This article was downloaded by: [University of Otago] On: 09 July 2015, At: 02:02 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: 5 Howick Place, London, SW1P 1WG
Journal of Asian Natural Products Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ganp20
Triterpenoids from the barks of Terminalia chebula a
a
a
a
a
Chao Zhang , Kun Jiang , Shi-Jin Qu , Yi-Ming Zhai , Jun-Jie Tan a
& Chang-Heng Tan a
Department of Natural Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China Published online: 29 Jun 2015.
Click for updates To cite this article: Chao Zhang, Kun Jiang, Shi-Jin Qu, Yi-Ming Zhai, Jun-Jie Tan & Chang-Heng Tan (2015): Triterpenoids from the barks of Terminalia chebula, Journal of Asian Natural Products Research, DOI: 10.1080/10286020.2015.1052803 To link to this article: http://dx.doi.org/10.1080/10286020.2015.1052803
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Downloaded by [University of Otago] at 02:03 09 July 2015
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Journal of Asian Natural Products Research, 2015 http://dx.doi.org/10.1080/10286020.2015.1052803
Triterpenoids from the barks of Terminalia chebula Chao Zhang, Kun Jiang, Shi-Jin Qu, Yi-Ming Zhai, Jun-Jie Tan and Chang-Heng Tan* Department of Natural Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
Downloaded by [University of Otago] at 02:03 09 July 2015
(Received 22 March 2015; final version received 15 May 2015) Two new triterpenoids, termichebuloside A (1), an unusual dimeric triterpenoid saponin, and termichebulolide (2), an oleanolic acid-type lactone, along with 11 known triterpenoids, were isolated from MeOH extract of the barks of Terminalia chebula. The structures of 1 and 2 were elucidated to be arjunglucoside I-(3-O-190 ,23-O-190 )18,19-seco-19-hydroxyarjunglucoside I (1) and 2a,3b,23-trihydroxyolean-11,13(18)dien-28,19b-olide (2), respectively, on the basis of spectroscopic evidences and biogenetic consideration. Keywords: termichebuloside A; termichebulolide; Terminalia chebula; dimeric triterpenoid saponin; triterpenoid lactone
1. Introduction Terminalia chebula Retz. (Combretaceae) is a tall tree indigenous to southern China, India, and Southeast Asia. Its dried ripe fruit is called ‘King of the medicine’ in Tibet’s and Ayurvedic medicine because of its extraordinary healing power for asthma, sore throat, vomiting, hiccough, diarrhea, dysentery, bleeding piles, ulcers, gout, heart and bladder diseases, etc. [1]. Pharmacological studies showed that the alcohol extract or ingredients of T. chebula possessed antioxidant, antimicrobial, antidiabetic, hepatoprotective, anti-inflammatory, antimutagenic, antiproliferative, radioprotective, cardioprotective, antiarthritic, anticaries, gastrointestinal motility, and wound-healing activities [1]. Recently, the barks of T. chebula were reported to contain antifungal flavonoids and triterpenoids [2], and its methanol extract had anti-bacterial and anti-viral activities [3]. As a continuing interest in the anti-viral ingredients of medicinal plants [4 –7], we conducted a phytochemical investigation on the barks of *Corresponding author. Email: [email protected] q 2015 Taylor & Francis
T. chebula, which led to the isolation of two new triterpenoids charactered with an unusual dimeric triterpenoid saponin and an oleanolic acid-type lactone, named as termichebuloside A (1) and termichebulolide (2) (Figure 1), respectively, together with 11 known triterpenoids comprising terminalin A [8], ivorengenin B [9], arjunglucoside I (3) [10], arjungenin (4) [11], euscaphic acid [12], ursolic acid lactone [13], arjunolic acid [14], pomonic acid [15], actinidic acid [16], belleric acid [17], and terminolic acid [18]. In this paper, we describe the isolation and structure elucidation of compounds 1 and 2.
2.
Results and discussions
Termichebuloside A (1) was obtained as white amorphous powders. It had quasi molecular ion peaks at m/z 1315 [M þ H]þ and 1337 [M þ Na]þ in the positive-ion-mode ESI-MS, suggesting the molecular formula of C72H114O21, which was in agreement with the HR-ESI-MS.
2
C. Zhang et al. 29
30
HO
HO
26
1
2
unit b
A
3
HO HO
OH
H
HO
23
O
unit a
OH
OH OH
HO
2 HO O
O
OH
4'
HO
OR
O 23'
Downloaded by [University of Otago] at 02:03 09 July 2015
5
O 2
O
D'
1'
28
23
O
17'
HO
O
8
O 28
O
17
24
19'
18'
9
13 14
E
27
4
O 20'
10
20
18
11 25
19
19
OH OH
OH
4
HO
23 24
HO
OH
3 (4R), R = Glu 3a (4S), R = Glu 4 (4R), R = H
1 (4R, 4'R) 1a (4S, 4'S)
Figure 1. Structures of triterpenoids 1 – 4, 1a and 3a.
A fragment ion peak at m/z 989 [M – H –2 £ 162]2 in the negative-ion-mode ESI-MS was attributed to the loss of two hexoses. The 1H and 13C NMR spectra (Table 1) of 1 showed signals for 72 C-atoms and 101 carbon-bearing H-atoms (12 methyls, 23 methylenes, 23 methines, and 14 quaternary carbons), which was resolved into two terminal b-glucopyranosyls ( dH 5.43/5.37, d, J ¼ 8.0/8.2 Hz; d C
95.8/95.9, 78.6/78.7, 78.3/78.3, 73.9/73.9, 71.0/71.1, and 62.3/62.5), 12 tertiary methyls (dH 1.30, 1.15, 1.05 £ 2, 0.98, 0.95, 0.94, 0.91, 0.90, 0.86, 0.74, and 0.67), two carboxyls (dC 178.5/176.7), two oxygen-bearing methylenes (dC 79.4/66.1), two pairs of double bonds (dC 144.4/145.7 and 124.6/124.5, dH 5.33/5.32, each br. s), five oxygenated methines (dC 91.0, 82.4, 78.1, 69.9, and 66.3), and a hemiacetal
HO O HO
O OH O
O O
HO
OH OH
O HO
O
O OH
A'
HO
O
O
HO
OH OH
OH
HO OH
HO 1
Figure 2. Significant HMBC correlations (H to C) of 1 and 2.
2
Journal of Asian Natural Products Research Table 1.
