Xanthones from the heartwood of Garcinia mangostana

Biochemical features and therapeutic potential of α-Mangostin: Mechanism of action, medicinal values, and health benefits

α-Mangostin (α-MG) is a natural xanthone obtained from the pericarps of mangosteen. It exhibits excellent potential, including anti-cancer, neuroprotective, antimicrobial, antioxidant, and anti-inflammatory properties, and induces apoptosis. α-MG controls cell proliferation by modulating signaling molecules, thus implicated in cancer therapy. It possesses incredible pharmacological features and modulates crucial cellular and molecular factors. Due to its lesser water solubility and pitiable target selectivity, α-MG has limited clinical application. As a known antioxidant, α-MG has gained significant attention from the scientific community, increasing interest in extensive technical and biomedical applications. Nanoparticle-based drug delivery systems were designed to improve the pharmacological features and efficiency of α-MG. This review is focused on recent developments on the therapeutic potential of α-MG in managing cancer and neurological diseases, with a special focus on its mechanism of action. In addition, we highlighted biochemical and pharmacological features, metabolism, functions, anti-inflammatory, antioxidant effects and pre-clinical applications of α-MG.

Xanthones from the latex and twig extracts of Garcinia nigrolineata Planch. ex T. Anderson (Clusiaceae) and their antidiabetic and cytotoxic activities

A new geranylated xanthone, nigrolineaxanthone AA (1) together with 18 known compounds (2-19) were isolated from latex and twig extracts of Garcinia nigrolineata Planch. ex T. Anderson. Some of the isolated compounds were assessed for their antidiabetic activities and cytotoxicity against three cancer cell lines. Of these, compounds 12 (IC₅₀ value of 25.8 ± 0.2 µM), 16 (IC₅₀ value of 124.8 ± 0.7 µM), and 17 (IC₅₀ value of 44.4 ± 1.1 µM) exhibited the highest α-glucosidase inhibitory, α-amylase inhibitory, and glycation inhibition activities, respectively. Compound 11 showed glucose consumption and glucose uptake with IC₅₀ values of 14.2 ± 0.8 µM and 3.1-fold. Compound 10 displayed cytotoxic activity against colon cancer (SW480) with an IC₅₀ value of 4.3 ± 0.1 µM), while compound 2 showed cytotoxicity against leukemic cancer (K562) with IC₅₀ value of 4.4 ± 0.3 µM.

Xanthones: Biosynthesis and Trafficking in Plants, Fungi and Lichens

Xanthones are a class of secondary metabolites produced by plant organisms. They are characterized by a wide structural variety and numerous biological activities that make them valuable metabolites for use in the pharmaceutical field. This review shows the current knowledge of the xanthone biosynthetic pathway with a focus on the precursors and the enzymes involved, as well as on the cellular and organ localization of xanthones in plants. Xanthone biosynthesis in plants involves the shikimate and the acetate pathways which originate in plastids and endoplasmic reticulum, respectively. The pathway continues following three alternative routes, two phenylalanine-dependent and one phenylalanine-independent. All three routes lead to the biosynthesis of 2,3',4,6-tetrahydroxybenzophenone, which is the central intermediate. Unlike plants, the xanthone core in fungi and lichens is wholly derived from polyketide. Although organs and tissues synthesizing and accumulating xanthones are known in plants, no information is yet available on their subcellular and cellular localization in fungi and lichens. This review highlights the studies published to date on xanthone biosynthesis and trafficking in plant organisms, from which it emerges that the mechanisms underlying their synthesis need to be further investigated in order to exploit them for application purposes.

