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Journal of Asian Natural Products Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ganp20
A new furanoxanthone from Garcinia mangostana a
a
a
Gwendoline Cheng Lian Ee , Irene See , Soek Sin Teh & Shaari ab
Daud a
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia b
Department of Chemistry, Faculty of Applied Sciences, Universiti Teknologi MARA, Jengka 26400, Pahang, Malaysia Published online: 27 Mar 2014.
Click for updates To cite this article: Gwendoline Cheng Lian Ee, Irene See, Soek Sin Teh & Shaari Daud (2014) A new furanoxanthone from Garcinia mangostana, Journal of Asian Natural Products Research, 16:7, 790-794, DOI: 10.1080/10286020.2014.901313 To link to this article: http://dx.doi.org/10.1080/10286020.2014.901313
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 &
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Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Journal of Asian Natural Products Research, 2014 Vol. 16, No. 7, 790–794, http://dx.doi.org/10.1080/10286020.2014.901313
A new furanoxanthone from Garcinia mangostana Gwendoline Cheng Lian Eea*, Irene Seea, Soek Sin Teha and Shaari Daudab a
Downloaded by [Istanbul Universitesi Kutuphane ve Dok] at 15:46 20 December 2014
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia; bDepartment of Chemistry, Faculty of Applied Sciences, Universiti Teknologi MARA, Jengka 26400, Pahang, Malaysia (Received 3 January 2014; final version received 3 March 2014) Our phytochemical study on the stem bark of Garcinia mangostana has led to the discovery of a new furanoxanthone, mangaxanthone A (1), together with five known analogs. The five known analogs that were isolated are a-mangostin (2), b-mangostin (3), cowagarcinone B (4), and dulcisxanthone F (5). The structural elucidations of these compounds were carried out by interpreting their spectroscopic data, mainly 1D and 2D NMR spectra and MS. Keywords: Guttiferae; Garcinia mangostana; xanthones; furanoxanthone
1.
Introduction
Garcinia mangostana (Guttiferae family) are easily available throughout South and Southeast Asia, especially Malaysia [1]. Its native name is mangosteen. G. mangostana is widely known as “the queen of fruits” for its sweetness and juiciness as well as its importance in enhancing a person’s health [2]. Traditionally, this fruit was used as medicine to treat skin infections, wounds, and diarrhea [3 –5]. It is also commonly consumed to expel heat from the body. Biologically active secondary metabolites from mangosteen plants have been reported to possess cytotoxicity against various cancer cells, such as human breast cancer, leukemia [6,7], and anti-inflammatory [8] property as well as antifungal activity [9]. Due to our continuing keen interest to further investigate the bioactive natural products from stem bark of Malaysian G. mangostana, our thorough detail research on the chemistry of the chloroform and ethyl acetate extracts has led to the isolation of five chemical constituents, including a new furanoxanthone (Figure 1). Here, we describe the isolation and structural eluci*Corresponding author. Email: [email protected] q 2014 Taylor & Francis
dation of these analogs based on the analysis of their spectroscopic data. 2.
Results and discussion
Various chromatographic techniques were carried out in order to isolate all the compounds. The structures of these compounds were elucidated through the interpretation of the spectroscopic data, such as 1D and 2D NMR, UV, IR, and MS. Compounds 2 – 5 were identified by comparing their spectrocopic data with those in the literature [10 –13]. Compound 1 was isolated as a yellow amorphous powder. The EI-MS showed a molecular ion peak at m/z 438, which is consistent with the molecular formula C 25H 26 O7 . The IR absorption at 3217 cm21 indicated the presence of an OZH group while the absorption at 1168 cm21 showed the presence of a CZO group. The existence of alkane and aromatic groups were confirmed by the IR absorptions at 2925 cm21 (alkane CZH), 1465 cm21 (alkane ZCH2Z), 1611 cm21 (aromatic CvC), and 806 cm21 (aromatic CZH). On the other hand, the maximum
Journal of Asian Natural Products Research 4˝
3˝
2˝
791
5˝
OH
O
1˝
O 8
H3CO
7
8a
HO
6
5a
9
9a
1 2
H3CO OCH3
2´ 3´ O
5
4a
3 4
O
4´
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OH
O
HO
1
O
OH
5´
1´
2
OH
O
OH H3CO
H3CO
HO
O
OCH3
OCH3
O
HO
3
4 2˝
3˝ 4˝
O
OH
O
HO
OCH3
O 5
Figure 1. Structures of compounds 1 –5.
