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Chinese Chemical Letters 22 (2011) 81–84 www.elsevier.com/locate/cclet
A novel bacteriohopanoid from Celtis australis L. bark Ruchi Badoni a, Deepak Kumar Semwal a,b,*, Prabhakar P. Badoni c, Sudhir Kumar Kothiyal a, Usha Rawat a a
Department of Chemistry, H.N.B. Garhwal University, Srinagar 246 174, Uttarakhand, India Department of Chemistry, Punjab University, Sector 14, Chandigarh 160 014, Punjab, India c Department of Chemistry, H.N.B. Garhwal University Campus Pauri (Garhwal), Uttarakhand, India b
Received 21 May 2010
Abstract A novel bacteriohopanoid elucidated as 3b-hydroxy-35-(cyclohexyl-50 -propan-70 -one)-33-ethyl-34-methyl-bactereohopane (1) has been isolated from the bark of Celtis australis (Ulmaceae) together with three known compounds apigenin, quercetin and its glucoside. The structure of 1 was characterized by means of chemical and spectral methods including advanced 2D NMR studies. # 2010 Deepak Kumar Semwal. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Celtis australis; Ulmaceae; Bacteriohopane
Celtis australis of family Ulmaceae is a deciduous tree distributed to montane and submontane Himalaya. The plant is an important remedy for bone fracture, pimples, contusions, sprains and joint pains in Indian traditional medicine [1]. Previous studies on the plants of this genus led to isolation of phenolic glycosides [2], steroids [3], terpenoids [4,5], tannins, saponins and alkaloids [6]. In addition, three compounds acacetin 7-O-glucoside, isovitexin and cytisoside were reported from leaves of C. australis [7]. Recently, we have isolated and characterized fatty acid [8] and a sulphonated phenolic celtisanin [9] from fruits of this plant. The present paper illustrates the isolation and structure elucidation of a novel bacteriohopanoid 1 (Fig. 1) with the help of modern spectroscopic methods. The isolation and structure elucidation of 1 has been reported for the first time from this source. Compound 1 was obtained as shiny white needle shaped crystals (0.263 g); mp 259–260 8C and proposed molecular formula C47H82O2 from its quasi-molecular ion at m/z 679.6056 [M+H]+ in HR-ESIMS (positive mode, calcd. 679.6387). The IR spectrum exhibited bands at 3417 cm1 characteristic of hydroxyl group and a band at 1715 cm1 was clearly expressive for the stretching in a carbonyl group. The 13C NMR and DEPT spectra of 1 showed 47 carbon signals including ten methyl, twenty methylene, eleven methine and six quaternary carbons. A highly downfield singlet at d 213.2 in the 13C NMR spectrum was corroborated to a carbonyl group whereas the signals appeared at d 6.8, 11.6, 14.6, 15.7, 16.3, 17.5, 17.9, 18.2, 22.2 and 30.5 were due to the presence of ten methyl groups. A signal at d 3.73 (overlap) in the 1H NMR for a H-3 and its NOESY correlation with d 0.94 (H-5) and d 0.95 (H-24) confirmed the b position of hydroxyl group at C-3. The stereochemistry of various other key positions in 1 was determined by NOESY experiment. In NOESY spectrum, the strong correlation of H-16 to H-29 and H-21 to H-30 determined the position of side chain at C-21 (Fig. 2a). This fact was further confirmed by the HMBC correlation (Fig. 2b) * Corresponding author at: Department of Chemistry, H.N.B. Garhwal University, Srinagar 246 174, Uttarakhand, India. E-mail address:
[email protected] (D.K. Semwal). 1001-8417/$ – see front matter # 2010 Deepak Kumar Semwal. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.07.029
[()TD$FIG] 82
[()TD$FIG]
R. Badoni et al. / Chinese Chemical Letters 22 (2011) 81–84
Fig. 1. Chemical structure of 1.
Fig. 2. Selected NOESY (a) and HMBC (b) correlations in 1.
of H-21 to C-30 (d 30.6). The above spectral studies led us to deduce that 1 is a hopane type triterpene consist a side chain [10,11]. The long range correlation of H-90 (d 0.72) to C-50 (d 59.4), C-70 (d 213.2) and C-80 (d 41.7) in HMBC spectrum (Fig. 3) was corroborated for a terminal propanoyl moiety. The index of hydrogen deficiency for C47H82O2 (=7) showed the presence of six rings and one double bond (carbonyl). Moreover, except in carbonyl group, there was no another multiple bond present in 1 (confirmed by IR and NMR spectra). Thus, it is clear that sixth ring must be present with side chain. Relatively downfield values at d 41.2 (C-10 ) and d 59.4 (C-50 ) suggested bisubstituted aliphatic ring with [()TD$FIG]substitution of a propanoyl moiety. The HMBC correlation of H-90 and H-80 to C-50 confirmed the position of propanoyl
Fig. 3. Long range HMBC (up field) spectrum of 1.