Mangosteen for malignancy prevention and intervention: Current evidence, molecular mechanisms, and future perspectives

Mangosteen (Garcinia mangostana L.), also known as the "queen of fruits", is a tropical fruit of the Clusiacea family. While native to Southeast Asian countries, such as Thailand, Indonesia, Malaysia, Myanmar, Sri Lanka, India, and the Philippines, the fruit has gained popularity in the United States due to its health-promoting attributes. In traditional medicine, mangosteen has been used to treat a variety of illnesses, ranging from dysentery to wound healing. Mangosteen has been shown to exhibit numerous biological and pharmacological activities, such as antioxidant, anti-inflammatory, antibacterial, antifungal, antimalarial, antidiabetic, and anticancer properties. Disease-preventative and therapeutic properties of mangosteen have been ascribed to secondary metabolites called xanthones, present in several parts of the tree, including the pericarp, fruit rind, peel, stem bark, root bark, and leaf. Of the 68 mangosteen xanthones identified so far, the most widely-studied are α-mangostin and γ-mangostin. Emerging studies have found that mangosteen constituents and phytochemicals exert encouraging antineoplastic effects against a myriad of human malignancies. While there are a growing number of individual research papers on the anticancer properties of mangosteen, a complete and critical evaluation of published experimental findings has not been accomplished. Accordingly, the objective of this work is to present an in-depth analysis of the cancer preventive and anticancer potential of mangosteen constituents, with a special emphasis on the associated cellular and molecular mechanisms. Moreover, the bioavailability, pharmacokinetics, and safety of mangosteen-derived agents together with current challenges and future research avenues are also discussed.

Biphenyls in Clusiaceae: Isolation, structure diversity, synthesis and bioactivity

Clusiaceae plants contain a wide range of biologically active metabolites that have gotten a lot of interest in recent decades. The chemical compositions of these plants have been demonstrated to have positive effects on a variety of ailments. The species has been studied for over 70 years, and many bioactive compounds with antioxidant, anti-proliferative, and anti-inflammatory properties have been identified, including xanthones, polycyclic polyprenylated acylphloroglucinols (PPAPs), benzophenones, and biphenyls. Prenylated side chains have been discovered in many of these bioactive substances. To date, there have been numerous studies on PPAPs and xanthones, while no comprehensive review article on biphenyls from Clusiaceae has been published. The unique chemical architectures and growing biological importance of biphenyl compounds have triggered a flurry of research and interest in their isolation, biological evaluation, and mechanistic studies. In particular, the FDA-approved drugs such as sonidegib, tazemetostat, daclatasvir, sacubitril and trifarotene are closely related to their biphenyl-containing moiety. In this review, we summarize the progress and development in the chemistry and biological activity of biphenyls in Clusiaceae, providing an in-depth discussion of their structural diversity and medicinal potential. We also present a preliminary discussion of the biological effects with or without prenyl groups on the biphenyls.

Xanthone: A Promising Antimycobacterial Scaffold

BACKGROUND

Tuberculosis (TB) is one of the infectious diseases associated with high rate of morbidity and mortality and still remains one of the top-ten leading causes of human death in the world. The development of new anti-TB drugs is mandatory due to the existence of latent infection as well as the expansion of the resistant Mycobacterium tuberculosis (MBT) strains. Xanthones encompass a wide range of structurally diverse bioactive compounds, obtained either naturally or through chemical synthesis. There is a growing body of literature that recognizes the antitubercular activity of xanthone derivatives.

OBJECTIVE

The objective of this review is to highlight the main natural sources along with the critical design elements, structure-activity relationships (SARs), modes of action and pharmacokinetic profiles of xanthone-based anti-TB compounds.

METHODS

In the present review, the anti-TB activity of xanthones reported in the literature from 1972 to date is presented and discussed.

RESULTS

Exploration of xanthone scaffold led to the identification of several members of this class having superior activity against both sensitive and resistant MBT strains with distinctive mycobacterial membrane disrupting properties. However, studies regarding their modes of action, pharmacokinetic properties and safety are limited.

CONCLUSION

Comprehendible data and information are afforded by this review and it would certainly provide scientists with new thoughts and means which will be conducive to design and develop new drugs with excellent anti-TB activity through exploration of xanthone scaffold.

