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Canthin-6-one alkaloids from Brucea mollis var. Tonkinensis
Pergamon
CANTHIN-6-ONE
0031~9422(!M)EO177-T
ALKALOIDS
Phytahemimy. Vol. 36. No. 6. pp. 1543 1546, 1994 Copyright Q 1% Elwier Scmce Ltd Pmtcd in Grat Britun. All nghts merved rml-9422/w f7.00 + 0.00
FROM BRUCEA MOLLZS VAR. TONKZNENSZS
YISHANOUYANG, KAZUO KOIKE and TAICHI OHMOTO+
School of Pharmaceutical Sciences, Toho University, 2-2-l Miyama, Funabashi, Chiba 274, Japan (Received 22 December 1993) Key Word Index-Brucea
mollis var. tonkinensis; Simaroubaceae; root-wood; canthin-Cone
alkaloids.
Abstract-Three new alkaloids were isolated from the root-wood of Brucea mollis var. tonkinensis collected in China. Their structures were determined to be 1 ~-O-~-D-g~ucopyranosyl-(l-+6)-~-Dglucopyranosylcanthin-6-one, 5-0+-Dglucopyranosyl-(l+6)-~-D-ghtcopyranosylcanthin-6-one and 11-hydroxycanthin-6-one-N-oxide, by chemical and spectral methods. In addition, two known alkaloids, canthind-one and canthind-one-N-oxide, were isolated.
INTRODUClTON
Brucea mollis var. tonkinensis (Chinese name, Dao guo ya dan zi) [ 11, an important drug in Chinese folk medicine in south China, is used as a remedy for malaria and other parasitic diseases. However, until now, little was known about its chemical constituents. Many quassinoids and several alkaloids from species of the same genus, B. antidysenterica and B. jauanica, have been characterized and pharmacological studies on their substances have indicated antimalarial, antiamoebic, antibacterial, antineoplastiq antitumour and antileukaemic activities [2]. In our research on the biologically active substances of B. mollis var. tonkinensis, we found three new alkaloids, bruceollines A (l), B (2) and l l-hydroxycanthin-6-one-Noxide (3), along with two known canthin-6-one alkaloids, 4 and 5. In this paper, we describe the isolation and structural elucidation of these compounds. RESULTS AND DI!SCUSION
Compound 1 was obtained as a pale-yellow amorphous powder, [a]n -62.2” (pyridine), showed a positive Dragendorff test and a peak due to a [M + H]+ ion at m/z 561 in the positive FAB mass spectrum, and in combination with the 1% NMR, suggested a molecular formula of CZ~HZBN,O,~. The IR spectrum showed absorption bands due to a lactam (1668 cm- *) and an aromatic ring (1636 and 1559 cm- I). The UV behaviour was similar to that of canthin-6-one alkaloids [3], which suggested that 1 had a canthin-6-one skeleton. Since no bathochromic shift was observed on addition of base, it was supposed that 1 had no free phenolic hydroxyl group. The ‘H NMR spectrum (Table 1) showed the characteristic doublets of protons H-4 at 68.10 and H-5 at 66.95 with coupling constants J=9.8 Hz, a pair of vicinal protons H-l at 68.32 and H-2 at 68.80 with J=4.9 Hz, three adjacent
*Author to whom correspondence
should lx addressed.
1: R&t,
r+po$&
2: R,&;
M
3: boti 5: R-H
4: R,=RpH B: R,IH;RpoH 7: R,-c+l;
i+tl
protonsat68.18(1H,d, J=7.9Hz),7.71 (lH, t, J=7.9Hz) and 7.47 (lH, d, J=7.9 Hz), corresponding to the aromatic protons of an 8- or 1l-substituted indolic part, and two anomeric protons at 64.26 (lH, d, J=7.9 Hz) and 5.20 (lH, d, J = 7.9 Hz). The ’ %I NMR spectrum (Table 2) of 1 showed two anomeric carbons at 6100.5 and 103.0. Acid hydrolysis gave l l-hydroxycanthin-6-one (6) and Dglucose; the former alkaloid was obtained earlier in our laboratory as an isolate from Eurycoma longifolia [4]. ‘H-‘H COSY and ‘H-13C HETCOR indicated the presence of two glucopyranosyl moieties. The glywsidic linkage of two glucose moieties was determined from the 13C NMR spectrum which showed a downfield shift of ca 8 ppm at C-6 of the inner ghrcose through a glycosylation shift. The above data suggested that 1 had a glucopyranosyl-(l-r6)-glucopyranosyl residue that was located at C-l 1 of a canthind-one moiety. This was supported by the fragment ion peaks at m/z 399 and 231, which were ascribable to fragments due to the successive losses of terminal glucose and glucosyl-glucosyl residue, respectively, in the positive FAB-mass spectrum. The configurations of the anomeric positions of two glucose moieties were each assigned fi from the coupling constants of the anomeric protons at 64.26 (J = 7.9 Hz) and
1543
1546
Y.
