Acetyl- and O-alkyl- derivatives of β-mangostin from Garcinia mangostana and their anti-inflammatory activities

Article abstract of DOI:10.1080/14786419.2017.1350666

Pure β-mangostin (1) was isolated from the stem bark of Garcinia mangostana L. One monoacetate (2) and five O-alkylated β-mangostin derivatives (3–7) were synthesised from β-mangostin. The structures of these compounds were elucidated and determined using spectroscopic techniques such as 1D NMR and MS. The cytotoxicities and anti-inflammatory activities of these five compounds against RAW cell 264.7 were tested. The structural-activity relationship studies indicated that β-mangostin showed a significant activity against the LPS-induced RAW cell 264.7, while the acetyl- as well as the O-alkyl- β-mangostin derivatives did not give good activity. Naturally occurring β-mangostin demonstrated comparatively better anti-inflammatory activity than its synthetic counterparts.

Full text of DOI:10.1080/14786419.2017.1350666

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
Acetyl- and O-alkyl- derivatives of β-mangostin
from Garcinia mangostana and their anti-
inflammatory activities
Thiruventhan Karunakaran, Gwendoline Cheng Lian Ee, Intan Safinar Ismail,
Siti Mariam Mohd Nor & Nor Hisam Zamakshshari
To cite this article: Thiruventhan Karunakaran, Gwendoline Cheng Lian Ee, Intan Safinar Ismail,
Siti Mariam Mohd Nor & Nor Hisam Zamakshshari (2017): Acetyl- and O-alkyl- derivatives of
β-mangostin from Garcinia mangostana and their anti-inflammatory activities, Natural Product
Research, DOI: 10.1080/14786419.2017.1350666
To link to this article: http://dx.doi.org/10.1080/14786419.2017.1350666
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Date: 18 July 2017, At: 01:52

Natural Product research, 2017
https://doi.org/10.1080/14786419.2017.1350666
Acetyl- and O-alkyl- derivatives of β-mangostin from Garcinia
mangostana and their anti-inflammatory activities
Thiruventhan Karunakarana, Gwendoline Cheng Lian Eea, Intan Safinar Ismaila,b
,
Siti Mariam Mohd Nora and Nor Hisam Zamakshsharia
aFaculty of science, department of chemistry, universiti Putra Malaysia, serdang, Malaysia; blaboratory of
Natural Products, Institute of Biosience, universiti Putra Malaysia, serdang, Malaysia
ABSTRACT
ARTICLE HISTORY
received 27 March 2017
accepted 12 June 2017
Pure β-mangostin (1) was isolated from the stem bark of Garcinia
mangostana L. One monoacetate (2) and five O-alkylated β-mangostin
derivatives (3–7) were synthesised from β-mangostin. The structures
of these compounds were elucidated and determined using
spectroscopic techniques such as 1D NMR and MS. The cytotoxicities
and anti-inflammatory activities of these five compounds against RAW
cell 264.7 were tested. The structural-activity relationship studies
indicated that β-mangostin showed a significant activity against
the LPS-induced RAW cell 264.7, while the acetyl- as well as the O-
alkyl- β-mangostin derivatives did not give good activity. Naturally
occurring β-mangostin demonstrated comparatively better anti-
inflammatory activity than its synthetic counterparts.
KEYWORDS
acetyl- and O-alkyl-
β-mangostin; anti-
inflammation; β-mangostin
OH
O
H
3CO
HO
O
OCH3
β-mangostin
OH
O
H
3CO
RO
O
OCH3
R=
H (1); R= COCH3 (2); R= CH3 (3); R= CH2C6H5 (4); R= CH2CH2CH2CH2CH2CH3 (5); R=
CH2CH2CH2CH3 (6); R= CH(CH3)CH2CH3 (7)
1. Introduction
Garcinia is a plant genus from the family Clusiaceae. It is a large genus of evergreen trees
and shrubs distributed in tropical Asia, Africa and Polynesia. The genus Garcinia is known to
be a rich source of xanthones and polyisoprenylated benzophenones (Ee et al. 2006, 2012;
CONTACT Gwendoline cheng lian ee
gwen@upm.edu.my
supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2017.1350666.
© 2017 Informa uK limited, trading as taylor & Francis Group