Biofabrication of AuNPs using Coriandrum sativum leaf extract and their antioxidant, analgesic activity

In this work, Gold nanoparticles (AuNPs) were synthesized by reducing aqueous Au metal ions upon interaction with Coriandrum sativum (C. sativum) leaf extract. The optical absorption peak for the synthesized AuNPs was obtained by using UV-visible spectroscopy within a range of 540-550 nm. The formation of diffraction peaks found at 2θ values of 78.00°, 66.05°, 44.85° and 38.48° that corresponds to the index planes (311), (220), (200), and (111) validate the effective synthesis of AuNPs. Transmission electron microscopy (TEM) was utilized to measure the size range of the spherical shaped nanoparticles, which is obtained to be 32.96 ± 5.25 nm. The peaks obtained from the FTIR results are closely linked to anthocyanins, benzophenones, flavonoids and phenols, which indicated that these biomolecules may serve as reducing agents. Additionally, studies of antioxidant function in vitro revealed that the activities of ABTS (2, 2'-azino-bis 3-ethylbenzthiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) were improved dose-dependently. Further, the results of analgesic analysis showed that the cumulative action of AuNPs and the C. sativum leaf extract in pain relief is more efficient than independent C. sativum leaf extract and the aspirin drug.

Simultaneous identification and quantification of three biologically active xanthones in Garcinia species using a rapid UHPLC-PDA method

Xanthones are well recognized as chemotaxonomic markers for the plants belonging to the genus Garcinia. Xanthones have many interesting pharmacological properties. Efficient extraction and rapid liquid chromatography methods are essentially required for qualitative and quantitative determination of xanthones in their natural sources. In the present investigation, fruit rinds extracts of 8 Garcinia species from India, were prepared with solvents of varying polarity. Identification and quantification of 3 xanthones, namely, α-mangostin, β-mangostin, and γ-mangostin in these extracts were carried out using a rapid and validated ultra-high-performance liquid chromatography–photodiode array detection (UHPLC–PDA) method at 254 nm. γ-Mangostin (3.97 ± 0.05 min) was first eluted, and it was followed by α-mangostin (4.68 ± 0.03 min) and β-mangostin (5.60 ± 0.04 min). The calibration curve for α-mangostin, β-mangostin, and γ- mangostin was linear in the concentration range 0.781–100 μg/mL. α-Mangostin was quantified in all 4 extracts of Garcinia mangostana. Its content (%) in hexane, chloroform, ethyl acetate, and methanol extracts of G. mangostana was 10.36 ± 0.10, 4.88 ± 0.01, 3.98 ± 0.004, and 0.044 ± 0.002, respectively. However, the content of α-mangostin was below the limit of detection or limit of quantification in the extracts of other Garcinia species. Similarly, β-mangostin was quantified only in hexane (1.17 ± 0.01%), chloroform (0.39 ± 0.07%), and ethyl acetate (0.28 ± 0.03%) extracts of G. mangostana. γ-Mangostin was quantified in all 4 extracts of G. mangostana. Its content (%) in hexane, chloroform, ethyl acetate, and methanol extracts of G. mangostana was 0.84 ± 0.01, 1.04 ± 0.01, 0.63 ± 0.04, and 0.15 ± 0.01, respectively. γ-Mangostin was also quantified in hexane (0.09 ± 0.01), chloroform (0.05 ± 0.01), and ethyl acetate (0.03 ± 0.01) extracts of G. cowa, ethyl acetate extract of G. cambogia (0.02 ± 0.01), G. indica (0.03 ± 0.01), and G. loniceroides (0.07 ± 0.01). Similarly, γ-mangostin was quantified in 3 extracts of G. morella, namely, hexane (0.03 ± 0.01), chloroform (0.04 ± 0.01), and methanol (0.03 ± 0.01). In the case of G. xanthochymus, γ-mangostin was quantified in chloroform (0.03 ± 0.001) extract only. α-Mangostin and β-mangostin were not detected in any of 4 extracts of G. pedunculata.

Chiral Derivatives of Xanthones with Antimicrobial Activity

According to the World Health Organization, the exacerbated use of antibiotics worldwide is increasing multi-resistant infections, especially in the last decade. Xanthones are a class of compounds receiving great interest in drug discovery and development that can be found as natural products or obtained by synthesis. Many derivatives of xanthones are chiral and associated with relevant biological activities, including antimicrobial. The aim of this review is to compile information about chiral derivatives of xanthones from natural sources and their synthesized examples with antimicrobial activity.