OUYANG et al.
N-oxide (3, I4 mg). Fr. 6 was chromatographed on a silica gel column and eluted with CHCl,-MeOH (9:l). The Dragendorff-positive fr. was repeatedly chromatographed by CPC (4 mm silica gel plate, solvent system CH,Clz, flow rate 3.5 ml min- ‘) to give canthin-&one (4, 60 mg). Fr. 7 was chromatographed on a silica gel column and eluted with CHCl,-MeOH (49: 1). The Dragendorffpositive fr. 7 was repeatedly chromatographed by CPC (4 mm silica gel plate, solvent system CHCI,, Bow rate 3.5 ml min - ‘) to give canthin-&one-N-oxide (5, 60 mg). Brucedbie A (i f -O-p-D-gIucopy~anosyl~! +6)-p-Dglucopyranosylcanthin-6-one) (1). Pale yellow amorphous
powder (MeOH), mp 241-243” (dec.). [ali - 62.2” (pyridine; c 1.O).UV J.fg’” nm (log E):250 (sh, 4.02). 267 (4.07), 312 (4.07). 355 (sh, 4.07), 370 (4.10), 376 (4.07); (MeOH + HCl) 250 (sh, 4.02), 267 (4.07), 312 (4.07), 355 (sh, 4.07) 370 (4. IO), 376 (4.07); (MeOH + NaOH) 250 (sh, 4.02), 267 (4.07), 312 (4.07), 355 (sh, 4.07). 370 (4.!0), 376 (4.07). IR v:z cm-‘: 34!O,!669,!636,!559,154O,!498,!44!, 1271, 1073. Positive FAB-MS m/z: 561 [M +H]+, 399 [M +H -Glc] +, 309,279, 263, 237 [M + H - 2 x Glc] +. EI-MS m/z (rel. int.): 236 ([M - 2 x Glc] +, !oO), 208 (60), 179 (!8), 153 (9). ‘H NMR, Table 1. 13C NMR, Table 2. Acid hydrolysis of bruceolline A (1). Bruceolline A (1, 10 mg) was heated in MeOH with 1 M HCI (2 ml) for 4.5 hr. After the MeOH was removed, the ppts were filtered ofI and washed with Hz0 to give the aglycone 6. The filtrate was extracted with EtOAc (2 ml x 3), neutralized with ion-exchange resin (Amberlite MB-3) and evapd under red. pres. The residue was treated with N-trimethylsilylimid~ole at 90” for 1 hr and Hz0 added to the reaction mixt. to decompose the excess reagent; the reaction product was extracted with hexane (1 ml x 3). The hexane soln was subjected to GC whereby the TMSi derivative was identified as a derivative of vkfi cm-‘: 1245, 1217, 1167, 1144, 1127, EI-MS m/z (rel. Table 2. Aglycone (mmp, UV, IR, ‘H [solvent
3422,1684,1645,1607,1584,1558,1440,1337,!292,!268, 1225, 1197, 1129, 1079, 1066. EI-MS m/z (rel. int.): 236 ([Ml’, 100),208(4), 180(45), 153(16). ‘H NMR,Table 1. Aglycone 7 was identified by direct comparison (mmp, UV, IR, ‘H NMR, MS and co-TLC [solvent system, CHCl,-MeOH, 5: 11) with authentic 5-hydroxycanthin6-one [5]. 1l-~ydroxycanrhjn-6-ore-N-oxide (3). Yellow crystals, needles, mp>300”. UV ,lz:z” nm (log E): 276 (4.27), 342 (3.95), 356 (3.94), 416 (3.89); (MeOH + HCI) 276 (4.27). 342 (4.03), 356 (3.94) 416 (3.91); (MeOH+NaOH) 273 (4.22), 302 (3.81) 342 (sh, 3.84), 354 (3.89). 