2
T. KARUNAKARAN ET AL.
Zhao et al. 2012; Zhou et al. 2015). G. mangostana has a vast history of its use as a medicinal
plant especially in some parts of South-east Asia (Ee et al. 2014) and has been reported for
its anti-inflammatory and cytotoxic properties and is used in therapy for various conditions
such as urinary disorders, gonorrhoea and skin disorders (Han et al. 2009; Mohamed et al.
2014). The major bioactive secondary metabolites of G. mangostana are xanthone derivatives
which consist of α-mangostin and β-mangostin. (Zhao et al. 2010; Dharmaratne et al. 2013;
Morelli et al. 2015). β-mangostin was reported to possess several bioactivities such as cyto-
toxicity towards selective cancer cell lines, anti-microbial and anti-inflammatory (Obolskiy
et al. 2009). Much research has also been focused on the potential bioactivities of α-mango-
stin as it is an equally dominant constituent as β-mangostin. There have been attempts to
produce semi-synthetic derivatives of α-mangostin and their structural-activity relationship
studies are conducted. It is reported that β-mangostin is a very potent anti-inflammatory
agent and suppresses LPS-induced inflammatory response in RAW 264.7 macrophage (Syam
et al. 2014). In this study, naturally occurring β-mangostin was modified to six semi-synthetic
derivatives (2–7) via acetylation and O-alkylation reactions. β-mangostin (1) and compounds
2–5 were tested for cytotoxicity and reduction of nitrite production (NO) on RAW 264.7
macrophages for anti-inflammatory activity and the structure-activity relationship
studied.
2. Results and discussion
β-mangostin (1) (about 300 mg/3 kg) was isolated from the hexane and chloroform extracts
of the stem bark of Garcinia mangostana through column chromatographic techniques. The
structural elucidation of β-mangostin (1) using 1D NMR and MS as well as by comparison
with previous reported data was carried out (Yahayu et al. 2013). For the acetylation reaction,
β-mangostin (1) (20 mg) was treated with pyridine and acetic anhydride at room temperature
for 48 h to give 6-monoacetate-β-mangostin (2) (12 mg, Figure 1). For the O-alkylation reac-
tion, β-mangostin (1) (20 mg) was reacted with 0.02 mL of the following alkanes: iodometh-
ane or iodohexane or bromomethylbenzene or 1-bromobutane and 2-bromobutane and
K2CO3 (1.5 g). The reactions yielded 6-O-methyl β-mangostin (3) (7 mg), 6-O-benzyl β-man-
gostin (4) (10 mg), 6-O-hexyl β-mangostin (5) (14 mg), 6-O-sec-butyl β-mangostin (6) (5 mg)
and 6-O-isobutyl β-mangostin (7) (3 mg), respectively. The reaction equation and summary
of results are shown in Figure 2 and Table S1.
Compounds 4–7 are newly synthetised derivatives of β-mangostin. From the 13C NMR
spectra, it was observed that the signals of C-5 in the O-alkylated derivatives of β-mangostin
had shifted 2–3 ppm upfield as the presence of the alkyl chain causes shielding to C-5 (δC
101.5) (Ha et al. 2009). For the 6-O-monoacetate β-mangostin (2) the change in the proton
chemical shift for H-5 by 1.2 ppm towards downfield, i.e. δH 7.09 (s, 1H) compared to H-5 (δH
6.81) for pure β-mangostin (1) is due to the electron withdrawing effect of the carbonyl
carbon from the acyl group. The same goes for the carbon peak at position 5 (C-5) δC 110.4
which was shifted by 9.9 ppm in 6-O-monoacetate β-mangostin (2). The 13C NMR data for
compounds 4–7 are summarised in Table S2. Compounds 1–5 were subjected to biological
evaluation for cytotoxicity and anti-inflammatory effects, while compounds 6 and 7 were
not tested for these biological activities due to the low yield which is below 5 mg.
Cytotoxic tests indicated β-mangostin (1) to be toxic towards the RAW 264.7 macrophages
in a concentration ranging from 500 to 125 μg/mL. The concentration of β-mangostin

NATURAL PRODUCT RESEARCH
3
R= H (1); R= COCH3 (2); R= CH3 (3); R=CH2C6H5 (4); R= CH2CH2CH2CH2CH2CH3 (5); R=
CH2CH2CH2CH3 (6); R= CH(CH3)CH2CH3 (7)
Figure 1. structures of β-mangostin (1), monoacetylated (2) and O-alkylated β-mangostin.
*B (Reactant), C (Base), D (Solvent), E (Condition), F (Product)
Figure 2. reaction scheme for semisynthetic β-mangostin derivatives.
showed more than 80% cell viability from a concentration of 62.5 μg/mL and below. For the
β-mangostin derivatives 2–5, all the compounds showed more than 80% cell viability for
concentrations ranging up to 500 μg/mL. It can be deduced that semi-synthetic modifica-
tions of β-mangostin resulted in reduction of the toxicity of pure β-mangostin. The cytotox-
icity of compounds 1–5 against RAW 264.7 macrophages with concentrations ranging from
500 to 7.8125 μg/mL is plotted in the line graph in Figure 3.
The anti-inflammatory tests conducted using Griess assay showed that β-mangostin (1)
is still the best candidate to inhibit nitric oxide production at a low IC50 value of 11.72 1.16 μM
compared to the selected derivatives of β-mangostin 2–5 which gave IC50 values more than
50 μM. Thus, it can be concluded that the acetylation and O-alkylation reactions of
β-mangostin did not improve the anti-inflammatory property possessed by pure β-mangostin
(1) even though the toxicity of compound 1 has been decreased for higher concentrations
up to 500 μg/mL. From the structure-activity relationship studies predicted through
comparison of the biological activities, the OH is an important functional group that
determines the bioactivity of the compound. Replacement of the OH functional group at
position C-6 with acetyl or alkyl group decreases or makes it inactive against the inflammation.
The anti-inflammatory test results are summarised in Table 1.
3. Experimental
See supplementary data.