Xanthones from the Pericarp of Garcinia mangostana

Mangosteen (Garcinia mangostana L.) is one of the most popular tropical fruits (called the "Queen of Fruits"), and is a rich source of oxygenated and prenylated xanthone derivatives. In the present work, phytochemical investigation has resulted in one new prenylated xanthone and 13 known xanthones isolated from the pericarp of G. mangostana. Their structures were established by spectroscopic data analysis, including X-ray diffraction. The new one was further tested for cytotoxic activity against seven cancer cell lines (CNE-1, CNE-2, A549, H490, PC-3, SGC-7901, U87), displaying the half maximal inhibitory concentration (IC₅0) values 3.35, 4.01, 4.84, 7.84, 6.21, 8.09, and 6.39 μM, respectively. It is noteworthy that the new compound can promote CNE-2 cells apoptosis in late stage, having a remarkable inhibition effect on the side population growth of CNE-2 at 1.26 μM. The bioactive compound was also detected in extract from fresh mangosteen flesh, which indicated that the popular fruit could have potential cytotoxic activity for cancer cell lines.

Two new chemical constituents from the stem bark of Garcinia mangostana

A detailed chemical study on the ethyl acetate and methanol extracts of the stem bark of Garcinia mangostana resulted in the successful isolation of one new prenylated xanthone, mangaxanthone B (1), one new benzophenone, mangaphenone (2), and two known xanthones, mangostanin (3) and mangostenol (4). The structures of these compounds were elucidated through analysis of their spectroscopic data obtained using 1D and 2D NMR and MS techniques.

Rapid identification of cholinesterase inhibitors from the seedcases of mangosteen using an enzyme affinity assay

Enzyme binding affinity has been recently introduced as a selective screening method to identify bioactive substances within complex mixtures. We used an assay which identified small molecule binders of acetylcholinesterase (AChE) using the following series of steps: incubation of enzyme with extract; centrifugation and filtration; identification of small molecule content in the flow through. The crude extract contained 10 peaks in the UPLC chromatogram. However, after incubation the enzyme, six peaks were reduced, indicating these compounds bound AChE. All these isolated compounds (2, 3, and 5-8) significantly inhibited human AChE with IC₅₀s = 5.4-15.0 μM and butyrylcholinsterase (IC₅₀s = 0.7-11.0 μM). All compounds exhibited reversible mixed kinetics. Consistent with the binding screen and fluorescence quenching, γ-mangostin 6 had a much higher affinity for AChE than 9-hydroxycalabaxanthone 9. This validates this screening protocol as a rapid method to identify inhibitors of AChE.

8-Hydroxycudraxanthone G Suppresses IL-8 Production in SP-C1 Tongue Cancer Cells

Production of IL-8 primarily promotes angiogenic responses in cancer cells, which lead to favorable disease progression. Suppressing this production may, therefore, be a significant therapeutic intervention in targeting tumor angiogenesis. This study aimed to evaluate the reduction effects of xanthones in cancer cell lines. Nine known prenylated xanthones (1–9), isolated from the pericarp of Garcinia mangostana Linn (GML), were tested for their ability to suppress IL-8 (interleukin-8) of the SP-C1 (Supri's Clone 1) tongue cancer cell line. Of these compounds, 8-hydroxycudraxanthone-G (4) suppressed IL-8 within 48 hours. This is the first report of 8-hydroxycudraxanthone G suppressing the production of IL-8 (45% at 15.7 μg/mL in 48 hours). These results suggest that the prolonged suppression of IL-8 production by cancer cell lines is concerned in the anti-cancer activity of 8-hydroxycudraxanthone.

Phytochemical, antimicrobial and antiprotozoal evaluation of Garcinia mangostana pericarp and α-mangostin, its major xanthone derivative

