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Two new xanthones from the pericarp of Garcinia mangostana ab
ac
ac
a
Xiaojun Zhou , Luan He , Xinxing Wu , Yanxia Zhong , Juan d
d
b
a
Zhang , Yuanxing Wang , Bin Wang , Zhifang Xu & Shengxiang Qiu
a
a
Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, P.R. China b
Department of Pharmacy, Medical College, Nanchang University, Nanchang, P.R. China c
University of Chinese Academy of Sciences, Beijing, 100049, P.R. China d
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047, P.R. China Published online: 09 Oct 2014.
To cite this article: Xiaojun Zhou, Luan He, Xinxing Wu, Yanxia Zhong, Juan Zhang, Yuanxing Wang, Bin Wang, Zhifang Xu & Shengxiang Qiu (2015) Two new xanthones from the pericarp of Garcinia mangostana, Natural Product Research: Formerly Natural Product Letters, 29:1, 19-23, DOI: 10.1080/14786419.2014.927873 To link to this article: http://dx.doi.org/10.1080/14786419.2014.927873
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Natural Product Research, 2015 Vol. 29, No. 1, 19–23, http://dx.doi.org/10.1080/14786419.2014.927873
Two new xanthones from the pericarp of Garcinia mangostana
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Xiaojun Zhouab, Luan Heac, Xinxing Wuac, Yanxia Zhonga, Juan Zhangd, Yuanxing Wangd*, Bin Wangb, Zhifang Xua and Shengxiang Qiua* a Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, P.R. China; bDepartment of Pharmacy, Medical College, Nanchang University, Nanchang, P.R. China; cUniversity of Chinese Academy of Sciences, Beijing 100049, P.R. China; dState Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, P.R. China
(Received 7 April 2014; final version received 20 May 2014) Two new xanthones, designated garcimangosxanthone F (1) and garcimangosxanthone G (2), were isolated from the EtOAc-soluble fraction of ethanolic extract from the pericarp of Garcinia mangostana. Their structures were established as 1,6,7trihydroxy-5-(3-methylbut-2-enyl)-8-(3-hydroxy-3-methylbutyl)-60 ,60 -dimethylpyrano [20 ,30 :3,2]xanthone and 1,6,7-trihydroxy-5-(3-methylbut-2-enyl)-8-(3-hydroxy-3methylbutyl)-60 ,60 -dimethyl-40 ,50 -dihydropyrano[20 ,30 :3,2]xanthone, respectively, on the basis of their 1D, 2D NMR and MS data interpretation. Keywords: Garcinia mangostana; xanthone; garcimangosxanthone F; garcimangosxanthone G
1. Introduction Garcinia mangostana L. (Guttiferae), colloquially known simply as purple mangosteen or mangosteen, is a tropical evergreen tree believed to have originated in the Sunda Islands and the Moluccas of Indonesia. It grows mainly in Southeast Asia, and also grows in tropical South American countries such as Colombia, where the tree has been introduced (Morton 1987; Obolskiy et al. 2009). The fruit of the mangosteen is sweet, tangy, juicy and somewhat fibrous, with an inedible, deep reddish-purple coloured rind (exocarp) when ripe. Mangosteen pericarp has been used as a folklore remedy for inflammation, diarrhoea and as an astringent since ancient times (Chairungsrilerd et al. 1996). The chemical constituents of the mangosteen pericarp comprise an array of polyphenols, including tannins and xanthones with a-mangostin and gmangostin as the major secondary metabolites (Mahabusarakam et al. 1987; Iinuma et al. 1996; Gopalakrishnan & Balaganesan 2000; Huang et al. 2001; Suksamrarn et al. 2003; Hu et al. 2006; Jung et al. 2006; Suksamrarn et al. 2006). With the aim of searching for chemical components responsible for the pharmacology documented for the mangosteen pericarp, we performed an extensive phytochemical study on an ethanolic extract from mangosteen peels. Previously, we reported the isolation of five new xanthones, namely garcimangosxanthones A – C (Zhang et al. 2010) and D, E (Zhou et al. 2011). A biological evaluation indicated that garcimangosxanthone A and B exhibited potent growthinhibitory activity against human cancer cell lines A549 (lung cancer), LAC (pulmonary carcinoma) and A375 (human hepatoma) with IC50 values of 5.7– 24.9 mM, which were
*Corresponding authors. Email: [email protected]; [email protected] q 2014 Taylor & Francis
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comparable to those of the positive control substance doxorubicin, while the others exhibited only moderate cytotoxicity (Zhang et al. 2010). As part of our ongoing study of the chemical constituents from mangosteen pericarp, a scaleup extraction was conducted with an aim to isolate more compounds, which resulted in the isolation of two new xanthones 1 and 2 from the EtOAc partition of the ethanol extract. Herein, we report the isolation and structural identification of compounds 1 and 2.