[()TD$FIG]
R. Badoni et al. / Chinese Chemical Letters 22 (2011) 81–84
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Fig. 4. Low resolution ESI mass spectrum of 1. 0
group at C-5 . The detailed study of HMBC, NOESY and DEPT spectra gave the evidences for bacteriohopane type structure of 1 [12]. The ESI-MS of 1 was found very informative in support of the structural confirmation (Fig. 4). It showed a quasi-molecular ion peak at m/z 679.60 (100%), which loses H2O to furnish an ion at 661.53 (10%) whereas the important ions at 219.20 and 427.40 were due to the rupture of ring C [13] (Scheme 1). Hence, the structure of 1 was elucidated as 3b-hydroxy-35-(cyclohexyl-50 -propan-70 -one)-33-ethyl-34-methylbactereohopane. 1. Experimental Melting point was recorded on Perfit melting point apparatus. UV spectrum was measured on a Perkin-Elmer Lambda-25 spectrometer in MeOH. IR spectrum recorded on Perkin-Elmer Spectrum RX I FT-IR spectrometer (KBr discs). NMR spectra were obtained on Bruker, 400, Ultra ShieldTM NMR spectrometer (400 MHz for 1H and 100 MHz 13 [()TD$FIG]for C NMR in CDCl3, TMS as internal standard). MS were recorded on LCMS Q-TOF Micro mass spectrometer and
Scheme 1. Proposed mass fragmentation in 1.
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R. Badoni et al. / Chinese Chemical Letters 22 (2011) 81–84
Table 1 13 C (100 MHz), 1H (400 MHz) NMR, NOESY and HMBC data of compound 1 in CDCl3. No.
dC
dH
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
38.2 28.1 72.7 39.7 49.1 18.6 32.0 42.8 53.1 37.8 20.1 20.2 53.2 41.5 32.8 36.0 58.2 42.1 39.2 30.0 61.3 35.0 30.5 22.2
0.92 1.32 3.73 – 0.94 1.36 1.47 – 0.99 – 0.91 0.91 2.37 – 0.96 0.96 1.21 – 0.90 0.90 1.04 1.98 0.96 0.95
NOESY
HMBC
No.
dC
dH
(m), 2.31 (m) (m), 2.33 (m) (broad)
H-2, 25 H-3 H-5, H-24
C-2, 3 C-4, 10 C-1, 5
(m) (m), 2.25 (m) (m), 2.25 (m)
H-24, H-3 H-24 H-27
C-1, 3, 7, 9, 23, 24 C-8, 10 C-5, 9, 14, 26
25 26 27 28 29 30 31 32 33 34 35 10 20 30 40 50 60 70 80 90 100 110 120
16.3 18.2 17.5 14.6 17.9 30.6 32.4 35.3 37.1 38.3 37.4 41.2 35.1 32.3 35.6 59.4 32.7 213.2 41.7 6.8 31.7 11.6 15.7
0.88 0.90 0.91 0.85 1.18 1.94 1.90 1.93 2.17 2.22 1.47 2.12 1.37 1.30 1.38 2.41 1.90 – 2.38 0.72 1.08 0.85 0.91
(m)
C-1, 5, 7, 12, 14
(m), 1.93 (m) (m), 1.93 (m) (m)
H-25 H-19
(m), 2.38 (m) (m), 2.38 (m) (overlap)
H-27 H-29 H-29
C-13, 17 C-14, 18, 21 C-16, 18, 19, 20
(m), 2.23 (m) (m), 2.23 (m) (overlap) (m) (overlap) (overlap)
H-12, 20
C-13, 17, C-17, 18, C-16, 18, C-17, 20, C-3, 5 C-3, 5
H-30
C-8, 10, 13 C-9, 14, 18 C-8, 11, 15, 17
21 22 19, 30 31
(s) (s) (s) (s) (s) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (s) (m) (m) (m)
NOESY
HMBC
H-11
C-1, 9 C-9, 14 C-8, 15 C-13, 17 C-21, 30 C-21, 29, 32 C-22, 33 C-30, 34, 100 C-31, 35, 110 , 120 C-32, 10 , 100 C-33, 20 , 120 C-34, 30 , 50 C-35, 40 , 60 C-10 , 50 C-20 , 70 , 60 C-10 , 30 , 80 C-20 , 40 , 35
H-7, 15 H-16, 17 H-21 H-100 , 29
H-30 , 120 H-40 H-30
H-31, 110 H-100 H-20
C-50 C-50 , 70 C-110 , 32, 34 C-100 , 33 C-33, 35
LCMS-LCQ, Finnigan, MAT mass spectrometer. TLC was performed on silica gel (Merck, 10–40 mm) pre-coated plates, spots were visualized by spraying with 7% H2SO4. Fresh bark of C. australis was collected from Bhatwara, Tehri Garhwal during the month of November and identified by Taxonomical Laboratory, Department of Botany, H.N.B. Garhwal University Srinagar. A voucher specimen (GUH-17595) of the plant was deposited in Departmental Herbarium for future records. Air dried powdered bark (3 kg) was extracted exhaustively with 95% ethanol at 30–50 8C (for 18 h, repeatedly). The extraction mixture was filtered and solvent evaporated to dryness under reduced pressure to yield black brown residue (250 g). The vacuum dried black brown residue was pre-adsorbed onto silica gel (Merck 60–120 mesh, 150 g) and allowed to run over silica gel (500 g) packed column. The elution was first started with CHCl3:MeOH (19:1) by increasing polarity of MeOH (19:1 ! 41:9). The elution with CHCl3:MeOH (23:2) afforded compound 1. Shiny white 1 + crystals (0.263 g); mp 259–260 8C; UV: inactive; IR yKBr max : 3417, 1715, 2850 cm ; ESI-MS (m/z): 679.60 [M+H] (100%), 661.53 (10%), 607.53 (4%), 427.40 (9%), 219.20 (20%); NMR data: see Table 1; elemental analysis: (found C, 83.12; H, 12.17; O, 4.71%; calcd. for C47H82O2: C, 82.81; H, 12.06; O, 4.63%). Acknowledgments The authors pay their sincere thanks to NIPER, Chandigarh for scanning spectra and UGC New Delhi, India [No. 33-282/2007(SR)], for financial assistance. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
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