Five xanthone derivatives and one flavanol were isolated from the dichloromethane extract of Garcinia mangostana. Dichloromethane, ethyl acetate extract and the major xanthone (α-mangostin) were evaluated in vitro against erythrocytic schizonts of Plasmodium falciparum, intracellular amastigotes of Leishmania infantum and Trypanosoma cruzi and free trypomastigotes of T. brucei. The major constituent α-mangostin was also checked for antimicrobial potential against Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Bacillius subtilis, Staphylococcus aureus, Mycobacterium smegmatis, M. cheleneoi, M. xenopi and M. intracellulare. Activity against P.falciparum (IC₅₀ 2.7 μg/mL) and T. brucei (IC₅₀ 0.5 μg/mL) were observed for the dichloromethane extract, however, with only moderate selectivity was seen based on a parallel cytotoxicity evaluation on MRC-5 cells (IC₅₀ 9.4 μg/mL). The ethyl acetate extract was inactive (IC₅₀ > 30 µg/mL). The major constituent α-mangostin showed rather high cytotoxicity (IC₅₀ 7.5 µM) and a broad but non-selective antiprotozoal and antimicrobial activity profile. This in vitro study endorses that the antiprotozoal and antimicrobial potential of prenylated xanthones is non-conclusive in view of the low level of selectivity.

1,4-Dioxane and ergosterol derivatives from Withania somnifera roots

The chemical investigation on the n-hexane extract of Withania somnifera roots has yielded octacosane, oleic and stearic fatty acids, stigmasterone, stigmasterol, sitostanone, oleanolic acid along with the ergosterol and 1,4-dioxane derivatives as new compounds. The isolation of alkenyl-1,4-dioxane compound is rare, whereas the ergosterol derivative may have biogenetic significance in the lactone formation in the E ring of withanolides. The presence of a 1,4-dioxane derivative in the nonpolar extract of roots assumes importance as this type of compound has not been reported earlier from W. somnifera. The structures of new compounds were elucidated by spectroscopic methods and chemical transformations.

α-Glucosidase inhibition and antihyperglycemic activity of prenylated xanthones from Garcinia mangostana

An ethanol extract of the fruit case of Garcinia mangostan, whose most abundant chemical species are xanthones, showed potent α-glucosidase inhibitory activity (IC(50)=3.2 μg/ml). A series of isolated xanthones (1-16) demonstrated modest to high inhibition of α-glucosidase with IC(50) values of 1.5-63.5 μM. In particular, one hitherto unknown xanthone 16 has a very rare 2-oxoethyl group on C-8. Kinetic enzymatic assays with a p-nitrophenyl glucopyranoside indicated that one of them, compound (9) exhibited the highest activity (K(i)=1.4 μM) and mixed inhibition. Using, a physiologically relevant substrate, maltose, as substrate, many compounds (6, 9, 14, and 15) also showed potent inhibition which ranged between 17.5 and 53.5 μM and thus compared favorably with deoxynojirimycin (IC(50)=68.8 μM). Finally, the actual pharmacological potential of the ethanol extract was demonstrated by showing that it could elicit reduction of postprandial blood glucose levels. Furthermore, the most active α-glucosidase inhibitors (6, 9, and 14) were proven to be present in high quantities in the native seedcase by a HPLC chromatogram.

Microbial metabolism of α-mangostin isolated from Garcinia mangostana L

α-Mangostin (1), a prenylated xanthone isolated from the fruit hull of Garcinia mangostana L., was individually metabolized by two fungi, Colletotrichum gloeosporioides (EYL131) and Neosartorya spathulata (EYR042), repectively. Incubation of 1 with C. gloeosporioides (EYL131) gave four metabolites which were identified as mangostin 3-sulfate (2), mangostanin 6-sulfate (3), 17,18-dihydroxymangostanin 6-sulfate (4)and isomangostanin 3-sulfate (5). Compound 2 was also formed by incubation with N. spathulata (EYR042). The structures of the isolated compounds were elucidated by spectroscopic data analysis. Of the isolated metabolites, 2 exhibited significant anti-mycobacterial activity against Mycobacterium tuberculosis.

Isoprenylated flavonoids and adipogenesis-promoting constituents from Morus nigra

Ten new isoprenylated flavonoids, nigrasins A-J (1-10), and three known compounds were isolated from the twigs of Morus nigra. Compounds 8 and 9 promoted adipogenesis, characterized by increased lipid droplet and triglyceride content in 3T3L1 cells, and induced up-regulation of the expression of adipocyte-specific genes, aP2 and GLUT4.

Pharmacokinetics of α-mangostin in rats after intravenous and oral application

SCOPE

The xanthone α-mangostin is one of the major bioactive secondary metabolites in Garcinia mangostana. Until now, in vivo studies on the absorption, bioavailability, disposition, and metabolism of α-mangostin are limited.