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2. Results and discussion Garcimangosxanthone F (1) was obtained as a yellow powder. Its molecular formula was established as C28H32O7 by HR-EI-MS based on the molecular ion observed at m/z 480.2141 [M]þ (calcd 480.2143 for C28H32O7). The 1H NMR revealed one chelated phenolic hydroxyl proton at dH 14.12 (1H, s, 1-OH) and one isolated aromatic proton at dH 6.31 (1H, s, H-4). Other signal sets could be attributed to a 2,2-dimethylchromene ring at dH 6.69 (1H, s, J ¼ 10.0 Hz, H11), 5.71 (1H, s, J ¼ 10.0 Hz, H-12), 1.47 (6H, s, H-14, 15), a prenyl group at dH 3.60 (2H, d, J ¼ 6.9 Hz, H-16), 5.31 (1H, t, J ¼ 6.9 Hz, H-17), 1.67 (3H, s, H-19), 1.90 (3H, s, H-20) and a 3hydroxy-3-methylbutyl moiety at dH 3.42 (2H, t, J ¼ 6.5 Hz, H-21), 1.93 (1H, t, J ¼ 6.5 Hz, H22), 1.30 (6H, s, H-24, 25), respectively. Closer inspection revealed that the 1H and 13C NMR data of 1 were similar to those of caloxanthone A (Iinuma et al. 1994), with a 3-hydroxy-3methylbutyl group replacing the aromatic H-atom at C-8. The structure assignment of 1 was further supported by the HMBC spectrum. The correlations from H-11 to C-1, C-2, and C-3, and from H-12 to C-2 were suggestive of the connectivity of the 2,2-dimethylchromene ring positioned between C-2 and C-3. The correlations from H-16 to C-5, C-6 and C-10a, as well as between H-17 to C-5, revealed that the prenyl group was attached at C-5. The aromatic proton was readily assigned at C-4, on the basis of the HMBC correlations from H-4 to C-2, C-3, C-4a and C-9a. Moreover, the 3-hydroxy-3methylbutyl moiety was located at C-8, according to the HMBC correlations from H-21 to C-7, C-8 and C-8a, and from H-22 to C-8. Thus, the structure of 1 was elucidated as 1,6,7-trihydroxy5-(3-methylbut-2-enyl)-8-(3-hydroxy-3-methylbutyl)-60 ,60 -dimethylpyrano[20 ,30 :3,2]xanthone. Garcimangosxanthone G (2) was obtained as a yellow amorphous powder. Its HR-EI-MS (482.2295 [M]þ) established a molecular formula of C28H34O7. The 1H and 13C NMR data of 2 were similar to those of 1. The only difference was that the two doublets at H-11 and H-12 in 1 were replaced by two triplet methylenes at H-11 and H-12 in 2. This structure assignment for 2 (Figure 1) was confirmed by its HMBC spectrum (key correlations depicted in Figure 1). The HMBC correlations from H-11 to C-1, C-2, and C-3, and from H-12 to C-2 were suggestive of the connectivity of 2,2-dimethylchroman ring positioned between C-2 and C-3. Thus, the
Figure 1. Structures of compounds 1 and 2.
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structure of 2 was determined as 1,6,7-trihydroxy-5-(3-methylbut-2-enyl)-8-(3-hydroxy-3methylbutyl)-60 ,60 -dimethyl-40 ,50 -dihydropyrano[20 ,30 :3,2]-xanthone, which is also a new structure and therefore named garcimangosxanthone G. It is well known that the mangosteen exocarp contains an array of polyphenols, including xanthones and tannins. This study not only shed new light on the constituent chemistry of the mangosteen exocarp, but also enriched the chemical diversity of the compound library for new drug discovery.
3. Experimental
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3.1. General The 1D and 2D 1H, 13C NMR including HMQC and HMBC spectra were recorded on a Bruker DRX-400 instrument (Bruker Corp., Billerica, MA, USA) operating at 400 and 100 MHz, respectively, in (CD3)2CO-d6 using TMS as the internal standard. The chemical shift values are reported in ppm (d) units and the coupling constants (J) are in Hz. HR-EI-MS data were obtained on a MAT95XP mass spectrometer (Thermo Electron Corp., San Jose, CA). ESI-MS were collected on MDS SCIEX API 2000 LC/MS/MS instrument (Applied Biosystems Corp., Foster City, CA, USA). For column chromatography (CC), silica gel (80–100, 100–200 and 200–300 mesh, Qingdao Marine Chemical Ltd, Qingdao, China), and Sephadex LH-20 (Amersham Biosciences Corp., Uppsala, Sweden) was used. HPLC: Kromasil C18 (Akzo Nobel Corp., Partille, Sweden) (4.6 mm £ 250 mm, 5 mm), DAD (UV6000LP) detection. TLC was performed on GF254 plates (Qingdao Marine Chemical Ltd) while its detection was observed at 254 nm.