430 (3.68), 490 (3.68). IR v;t: cn-‘: 3428, 2923, 1683, 1652, 1446, 1399, 1304, 1261, 1213, 1135, 1111, 1032. EI-MS m/z (rel. int.): 252 ([Ml+, !00),236(56),224(12),208(4!), 196(!4), 179(24), 169 (15). HR-MS m/z 252.0520 CM]‘, calcd for Ci,HsNzO,; 252.0533. ‘H NMR, Table 1. 13CNMR, Table 2. Conuersion hydrox~~canrhin-6-ode-N-oxide (3). A mixt. l-hydroxycanthind-one acid (10 mg) in CHCl,-MeOH room temp. soln was washed with soln. Yellow crystals were in the organic which was filtered with to 3 (3 mg) as yellow needles. (4). Yellow needles, 155- 156”. cm’: 1665, 1630, 1430, 1325, !300,!!35. EI-MS m/z (rel. (51), 164 139 (6),95 (5). This compound (mmp, UV, IR, ‘HNMR, MS and co-TLC [solvent with authentic canthin-6one Canthin-6-one-N-oxide (7). Yellow needles, mp 244-245” (dec.). IR v$$ cm-‘: 1670, 1645, 1575, 1430, 1400, 1330, 1230, 1135. EI-MS (rel. int.): 236 (!OO),220(27), (lo), 192 (28). (11). compound (mmp, UV, IR, ‘H MS and co-TLC [solvent MeOH, 10: I]) authentic canthin-6-one-~-oxide
MS and co-TLC with authentic
(4). Bruceolline
REFEREIWXS
Institute of (1974) in Hain3, p. Science Publishing Beijing. 2. M., Fukamiya, and Lee, (1990) in in Naturai Chemistry. (Rahman, ed.), Vol. p. 369. Amsterdam. 3. T., Tanaka, and Nikaido, (1976) Chem. 1.
anco
8),
Bull. 24, 4. Mitsunaga, K., Koike, K., Tanaka, Acid hydrolysis
B (2).
the same of acid used for bruceolline A, bruceolline B (IOmg) was hydrolysed to aglycone 7 and D-g!umSe. Aglycone 7. yellow needles, mp> 300”. IR vi:; cm-i:
T., Ohkawa, Y., Kobayashi, Y., Sawaguchi, T. and Ohmoto, T. (1994)
Phytochemistry 35, 799. 5. Ohmoto, T. and Koike, K. (1985) Chem. Pharm. Bulf.
33, 3847.
CANTHIN-6-ONE
0031~9422(!M)EO177-T
ALKALOIDS
Phytahemimy. Vol. 36. No. 6. pp. 1543 1546, 1994 Copyright Q 1% Elwier Scmce Ltd Pmtcd in Grat Britun. All nghts merved rml-9422/w f7.00 + 0.00
FROM BRUCEA MOLLZS VAR. TONKZNENSZS
YISHANOUYANG, KAZUO KOIKE and TAICHI OHMOTO+
School of Pharmaceutical Sciences, Toho University, 2-2-l Miyama, Funabashi, Chiba 274, Japan (Received 22 December 1993) Key Word Index-Brucea
mollis var. tonkinensis; Simaroubaceae; root-wood; canthin-Cone
alkaloids.
Abstract-Three new alkaloids were isolated from the root-wood of Brucea mollis var. tonkinensis collected in China. Their structures were determined to be 1 ~-O-~-D-g~ucopyranosyl-(l-+6)-~-Dglucopyranosylcanthin-6-one, 5-0+-Dglucopyranosyl-(l+6)-~-D-ghtcopyranosylcanthin-6-one and 11-hydroxycanthin-6-one-N-oxide, by chemical and spectral methods. In addition, two known alkaloids, canthind-one and canthind-one-N-oxide, were isolated.