METHODS AND RESULTS

In the present study, an LC-MS/MS assay has been established for the determination of α-mangostin in rat plasma. The validated method was used successfully to support pharmacokinetic studies in rats after intravenous (i.v.) and oral administration. Both non-compartmental and compartmental analyses were performed, where the two-compartment body model had a good fit with the i.v. data. Following i.v. administration, the disposition of α-mangostin in rat plasma was biphasic, subdivided into a fast distribution and a slow elimination phase. The half-life of the distribution phase was 3 min, and that of the terminal elimination phase 3.5 h, indicating a high tissue binding. However, for oral administration, the bioavailability was so low that it was not possible to obtain a full concentration-time profile.

CONCLUSION

Although pure α-mangostin has shown a variety of pharmacological activities in in vitro assays at present it is uncertain if the same magnitude of effects will be achieved in vivo when its low bioavailability is considered.

Cytotoxic xanthone constituents of the stem bark of Garcinia mangostana (mangosteen)

Bioassay-guided fractionation of a chloroform-soluble extract of Garcinia mangostana stem bark, using the HT-29 human colon cancer cell line and an enzyme-based ELISA NF-kappaB assay, led to the isolation of a new xanthone, 11-hydroxy-3-O-methyl-1-isomangostin (1). The structure of 1 was elucidated by spectroscopic data analysis. In addition, 10 other known compounds, 11-hydroxy-1-isomangostin (2), 11alpha-mangostanin (3), 3-isomangostin (4), alpha-mangostin (5), beta-mangostin (6), garcinone D (7), 9-hydroxycalabaxanthone (8), 8-deoxygartanin (9), gartanin (10), and cratoxyxanthone (11), were isolated. Compounds 4-8 exhibited cytotoxicity against the HT-29 cell line with ED50 values of 4.9, 1.7, 1.7, 2.3, and 9.1 microM, respectively. In an ELISA NF-kappaB assay, compounds 5-7, 9, and 10 inhibited p65 activation with IC50 values of 15.9, 12.1, 3.2, 11.3, and 19.0 microM, respectively, and 6 showed p50 inhibitory activity with an IC50 value of 7.5 microM. Alpha-mangostin (5) was further tested in an in vivo hollow fiber assay, using HT-29, LNCaP, and MCF-7 cells, but it was found to be inactive at the highest dose tested (20 mg/kg).

Garcinia mangostana L.: a phytochemical and pharmacological review

Garcinia mangostana L. (mangosteen, Clusiaceae) has a long history of use as a medical plant, mostly in Southeast Asia. This is a review of the phytochemistry and pharmacology of mangosteen. Traditionally mangosteen is famous for its antiinflammatory properties and is used in the treatment of skin infections and wounds. Other applications include the therapy of various conditions such as dysentery, different urinary disorders, cystitis and gonorrhoea. This review highlights the development of this botanical drug into a widely used nutraceutical. Products derived from G. mangostana are now distributed increasingly all over the world. This has given rise to a concomitant increase in research on the phytochemical constituents and biological activity of mangosteen. Central to the biological activity of the species are xanthones which are reviewed in detail. A comprehensive assessment of the biological activities of individual xanthones as well as extracts of G. mangostana is included. In addition, its potential in terms of developing novel drug leads is assessed. Products containing its fruits are now sold widely as 'liquid botanical supplements', but evidence for the health benefits of these products is still lacking. As shown here, a serious weakness in our knowledge is the lack of clinical data and it is not yet clear to what extent the findings about pharmacological activities are of potential clinical relevance.

Two new xanthones from the stems of Cratoxylum cochinchinense

Two new xanthones, 6-hydroxy-3,7-dimethoxy-8-(3-methylbut-2-enyl)-6',6'-dimethyl-5'-hydroxy-4',5'-dihydropyrano(2',3':1,2)xanthone (1) and 6-hydroxy-3,7-dimethoxy-8-(2-oxo-3-methylbut-3-enyl)-6',6'-dimethyl-5'-hydroxy-4',5'-dihydropyrano(2',3':1,2)xanthone (2), have been isolated from the stems of Cratoxylum cochinchinense (Lour.) Blume. Their structures were established on the basis of spectroscopic analysis.