4
T. KARUNAKARAN ET AL.
Cell Viability (%of control) vs Concentration (µg/mL)
140
120
100
80
2
3
4
5
1
60
40
20
0
500
250
125
62.5
31.25
15.625
7.8125 Control
Concentration (µg/mL)
Figure 3. cell Viability of compounds 1–5.
Notes: all experiments were conducted in triplicate and results are expressed as mean sd. p-values were determined
by one way analysis of variance followed by dunnett test (*** p < 0.0001, ** p < 0.005 and * < 0.05 vs. control (0 μg/ml)).
statistically, p-values < 0.05 were considered to be significant.
Table 1. Ic50 values of compounds 1–5.
Compounds
IC50 (μM)
1
11.72 1.16
>50
>50
>50
>50
20.0 00
2
3
4
5
Curcumin
Note: each value of Ic50 represented mean s.e.M of three independent experiments.
Acknowledgements
The authors wish to express gratitude to the Malaysian Ministry of Higher Education for providing
financial support under the FRGS research grant and Universiti Putra Malaysia for providing research
facilities and technical support.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by Malaysian Ministry of Higher Education.

NATURAL PRODUCT RESEARCH
5
References
Dharmaratne HRW, SakagamiY, Piyasena KGP, Thevanesam V. 2013. Antibacterial activity of xanthones
from Garcinia mangostana (L.) and their structure-activity relationship studies. Nat Prod Res.
27(10):938–941.
Ee GCL, Daud BS, Yap YHT, Ismail NH, Rahmani M. 2006. Xanthones from Garcinia mangostana
(Guttiferae). Nat Prod Res. 20(12):1067–1073.
Ee GCL, Foo CH, Jong VYM, Ismail NM, Sukari MA, Yap YHT, Awang K. 2012. A new xanthone from
Garcinia nitida. Nat Prod Res. 26(9):830–835.
Ee GCL, See I, Teh SS, Daud BS. 2014. A new furanoxanthone from Garcinia mangostana. J Asian Nat
Prod Res. 16:790–794.
Ha LD, Hansen PE, Vang O, Duus F, Pham HD, Nguyen LHD. 2009. Cytotoxic geranylated xanthones and
O-Alkylated derivatives of α-mangostin. Chem Pharm Bull. 57(8):830–834.
Han AR, Kim AJ, Lantvit DD, Kardono LBS, Riswan S, Chai H, Blanco ECJ, Farnsworth NR, Swanson
SM, Kinghorn AD. 2009. Cytotoxic xanthone constituents of the stem bark of Garcinia mangostana
(Mangosteen). J Nat Prod. 72(11):2028–2031.
Mohamed GA, Ibrahim SR, Shabaan MI, Ross SA. 2014. Mangostanaxanthones I and II, new xanthones
from the pericarp of Garcinia mangostana. Fitoterapia. 98:215–221.
Morelli CF, Biagiotti M, Papplardo VM, Rabuffetti M, Speranza G. 2015. Chemistry of α-mangostin. Studies
on the semisynthesis of minor xanthones from Garcinia mangostana. Nat Prod Res. 29(8):750–755.
Obolskiy D, Pischel I, Siriwatanametanon N, Heinrich M. 2009. Garcinia mangostana L.: A phytochemical
and pharmacological review. Phytother Res. 23:1047–1065.
Syam S, Bustamam A, Abdullah R, Sukari MA, Hashim NM, Mohan S, Looi CY, Wong WF, Yahayu MA,
Abdelwahab SI. 2014. β Mangostin suppress LPS-induced inflammatory response in RAW264.7
macrophages in vitro and carrageenan-induced peritonitis in vivo. J Ethnopharmacol. 153:435–445.
Yahayu MA, Rahmani M, Hashim NM, Ee GCL, Sukari MA, Akim MA. 2013. Cytotoxic and Antimicrobial
Xanthones from Cratoxylum arborescens (Guttiferae). Malays J Sci. 32(1):53–60.
Zhao Y, Liu JP, Lu D, Li PY, Zhang LX. 2010. A new antioxidant xanthone from the pericarp of Garcinia
mangostana Linn. Nat Prod Res. 24(17):1664–1670.
Zhao Y, Liu JP, Li PY, Zhang LX. 2012. Two new xanthones from the pericarp of Garcinia mangostana.
Nat Prod Res. 26(1):61–65.
Zhou X, He L, Wu X, Zhong Y, Zhang J, Wang Y, Wang B, Xu S. 2015. Two new xanthones from pericarp
of Garcinia mangostana. Nat Prod Res. 29(1):19–23.