3.2. Plant material The pericarp of G. mangostana was obtained by peeling the fruits bought from a local grocery store in Guangzhou, China, and identified by Prof. Yun-Fei Deng of South China Botanical Garden. A voucher specimen (No. 0233559) has been deposited in the Laboratory of Natural Products Chemical Biology of South China Botanical Garden, Chinese Academy of Sciences.
3.3. Extraction and isolation The extraction procedures of extracting xanthones from mangosteen pericarps have been described previously (Zhang et al. 2010; Zhou et al. 2011). Briefly, the powdered dry pericarps of G. mangostana (4 kg) were extracted three times with 95% ethanol (8 L £ 3) at room temperature, for 3 days each. After evaporation of the pooled solvents in vacuo, the combined crude ethanolic extract residue (855.8 g) was obtained, which was shown to contain mainly xanthones as expected by TLC analysis with xanthones we isolated previously. The ethanolic extract residue was then partitioned with EtOAc (2 L £ 3) to afford EtOAc (344.5 g) extract. The EtOAc-soluble extract was subjected to a silica gel CC and eluted with petroleum ether – acetone with increasing polarities (10:1 2 1:1, v/v) to yield 17 fractions (A – Q). Fraction F (19.5 g) was then subjected to a silica gel CC using mixture solvents of petroleum ether 2 EtOAc with increasing polarity (from a ratio of 8:1 to 1:1, v/v) to obtain five fractions F1 – F5. F2 (1.2 g), which was further subjected to Sephadex LH-20 CC and eluted with MeOH to obtain four subfractions F2-1 – F2-4. Sub-fraction F2-2 (25 mg) was eventually separated by reversed-phase HPLC eluting with 90% MeOH/H2O to yield 1 (8 mg, 4 mg, tR ¼ 27.4 min) and 2 (5 mg, 5 mg, tR ¼ 25.6 min).
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3.3.1. Garcimangosxanthone F (1) Yellow amorphous powder; HR-EI-MS m/z 480.2141 [M]þ (calcd 480.2143 for C28H32O7); 1H NMR: d 14.12 (1H, s, OH-1), 6.31 (1H, s, H-4), 6.69 (1H, d, J ¼ 10.0 Hz, H-11), 5.71 (1H, d, J ¼ 10.0 Hz, H-12), 3.60 (2H, d, J ¼ 7.3 Hz, H-16), 5.31 (1H, t, J ¼ 7.3 Hz, H-17), 3.42 (2H, t, J ¼ 6.7 Hz, H-21), 1.93 (1H, t, J ¼ 6.7 Hz, H-22), 1.47 (6H, s, H-14, 15), 1.67 (3H, s, H-19), 1.89 (3H, s, H-20), 1.29 (6H, s, H-24, 25); 13C NMR: d 183.3 (C-9), 160.4 (C-3), 158.7 (C-1), 157.2 (C-4a), 152.4* (C-6), 152.1* (C-10a), 140.8 (C-7), 132.3 (C-18), 128.7 (C-8), 128.3 (C12), 122.6 (C-17), 116.0 (C-11), 113.9 (C-5), 111.3 (C-8a), 104.7 (C-2), 104.1 (C-9a), 94.5 (C4), 78.5 (C-13), 71.5 (C-23), 43.8 (C-22), 29.7 (C-24), 29.7 (C-25), 28.4 (C-14), 28.4 (C-15), 25.8 (C-19), 23.0 (C-16), 22.1 (C-21), 18.1 (C-20) (*Interchangable). 