INTRODUClTON
Brucea mollis var. tonkinensis (Chinese name, Dao guo ya dan zi) [ 11, an important drug in Chinese folk medicine in south China, is used as a remedy for malaria and other parasitic diseases. However, until now, little was known about its chemical constituents. Many quassinoids and several alkaloids from species of the same genus, B. antidysenterica and B. jauanica, have been characterized and pharmacological studies on their substances have indicated antimalarial, antiamoebic, antibacterial, antineoplastiq antitumour and antileukaemic activities [2]. In our research on the biologically active substances of B. mollis var. tonkinensis, we found three new alkaloids, bruceollines A (l), B (2) and l l-hydroxycanthin-6-one-Noxide (3), along with two known canthin-6-one alkaloids, 4 and 5. In this paper, we describe the isolation and structural elucidation of these compounds. RESULTS AND DI!SCUSION
Compound 1 was obtained as a pale-yellow amorphous powder, [a]n -62.2” (pyridine), showed a positive Dragendorff test and a peak due to a [M + H]+ ion at m/z 561 in the positive FAB mass spectrum, and in combination with the 1% NMR, suggested a molecular formula of CZ~HZBN,O,~. The IR spectrum showed absorption bands due to a lactam (1668 cm- *) and an aromatic ring (1636 and 1559 cm- I). The UV behaviour was similar to that of canthin-6-one alkaloids [3], which suggested that 1 had a canthin-6-one skeleton. Since no bathochromic shift was observed on addition of base, it was supposed that 1 had no free phenolic hydroxyl group. The ‘H NMR spectrum (Table 1) showed the characteristic doublets of protons H-4 at 68.10 and H-5 at 66.95 with coupling constants J=9.8 Hz, a pair of vicinal protons H-l at 68.32 and H-2 at 68.80 with J=4.9 Hz, three adjacent
*Author to whom correspondence
should lx addressed.
1: R&t,
r+po$&
2: R,&;
M
3: boti 5: R-H
4: R,=RpH B: R,IH;RpoH 7: R,-c+l;
i+tl
protonsat68.18(1H,d, J=7.9Hz),7.71 (lH, t, J=7.9Hz) and 7.47 (lH, d, J=7.9 Hz), corresponding to the aromatic protons of an 8- or 1l-substituted indolic part, and two anomeric protons at 64.26 (lH, d, J=7.9 Hz) and 5.20 (lH, d, J = 7.9 Hz). The ’ %I NMR spectrum (Table 2) of 1 showed two anomeric carbons at 6100.5 and 103.0. Acid hydrolysis gave l l-hydroxycanthin-6-one (6) and Dglucose; the former alkaloid was obtained earlier in our laboratory as an isolate from Eurycoma longifolia [4]. ‘H-‘H COSY and ‘H-13C HETCOR indicated the presence of two glucopyranosyl moieties. The glywsidic linkage of two glucose moieties was determined from the 13C NMR spectrum which showed a downfield shift of ca 8 ppm at C-6 of the inner ghrcose through a glycosylation shift. The above data suggested that 1 had a glucopyranosyl-(l-r6)-glucopyranosyl residue that was located at C-l 1 of a canthind-one moiety. This was supported by the fragment ion peaks at m/z 399 and 231, which were ascribable to fragments due to the successive losses of terminal glucose and glucosyl-glucosyl residue, respectively, in the positive FAB-mass spectrum. The configurations of the anomeric positions of two glucose moieties were each assigned fi from the coupling constants of the anomeric protons at 64.26 (J = 7.9 Hz) and
1543
1546
Y.
OUYANG et al.
N-oxide (3, I4 mg). Fr. 6 was chromatographed on a silica gel column and eluted with CHCl,-MeOH (9:l). The Dragendorff-positive fr. was repeatedly chromatographed by CPC (4 mm silica gel plate, solvent system CH,Clz, flow rate 3.5 ml min- ‘) to give canthin-&one (4, 60 mg). Fr. 7 was chromatographed on a silica gel column and eluted with CHCl,-MeOH (49: 1). The Dragendorffpositive fr. 7 was repeatedly chromatographed by CPC (4 mm silica gel plate, solvent system CHCI,, Bow rate 3.5 ml min - ‘) to give canthin-&one-N-oxide (5, 60 mg). Brucedbie A (i f -O-p-D-gIucopy~anosyl~! +6)-p-Dglucopyranosylcanthin-6-one) (1). Pale yellow amorphous