Structural Characterization, Biological Effects, and Synthetic Studies on Xanthones from Mangosteen (Garcinia mangostana), a Popular Botanical Dietary Supplement

Mangosteen (Garcinia mangostana L., Clusiaceae) is a popular botanical dietary supplement in the United States, where it is used principally as an antioxidant. It is referred to as the "queen of fruits" in Thailand, a country of origin. The major secondary metabolites of mangosteen, the xanthones, exhibit a variety of biological activities including antibacterial, antifungal, antiinflammatory, antioxidant, antiplasmodial, cytotoxic, and potential cancer chemopreventive activities. Moreover, some of the xanthones from mangosteen have been found to influence specific enzyme activities, such as aromatase, HIV-1 protease, inhibitor κB kinase, quinone reductase, sphingomyelinase, topoisomerase and several protein kinases, and they also modulate histamine H(1) and 5-hydroxytryptamine(2A) receptor binding. Several synthetic procedures for active xanthones and their analogs have been conducted to obtain a better insight into structure-activity relationships for this compound class. This short review deals with progress made in the structural characterization of the chemical constituents of mangosteen, as well as the biological activity of pure constituents of this species and synthetic methods for the mangosteen xanthones.

Medicinal properties of mangosteen (Garcinia mangostana)

Many tropical plants have interesting biological activities with potential therapeutic applications. Garcinia mangostana Linn. (GML) belongs to the family of Guttiferae and is named "the queen of fruits". It is cultivated in the tropical rainforest of some Southeast Asian nations like Indonesia, Malaysia, Sri Lanka, Philippines, and Thailand. People in these countries have used the pericarp (peel, rind, hull or ripe) of GML as a traditional medicine for the treatment of abdominal pain, diarrhea, dysentery, infected wound, suppuration, and chronic ulcer. Experimental studies have demonstrated that extracts of GML have antioxidant, antitumoral, antiallergic, anti-inflammatory, antibacterial, and antiviral activities. The pericarp of GML is a source of xanthones and other bioactive substances. Prenylated xanthones isolated from GML have been extensively studied; some members of these compounds possess antioxidant, antitumoral, antiallergic, anti-inflammatory, antibacterial, antifungal and antiviral properties. Xanthones have been isolated from pericarp, whole fruit, heartwood, and leaves. The most studied xanthones are alpha-, beta-, and gamma-mangostins, garcinone E, 8-deoxygartanin, and gartanin. The aim of this review is to summarize findings of beneficial properties of GML's extracts and xanthones isolated from this plant so far.

Xanthones with quinone reductase-inducing activity from the fruits of Garcinia mangostana (Mangosteen)

Bioactivity-guided fractionation of a dichloromethane-soluble extract of Garcinia mangostana fruits has led to the isolation and identification of five compounds, including two xanthones, 1,2-dihydro-1,8,10-trihydroxy-2-(2-hydroxypropan-2-yl)-9-(3-methylbut-2-enyl)furo[3,2-a]xanthen-11-one (1) and 6-deoxy-7-demethylmangostanin (2), along with three known compounds, 1,3,7-trihydroxy-2,8-di-(3-methylbut-2-enyl)xanthone (3), mangostanin (4), and alpha-mangostin (5). The structures of compounds 1 and 2 were determined from analysis of their spectroscopic data. All isolated compounds in the present study together with eleven other compounds previously isolated from the pericarp of mangosteen, were tested in an in vitro quinone reductase-induction assay using murine hepatoma cells (Hepa 1c1c7) and an in vitro hydroxyl radical antioxidant assay. Of these, compounds 1-4 induced quinone reductase (concentration to double enzyme induction, 0.68-2.2microg/mL) in Hepa 1c1c7 cells and gamma-mangostin (6) exhibited hydroxyl radical-scavenging activity (IC50, 0.20microg/mL).