absorptions at 209, 239, 260, 279, 313, and 368 in the UV spectrum indicated the existence of a xanthone skeleton. From the 1H NMR spectrum, two characteristic signals of the xanthone were observed at dH 6.96 (s, 1H, H-4) and dH 6.91 (s, 1H, H-5), a chelated hydroxy proton at dH 14.14 (s, 1H, 1-OH) and a methoxyl group at dH 3.82 (s, 3H, 7OCH3). The existence of a prenyl side chain was deduced from the signals at dH 4.11 (d, 2H, J ¼ 6.9 Hz, H-100 ), 5.29 (t, 1H, J ¼ 6.9 Hz, H-200 ), 1.84 (s, 3H, H-400 ), and 1.70 (s, 3H, H-500 ). The characteristic proton resonance of a 2-(1-methoxy-1methylethyl) furan-2-yl moiety was evident at dH 6.85 (s, 1H, H-10 ), 1.63 (s, 6H, H-40 , H-50 ), and 3.14 (s, 3H, 30 -OCH3). The 13C NMR spectrum revealed the existence of 26 carbons while the DEPT experiment indicated the presence of six methyls (dC 18.4, 25.2 £ 2, 25.9, 51.2, and
62.2), one methylene (dC 26.7), four methines (dC 89.9, 101.7 £ 2, and 123.1), and 14 quaternary carbons (dC 73.4, 104.6, 111.7, 112.6, 132.5, 137.3, 142.7, 153.5, 155.1, 156.3, 156.5, 159.2, 159.5, and 183.7). Another characteristic signal of xanthone skeleton was displayed in the 13C NMR spectrum at dC 183.7 which is for the carbonyl group. Further inspection on the DEPT spectrum showed the presence of eight oxygenated aromatic carbons which are C-1 (dC 156.3), C-3 (dC 159.5), C-20 (dC 159.2), C-30 (dC 73.4), C-4a (dC 156.5), C-5a (dC 153.5), C-6 (dC 155.1), and C-7 (dC 142.7). The position of the prenyl side chain at C-8 was confirmed by the cross-peaks of the methylene proton H-100 at dH 4.11 (d, 2H, J ¼ 6.9 Hz) with C-7 (dC 142.7), C-8 (dC 137.3), and C-8a (dC 111.7) while the position of the methoxyl group at C-7 was determined by the correlation of the
Downloaded by [Istanbul Universitesi Kutuphane ve Dok] at 15:46 20 December 2014
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G.C.L. Ee et al.
methoxyl proton at dH 3.82 (s, 3H) with C-7 (dC 142.7). Two aromatic protons were assigned to positions C-4 and C-5 from the 3J HMBC correlations of H-4 at dH 6.96 (s, 1H) with C-2 (dC 112.6) and C9a (dC 104.6) and the 2J and 3J HMBC correlations of H-5 at dH 6.91 (s, 1H) with C-6 (dC 155.1), C-7 (dC 142.7), and C-8a (dC 111.7) (Figure 2). These aromatic protons establish the xanthone skeleton of compound 1. In addition, the chelated hydroxyl group was attached to C-1 of the xanthone skeleton based on the 2J and 3J HMBC correlations of the hydroxyl proton at dH 14.14 (s, 1H) with C-1 (dC 156.3), C2 (dC 112.6), and C-9a (dC 104.6). The 2J HMBC correlations of H-10 at dH 6.85 (s, 1H) with C-20 (dC 159.2) and the correlations of H-40 and H-50 with C-20 (dC 159.2) and C-30 (dC 73.4) as well as the methoxyl proton of 30 -OCH3 at dH 3.14 (s, 3H) with C-30 (dC 73.4) implied the existence of 2-(1-methoxy-1-methylethyl) furan-2-yl moiety. This moiety is attached to C-2 (dC 112.6) and C-3 (dC 159.5) of the xanthone skeleton due to the observation of the 2J correlation between H-10 at dH 6.85 (s, 1H) and C-2 (dC 112.6). Based on the above-mentioned data, compound 1 is therefore elucidated as 1,6-dihydroxy7-methoxy-8-(3-methylbut-2-enyl)-2 0 (2-methoxypropane)furano-[2000 ,3000 :3,2]xanthone and given the trivial name mangaxanthone A. 4˝
