Chemical Components of the Whole Herb of Mosla dianthera
Chem. Pharm. Bull. 47( 1152—1153 (1999) Vol. 47, No. 8http://cpb.pharm.or.jp/cpb/199908/C08_1152.pdf
Yueh-Hsiung KUO* and Shu-Ling LIN
Department of Chemistry, National Taiwan University, Taipei, Taiwan, R.O.C.
Received February 17, 1999; accepted May 6, 1999
Abstract:Extracts of the whole herb of
Mosla dianthera were found to contain three new compounds, 4,5-dimethoxy-2,3-methylenedioxy-1-propenylbenzene, 4,5-dimethoxy-2,3-methylenedioxycinnamaldehyde, and 4,5-dimethoxy-2,3-methylenedioxybenzaldehyde together with eleven known compounds, fatty alcohols, 2,4,5-trimethoxybenzaldehyde, a mixture of
beta-sitosterol and stigmasterol, betulinic acid, oleanolic acid, ursolic acid, arjunolic acid,
beta-sitosteryl glucopyranoside, palmitic acid, myo-inositol, luteolin and rosmarinic acid.
Key words Mosla dianthera; Labiatae; 4,5-dimethoxy-2,3-methylenedioxy-1-propenylbenzene; 4,5-dimethoxy-2,3-methylenedioxycinnamaldehyde; 4,5-dimethoxy-2,3-methylenedioxybenzaldehyde
There are five species of Mosla genus (Labiatae) indigenous to Taiwan and all of them are herb plants; however, only
M. chinensis has had its chemical components investigated.
1)Probably because the species of Mosla genus are scarce, only one other species
M. soochowensis2) has been studied. The chemical components included flavones and their glycosides. One of the flavones, mosloflavone
1), showed analgesic and antiinflammation effects. This led us to study the chemical constituents of
M. dianthera Buch.-Ham. Maxim.
The whole herbs of
M. dianthera were extracted with methanol, and the extracts were suspended in water and then
partitioned with chloroform and n-butanol, successively. The chloroform soluble part was subjected to repeated chromatography on silica gel. Fourteen components were isolated, including three new dimethoxymethylenedioxyphenyl derivatives, 4,5-dimethoxy-2,3-methlenedioxy-1-propenylbenzene (
1), 4,5-dimethoxy-2,3-methylenedioxycinnamaldehyde (
2), and 4,5-dimethoxy-2,3-methylenedioxybenzaldehyde (
3), and eleven known compounds, fatty alcohols [mixture of CH
3(CH
2)
nOH, n529, 31, 33, 35], 2,4,5-trimethoxybenzaldehyde (asarylaldehyde)
3), steroidal mixtures (
beta-sitosterol and stigmasterol)
4), betulinic acid
5), oleanolic acid
6), ursolic acid
6), arjunolic acid
7),
beta-sitosteryl glucopyranoside
, myo-inositol
9), luteolin
4), and rosmarinic acid
10).
The known compounds were identified through comparison of their IR, MS, and NMR spectra with anthentic samples or with value taken from the literature. In this paper, we report structure of three new compounds.
The molecular formula of
1 was determined as C
12H
14O
4 by HR-EI-MS. Analysis of the IR spectrum of
1 suggested it contained an aromatic group (3045, 1601, 1490 cm
-1), transconjugated double bond (1628, 958 cm
-1) and a methylenedioxy group (2837, 1230, 1064, 927 cm
-1). The 1H-NMR spectrum exhibited signals for one vinyl methyl group at d 1.86 (dd, J56.6, 1.7 Hz), two singlet phenolic methyl groups at d 3.84 and 3.85, a singlet methylenedioxy group at d 5.93 (2H), two trans-olefinic protons at d 6.09 (dq, 1H, J515.7, 6.6 Hz) and 6.57 (dq, 1H, J515.7, 1.7 Hz), and a singlet phenyl proton at d 6.54. The UV absorption at lmax 246 and 288 nm suggested compound
1 has an double bond conjugated with aromatic group. Six aromatic carbon signals exhibited at d 104.4, 124.6, 135.6, 135.7, 138.9, and 139.5. The signal at d 104.4 (CH) is assigned as a substituted free aromatic carbon and ortho to oxygenated carbon. And the signal at d 124.6 (C) was considered to be linking to the 1-propenylgroup and vicinal to oxygenated carbon. The other four phenyl carbons are higher field than d 140; this result indicates that the four oxygenated phenyl carbons are contiguous.
Therefore three possible structures (
1,
4, and
5) for compound
1 were proposed. The correct structure of
1 was confirmed by chemical transformation and spectral evidence.