powder (MeOH), mp 241-243” (dec.). [ali - 62.2” (pyridine; c 1.O).UV J.fg’” nm (log E):250 (sh, 4.02). 267 (4.07), 312 (4.07). 355 (sh, 4.07), 370 (4.10), 376 (4.07); (MeOH + HCl) 250 (sh, 4.02), 267 (4.07), 312 (4.07), 355 (sh, 4.07) 370 (4. IO), 376 (4.07); (MeOH + NaOH) 250 (sh, 4.02), 267 (4.07), 312 (4.07), 355 (sh, 4.07). 370 (4.!0), 376 (4.07). IR v:z cm-‘: 34!O,!669,!636,!559,154O,!498,!44!, 1271, 1073. Positive FAB-MS m/z: 561 [M +H]+, 399 [M +H -Glc] +, 309,279, 263, 237 [M + H - 2 x Glc] +. EI-MS m/z (rel. int.): 236 ([M - 2 x Glc] +, !oO), 208 (60), 179 (!8), 153 (9). ‘H NMR, Table 1. 13C NMR, Table 2. Acid hydrolysis of bruceolline A (1). Bruceolline A (1, 10 mg) was heated in MeOH with 1 M HCI (2 ml) for 4.5 hr. After the MeOH was removed, the ppts were filtered ofI and washed with Hz0 to give the aglycone 6. The filtrate was extracted with EtOAc (2 ml x 3), neutralized with ion-exchange resin (Amberlite MB-3) and evapd under red. pres. The residue was treated with N-trimethylsilylimid~ole at 90” for 1 hr and Hz0 added to the reaction mixt. to decompose the excess reagent; the reaction product was extracted with hexane (1 ml x 3). The hexane soln was subjected to GC whereby the TMSi derivative was identified as a derivative of vkfi cm-‘: 1245, 1217, 1167, 1144, 1127, EI-MS m/z (rel. Table 2. Aglycone (mmp, UV, IR, ‘H [solvent
3422,1684,1645,1607,1584,1558,1440,1337,!292,!268, 1225, 1197, 1129, 1079, 1066. EI-MS m/z (rel. int.): 236 ([Ml’, 100),208(4), 180(45), 153(16). ‘H NMR,Table 1. Aglycone 7 was identified by direct comparison (mmp, UV, IR, ‘H NMR, MS and co-TLC [solvent system, CHCl,-MeOH, 5: 11) with authentic 5-hydroxycanthin6-one [5]. 1l-~ydroxycanrhjn-6-ore-N-oxide (3). Yellow crystals, needles, mp>300”. UV ,lz:z” nm (log E): 276 (4.27), 342 (3.95), 356 (3.94), 416 (3.89); (MeOH + HCI) 276 (4.27). 342 (4.03), 356 (3.94) 416 (3.91); (MeOH+NaOH) 273 (4.22), 302 (3.81) 342 (sh, 3.84), 354 (3.89). 430 (3.68), 490 (3.68). IR v;t: cn-‘: 3428, 2923, 1683, 1652, 1446, 1399, 1304, 1261, 1213, 1135, 1111, 1032. EI-MS m/z (rel. int.): 252 ([Ml+, !00),236(56),224(12),208(4!), 196(!4), 179(24), 169 (15). HR-MS m/z 252.0520 CM]‘, calcd for Ci,HsNzO,; 252.0533. ‘H NMR, Table 1. 13CNMR, Table 2. Conuersion hydrox~~canrhin-6-ode-N-oxide (3). A mixt. l-hydroxycanthind-one acid (10 mg) in CHCl,-MeOH room temp. soln was washed with soln. Yellow crystals were in the organic which was filtered with to 3 (3 mg) as yellow needles. (4). Yellow needles, 155- 156”. cm’: 1665, 1630, 1430, 1325, !300,!!35. EI-MS m/z (rel. (51), 164 139 (6),95 (5). This compound (mmp, UV, IR, ‘HNMR, MS and co-TLC [solvent with authentic canthin-6one Canthin-6-one-N-oxide (7). Yellow needles, mp 244-245” (dec.). IR v$$ cm-‘: 1670, 1645, 1575, 1430, 1400, 1330, 1230, 1135. EI-MS (rel. int.): 236 (!OO),220(27), (lo), 192 (28). (11). compound (mmp, UV, IR, ‘H MS and co-TLC [solvent MeOH, 10: I]) authentic canthin-6-one-~-oxide
MS and co-TLC with authentic
(4). Bruceolline
REFEREIWXS
Institute of (1974) in Hain3, p. Science Publishing Beijing. 2. M., Fukamiya, and Lee, (1990) in in Naturai Chemistry. (Rahman, ed.), Vol. p. 369. Amsterdam. 3. T., Tanaka, and Nikaido, (1976) Chem. 1.
anco
8),
Bull. 24, 4. Mitsunaga, K., Koike, K., Tanaka, Acid hydrolysis
B (2).
the same of acid used for bruceolline A, bruceolline B (IOmg) was hydrolysed to aglycone 7 and D-g!umSe. Aglycone 7. yellow needles, mp> 300”. IR vi:; cm-i:
T., Ohkawa, Y., Kobayashi, Y., Sawaguchi, T. and Ohmoto, T. (1994)
Phytochemistry 35, 799. 5. Ohmoto, T. and Koike, K. (1985) Chem. Pharm. Bulf.
33, 3847.