3.3.2. Garcimangosxanthone G (2) Yellow amorphous powder; HR-EI-MS m/z 482.2293 [M]þ (calcd 482.2295 for C28H34O7); 1H NMR: d 14.04 (1H, s, OH-1), 6.27 (1H, s, H-4), 2.68 (2H, t, J ¼ 6.8 Hz, H-11), 1.87 (2H, t, J ¼ 6.8 Hz, H-12), 3.59 (2H, d, J ¼ 7.3 Hz, H-16), 5.32 (1H, t, J ¼ 7.3 Hz, H-17), 3.43 (2H, t, J ¼ 6.6 Hz, H-21), 1.93 (1H, t, J ¼ 6.6 Hz, H-22), 1.37 (6H, s, H-14, 15), 1.66 (3H, s, H-19), 1.89 (3H, s, H-20), 1.29 (6H, s, H-24, 25); 13C NMR: d 183.3 (C-9), 161.3 (C-1), 161.1 (C-3), 155.5 (C-4a), 152.2* (C-6), 152.0* (C-10a), 140.3 (C-7), 132.1 (C-18), 128.7 (C-8), 122.7 (C17), 113.8 (C-5), 111.3 (C-8a), 104.1 (C-2), 103.2 (C-9a), 94.3 (C-4), 76.7 (C-13), 71.3 (C-23), 43.7 (C-22), 32.3 (C-12), 29.6 (C-24), 29.6 (C-25), 26.8 (C-11), 25.8 (C-19), 23.0 (C-16), 22.2 (C-21), 18.0 (C-20), 16.6 (C-14), 16.6 (C-15) (*Interchangable). Supplementary material Supplementary figures relating to this article are available online. Acknowledgements This work was jointly supported by funds from the Chinese Academy of Sciences 100 Talents Program, the National Natural Science Foundation (30973635, 81373293) and the National Science and Technology Major Projects (2014ZX10005002).
References Chairungsrilerd N, Yakeuchi K, Ohizum Y, Nozoe S, Ohta T. 1996. Mangostanol, a prenyl xanthone from Garcinia mangostana. Phytochemistry. 43:1009–1102. Gopalakrishnan G, Balaganesan B. 2000. Two new xanthones from Garcinia mangostana. Fitoterapia. 71:607–609. Hu JM, Chen JJ, Zhao YX, Wang RR, Zheng YT, Zhou J. 2006. Chemical constituents from fruit hulls of Garcinia mangostana (Cuttiferae). Acta Bot Yunnanica. 28:319–322. Huang YL, Chen CC, Chen YJ, Huang RL, Shieh BJ. 2001. Three xanthones and a benzophenone from Garcinia mangostana. J Nat Prod. 64:903–906. Iinuma M, Tosa H, Tanaka T, Asai F, Kobayashl Y, Shimano R, Miyauchi KI. 1996. Antibacterial activity of xanthone from Guttiferaeous plants against methicillin-resistant Staphylococcus aureus. J Pharm Pharmacol. 48:861–865. Iinuma M, Tosa H, Tanaka T, Yonemori S. 1994. Two xanthones from root bark of Calophyllum inophyllum. Phytochemistry. 35:527–532. Jung HA, Su BA, Keller WJ, Mehta RG, Kinghorn AD. 2006. Antioxidant xanthone from the pericarp of Garcinia mangostana (mangosteen). J Agric Food Chem. 54:2077–2082. Mahabusarakam W, Wiriyachitra P, Taylor WC. 1987. Chemical constituents of Garcinia mangostana. J Nat Prod. 50:474–478. Morton, JF. 1987. Mangosteen. In: Fruits of Warm Climates. Miami: Julia F. Morton; p. 301 –304. Obolskiy D, Pischel I, Siriwatanametanon N, Heinrich M. 2009. Garcinia mangostana L.: a phytochemical and pharmacological review. Phytochemistry. 23:1047–1065.
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Suksamrarn S, Komutiban O, Ratananukul P, Chimnoi N, Lartpornmatulee N, Suksamrarn A. 2006. Cytotoxic prenylated xanthone from the young fruit of Garcinia mangostana. Chem Pharm Bull. 54:301– 305. Suksamrarn S, Suwannapoch N, Phakhodee W, Thanuhiranlert J, Ratananukul P, Chimnoi N, Suksamrarn A. 2003. Antimycobacterial activity of prenylated xanthones from the fruits of Garcinia mangostana. Chem Pharm Bull. 51:857–859. Zhang YZ, Song ZJ, Hao J, Qiu SX, Xu ZF. 2010. Two new prenylated xanthones and a new prenylated tetrahydroxanthone from the pericarp of Garcinia mangotana. Fitoterapia. 81:595–599. Zhou XJ, Huang RM, Hao J, Huang HJ, Fu MQ, Xu ZF, Zhou YM, Li XE, Qiu SX, Wang B. 2011. Two new prenylated xanthones from the pericarp of Garcinia mangostana (mangosteen). Helv Chim Acta. 94:2092–2098.
Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Two new xanthones from the pericarp of Garcinia mangostana ab
ac
ac
a
Xiaojun Zhou , Luan He , Xinxing Wu , Yanxia Zhong , Juan d
d
b
a
Zhang , Yuanxing Wang , Bin Wang , Zhifang Xu & Shengxiang Qiu
a
a
Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, P.R. China b
Department of Pharmacy, Medical College, Nanchang University, Nanchang, P.R. China c
University of Chinese Academy of Sciences, Beijing, 100049, P.R. China d
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047, P.R. China Published online: 09 Oct 2014.
To cite this article: Xiaojun Zhou, Luan He, Xinxing Wu, Yanxia Zhong, Juan Zhang, Yuanxing Wang, Bin Wang, Zhifang Xu & Shengxiang Qiu (2015) Two new xanthones from the pericarp of Garcinia mangostana, Natural Product Research: Formerly Natural Product Letters, 29:1, 19-23, DOI: 10.1080/14786419.2014.927873 To link to this article: http://dx.doi.org/10.1080/14786419.2014.927873
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
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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 & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Natural Product Research, 2015 Vol. 29, No. 1, 19–23, http://dx.doi.org/10.1080/14786419.2014.927873
Two new xanthones from the pericarp of Garcinia mangostana
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Xiaojun Zhouab, Luan Heac, Xinxing Wuac, Yanxia Zhonga, Juan Zhangd, Yuanxing Wangd*, Bin Wangb, Zhifang Xua and Shengxiang Qiua* a Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, P.R. China; bDepartment of Pharmacy, Medical College, Nanchang University, Nanchang, P.R. China; cUniversity of Chinese Academy of Sciences, Beijing 100049, P.R. China; dState Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, P.R. China
(Received 7 April 2014; final version received 20 May 2014) Two new xanthones, designated garcimangosxanthone F (1) and garcimangosxanthone G (2), were isolated from the EtOAc-soluble fraction of ethanolic extract from the pericarp of Garcinia mangostana. Their structures were established as 1,6,7trihydroxy-5-(3-methylbut-2-enyl)-8-(3-hydroxy-3-methylbutyl)-60 ,60 -dimethylpyrano [20 ,30 :3,2]xanthone and 1,6,7-trihydroxy-5-(3-methylbut-2-enyl)-8-(3-hydroxy-3methylbutyl)-60 ,60 -dimethyl-40 ,50 -dihydropyrano[20 ,30 :3,2]xanthone, respectively, on the basis of their 1D, 2D NMR and MS data interpretation. Keywords: Garcinia mangostana; xanthone; garcimangosxanthone F; garcimangosxanthone G
1. Introduction Garcinia mangostana L. (Guttiferae), colloquially known simply as purple mangosteen or mangosteen, is a tropical evergreen tree believed to have originated in the Sunda Islands and the Moluccas of Indonesia. It grows mainly in Southeast Asia, and also grows in tropical South American countries such as Colombia, where the tree has been introduced (Morton 1987; Obolskiy et al. 2009). The fruit of the mangosteen is sweet, tangy, juicy and somewhat fibrous, with an inedible, deep reddish-purple coloured rind (exocarp) when ripe. Mangosteen pericarp has been used as a folklore remedy for inflammation, diarrhoea and as an astringent since ancient times (Chairungsrilerd et al. 1996). The chemical constituents of the mangosteen pericarp comprise an array of polyphenols, including tannins and xanthones with a-mangostin and gmangostin as the major secondary metabolites (Mahabusarakam et al. 1987; Iinuma et al. 1996; Gopalakrishnan & Balaganesan 2000; Huang et al. 2001; Suksamrarn et al. 2003; Hu et al. 2006; Jung et al. 2006; Suksamrarn et al. 2006). With the aim of searching for chemical components responsible for the pharmacology documented for the mangosteen pericarp, we performed an extensive phytochemical study on an ethanolic extract from mangosteen peels. Previously, we reported the isolation of five new xanthones, namely garcimangosxanthones A – C (Zhang et al. 2010) and D, E (Zhou et al. 2011). A biological evaluation indicated that garcimangosxanthone A and B exhibited potent growthinhibitory activity against human cancer cell lines A549 (lung cancer), LAC (pulmonary carcinoma) and A375 (human hepatoma) with IC50 values of 5.7– 24.9 mM, which were
*Corresponding authors. Email: [email protected]; [email protected] q 2014 Taylor & Francis
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X. Zhou et al.
comparable to those of the positive control substance doxorubicin, while the others exhibited only moderate cytotoxicity (Zhang et al. 2010). As part of our ongoing study of the chemical constituents from mangosteen pericarp, a scaleup extraction was conducted with an aim to isolate more compounds, which resulted in the isolation of two new xanthones 1 and 2 from the EtOAc partition of the ethanol extract. Herein, we report the isolation and structural identification of compounds 1 and 2.