Hydrogenation of compound
1 under catalytic hydrogenation conditions with Pd/C as catalyst in methanol solution gave compound 6 [liquid; d 0.91 (t, 3H, J57.2 Hz), 1.54 (sex, 2H, J57.2 Hz), 2.48 (t, 2H, J57.2 Hz), 3.82, 3.85 (s, each 3H), 5.90 (s, 2H), and 6.27 (s, 1H)]. The relative position was elucidated by NOE evidence (see structure
6). Irradiation of the phenyl proton at d 6.27 afforded an nuclear Overhauser effect (NOE) at the benzyl proton ( d 2.48) (5.7% enhancement) and one of the methoxy groups ( d 3.82) (10.7% enhancement).
And irradiation of the signal at d 2.48 gave only an NOE to the phenyl proton ( d 6.27, 5.2% enhancement). The above evidence determined the structure of
1 as 4,5-dimethoxy-2,3-methylenedioxy-1-propenylbenzene. This is the first time that compound
1 has been isolated from nature though the same compound had been prepared from compound
7 by basic isomerization
11).
Compound
2 was isolated as a needle crystal (mp 140—142°C), and showed the molecular formula C
12H
12O
5, based on HR-EI-MS. The IR spectrum of
2 showed the presence of an aromatic group and a conjugated carbonyl system. The 1H-NMR spectrum of
2 is very similar to that of
1 indicating the presence of a methylenedioxy group [ d 6.02 (s, 2H)], two phenolic methyl groups ( d 3.86, 3.97), and a phenyl proton [ d 6.71 (s, 1H)]. It also contained two trans-olefinic protons [ d 6.63 (dd, 1H, J515.9, 7.7 Hz), 7.69 (d, 1H, J515.9 Hz)], and one aldehyde proton [ d 9.62 (d, J57.7 Hz)]. The above spectrum indicated
2 has an aldehyde group conjugated with an olefinic group instead of a methyl group in
1. The longer wave length absorptions of UV spectrum at lmax 234, 249, and 335 nm further proved the assignment. The phenyl proton ( d 6.71) showed an NOE with a methoxy group ( d 3.86) and an olefinic proton ( d 7.69); this decided the structure of compound
2 as 4,5-dimethoxy-2,3-methylenedioxycinnamaldehyde. The 13C-NMR data also agreed to the assigned structure.
Compound
1 was oxidized with selenium dioxide in dioxane under reflux to yield a product, which was identified as compound
2.
Aldehyde
3 melted at mp 106—108 °C with formula C
10H
10O
5 based on HR-MS. Its IR spectrum indicated aromatic (1590, 1497 cm
-1) and conjugated carbonyl groups (1655 cm
-1). The 1H-NMR signal at d 10.21 (s) in addition to the UV absorption bands at lmax 230 and 301 nm indicated an oxygenated benzaldehyde functionality. The 1H-NMR signals presented a singlet phenyl proton at d 7.06, a methylenedioxyl group at d 6.07 (s, 2H), and two phenolic methyl groups at 3.86 and 4.03. Four contiguous oxygenated aromatic carbons were discernible from the 13C-NMR signals at d 138.1, 139.8, 142.2, and 143.1. NOE correlation of aldehyde
3 is shown in structure
8, which confirmed the structure of
3 as 4,5-dimethoxy-2,3-methylenedioxycinnamaldehyde.
Reduction of
3 with sodium borohydride in methanol produced alcohol
9 [amorphous; 3305 cm
-1; d 4.57 (s, 2H, –CH2OH) and 6.46 (s, 1H, phenyl H)].
Aldehyde
3 could be prepared from
1 by oxidation with osmium tetraoxide and sodium periodate in dioxane. Aldehyde
3 had been synthesized by Dallacher
12), but this is the first time thus isolated from a natural source.
ExperimentalMelting points were determined on a Yanagimoto micro melting point apparatus and are uncorrected. Optical rotations were measured with a JASCO DIP-4 polarimeter. 1H- and 13C-NMR spectra were run on a Brucker AM 300 in CDCl
3 solution with tetramethylsilane (TMS) as internal standard.
Chemical shifts are given in hertz (Hz). EI-MS and UV spectra were taken on a JEOL-JMS-100 and Hitachi RMS-4 spectrometer, respectively.
Extraction and Isolation Air-dry whole herb of
Mosla dianthera (4.4 kg) was extracted with MeOH (60 l) at room temperature three times (6 d each time). The crude extracted was evaporated in vacuo to leave a black syrup (400 g), and then water was added to a total volume of 1.3 l. The aqueous layer was partitioned with CHCl
3 (1l x3) and n-BuOH (1l x3), successively. The weight of the CHCl
3 extract was about 230 g, and a portion of this residue (120 g) was subjected to repeated chromatography on silica gel. The eluent solvent system was a combination of hexane and ethyl acetate.