1
H and 13C NMR spectral data of 1 and 2 (500 and 125 MHz, in CD3OD). Unit a of 1
Downloaded by [University of Otago] at 02:03 09 July 2015
Site
Unit b of 1
dC
dH
1
48.0
a
2.08 , 0.98
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
66.3 91.0 38.7 52.5 18.8 33.3 40.9 48.9 38.7 24.6 124.6 144.4 42.7 29.4 28.3 47.1 45.0 82.4 36.0 29.4 33.3 79.4
24 25 26 27 28 29 30 Glu-1 Glu-2 Glu-3 Glu-4 Glu-5 Glu-6
14.8 18.4 18.1 25.1 178.5 28.6 25.1 95.8 73.9 78.7 71.0 78.3 62.3
3.66a 3.04 d (10.2) – 0.98a 1.63a, 1.42a 1.42a, 1.36a – 1.72a – 1.92a 5.33 br. s – – 1.66a,1.20a 2.32a, 1.70a – 2.29a, 2.16a 4.22 s – 1.72a,1.30a 1.35a,1.30a 3.75 d (10.5) 3.24 d (10.4) 1.05 s 1.05 s 0.74 s 1.30 s – 0.94 s 0.95 s 5.43 d (8.0) 3.22 –3.43a 3.22 –3.43a 3.22 –3.43a 3.22 –3.43a 3.82a, 3.70a
a
3
a
dC
dH
48.2
a
69.9 78.1 44.1 48.3 18.9 35.1 42.4 52.1 39.4 24.7 124.5 145.7 44.2 29.1 28.4 48.2 35.1 109.0 38.2 32.7 29.0 66.1 13.8 17.7 18.6 21.2 176.7 22.7 22.6 95.9 73.9 78.6 71.1 78.3 62.5
2
dC
dH
2.01 , 0.90
47.6
3.66a 3.36a – 0.93a 1.63a, 1.42a 1.42a, 1.30a – 1.52a – 2.08a 5.32 br. S – – 1.67a,1.20a 2.21a,1.70a – 3.05 br. S 3.27 d (3.8) – 1.30a 1.72a,1.69a 3.50 d (11.2) 3.26 d (11.2) 0.67 s 0.98 s 0.86 s 1.15 s – 0.91 s 0.90 s 5.37 d (8.2) 3.22 – 3.43a 3.22 – 3.43a 3.22 – 3.43a 3.22 – 3.43a 3.80a,3.70a
69.6 78.0 44.2 47.9 18.8 33.7 42.2 54.2 38.6 130.6 124.4 136.5 41.8 26.6 25.3 45.4 133.9 86.6 36.7 33.6 35.5 65.8
2.20 dd (12.2, 4.5) 0.95 dd (12.2, 11.4) 3.78 ddd (11.4, 9.6, 4.5) 3.40 d (9.6) – 1.35 br. d (11.8) 1.54a, 1.42a 1.58a, 1.48a – 2.24 dd (3.0, 2.1) – 5.89 dd (10.2, 2.1) 6.29 dd (10.2, 3.0) – – 1.37a, 1.33a 2.24a, 1.61a – – 4.85 s – 1.51a, 1.44a 1.75a, 1.70a 3.53 d (11.1) 3.28 d (11.1) 0.69 s 1.07 s 0.81 s 1.08 s – 1.09 s 0.97 s
a
13.4 20.1 17.5 19.5 180.3 28.1 23.4
Overlapping signals, d value was estimated according to HSQC and HMBC spectra.
(dC 109.0, dH 4.22, s), indicating 1 to be a trihydroxylated olean-12-ene type triterpenoid saponin-based dimer. Two methyls at dC 14.8/13.8 were assigned as 24/240 -Me of each triterpenoid unit on the basis of their upfield shifts [10]. Their HSQC correlated proton signals at dH 1.05/0.67 had HMBC cross-peaks with a quaternary carbon (dC-4/40 38.7/44.1), a saturated methine (dC-5/50 52.5/48.3), an oxygenated methylene (dC-
23/230 79.4/66.1), and an oxygen-bearing methine (dC-3/30 91.0/78.1), respectively (Figure 2). In addition, HMBC correlations between H-3/30 with C-2/20 (dC 66.3/69.9) were also observed. The above information indicated a 2,3,23-trihydroxylated A-ring for both units. Compared the 1H and 13C NMR data of 1 with those of arjunglucoside I (3) [10], a closely related triterpenoid saponin, the main differences were found at the A-
Downloaded by [University of Otago] at 02:03 09 July 2015
4
C. Zhang et al.
ring of unit a, and at the D0 - and E0 -rings of unit b. The unit b absented two methines (C18 and C-19 of 3) and presented a methylene (dC 35.1) and a hemiacetal (dC 109.0), suggesting a 18,19-seco-oleanolic acid triterpenoid. C-3 and C-23 of unit a had more downfield shifts in contrast with those of 3, suggesting etherification to be happened between them and the hemiacetal. This assumption was proved by HMBC correlations (Figure 2) between the hemiacetal carbon (dC 109.0) with H-3 (dH 3.04), H2-23 (dH 3.75 and 3.24), 290 -Me (dH 0.91), and 300 -Me (dH 0.90), and HMBC crosspeaks of H-120 (dH 5.32)/C-180 (dC 35.1), and H2-180 (dH 3.05)/C-170 (dC 48.2). Based on the upfield shifts of the anomeric carbons at dC 95.8/95.9 and HMBC correlations of the anomeric protons (dH 5.43/5.37) with dC 178.5/176.7, two b-glucopyranosyls were assigned to be linked with two carboxyls (C-28/280 ), respectively. The relative configurations of H-2/20 , H-3/30 , and H-19 were assigned as b-,a-,a-orientation based on the similarities of 13C NMR of those corresponding carbons with those of 3 and biogenetic consideration of 1 from 3. Therefore, the structure of 1 was determined to be arjunglucoside I-(3-O190 ,23-O-190 )-180 ,190 -seco-190 -hydroxyarjunglucoside I (1). Termichebuloside A (1) is a second example in nature of dimeric triterpenoid saponin with a 18,19-seco E-ring unit after ivorenosides A (1a) and B, two sericoside (3a)-based dimers isolated from Terminalia ivorensis [19]. The main 13C NMR differences between 1 and 1a were observed at C190 (d 109.0/101.2, 1/1a), the oxygenated methines (C-3 and C-30 ), the oxy-bearing methylenes (C-23/230 of 1 Vs C-24/240 of 1a), the methyls (C-24/240 of 1 Vs C-23/230 of 1a) of A/A0 -rings, which was consistent with different g-gauche effect caused by opposite orientations of the methyls and oxygenated methylenes on C-4/40 of 1 and 1a. However, the configuration for C-190 of 1 was likewise uncertain because of the opening E0 -ring.