3. Experimental 3.1 General experimental procedures Melting points were measured through Leica Galen III microscope (Leica Microsystems, Redwood city, CA, USA) that was equipped with Testo 720 temperature recorder. The ultraviolet spectra were recorded in CHCl3 on a Shimadzu UV160A UV-Visible Recording Spectrophotometer (Shimadzu Scientific Instruments , Kyoto, Japan) while the infrared spectra were measured by using the universal attenuated total reflection technique on a Perkin-Elmer 100 Series FT-IR spectrometer (Perkin Elmer, Waltham, MA, USA). The 1D (1H, 13C, and DEPT) and 2D (COSY, HMQC, and HMBC) NMR spectra were recorded on a Jeol Unity INOVA 500 MHz NMR (Jeol, Tachikawa, Japan) in CDCl 3 with tetramethylsilane as the internal standard. EI-MS were obtained from a Shimadzu GCMS model QP2010 Plus spectrophotometer (Shimadzu Scientific Instruments, Kyoto, Japan). 3.2
Plant material
The stem bark of G. mangostana was collected in January 2012 from Alor Gajah, Melaka, Malaysia, and kept in UPM. It was identified by Associate Prof. Dr Rusea Go from Biology Department, UPM. 3.3
Extraction and isolation
Air-dried stem bark of G. mangostana (2.0 kg) was ground into powder form and
5˝ 3˝
1˝ H3CO
OH
O
H
1
8 8a
9
5´
1´
9a
OCH3
2´ HO
5a 5
O
3
4a
O
4
H 2
3
Figure 2. Key J and J HMBC correlations in compound 1.
4´
Journal of Asian Natural Products Research Table 1. 1H and 13C NMR spectroscopic data for compound 1 in CDCl3.
dH
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Position 1 2 3 4 4a 5 5a 6 7 8 8a 9 9a 10 20 30 40 50 100 200 300 400 500 1-OH 7-OCH3 30 -OCH3
6.96 (s, 1H) 6.91 (s, 1H)
6.85 (s, 1H) 1.63 (s, 3H) 1.63 (s, 3H) 4.11 (d, 2H, J ¼ 6.9 Hz) 5.29 (t, 1H, J ¼ 6.9 Hz) 1.84 (s, 1.70 (s, 14.14 (s, 3.82 (s, 3.14 (s,
3H) 3H) 1H) 3H) 3H)
dC 156.3 112.6 159.5 89.9 156.5 101.7 153.5 155.1 142.7 137.3 111.7 183.7 104.6 101.7 159.2 73.4 25.2 25.2 26.7 123.1 132.5 18.4 25.9 62.2 51.2
defated with hexane. Then, the stem bark was extracted with chloroform (5 l £ 3) and ethyl acetate (5 l £ 3), respectively, for 3 days at room temperature. The extracts were combined and concentrated under reduced pressure to give 69.48 g of chloroform extract and 14.22 g of ethyl acetate extract. The chloroform extract was subjected to silica gel-packed column chromatography and eluted with gradient system of hexane, chloroform, ethyl acetate, and methanol to furnish 11 fractions. Fractions 5 (2.35 g), 7 (0.83 g), and 9 (7.81 g) were further separated on a silica gel column by eluting with a stepwise gradient system (hexane – chloroform and chloroform – methanol) and purified using Sephadex LH-20 by eluting with 100% methanol to obtain a-mangostin (2), b-mangostin (3), and cowagarcinone B (4). Meanwhile, the ethyl acetate
793
extract was chromatographed on a silica gel column using stepwise gradient system (hexane, hexane – chloroform, chloroform –ethyl acetate, and ethyl acetate – methanol) which resulted in six fractions. The new furanoxanthone, mangaxanthone A (1), and dulcisxanthone F (5) were isolated from fraction 4 (13.42 g) through a silica gel-packed column chromatography by eluting with a mixture of hexane – chloroform (9:1 and 3:2). 3.3.1
Mangaxanthone A (1)