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2. Results and discussion Garcimangosxanthone F (1) was obtained as a yellow powder. Its molecular formula was established as C28H32O7 by HR-EI-MS based on the molecular ion observed at m/z 480.2141 [M]þ (calcd 480.2143 for C28H32O7). The 1H NMR revealed one chelated phenolic hydroxyl proton at dH 14.12 (1H, s, 1-OH) and one isolated aromatic proton at dH 6.31 (1H, s, H-4). Other signal sets could be attributed to a 2,2-dimethylchromene ring at dH 6.69 (1H, s, J ¼ 10.0 Hz, H11), 5.71 (1H, s, J ¼ 10.0 Hz, H-12), 1.47 (6H, s, H-14, 15), a prenyl group at dH 3.60 (2H, d, J ¼ 6.9 Hz, H-16), 5.31 (1H, t, J ¼ 6.9 Hz, H-17), 1.67 (3H, s, H-19), 1.90 (3H, s, H-20) and a 3hydroxy-3-methylbutyl moiety at dH 3.42 (2H, t, J ¼ 6.5 Hz, H-21), 1.93 (1H, t, J ¼ 6.5 Hz, H22), 1.30 (6H, s, H-24, 25), respectively. Closer inspection revealed that the 1H and 13C NMR data of 1 were similar to those of caloxanthone A (Iinuma et al. 1994), with a 3-hydroxy-3methylbutyl group replacing the aromatic H-atom at C-8. The structure assignment of 1 was further supported by the HMBC spectrum. The correlations from H-11 to C-1, C-2, and C-3, and from H-12 to C-2 were suggestive of the connectivity of the 2,2-dimethylchromene ring positioned between C-2 and C-3. The correlations from H-16 to C-5, C-6 and C-10a, as well as between H-17 to C-5, revealed that the prenyl group was attached at C-5. The aromatic proton was readily assigned at C-4, on the basis of the HMBC correlations from H-4 to C-2, C-3, C-4a and C-9a. Moreover, the 3-hydroxy-3methylbutyl moiety was located at C-8, according to the HMBC correlations from H-21 to C-7, C-8 and C-8a, and from H-22 to C-8. Thus, the structure of 1 was elucidated as 1,6,7-trihydroxy5-(3-methylbut-2-enyl)-8-(3-hydroxy-3-methylbutyl)-60 ,60 -dimethylpyrano[20 ,30 :3,2]xanthone. Garcimangosxanthone G (2) was obtained as a yellow amorphous powder. Its HR-EI-MS (482.2295 [M]þ) established a molecular formula of C28H34O7. The 1H and 13C NMR data of 2 were similar to those of 1. The only difference was that the two doublets at H-11 and H-12 in 1 were replaced by two triplet methylenes at H-11 and H-12 in 2. This structure assignment for 2 (Figure 1) was confirmed by its HMBC spectrum (key correlations depicted in Figure 1). The HMBC correlations from H-11 to C-1, C-2, and C-3, and from H-12 to C-2 were suggestive of the connectivity of 2,2-dimethylchroman ring positioned between C-2 and C-3. Thus, the
Figure 1. Structures of compounds 1 and 2.
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structure of 2 was determined as 1,6,7-trihydroxy-5-(3-methylbut-2-enyl)-8-(3-hydroxy-3methylbutyl)-60 ,60 -dimethyl-40 ,50 -dihydropyrano[20 ,30 :3,2]-xanthone, which is also a new structure and therefore named garcimangosxanthone G. It is well known that the mangosteen exocarp contains an array of polyphenols, including xanthones and tannins. This study not only shed new light on the constituent chemistry of the mangosteen exocarp, but also enriched the chemical diversity of the compound library for new drug discovery.