Termichebulolide (2) had the molecular formula C30H44O5 with nine unsaturated degrees deduced from the pseudo molecular ion peak [M þ H]þ at m/z 485.3271 in the positive-ion-mode HRESI-MS. The 1H and 13C NMR spectra (Table 1) exhibited signals for 30 carbon signals, including a carboxyl (dC 180.3), a 1,2-disubstituted double bond (dH 6.29, dd, J ¼ 10.2, 3.0 Hz, and 5.89, dd, J ¼ 10.2, 2.1 Hz; dC 124.4 and 130.6), a tetrasubstituted double bond (dC 136.5 and 133.9), three oxygenated methines (dC 86.6, 78.0 and 69.6), one isolated hydroxymethyl (dC 65.8; dH 3.53 and 3.28, each d, J ¼ 11.1 Hz), and six methyl singlets (dH 0.69, 0.81, 0.97, 1.07, 1.08, and 1.09; dC 13.4, 17.5, 19.5, 20.1, 23.4, and 28.1), diagnostic of a trihydroxydiene-oleanolic acid derivative. Nine unsaturated degrees for 2 and the downfield shifts of related carbons (dC 180.3 and 86.6) suggested a lactone ring formation between C-28 and C-19. The two double bonds were positioned on C11 –C12 and C13 – C18 based on a biogenesis consideration of 2 from arjungenin (4). The three hydroxyls were assigned on C-2a, C-3b, and C-23 according to observed NMR data of J1a,2 ¼ 11.4 Hz, J2,3 ¼ 9.6 Hz, and dC-24 at 13.4, as well as the NMR similarities of the A-ring of 2 and 4, especially observed J1a,2 ¼ 11.4 Hz, J2,3 ¼ 9.6 Hz, and dC-24 at 13.4. Such a structure for 2 was finally corroborated by the HMBC cross-peaks (Figure 2) of H-11/C-8, C-10, and C-13; H-12/C-9, C-13, and C-18; H-19 /C-13, C-17, C-18, C-20, C-28, C-29, and C-30, as well as C-4/H-2, H-3, H-5, H2-23, and Me-24. The structure of 2 was accordingly assigned to be 2a,3b,23-trihydroxyolean-11,13(18)-dien-28,19 b-olide. Mahato et al. treated 3 with 5% methanolic hydrochloric acid to yield 2a,3b,23-trihydroxyolean-11,13(18)-dien28-oic acid and 2a,3b,23-trihydroxyolean12-ene-28,19b-olide as two minor products [20]. As a similar structure, termichebulo-
Journal of Asian Natural Products Research lide (2) was also deduced to be derived from 3 or 4.
Downloaded by [University of Otago] at 02:03 09 July 2015
3. Experimental 3.1 General experimental procedures Optical rotations were determined on a Perkin-Elmer 341 polarimeter (PerkinElmer, Waltham, MA, USA). The IR spectra were recorded on a Nicolet-Magna-750FTIR spectrometer (ThermoFisher, Madison, WI, USA). The NMR spectra were taken on a Bruker AV-500 spectrometer (Bruker, Billerica, MA, USA) with TMS as the internal standard. ESI-MS and HR-ESIMS were obtained on a Bruker Esquire 3000plus (Bruker) and a Waters/Micromass Q-TOF-Ultima (Waters, Milford, MA, USA) mass spectrometers, respectively. Silica gel (200–300 mesh, Qingdao Haiyang Chemical Co. Ltd, Qingdao, China), Sephadex LH-20 (Pharmacia Biotech AB, Uppsala, Sweden), Rp-18 reversed-phase silica gel (150–200 mesh, Fuji Silysia Chemical Ltd., Aichi, Japan), and MCI Gel Chp20p (Mitsubishi Chemical, Tokyo, Japan) were used for column chromatography (CC). Silica gel HSGF254 (Yantai Jiangyou Guijiao Kaifa Co., Yantai, China) was used for TLC. Semi-prep HPLC preparation was run on a Waters HPLC system (Waters) with Waters-2545-HPLC pump, Waters-2489 detector, and XbridgeC18 column (5 mm, i.d. 10 mm £ 250 mm).
3.2 Plant material The barks of Terminalia chebula were collected in Xishuangbanna, Yunnan Province, China, in July 2013, and were identified by Prof. Da-Yuan Zhu of Shanghai Institute of Materia Medica. A voucher sample (No. 20130709) was deposited with the Herbarium of Shanghai Institute of Materia Medica, Chinese Academy of Sciences.
5
3.3 Extraction and isolation The dried barks of T. chebula (5 kg) were chopped and refluxed three times with MeOH. The MeOH extract was concentrated under reduced pressure to give a residue (600 g), which was suspended in H2O, and then partitioned with petroleum ether (PE), EtOAc, and n-BuOH, respectively. The EtOAc-soluble fraction (46 g) was subjected to CC of silica gel eluted with a gradient of CHCl3 – MeOH (1:0 ! 0:1) to get Frs. A1 –A10. Terminalin A (5 mg) was obtained as needle crystals from Fr. A1 (300 mg) after purification of silica gel CC eluted with gradient PE – acetone (100:1 ! 10:1). Fr. A2 (2.6 g) was repeatedly isolated by CC of silica gel eluted with PE –acetone (first 50:1 ! 5:1, then 30:1, finally 20:1) to afford ursolic acid lactone (5 mg). Ivorengenin B (4 mg) was got from Fr. A4 (1.3 g) via isolation of silica gel CC (PE –AcOEt, 2:1) and semiprep HPLC (MeOH – H2O, 7:3, UV 254/210 nm, flow rate 4 ml/min, tR ¼ 10.08 min). Fr. A5 (2.4 g) furnished pomonic acid (4 mg) after purification of silica gel CC (PE –AcOEt, 1:1) and semiprep HPLC (MeOH – H 2O, 85:15, 254/210 nm, 4 ml/min, tR ¼ 8.35 min). 2 (50 mg) was gained from Fr. A6 (2.0 g) via isolation of silica gel CC (PE – acetone 1:1) and recrystallization. Fr. A8 (4.0 g) was repeatedly purified on silica gel CC (CHCl3 – MeOH, 10:1) to yield euscaphic acid (3 mg). Fr. A9 (5.6 g) yielded 1 (9 mg) and 3 (13 mg) after purified process of CC over Rp-18 silica gel (MeOH – H2O, 1:0 ! 0:1), Sephadex LH-20 (MeOH), and semi-prep HPLC (MeOH –H2O, 6:4, 254/210 nm, 3 ml/min, tR ¼ 4.42 min for 1, CH3CN–H2O, 3:7, 254/210 nm, 4 ml/min, tR ¼ 11.32 min for 3). The n-BuOH layer (130 g) was subjected to CC of MCI (EtOH in H2O, 30%, 50%, 70%, and 95%) to give Frs. B1 – B4. Fr B3 (13 g) was isolated by CC of Rp-18 silica gel (EtOH in H2O, 30% ! 100%) to