Yellow amorphous powder; UV (CHCl3) lmax (log 1): 209 (6.74), 239 (4.66), 260 (4.91), 279 (4.89), 313 (4.62), and 368 (4.00) nm; IR n (cm21): 3217, 2925, 1611, 1465, 1168, and 806; for 1H NMR (500 MHz, CDCl3) and 13C NMR (125 MHz, CDCl3) spectral data, see Table 1; EI-MS m/z (rel. int.): 438 (62), 424 (11), 423 (41), 408 (27), 407 (100), 406 (39), 405 (12), 396 (15), 395 (61), 391 (15), 373 (16), 365 (13), 364 (18), 363 (65), 349 (18), 348 (17), 337 (14), 335 (11), 190 (23), 182 (18), 174 (9), 168 (14), 161 (13). References [1] Y. Zhao, J.P. Liu, D. Lu, P.Y. Li, and L.X. Zhang, Nat. Prod. Res. 24, 1664 (2010). [2] A.R. Garrity, G.A. Morton, J.C. Morton, US Patent No. 6730333 B1 20040504. 7 (2004). [3] N. Chairungsrilerd, K. Takeuchi, Y. Ohizumi, S. Nozoe, and T. Ohta, Phytochemistry 43, 1099 (1996). [4] W. Mahabusarakam and P. Wiriyachitra, J. Nat. Prod. 50, 474 (1987). [5] K. Balasubramanian and K. Rajagopalan, Phytochemistry 27, 1552 (1988). [6] K. Matsumoto, Y. Akao, E. Kobayashi, K. Ohguchi, T. Ito, T. Tanaka, M. Iinuma, and Y. Nozawa, J. Nat. Prod. 66, 1124 (2003). [7] P. Moongkarndi, N. Kosema, S. Kaslungka, O. Luanratana, N. Pongpan, and N. Neungton, J. Ethnopharmacol. 90, 161 (2004). [8] G. Gopalakrishnan and B. Balaganesan, Fitoterapia 71, 607 (2000).
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[9] G. Gopalakrishnan, B. Banumathi, and G. Suresh, J. Nat. Prod. 60, 519 (1997). [10] P. Yates and G.H. Stout, J. Am. Chem. Soc. 80, 1691 (1958). [11] P. Yates and H.B. Bhat, Can. J. Chem. 46, 3770 (1968).
[12] W. Mahabusarakam, P. Chairerk, and W.C. Taylor, Phytochemistry 66, 1148 (2005). [13] S. Deachathai, W. Mahabusarakam, S. Phongpaichit, W.C. Taylor, Y.J. Zhang, and C.R. Yang, Phytochemistry 67, 464 (2006).
Journal of Asian Natural Products Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ganp20
A new furanoxanthone from Garcinia mangostana a
a
a
Gwendoline Cheng Lian Ee , Irene See , Soek Sin Teh & Shaari ab
Daud a
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia b
Department of Chemistry, Faculty of Applied Sciences, Universiti Teknologi MARA, Jengka 26400, Pahang, Malaysia Published online: 27 Mar 2014.
Click for updates To cite this article: Gwendoline Cheng Lian Ee, Irene See, Soek Sin Teh & Shaari Daud (2014) A new furanoxanthone from Garcinia mangostana, Journal of Asian Natural Products Research, 16:7, 790-794, DOI: 10.1080/10286020.2014.901313 To link to this article: http://dx.doi.org/10.1080/10286020.2014.901313
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 [Istanbul Universitesi Kutuphane ve Dok] at 15:46 20 December 2014
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Journal of Asian Natural Products Research, 2014 Vol. 16, No. 7, 790–794, http://dx.doi.org/10.1080/10286020.2014.901313
A new furanoxanthone from Garcinia mangostana Gwendoline Cheng Lian Eea*, Irene Seea, Soek Sin Teha and Shaari Daudab a
Downloaded by [Istanbul Universitesi Kutuphane ve Dok] at 15:46 20 December 2014
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia; bDepartment of Chemistry, Faculty of Applied Sciences, Universiti Teknologi MARA, Jengka 26400, Pahang, Malaysia (Received 3 January 2014; final version received 3 March 2014) Our phytochemical study on the stem bark of Garcinia mangostana has led to the discovery of a new furanoxanthone, mangaxanthone A (1), together with five known analogs. The five known analogs that were isolated are a-mangostin (2), b-mangostin (3), cowagarcinone B (4), and dulcisxanthone F (5). The structural elucidations of these compounds were carried out by interpreting their spectroscopic data, mainly 1D and 2D NMR spectra and MS. Keywords: Guttiferae; Garcinia mangostana; xanthones; furanoxanthone
1.