3. Experimental
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3.1. General The 1D and 2D 1H, 13C NMR including HMQC and HMBC spectra were recorded on a Bruker DRX-400 instrument (Bruker Corp., Billerica, MA, USA) operating at 400 and 100 MHz, respectively, in (CD3)2CO-d6 using TMS as the internal standard. The chemical shift values are reported in ppm (d) units and the coupling constants (J) are in Hz. HR-EI-MS data were obtained on a MAT95XP mass spectrometer (Thermo Electron Corp., San Jose, CA). ESI-MS were collected on MDS SCIEX API 2000 LC/MS/MS instrument (Applied Biosystems Corp., Foster City, CA, USA). For column chromatography (CC), silica gel (80–100, 100–200 and 200–300 mesh, Qingdao Marine Chemical Ltd, Qingdao, China), and Sephadex LH-20 (Amersham Biosciences Corp., Uppsala, Sweden) was used. HPLC: Kromasil C18 (Akzo Nobel Corp., Partille, Sweden) (4.6 mm £ 250 mm, 5 mm), DAD (UV6000LP) detection. TLC was performed on GF254 plates (Qingdao Marine Chemical Ltd) while its detection was observed at 254 nm.
3.2. Plant material The pericarp of G. mangostana was obtained by peeling the fruits bought from a local grocery store in Guangzhou, China, and identified by Prof. Yun-Fei Deng of South China Botanical Garden. A voucher specimen (No. 0233559) has been deposited in the Laboratory of Natural Products Chemical Biology of South China Botanical Garden, Chinese Academy of Sciences.
3.3. Extraction and isolation The extraction procedures of extracting xanthones from mangosteen pericarps have been described previously (Zhang et al. 2010; Zhou et al. 2011). Briefly, the powdered dry pericarps of G. mangostana (4 kg) were extracted three times with 95% ethanol (8 L £ 3) at room temperature, for 3 days each. After evaporation of the pooled solvents in vacuo, the combined crude ethanolic extract residue (855.8 g) was obtained, which was shown to contain mainly xanthones as expected by TLC analysis with xanthones we isolated previously. The ethanolic extract residue was then partitioned with EtOAc (2 L £ 3) to afford EtOAc (344.5 g) extract. The EtOAc-soluble extract was subjected to a silica gel CC and eluted with petroleum ether – acetone with increasing polarities (10:1 2 1:1, v/v) to yield 17 fractions (A – Q). Fraction F (19.5 g) was then subjected to a silica gel CC using mixture solvents of petroleum ether 2 EtOAc with increasing polarity (from a ratio of 8:1 to 1:1, v/v) to obtain five fractions F1 – F5. F2 (1.2 g), which was further subjected to Sephadex LH-20 CC and eluted with MeOH to obtain four subfractions F2-1 – F2-4. Sub-fraction F2-2 (25 mg) was eventually separated by reversed-phase HPLC eluting with 90% MeOH/H2O to yield 1 (8 mg, 4 mg, tR ¼ 27.4 min) and 2 (5 mg, 5 mg, tR ¼ 25.6 min).
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3.3.1. Garcimangosxanthone F (1) Yellow amorphous powder; HR-EI-MS m/z 480.2141 [M]þ (calcd 480.2143 for C28H32O7); 1H NMR: d 14.12 (1H, s, OH-1), 6.31 (1H, s, H-4), 6.69 (1H, d, J ¼ 10.0 Hz, H-11), 5.71 (1H, d, J ¼ 10.0 Hz, H-12), 3.60 (2H, d, J ¼ 7.3 Hz, H-16), 5.31 (1H, t, J ¼ 7.3 Hz, H-17), 3.42 (2H, t, J ¼ 6.7 Hz, H-21), 1.93 (1H, t, J ¼ 6.7 Hz, H-22), 1.47 (6H, s, H-14, 15), 1.67 (3H, s, H-19), 1.89 (3H, s, H-20), 1.29 (6H, s, H-24, 25); 13C NMR: d 183.3 (C-9), 160.4 (C-3), 158.7 (C-1), 157.2 (C-4a), 152.4* (C-6), 152.1* (C-10a), 140.8 (C-7), 132.3 (C-18), 128.7 (C-8), 128.3 (C12), 122.6 (C-17), 116.0 (C-11), 113.9 (C-5), 111.3 (C-8a), 104.7 (C-2), 104.1 (C-9a), 94.5 (C4), 78.5 (C-13), 71.5 (C-23), 43.8 (C-22), 29.7 (C-24), 29.7 (C-25), 28.4 (C-14), 28.4 (C-15), 25.8 (C-19), 23.0 (C-16), 22.1 (C-21), 18.1 (C-20) (*Interchangable). 