6
C. Zhang et al.
Downloaded by [University of Otago] at 02:03 09 July 2015
yield Frs. B3.1– B3.5. Fr. B3.4 (2.0 g) was purified by CCs (Silica gel, CHCl 3 2 MeOH, 10: 1; Sephadex LH-20, CHCl3 2 MeOH, 1: 1) to afford 4 (50 mg). Fr. B3.5 (1.0 g) was isolated by silica gel CC (CHCl3 2 MeOH, 10: 1) and Semi-Prep HPLC (CH3CN 2 H2O, 55: 45, 254/210 nm, 4 ml/min) to obtain arjunolic acid (35 mg. HPLC, tR ¼ 20.55 min), actinidic acid (7 mg. tR ¼ 8.35 min), terminolic acid (6 mg. tR ¼ 12.12 min), and belleric acid (20 mg. tR ¼ 15.77 min), respectively. 3.3.1
Termichebuloside A (1)
White amorphous powder; ½a22 D 2 6.25 (c 0.08, i-PrOH); IR (KBr): nmax (cm21): 3435, 3427, 2930, 2922, 2880, 1750, 1740, 1644, 1435, 1387, 1043; 1H and 13C NMR spectral data, see Table 1; ESI-MS (positive): m/z 1315 [M þ H]þ, 1337 [M þ Na]þ; HR-ESI-MS: m/z 1315.7937 [M þ H]þ (calcd for C72H 115O 21 , 1315.7931). 3.3.2
Termichebulolide (2)
White amorphous powder; ½a22 D 2 6.25 (c 0.2, MeOH); IR (KBr): nmax (cm21): 3505, 3394, 2938, 2666, 1769, 1453, 1388, 1048; 1 H and 13C NMR spectral data, see Table 1; ESI-MS (positive): m/z 485 [M þ H]þ, 991 [2M þ Na]þ; HR-ESIMS: m/z 485.3271 [M þ H]þ (calcd for C30H45O5, 485.3267). Disclosure statement No potential conflict of interest was reported by the author(s).
Funding The authors thank the National Natural Science Foundation of China [grant number 81072545], [grant number 21202182] for financial support.
References [1] A. Bag, S.K. Bhattacharyya, and R.R. Chattopadhyay, Asian Pac. J. Trop. Biomed. 3, 244 (2013).
[2] S.K. Srivastava and S.D. Srivastava, Indian J. Chem. B 43, 2731 (2004). [3] D. Lee, K.H. Boo, J.K. Woo, F. Duan, K.H. Lee, T.K. Kwon, H.Y. Lee, K.Z. Riu, and D.S. Lee, J. Korean Soc. Appl. Biol. 54, 295 (2011). [4] L.J. Yang, K. Jiang, J.J. Tan, S.J. Qu, H.F. Luo, C.H. Tan, and D.-Y. Zhu, Helv. Chim. Acta 96, 119 (2013). [5] Y. Zhang, L.J. Yang, K. Jiang, C.H. Tan, J.J. Tan, P.M. Yang, and D.Y. Zhu, Carbohydr. Res. 361, 114 (2012). [6] K. Jiang, J.Q. Bai, J. Chang, J.J. Tan, S.J. Qu, H.F. Luo, C.H. Tan, and D.Y. Zhu, Helv. Chim. Acta 97, 64 (2014). [7] Y.H. Qiu, Y.F. Yang, J.M. Tan, C.H. Tan, and J. Chang, J. Asian Nat. Prod. Res. 16, 318 (2014). [8] S. Atta-ur-Rahman, M.I. Zareen, F.N. Choudhary, A. Ngounou, and M. Yasin, Tetrahedron Lett. 43, 6233 (2002). [9] B.K. Ponou, R.B. Teponno, M. Ricciutelli, T.B. Nguelefack, L. Quassinti, M. Bramucci, G. Lupidi, L. Barboni, and L.A. Tapondjou, Chem. Biodiv. 8, 1301 (2011). [10] R.S. Pawar and K.K. Bhutani, Phytomedicine 12, 391 (2005). [11] A. Jossang, M. Seuleiman, E. Maidou, and B. Bodo, Phytochemistry 41, 591 (1996). [12] J. Chen, W.L. Li, J.L. Wu, B.R. Ren, and H.Q. Zhang, Pharmazie 63, 765 (2008). [13] H.C. Wang and Y. Fujimoto, Phytochemistry 33, 151 (1993). [14] J. Ghosh, J. Das, P. Manna, and P.C. Sil, Free. Radic. Biol. Med. 48, 535 (2010). [15] D.L. Cheng and X.P. Cao, Phytochemistry 31, 1317 (1992). [16] N. De Tommasi, L. Rastrelli, M.R. Lauro, and R. Aquino, Phytochemistry 49, 1123 (1998). [17] Y.H. Wang, L.M. Xiang, M. Chen, Z.X. Zhang, and X.J. He, J. Mol. Catal. B-Enzym. 83, 51 (2012). [18] J. Conrad, B. Vogler, I. Klaiber, G. Roos, U. Walter, and W. Kraus, Phytochemistry 48, 647 (1998). [19] B.K. Ponou, R.B. Teponno, M. Ricciutelli, L. Quassinti, M. Bramucci, G. Lupidi, L. Barboni, and L.A. Tapondjou, Phytochemistry 71, 2108 (2010). [20] S.B. Mahato, A.K. Nandy, P. Luger, and M. Weber, J. Chem. Soc. Perk. Trans. 2, 1445 (1990).