Introduction
Garcinia mangostana (Guttiferae family) are easily available throughout South and Southeast Asia, especially Malaysia [1]. Its native name is mangosteen. G. mangostana is widely known as “the queen of fruits” for its sweetness and juiciness as well as its importance in enhancing a person’s health [2]. Traditionally, this fruit was used as medicine to treat skin infections, wounds, and diarrhea [3 –5]. It is also commonly consumed to expel heat from the body. Biologically active secondary metabolites from mangosteen plants have been reported to possess cytotoxicity against various cancer cells, such as human breast cancer, leukemia [6,7], and anti-inflammatory [8] property as well as antifungal activity [9]. Due to our continuing keen interest to further investigate the bioactive natural products from stem bark of Malaysian G. mangostana, our thorough detail research on the chemistry of the chloroform and ethyl acetate extracts has led to the isolation of five chemical constituents, including a new furanoxanthone (Figure 1). Here, we describe the isolation and structural eluci*Corresponding author. Email: [email protected] q 2014 Taylor & Francis
dation of these analogs based on the analysis of their spectroscopic data. 2.
Results and discussion
Various chromatographic techniques were carried out in order to isolate all the compounds. The structures of these compounds were elucidated through the interpretation of the spectroscopic data, such as 1D and 2D NMR, UV, IR, and MS. Compounds 2 – 5 were identified by comparing their spectrocopic data with those in the literature [10 –13]. Compound 1 was isolated as a yellow amorphous powder. The EI-MS showed a molecular ion peak at m/z 438, which is consistent with the molecular formula C 25H 26 O7 . The IR absorption at 3217 cm21 indicated the presence of an OZH group while the absorption at 1168 cm21 showed the presence of a CZO group. The existence of alkane and aromatic groups were confirmed by the IR absorptions at 2925 cm21 (alkane CZH), 1465 cm21 (alkane ZCH2Z), 1611 cm21 (aromatic CvC), and 806 cm21 (aromatic CZH). On the other hand, the maximum
Journal of Asian Natural Products Research 4˝
3˝
2˝
791
5˝
OH
O
1˝
O 8
H3CO
7
8a
HO
6
5a
9
9a
1 2
H3CO OCH3
2´ 3´ O
5
4a
3 4
O
4´
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OH
O
HO
1
O
OH
5´
1´
2
OH
O
OH H3CO
H3CO
HO
O
OCH3
OCH3
O
HO
3
4 2˝
3˝ 4˝
O
OH
O
HO
OCH3
O 5
Figure 1. Structures of compounds 1 –5.
absorptions at 209, 239, 260, 279, 313, and 368 in the UV spectrum indicated the existence of a xanthone skeleton. From the 1H NMR spectrum, two characteristic signals of the xanthone were observed at dH 6.96 (s, 1H, H-4) and dH 6.91 (s, 1H, H-5), a chelated hydroxy proton at dH 14.14 (s, 1H, 1-OH) and a methoxyl group at dH 3.82 (s, 3H, 7OCH3). The existence of a prenyl side chain was deduced from the signals at dH 4.11 (d, 2H, J ¼ 6.9 Hz, H-100 ), 5.29 (t, 1H, J ¼ 6.9 Hz, H-200 ), 1.84 (s, 3H, H-400 ), and 1.70 (s, 3H, H-500 ). The characteristic proton resonance of a 2-(1-methoxy-1methylethyl) furan-2-yl moiety was evident at dH 6.85 (s, 1H, H-10 ), 1.63 (s, 6H, H-40 , H-50 ), and 3.14 (s, 3H, 30 -OCH3). The 13C NMR spectrum revealed the existence of 26 carbons while the DEPT experiment indicated the presence of six methyls (dC 18.4, 25.2 £ 2, 25.9, 51.2, and
62.2), one methylene (dC 26.7), four methines (dC 89.9, 101.7 £ 2, and 123.1), and 14 quaternary carbons (dC 73.4, 104.6, 111.7, 112.6, 132.5, 137.3, 142.7, 153.5, 155.1, 156.3, 156.5, 159.2, 159.5, and 183.7). Another characteristic signal of xanthone skeleton was displayed in the 13C NMR spectrum at dC 183.7 which is for the carbonyl group. Further inspection on the DEPT spectrum showed the presence of eight oxygenated aromatic carbons which are C-1 (dC 156.3), C-3 (dC 159.5), C-20 (dC 159.2), C-30 (dC 73.4), C-4a (dC 156.5), C-5a (dC 153.5), C-6 (dC 155.1), and C-7 (dC 142.7). The position of the prenyl side chain at C-8 was confirmed by the cross-peaks of the methylene proton H-100 at dH 4.11 (d, 2H, J ¼ 6.9 Hz) with C-7 (dC 142.7), C-8 (dC 137.3), and C-8a (dC 111.7) while the position of the methoxyl group at C-7 was determined by the correlation of the
Downloaded by [Istanbul Universitesi Kutuphane ve Dok] at 15:46 20 December 2014
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G.C.L. Ee et al.
