparison with an authentic sample. Fr. 2 eluted with CHJl,-MeOH (4: 1) provided the new alkaloid 14, mp 205”. UV I,,, nm: (loge) 226 (4.56), 288 (3.98). 295 (3.92). IR #a’ cm- ‘: 3380,1740,1690,1055. MS(EI)m/z 366, 307,292,279,263,250,227,225,216,214,206,195,188,186,170, 167, 156, 144, 136, 122, 108. ‘HNMR (CD&) 61.62 (3H, d, J =6.5 Hz), 62.28 (lH, d, J= 13.4 Hz), 63.05-3.20 (3H, m), 63.56 (lH, d, J= 13.6 Hz), S3.70 (3H, s), 63.82 (lH, dd, J= 17.6 Hz), 64.17 (lH, br d, J= 17.3 Hz), 64.32 (lH, q, J=6.5 Hz), 4.31 (lH, m), 65.90 (lH, dd, 5=3.2, 9.3 Hz), 66.06 (lH, qd, 5=1.2, 5.5, 9.3 Hz), 67.05 (lH, t, J=7.3 Hz), 67.15 (lH, 1, J=7.3 Hz), 7.28 (lH, d, 5=8.0 Hz), 67.45 (lH, d, J=8.2 Hz), 68.37 (lH, s). “CNMR see Table 1.
Short
3170
REFERENCES 1. Delectis Florae Republicae Popularis Sinicae Agendae Academiae sinicae Edita (1977) Flora Repuhlicae Popularis Sinicae Vol. 63. p. 22. 2. Au, K. S. and Gray, D. E. (1969) Biochemical Pharmacology 18, 2673. 3. Kompis, 1. and Mokry, J. (1968) Coil. Czech. Chem. Commun. 33, 4328. 4. Zhou, Y. L., Ye. J. H.. Li, Z. M. and Huang, Z. H. (1988) Planra Med. 54. 3 15.
Reports
5. Plat, M., Le Men, J., Janot, M. M., Budzikeewicz, H., Wilson, J. M., Durham, L. J. and Djerassi, C. (1962) Bull. Sot. Chim. Fr. 2237. 6. Dopke, M. (1968) Phurmuzie 23, 521. 7. Rabaron, A., Mehri, M. H., Sevenet, T. and Plat, M. M. (I 978) Phytochemistry 17. 1452. 8. Chiaroni, A., Riche. C., Diatta, L., Andriamialisoa, R. Z., Langlois, N. and Pofier. P. (1976) Terrahedron 32, 1988. 9. Aynilian, G. H., Weiss, S. G., Cordell, G. A., Abraham, D. J.. Crane, F. A. and Farnsworth, N. R. (1974) J. Phorm. Sci. 63. 536.