Anti-inflammatory activity of mangostins from Garcinia mangostana

The fruit hull of Garcinia mangostana Linn (Guttiferae) is used as an anti-inflammatory drug in Southeast Asia. Two xanthones, alpha- and gamma-mangostins, were isolated from the fruit hull of G. mangostana, and both significantly inhibited nitric oxide (NO) and PGE(2) production from lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The IC(50) values for the inhibition of NO production by alpha- and gamma-mangostins were 12.4 and 10.1 microM, respectively. After iNOS enzyme activity was stimulated by LPS for 12 h, treatment with either alpha- or gamma-mangostin at 5 microg/ml (12.2 and 12.6 microM, respectively) for 24 h did not significantly inhibit NO production. The data show that the inhibitory activities of alpha- and gamma-mangostins are not due to direct inhibition of iNOS enzyme activity. On the other hand, expression of iNOS was inhibited by alpha- and gamma-mangostins in LPS-stimulated RAW 264.7 cells, but not by COX-2. However, the level of PGE(2) production was reduced by the two xanthones. In an in vivo study, alpha-mangostin significantly inhibited mice carrageenan-induced paw edema. In conclusion, alpha- and gamma-mangostins from G. mangostana are bioactive substances with anti-inflammatory effects.

HPLC analysis of selected xanthones in mangosteen fruit

Xanthones are unique chemical compounds found in nature, composed of a tricyclic aromatic system with a variety of phenolic, methoxy, and isoprene substituents, giving rise to numerous derivatives. They dissolve to varying degrees in solvents ranging from alcohol to hexane. An optimum solvent mixture of acetone/water (80:20) selectively and effectively extracts a wide variety of xanthones. Subsequent HPLC analysis using standard C-18 RP and a 30-min gradient of 65-90% MetOH in 0.1% formic acid detects and separates numerous different xanthones with UV detection at 254 nm. The xanthones alpha-mangostin, 8-desoxygartanin, gartanin, beta-mangostin, 3-mangostin, and 9-hydroxycalabaxanthone have been extracted, identified, and quantitatively determined using this method. This analytical method is applied to the analysis of these xanthones in the rind of the mangosteen fruit, Garcinia mangostana.

Xanthones from Garcinia mangostana (Guttiferae)

Studies on the stem of Garcinia mangostana have led to the isolation of one new xanthone mangosharin (1) (2,6-dihydroxy-8-methoxy-5-(3-methylbut-2-enyl)-xanthone) and six other prenylated xanthones, alpha-mangostin (2), beta-mangostin (3), garcinone D (4), 1,6-dihydroxy-3,7-dimethoxy-2-(3-methylbut-2-enyl)-xanthone (5), mangostanol (6) and 5,9-dihydroxy-8- methoxy-2,2-dimethyl-7-(3-methylbut-2-enyl)-2H,6H-pyrano-[3,2-b]-xanthene-6-one (7). The structures of these compounds were determined by spectroscopic methods such as 1H NMR, 13C NMR, mass spectrometry (MS) and by comparison with previous studies. All the crude extracts when screened for their larvicidal activities indicated very good toxicity against the larvae of Aedes aegypti. This article reports the isolation and identification of the above compounds as well as bioassay data for the crude extracts. These bioassay data have not been reported before.

Tetraoxygenated xanthones from the fruits of Garcinia cowa

Tetraoxygenated xanthones, cowaxanthones A-E, together with 10 previously reported tetraoxygenated xanthones, were isolated from the crude hexane extract of the fruits of Garcinia cowa. Cowaxanthone B has previously been reported as a synthetic xanthone. Their structures were elucidated by analysis of spectroscopic data, especially by 1D and 2D NMR. The antibacterial activities of the isolated compounds were also evaluated.

Antimycobacterial activity of prenylated xanthones from the fruits of Garcinia mangostana

Prenylated xanthones, isolated from the fruit hulls and the edible arils and seeds of Garcinia mangostana, were tested for their antituberculosis potential. Alpha- and beta-mangostins and garcinone B exhibited strong inhibitory effect against Mycobacterium tuberculosis with the minimum inhibitory concentration (MIC) value of 6.25 microg/ml. Tri- and tetra-oxygenated xanthones with di-C5 units or with a C5 and a modified C5 groups are essential for high activities. Substitution in the A and C rings has been shown to modify the bioactivity of the compounds.