Journal of Asian Natural Products Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ganp20
Triterpenoids from the barks of Terminalia chebula a
a
a
a
a
Chao Zhang , Kun Jiang , Shi-Jin Qu , Yi-Ming Zhai , Jun-Jie Tan a
& Chang-Heng Tan a
Department of Natural Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China Published online: 29 Jun 2015.
Click for updates To cite this article: Chao Zhang, Kun Jiang, Shi-Jin Qu, Yi-Ming Zhai, Jun-Jie Tan & Chang-Heng Tan (2015): Triterpenoids from the barks of Terminalia chebula, Journal of Asian Natural Products Research, DOI: 10.1080/10286020.2015.1052803 To link to this article: http://dx.doi.org/10.1080/10286020.2015.1052803
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Downloaded by [University of Otago] at 02:03 09 July 2015
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Journal of Asian Natural Products Research, 2015 http://dx.doi.org/10.1080/10286020.2015.1052803
Triterpenoids from the barks of Terminalia chebula Chao Zhang, Kun Jiang, Shi-Jin Qu, Yi-Ming Zhai, Jun-Jie Tan and Chang-Heng Tan* Department of Natural Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
Downloaded by [University of Otago] at 02:03 09 July 2015
(Received 22 March 2015; final version received 15 May 2015) Two new triterpenoids, termichebuloside A (1), an unusual dimeric triterpenoid saponin, and termichebulolide (2), an oleanolic acid-type lactone, along with 11 known triterpenoids, were isolated from MeOH extract of the barks of Terminalia chebula. The structures of 1 and 2 were elucidated to be arjunglucoside I-(3-O-190 ,23-O-190 )18,19-seco-19-hydroxyarjunglucoside I (1) and 2a,3b,23-trihydroxyolean-11,13(18)dien-28,19b-olide (2), respectively, on the basis of spectroscopic evidences and biogenetic consideration. Keywords: termichebuloside A; termichebulolide; Terminalia chebula; dimeric triterpenoid saponin; triterpenoid lactone
1. Introduction Terminalia chebula Retz. (Combretaceae) is a tall tree indigenous to southern China, India, and Southeast Asia. Its dried ripe fruit is called ‘King of the medicine’ in Tibet’s and Ayurvedic medicine because of its extraordinary healing power for asthma, sore throat, vomiting, hiccough, diarrhea, dysentery, bleeding piles, ulcers, gout, heart and bladder diseases, etc. [1]. Pharmacological studies showed that the alcohol extract or ingredients of T. chebula possessed antioxidant, antimicrobial, antidiabetic, hepatoprotective, anti-inflammatory, antimutagenic, antiproliferative, radioprotective, cardioprotective, antiarthritic, anticaries, gastrointestinal motility, and wound-healing activities [1]. Recently, the barks of T. chebula were reported to contain antifungal flavonoids and triterpenoids [2], and its methanol extract had anti-bacterial and anti-viral activities [3]. As a continuing interest in the anti-viral ingredients of medicinal plants [4 –7], we conducted a phytochemical investigation on the barks of *Corresponding author. Email: [email protected] q 2015 Taylor & Francis
T. chebula, which led to the isolation of two new triterpenoids charactered with an unusual dimeric triterpenoid saponin and an oleanolic acid-type lactone, named as termichebuloside A (1) and termichebulolide (2) (Figure 1), respectively, together with 11 known triterpenoids comprising terminalin A [8], ivorengenin B [9], arjunglucoside I (3) [10], arjungenin (4) [11], euscaphic acid [12], ursolic acid lactone [13], arjunolic acid [14], pomonic acid [15], actinidic acid [16], belleric acid [17], and terminolic acid [18]. In this paper, we describe the isolation and structure elucidation of compounds 1 and 2.
2.
Results and discussions
Termichebuloside A (1) was obtained as white amorphous powders. It had quasi molecular ion peaks at m/z 1315 [M þ H]þ and 1337 [M þ Na]þ in the positive-ion-mode ESI-MS, suggesting the molecular formula of C72H114O21, which was in agreement with the HR-ESI-MS.
2
C. Zhang et al. 29
30
HO
HO
26
1
2
unit b
A
3
HO HO
OH
H
HO
23
O
unit a
OH
OH OH
HO
2 HO O
O
OH
4'
HO
OR
O 23'
Downloaded by [University of Otago] at 02:03 09 July 2015
5
O 2
O
D'
1'
28
23
O
17'
HO
O
8
O 28
O
17
24
19'
18'
9
13 14
E
27
4
O 20'
10
20
18
11 25
19
19
OH OH
OH
4
HO
23 24
HO
OH
3 (4R), R = Glu 3a (4S), R = Glu 4 (4R), R = H
1 (4R, 4'R) 1a (4S, 4'S)
Figure 1. Structures of triterpenoids 1 – 4, 1a and 3a.
A fragment ion peak at m/z 989 [M – H –2 £ 162]2 in the negative-ion-mode ESI-MS was attributed to the loss of two hexoses. The 1H and 13C NMR spectra (Table 1) of 1 showed signals for 72 C-atoms and 101 carbon-bearing H-atoms (12 methyls, 23 methylenes, 23 methines, and 14 quaternary carbons), which was resolved into two terminal b-glucopyranosyls ( dH 5.43/5.37, d, J ¼ 8.0/8.2 Hz; d C
95.8/95.9, 78.6/78.7, 78.3/78.3, 73.9/73.9, 71.0/71.1, and 62.3/62.5), 12 tertiary methyls (dH 1.30, 1.15, 1.05 £ 2, 0.98, 0.95, 0.94, 0.91, 0.90, 0.86, 0.74, and 0.67), two carboxyls (dC 178.5/176.7), two oxygen-bearing methylenes (dC 79.4/66.1), two pairs of double bonds (dC 144.4/145.7 and 124.6/124.5, dH 5.33/5.32, each br. s), five oxygenated methines (dC 91.0, 82.4, 78.1, 69.9, and 66.3), and a hemiacetal
HO O HO
O OH O
O O
HO
OH OH
O HO
O
O OH
A'
HO
O
O
HO
OH OH
OH
HO OH
HO 1
Figure 2. Significant HMBC correlations (H to C) of 1 and 2.
2
Journal of Asian Natural Products Research Table 1.