3.3.2. Garcimangosxanthone G (2) Yellow amorphous powder; HR-EI-MS m/z 482.2293 [M]þ (calcd 482.2295 for C28H34O7); 1H NMR: d 14.04 (1H, s, OH-1), 6.27 (1H, s, H-4), 2.68 (2H, t, J ¼ 6.8 Hz, H-11), 1.87 (2H, t, J ¼ 6.8 Hz, H-12), 3.59 (2H, d, J ¼ 7.3 Hz, H-16), 5.32 (1H, t, J ¼ 7.3 Hz, H-17), 3.43 (2H, t, J ¼ 6.6 Hz, H-21), 1.93 (1H, t, J ¼ 6.6 Hz, H-22), 1.37 (6H, s, H-14, 15), 1.66 (3H, s, H-19), 1.89 (3H, s, H-20), 1.29 (6H, s, H-24, 25); 13C NMR: d 183.3 (C-9), 161.3 (C-1), 161.1 (C-3), 155.5 (C-4a), 152.2* (C-6), 152.0* (C-10a), 140.3 (C-7), 132.1 (C-18), 128.7 (C-8), 122.7 (C17), 113.8 (C-5), 111.3 (C-8a), 104.1 (C-2), 103.2 (C-9a), 94.3 (C-4), 76.7 (C-13), 71.3 (C-23), 43.7 (C-22), 32.3 (C-12), 29.6 (C-24), 29.6 (C-25), 26.8 (C-11), 25.8 (C-19), 23.0 (C-16), 22.2 (C-21), 18.0 (C-20), 16.6 (C-14), 16.6 (C-15) (*Interchangable). Supplementary material Supplementary figures relating to this article are available online. Acknowledgements This work was jointly supported by funds from the Chinese Academy of Sciences 100 Talents Program, the National Natural Science Foundation (30973635, 81373293) and the National Science and Technology Major Projects (2014ZX10005002).
References Chairungsrilerd N, Yakeuchi K, Ohizum Y, Nozoe S, Ohta T. 1996. Mangostanol, a prenyl xanthone from Garcinia mangostana. Phytochemistry. 43:1009–1102. Gopalakrishnan G, Balaganesan B. 2000. Two new xanthones from Garcinia mangostana. Fitoterapia. 71:607–609. Hu JM, Chen JJ, Zhao YX, Wang RR, Zheng YT, Zhou J. 2006. Chemical constituents from fruit hulls of Garcinia mangostana (Cuttiferae). Acta Bot Yunnanica. 28:319–322. Huang YL, Chen CC, Chen YJ, Huang RL, Shieh BJ. 2001. Three xanthones and a benzophenone from Garcinia mangostana. J Nat Prod. 64:903–906. Iinuma M, Tosa H, Tanaka T, Asai F, Kobayashl Y, Shimano R, Miyauchi KI. 1996. Antibacterial activity of xanthone from Guttiferaeous plants against methicillin-resistant Staphylococcus aureus. J Pharm Pharmacol. 48:861–865. Iinuma M, Tosa H, Tanaka T, Yonemori S. 1994. Two xanthones from root bark of Calophyllum inophyllum. Phytochemistry. 35:527–532. Jung HA, Su BA, Keller WJ, Mehta RG, Kinghorn AD. 2006. Antioxidant xanthone from the pericarp of Garcinia mangostana (mangosteen). J Agric Food Chem. 54:2077–2082. Mahabusarakam W, Wiriyachitra P, Taylor WC. 1987. Chemical constituents of Garcinia mangostana. J Nat Prod. 50:474–478. Morton, JF. 1987. Mangosteen. In: Fruits of Warm Climates. Miami: Julia F. Morton; p. 301 –304. Obolskiy D, Pischel I, Siriwatanametanon N, Heinrich M. 2009. Garcinia mangostana L.: a phytochemical and pharmacological review. Phytochemistry. 23:1047–1065.
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Suksamrarn S, Komutiban O, Ratananukul P, Chimnoi N, Lartpornmatulee N, Suksamrarn A. 2006. Cytotoxic prenylated xanthone from the young fruit of Garcinia mangostana. Chem Pharm Bull. 54:301– 305. Suksamrarn S, Suwannapoch N, Phakhodee W, Thanuhiranlert J, Ratananukul P, Chimnoi N, Suksamrarn A. 2003. Antimycobacterial activity of prenylated xanthones from the fruits of Garcinia mangostana. Chem Pharm Bull. 51:857–859. Zhang YZ, Song ZJ, Hao J, Qiu SX, Xu ZF. 2010. Two new prenylated xanthones and a new prenylated tetrahydroxanthone from the pericarp of Garcinia mangotana. Fitoterapia. 81:595–599. Zhou XJ, Huang RM, Hao J, Huang HJ, Fu MQ, Xu ZF, Zhou YM, Li XE, Qiu SX, Wang B. 2011. Two new prenylated xanthones from the pericarp of Garcinia mangostana (mangosteen). Helv Chim Acta. 94:2092–2098.