The components were eluted in order as
1 (90 mg),
2 (20 mg), and
3 (10 mg) (5% EtOAc in hexane), fatty alcohol [CH
3(CH
2)
nOH, n529, 31, 33, 35; 30 mg], 2,4,5-trimethoxybenzaldehyde (110 mg), and steroidal mixture (
beta-sitosterol and stimasterol, 800 mg) (10% EtOAc in hexane), betulinic acid (100 mg), oleanolic acid (150 mg), and ursolic acid (120 mg) (20% EtOAc in hexane), arjunolic acid (80 mg) (80% EtOAc in hexane),
beta-sitosteryl glucopyranoside (300 mg) (EtOAc), luteolin (20 mg) (from 5% MeOH in EtOAc), rosmarinic acid (10 mg) (10% MeOH in EtOAc), and myo-inositol (150 mg) (30% EtOAc in MeOH).
4,5-Dimethoxy-2,3-methylenedioxy-1-propenylbenzene (
1) mp 56—57 °C. UV lmax MeOH nm (log e): 246 (4.36), 288 (4.00). IR (KBr) cm
-1: 3045, 2837, 1628, 1601, 1490, 1230, 1064, 958, and 927. 13C-NMR (CDCl
3) d: 18.7, 56.7, 60.3, 101.6, 104.4, 124.6, 124.9, 125.4, 135.6, 135.7, 138.9, 139.5. EI-MS (70 eV) (rel. int.) m/z: 222 (M1, 100), 207 (11), 177 (23), 149 (27). HR-EI-MS m/z: 222.0892 (M1, Calcd for C
12H
14O
4: 222.0895).
4,5-Dimethoxy-2,3-methylenedioxycinnamaldehyde (
2) mp 140—142 °C, UV lmax MeOH nm (log e): 234 (4.15), 249 (4.18), 335 (4.27). IR (KBr) cm21: 3035, 1683, 1615, 1600, 1500, 1352, 1242, 1188, 1116, 1064. 13CNMR (CDCl
3) d: 56.8, 60.3, 102.4, 106.9, 120.1, 127.8, 138.2, 138.6, 139.6, 140.1, 147.5, 194.1. EI-MS (70 eV) (rel. int.) m/z: 236 (44), 205 (89), 182 (66), 140 (100), 139 (54), 127 (18), 110 (54). HR-EI-MS m/z: 236.2243.(M1, Calcd for C
12H
12O
5: 236.2245).
4,5-Dimethoxy-2,3-methylenedioxybenzaldehyde (
3) mp 106—108 °C; UV lmax MeOH nm (log e): 230 (4.15), 301 (3.90). IR (KBr) cm21: 3041, 1655, 1590, 1497, 1237, 1045. 13C-NMR (CDCl
3) d: 55.5, 60.6, 102.7, 106.0, 122.2, 138.1, 139.8, 142.2, 143.1, 187.8. EI-MS (70 eV) (rel. int.): m/z 210 (100), 195 (30), 181 (12), 164 (23); HR-EI-MS m/z: 210.0528 (M1, Calcd for C
10H
10O
5: 210.0531).
Catalytic Hydrogenation of 1 A solution of
1 (20 mg) in 10 ml of MeOH was hydrogenated in the presence of 10% Pd/C (5 mg). After 5 h, the catalyst was removed by filtration and washed several times with MeOH. The combined filtrate and washings gave a product
6 (19 mg): liquid, IR (KBr) cm
-1: 3037, 1630, 1610, 1495, 1260, 1150, 1185, 1075, 960.
Selenium Dioxide Oxidized Compound 1 to Produce 2 Selenium dioxide (22.5 mg) was added to a solution of
1 (45 mg) in dioxane (1.2 ml). The reaction mixture was heated under reflux for 4.5 h. The reaction mixture was cooled to ambient temperature, and then 30 ml of H
2O was added. The reaction mixture was extracted with Et
2O (20 ml x3) to yield a solid which was purified to afford compound
2 (20 mg).
Reduction of 3 with NaBH4 in MeOH Excess NaBH
4 (10 mg) was added in small portion to a solution of
3 (20 mg) in MeOH (2 ml), and the reaction mixture was stirred for 30 min. The reaction mixture was diluted (15 ml 1 : 1 of EtOAc : hexane) and washed with H
2O (10 ml x3). Evaporation of the organic layer under reduced pressure gave a residue that was chromatographed on SiO
2 to produce
9 [amorphous; IR (KBr) nmax cm
-1: 3305, 1610, 1500, 1145. 1H-NMR (CDCl3) d: 3.46 (s, 1H, –OH), 3.84, 3.94 (s, each 3H), 4.57 (s, 2H, H-7), 5.94 (2H, m), 6.46 (s, 1H, H-6)].
Oxidation of 1 with OsO4 and NaIO4 in Dioxane Compound
1 (20 mg) was dissolved in a mixture of dioxane (1.2 ml) and H
2O (0.4 ml), and then a catalytic amount of OsO
4 (5 mg) was added. After 30 min, the oxidizing agent NaIO
4 (60 mg) was added, and then stirred at room temperature for 3 h. The reaction mixture was poured into 50 ml of water, and then the aqueous solution was extracted with ether (30 ml) three times. After purification on silica gel, the product (12 mg) was identified as
3.
Acknowledgments We thank the National Science Council of the Republic of China for financial support.
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