1
H and 13C NMR spectral data of 1 and 2 (500 and 125 MHz, in CD3OD). Unit a of 1
Downloaded by [University of Otago] at 02:03 09 July 2015
Site
Unit b of 1
dC
dH
1
48.0
a
2.08 , 0.98
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
66.3 91.0 38.7 52.5 18.8 33.3 40.9 48.9 38.7 24.6 124.6 144.4 42.7 29.4 28.3 47.1 45.0 82.4 36.0 29.4 33.3 79.4
24 25 26 27 28 29 30 Glu-1 Glu-2 Glu-3 Glu-4 Glu-5 Glu-6
14.8 18.4 18.1 25.1 178.5 28.6 25.1 95.8 73.9 78.7 71.0 78.3 62.3
3.66a 3.04 d (10.2) – 0.98a 1.63a, 1.42a 1.42a, 1.36a – 1.72a – 1.92a 5.33 br. s – – 1.66a,1.20a 2.32a, 1.70a – 2.29a, 2.16a 4.22 s – 1.72a,1.30a 1.35a,1.30a 3.75 d (10.5) 3.24 d (10.4) 1.05 s 1.05 s 0.74 s 1.30 s – 0.94 s 0.95 s 5.43 d (8.0) 3.22 –3.43a 3.22 –3.43a 3.22 –3.43a 3.22 –3.43a 3.82a, 3.70a
a
3
a
dC
dH
48.2
a
69.9 78.1 44.1 48.3 18.9 35.1 42.4 52.1 39.4 24.7 124.5 145.7 44.2 29.1 28.4 48.2 35.1 109.0 38.2 32.7 29.0 66.1 13.8 17.7 18.6 21.2 176.7 22.7 22.6 95.9 73.9 78.6 71.1 78.3 62.5
2
dC
dH
2.01 , 0.90
47.6
3.66a 3.36a – 0.93a 1.63a, 1.42a 1.42a, 1.30a – 1.52a – 2.08a 5.32 br. S – – 1.67a,1.20a 2.21a,1.70a – 3.05 br. S 3.27 d (3.8) – 1.30a 1.72a,1.69a 3.50 d (11.2) 3.26 d (11.2) 0.67 s 0.98 s 0.86 s 1.15 s – 0.91 s 0.90 s 5.37 d (8.2) 3.22 – 3.43a 3.22 – 3.43a 3.22 – 3.43a 3.22 – 3.43a 3.80a,3.70a
69.6 78.0 44.2 47.9 18.8 33.7 42.2 54.2 38.6 130.6 124.4 136.5 41.8 26.6 25.3 45.4 133.9 86.6 36.7 33.6 35.5 65.8
2.20 dd (12.2, 4.5) 0.95 dd (12.2, 11.4) 3.78 ddd (11.4, 9.6, 4.5) 3.40 d (9.6) – 1.35 br. d (11.8) 1.54a, 1.42a 1.58a, 1.48a – 2.24 dd (3.0, 2.1) – 5.89 dd (10.2, 2.1) 6.29 dd (10.2, 3.0) – – 1.37a, 1.33a 2.24a, 1.61a – – 4.85 s – 1.51a, 1.44a 1.75a, 1.70a 3.53 d (11.1) 3.28 d (11.1) 0.69 s 1.07 s 0.81 s 1.08 s – 1.09 s 0.97 s
a
13.4 20.1 17.5 19.5 180.3 28.1 23.4
Overlapping signals, d value was estimated according to HSQC and HMBC spectra.
(dC 109.0, dH 4.22, s), indicating 1 to be a trihydroxylated olean-12-ene type triterpenoid saponin-based dimer. Two methyls at dC 14.8/13.8 were assigned as 24/240 -Me of each triterpenoid unit on the basis of their upfield shifts [10]. Their HSQC correlated proton signals at dH 1.05/0.67 had HMBC cross-peaks with a quaternary carbon (dC-4/40 38.7/44.1), a saturated methine (dC-5/50 52.5/48.3), an oxygenated methylene (dC-
23/230 79.4/66.1), and an oxygen-bearing methine (dC-3/30 91.0/78.1), respectively (Figure 2). In addition, HMBC correlations between H-3/30 with C-2/20 (dC 66.3/69.9) were also observed. The above information indicated a 2,3,23-trihydroxylated A-ring for both units. Compared the 1H and 13C NMR data of 1 with those of arjunglucoside I (3) [10], a closely related triterpenoid saponin, the main differences were found at the A-
Downloaded by [University of Otago] at 02:03 09 July 2015
4
C. Zhang et al.
ring of unit a, and at the D0 - and E0 -rings of unit b. The unit b absented two methines (C18 and C-19 of 3) and presented a methylene (dC 35.1) and a hemiacetal (dC 109.0), suggesting a 18,19-seco-oleanolic acid triterpenoid. C-3 and C-23 of unit a had more downfield shifts in contrast with those of 3, suggesting etherification to be happened between them and the hemiacetal. This assumption was proved by HMBC correlations (Figure 2) between the hemiacetal carbon (dC 109.0) with H-3 (dH 3.04), H2-23 (dH 3.75 and 3.24), 290 -Me (dH 0.91), and 300 -Me (dH 0.90), and HMBC crosspeaks of H-120 (dH 5.32)/C-180 (dC 35.1), and H2-180 (dH 3.05)/C-170 (dC 48.2). Based on the upfield shifts of the anomeric carbons at dC 95.8/95.9 and HMBC correlations of the anomeric protons (dH 5.43/5.37) with dC 178.5/176.7, two b-glucopyranosyls were assigned to be linked with two carboxyls (C-28/280 ), respectively. The relative configurations of H-2/20 , H-3/30 , and H-19 were assigned as b-,a-,a-orientation based on the similarities of 13C NMR of those corresponding carbons with those of 3 and biogenetic consideration of 1 from 3. Therefore, the structure of 1 was determined to be arjunglucoside I-(3-O190 ,23-O-190 )-180 ,190 -seco-190 -hydroxyarjunglucoside I (1). Termichebuloside A (1) is a second example in nature of dimeric triterpenoid saponin with a 18,19-seco E-ring unit after ivorenosides A (1a) and B, two sericoside (3a)-based dimers isolated from Terminalia ivorensis [19]. The main 13C NMR differences between 1 and 1a were observed at C190 (d 109.0/101.2, 1/1a), the oxygenated methines (C-3 and C-30 ), the oxy-bearing methylenes (C-23/230 of 1 Vs C-24/240 of 1a), the methyls (C-24/240 of 1 Vs C-23/230 of 1a) of A/A0 -rings, which was consistent with different g-gauche effect caused by opposite orientations of the methyls and oxygenated methylenes on C-4/40 of 1 and 1a. However, the configuration for C-190 of 1 was likewise uncertain because of the opening E0 -ring.