methoxyl proton at dH 3.82 (s, 3H) with C-7 (dC 142.7). Two aromatic protons were assigned to positions C-4 and C-5 from the 3J HMBC correlations of H-4 at dH 6.96 (s, 1H) with C-2 (dC 112.6) and C9a (dC 104.6) and the 2J and 3J HMBC correlations of H-5 at dH 6.91 (s, 1H) with C-6 (dC 155.1), C-7 (dC 142.7), and C-8a (dC 111.7) (Figure 2). These aromatic protons establish the xanthone skeleton of compound 1. In addition, the chelated hydroxyl group was attached to C-1 of the xanthone skeleton based on the 2J and 3J HMBC correlations of the hydroxyl proton at dH 14.14 (s, 1H) with C-1 (dC 156.3), C2 (dC 112.6), and C-9a (dC 104.6). The 2J HMBC correlations of H-10 at dH 6.85 (s, 1H) with C-20 (dC 159.2) and the correlations of H-40 and H-50 with C-20 (dC 159.2) and C-30 (dC 73.4) as well as the methoxyl proton of 30 -OCH3 at dH 3.14 (s, 3H) with C-30 (dC 73.4) implied the existence of 2-(1-methoxy-1-methylethyl) furan-2-yl moiety. This moiety is attached to C-2 (dC 112.6) and C-3 (dC 159.5) of the xanthone skeleton due to the observation of the 2J correlation between H-10 at dH 6.85 (s, 1H) and C-2 (dC 112.6). Based on the above-mentioned data, compound 1 is therefore elucidated as 1,6-dihydroxy7-methoxy-8-(3-methylbut-2-enyl)-2 0 (2-methoxypropane)furano-[2000 ,3000 :3,2]xanthone and given the trivial name mangaxanthone A. 4˝
3. Experimental 3.1 General experimental procedures Melting points were measured through Leica Galen III microscope (Leica Microsystems, Redwood city, CA, USA) that was equipped with Testo 720 temperature recorder. The ultraviolet spectra were recorded in CHCl3 on a Shimadzu UV160A UV-Visible Recording Spectrophotometer (Shimadzu Scientific Instruments , Kyoto, Japan) while the infrared spectra were measured by using the universal attenuated total reflection technique on a Perkin-Elmer 100 Series FT-IR spectrometer (Perkin Elmer, Waltham, MA, USA). The 1D (1H, 13C, and DEPT) and 2D (COSY, HMQC, and HMBC) NMR spectra were recorded on a Jeol Unity INOVA 500 MHz NMR (Jeol, Tachikawa, Japan) in CDCl 3 with tetramethylsilane as the internal standard. EI-MS were obtained from a Shimadzu GCMS model QP2010 Plus spectrophotometer (Shimadzu Scientific Instruments, Kyoto, Japan). 3.2
Plant material
The stem bark of G. mangostana was collected in January 2012 from Alor Gajah, Melaka, Malaysia, and kept in UPM. It was identified by Associate Prof. Dr Rusea Go from Biology Department, UPM. 3.3
Extraction and isolation
Air-dried stem bark of G. mangostana (2.0 kg) was ground into powder form and
5˝ 3˝
1˝ H3CO
OH
O
H
1
8 8a
9
5´
1´
9a
OCH3
2´ HO
5a 5
O
3
4a
O
4
H 2
3
Figure 2. Key J and J HMBC correlations in compound 1.