Termichebulolide (2) had the molecular formula C30H44O5 with nine unsaturated degrees deduced from the pseudo molecular ion peak [M þ H]þ at m/z 485.3271 in the positive-ion-mode HRESI-MS. The 1H and 13C NMR spectra (Table 1) exhibited signals for 30 carbon signals, including a carboxyl (dC 180.3), a 1,2-disubstituted double bond (dH 6.29, dd, J ¼ 10.2, 3.0 Hz, and 5.89, dd, J ¼ 10.2, 2.1 Hz; dC 124.4 and 130.6), a tetrasubstituted double bond (dC 136.5 and 133.9), three oxygenated methines (dC 86.6, 78.0 and 69.6), one isolated hydroxymethyl (dC 65.8; dH 3.53 and 3.28, each d, J ¼ 11.1 Hz), and six methyl singlets (dH 0.69, 0.81, 0.97, 1.07, 1.08, and 1.09; dC 13.4, 17.5, 19.5, 20.1, 23.4, and 28.1), diagnostic of a trihydroxydiene-oleanolic acid derivative. Nine unsaturated degrees for 2 and the downfield shifts of related carbons (dC 180.3 and 86.6) suggested a lactone ring formation between C-28 and C-19. The two double bonds were positioned on C11 –C12 and C13 – C18 based on a biogenesis consideration of 2 from arjungenin (4). The three hydroxyls were assigned on C-2a, C-3b, and C-23 according to observed NMR data of J1a,2 ¼ 11.4 Hz, J2,3 ¼ 9.6 Hz, and dC-24 at 13.4, as well as the NMR similarities of the A-ring of 2 and 4, especially observed J1a,2 ¼ 11.4 Hz, J2,3 ¼ 9.6 Hz, and dC-24 at 13.4. Such a structure for 2 was finally corroborated by the HMBC cross-peaks (Figure 2) of H-11/C-8, C-10, and C-13; H-12/C-9, C-13, and C-18; H-19 /C-13, C-17, C-18, C-20, C-28, C-29, and C-30, as well as C-4/H-2, H-3, H-5, H2-23, and Me-24. The structure of 2 was accordingly assigned to be 2a,3b,23-trihydroxyolean-11,13(18)-dien-28,19 b-olide. Mahato et al. treated 3 with 5% methanolic hydrochloric acid to yield 2a,3b,23-trihydroxyolean-11,13(18)-dien28-oic acid and 2a,3b,23-trihydroxyolean12-ene-28,19b-olide as two minor products [20]. As a similar structure, termichebulo-
Journal of Asian Natural Products Research lide (2) was also deduced to be derived from 3 or 4.
Downloaded by [University of Otago] at 02:03 09 July 2015
3. Experimental 3.1 General experimental procedures Optical rotations were determined on a Perkin-Elmer 341 polarimeter (PerkinElmer, Waltham, MA, USA). The IR spectra were recorded on a Nicolet-Magna-750FTIR spectrometer (ThermoFisher, Madison, WI, USA). The NMR spectra were taken on a Bruker AV-500 spectrometer (Bruker, Billerica, MA, USA) with TMS as the internal standard. ESI-MS and HR-ESIMS were obtained on a Bruker Esquire 3000plus (Bruker) and a Waters/Micromass Q-TOF-Ultima (Waters, Milford, MA, USA) mass spectrometers, respectively. Silica gel (200–300 mesh, Qingdao Haiyang Chemical Co. Ltd, Qingdao, China), Sephadex LH-20 (Pharmacia Biotech AB, Uppsala, Sweden), Rp-18 reversed-phase silica gel (150–200 mesh, Fuji Silysia Chemical Ltd., Aichi, Japan), and MCI Gel Chp20p (Mitsubishi Chemical, Tokyo, Japan) were used for column chromatography (CC). Silica gel HSGF254 (Yantai Jiangyou Guijiao Kaifa Co., Yantai, China) was used for TLC. Semi-prep HPLC preparation was run on a Waters HPLC system (Waters) with Waters-2545-HPLC pump, Waters-2489 detector, and XbridgeC18 column (5 mm, i.d. 10 mm £ 250 mm).
3.2 Plant material The barks of Terminalia chebula were collected in Xishuangbanna, Yunnan Province, China, in July 2013, and were identified by Prof. Da-Yuan Zhu of Shanghai Institute of Materia Medica. A voucher sample (No. 20130709) was deposited with the Herbarium of Shanghai Institute of Materia Medica, Chinese Academy of Sciences.
5
3.3 Extraction and isolation The dried barks of T. chebula (5 kg) were chopped and refluxed three times with MeOH. The MeOH extract was concentrated under reduced pressure to give a residue (600 g), which was suspended in H2O, and then partitioned with petroleum ether (PE), EtOAc, and n-BuOH, respectively. The EtOAc-soluble fraction (46 g) was subjected to CC of silica gel eluted with a gradient of CHCl3 – MeOH (1:0 ! 0:1) to get Frs. A1 –A10. Terminalin A (5 mg) was obtained as needle crystals from Fr. A1 (300 mg) after purification of silica gel CC eluted with gradient PE – acetone (100:1 ! 10:1). Fr. A2 (2.6 g) was repeatedly isolated by CC of silica gel eluted with PE –acetone (first 50:1 ! 5:1, then 30:1, finally 20:1) to afford ursolic acid lactone (5 mg). Ivorengenin B (4 mg) was got from Fr. A4 (1.3 g) via isolation of silica gel CC (PE –AcOEt, 2:1) and semiprep HPLC (MeOH – H2O, 7:3, UV 254/210 nm, flow rate 4 ml/min, tR ¼ 10.08 min). Fr. A5 (2.4 g) furnished pomonic acid (4 mg) after purification of silica gel CC (PE –AcOEt, 1:1) and semiprep HPLC (MeOH – H 2O, 85:15, 254/210 nm, 4 ml/min, tR ¼ 8.35 min). 2 (50 mg) was gained from Fr. A6 (2.0 g) via isolation of silica gel CC (PE – acetone 1:1) and recrystallization. Fr. A8 (4.0 g) was repeatedly purified on silica gel CC (CHCl3 – MeOH, 10:1) to yield euscaphic acid (3 mg). Fr. A9 (5.6 g) yielded 1 (9 mg) and 3 (13 mg) after purified process of CC over Rp-18 silica gel (MeOH – H2O, 1:0 ! 0:1), Sephadex LH-20 (MeOH), and semi-prep HPLC (MeOH –H2O, 6:4, 254/210 nm, 3 ml/min, tR ¼ 4.42 min for 1, CH3CN–H2O, 3:7, 254/210 nm, 4 ml/min, tR ¼ 11.32 min for 3). The n-BuOH layer (130 g) was subjected to CC of MCI (EtOH in H2O, 30%, 50%, 70%, and 95%) to give Frs. B1 – B4. Fr B3 (13 g) was isolated by CC of Rp-18 silica gel (EtOH in H2O, 30% ! 100%) to