4´
Journal of Asian Natural Products Research Table 1. 1H and 13C NMR spectroscopic data for compound 1 in CDCl3.
dH
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Position 1 2 3 4 4a 5 5a 6 7 8 8a 9 9a 10 20 30 40 50 100 200 300 400 500 1-OH 7-OCH3 30 -OCH3
6.96 (s, 1H) 6.91 (s, 1H)
6.85 (s, 1H) 1.63 (s, 3H) 1.63 (s, 3H) 4.11 (d, 2H, J ¼ 6.9 Hz) 5.29 (t, 1H, J ¼ 6.9 Hz) 1.84 (s, 1.70 (s, 14.14 (s, 3.82 (s, 3.14 (s,
3H) 3H) 1H) 3H) 3H)
dC 156.3 112.6 159.5 89.9 156.5 101.7 153.5 155.1 142.7 137.3 111.7 183.7 104.6 101.7 159.2 73.4 25.2 25.2 26.7 123.1 132.5 18.4 25.9 62.2 51.2
defated with hexane. Then, the stem bark was extracted with chloroform (5 l £ 3) and ethyl acetate (5 l £ 3), respectively, for 3 days at room temperature. The extracts were combined and concentrated under reduced pressure to give 69.48 g of chloroform extract and 14.22 g of ethyl acetate extract. The chloroform extract was subjected to silica gel-packed column chromatography and eluted with gradient system of hexane, chloroform, ethyl acetate, and methanol to furnish 11 fractions. Fractions 5 (2.35 g), 7 (0.83 g), and 9 (7.81 g) were further separated on a silica gel column by eluting with a stepwise gradient system (hexane – chloroform and chloroform – methanol) and purified using Sephadex LH-20 by eluting with 100% methanol to obtain a-mangostin (2), b-mangostin (3), and cowagarcinone B (4). Meanwhile, the ethyl acetate
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extract was chromatographed on a silica gel column using stepwise gradient system (hexane, hexane – chloroform, chloroform –ethyl acetate, and ethyl acetate – methanol) which resulted in six fractions. The new furanoxanthone, mangaxanthone A (1), and dulcisxanthone F (5) were isolated from fraction 4 (13.42 g) through a silica gel-packed column chromatography by eluting with a mixture of hexane – chloroform (9:1 and 3:2). 3.3.1
Mangaxanthone A (1)
Yellow amorphous powder; UV (CHCl3) lmax (log 1): 209 (6.74), 239 (4.66), 260 (4.91), 279 (4.89), 313 (4.62), and 368 (4.00) nm; IR n (cm21): 3217, 2925, 1611, 1465, 1168, and 806; for 1H NMR (500 MHz, CDCl3) and 13C NMR (125 MHz, CDCl3) spectral data, see Table 1; EI-MS m/z (rel. int.): 438 (62), 424 (11), 423 (41), 408 (27), 407 (100), 406 (39), 405 (12), 396 (15), 395 (61), 391 (15), 373 (16), 365 (13), 364 (18), 363 (65), 349 (18), 348 (17), 337 (14), 335 (11), 190 (23), 182 (18), 174 (9), 168 (14), 161 (13). References [1] Y. Zhao, J.P. Liu, D. Lu, P.Y. Li, and L.X. Zhang, Nat. Prod. Res. 24, 1664 (2010). [2] A.R. Garrity, G.A. Morton, J.C. Morton, US Patent No. 6730333 B1 20040504. 7 (2004). [3] N. Chairungsrilerd, K. Takeuchi, Y. Ohizumi, S. Nozoe, and T. Ohta, Phytochemistry 43, 1099 (1996). [4] W. Mahabusarakam and P. Wiriyachitra, J. Nat. Prod. 50, 474 (1987). [5] K. Balasubramanian and K. Rajagopalan, Phytochemistry 27, 1552 (1988). [6] K. Matsumoto, Y. Akao, E. Kobayashi, K. Ohguchi, T. Ito, T. Tanaka, M. Iinuma, and Y. Nozawa, J. Nat. Prod. 66, 1124 (2003). [7] P. Moongkarndi, N. Kosema, S. Kaslungka, O. Luanratana, N. Pongpan, and N. Neungton, J. Ethnopharmacol. 90, 161 (2004). [8] G. Gopalakrishnan and B. Balaganesan, Fitoterapia 71, 607 (2000).
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[9] G. Gopalakrishnan, B. Banumathi, and G. Suresh, J. Nat. Prod. 60, 519 (1997). [10] P. Yates and G.H. Stout, J. Am. Chem. Soc. 80, 1691 (1958). [11] P. Yates and H.B. Bhat, Can. J. Chem. 46, 3770 (1968).
[12] W. Mahabusarakam, P. Chairerk, and W.C. Taylor, Phytochemistry 66, 1148 (2005). [13] S. Deachathai, W. Mahabusarakam, S. Phongpaichit, W.C. Taylor, Y.J. Zhang, and C.R. Yang, Phytochemistry 67, 464 (2006).