6
C. Zhang et al.
Downloaded by [University of Otago] at 02:03 09 July 2015
yield Frs. B3.1– B3.5. Fr. B3.4 (2.0 g) was purified by CCs (Silica gel, CHCl 3 2 MeOH, 10: 1; Sephadex LH-20, CHCl3 2 MeOH, 1: 1) to afford 4 (50 mg). Fr. B3.5 (1.0 g) was isolated by silica gel CC (CHCl3 2 MeOH, 10: 1) and Semi-Prep HPLC (CH3CN 2 H2O, 55: 45, 254/210 nm, 4 ml/min) to obtain arjunolic acid (35 mg. HPLC, tR ¼ 20.55 min), actinidic acid (7 mg. tR ¼ 8.35 min), terminolic acid (6 mg. tR ¼ 12.12 min), and belleric acid (20 mg. tR ¼ 15.77 min), respectively. 3.3.1
Termichebuloside A (1)
White amorphous powder; ½a22 D 2 6.25 (c 0.08, i-PrOH); IR (KBr): nmax (cm21): 3435, 3427, 2930, 2922, 2880, 1750, 1740, 1644, 1435, 1387, 1043; 1H and 13C NMR spectral data, see Table 1; ESI-MS (positive): m/z 1315 [M þ H]þ, 1337 [M þ Na]þ; HR-ESI-MS: m/z 1315.7937 [M þ H]þ (calcd for C72H 115O 21 , 1315.7931). 3.3.2
Termichebulolide (2)
White amorphous powder; ½a22 D 2 6.25 (c 0.2, MeOH); IR (KBr): nmax (cm21): 3505, 3394, 2938, 2666, 1769, 1453, 1388, 1048; 1 H and 13C NMR spectral data, see Table 1; ESI-MS (positive): m/z 485 [M þ H]þ, 991 [2M þ Na]þ; HR-ESIMS: m/z 485.3271 [M þ H]þ (calcd for C30H45O5, 485.3267). Disclosure statement No potential conflict of interest was reported by the author(s).
Funding The authors thank the National Natural Science Foundation of China [grant number 81072545], [grant number 21202182] for financial support.
References [1] A. Bag, S.K. Bhattacharyya, and R.R. Chattopadhyay, Asian Pac. J. Trop. Biomed. 3, 244 (2013).
[2] S.K. Srivastava and S.D. Srivastava, Indian J. Chem. B 43, 2731 (2004). [3] D. Lee, K.H. Boo, J.K. Woo, F. Duan, K.H. Lee, T.K. Kwon, H.Y. Lee, K.Z. Riu, and D.S. Lee, J. Korean Soc. Appl. Biol. 54, 295 (2011). [4] L.J. Yang, K. Jiang, J.J. Tan, S.J. Qu, H.F. Luo, C.H. Tan, and D.-Y. Zhu, Helv. Chim. Acta 96, 119 (2013). [5] Y. Zhang, L.J. Yang, K. Jiang, C.H. Tan, J.J. Tan, P.M. Yang, and D.Y. Zhu, Carbohydr. Res. 361, 114 (2012). [6] K. Jiang, J.Q. Bai, J. Chang, J.J. Tan, S.J. Qu, H.F. Luo, C.H. Tan, and D.Y. Zhu, Helv. Chim. Acta 97, 64 (2014). [7] Y.H. Qiu, Y.F. Yang, J.M. Tan, C.H. Tan, and J. Chang, J. Asian Nat. Prod. Res. 16, 318 (2014). [8] S. Atta-ur-Rahman, M.I. Zareen, F.N. Choudhary, A. Ngounou, and M. Yasin, Tetrahedron Lett. 43, 6233 (2002). [9] B.K. Ponou, R.B. Teponno, M. Ricciutelli, T.B. Nguelefack, L. Quassinti, M. Bramucci, G. Lupidi, L. Barboni, and L.A. Tapondjou, Chem. Biodiv. 8, 1301 (2011). [10] R.S. Pawar and K.K. Bhutani, Phytomedicine 12, 391 (2005). [11] A. Jossang, M. Seuleiman, E. Maidou, and B. Bodo, Phytochemistry 41, 591 (1996). [12] J. Chen, W.L. Li, J.L. Wu, B.R. Ren, and H.Q. Zhang, Pharmazie 63, 765 (2008). [13] H.C. Wang and Y. Fujimoto, Phytochemistry 33, 151 (1993). [14] J. Ghosh, J. Das, P. Manna, and P.C. Sil, Free. Radic. Biol. Med. 48, 535 (2010). [15] D.L. Cheng and X.P. Cao, Phytochemistry 31, 1317 (1992). [16] N. De Tommasi, L. Rastrelli, M.R. Lauro, and R. Aquino, Phytochemistry 49, 1123 (1998). [17] Y.H. Wang, L.M. Xiang, M. Chen, Z.X. Zhang, and X.J. He, J. Mol. Catal. B-Enzym. 83, 51 (2012). [18] J. Conrad, B. Vogler, I. Klaiber, G. Roos, U. Walter, and W. Kraus, Phytochemistry 48, 647 (1998). [19] B.K. Ponou, R.B. Teponno, M. Ricciutelli, L. Quassinti, M. Bramucci, G. Lupidi, L. Barboni, and L.A. Tapondjou, Phytochemistry 71, 2108 (2010). [20] S.B. Mahato, A.K. Nandy, P. Luger, and M. Weber, J. Chem. Soc. Perk. Trans. 2, 1445 (1990).
