Novel xanthones with superoxide scavenging activity from Garcinia subelliptica

Synthesis of benzylated amine-substituted xanthone derivatives and their antioxidant and anti-inflammatory activities

Oxidative stress and its constant companion, inflammation, play a critical part in the pathogenesis of many acute and chronic illnesses. The discovery of new multi-targeted drug candidates with antioxidant and anti-inflammatory properties is deemed necessary. Thus, a series of novel xanthone derivatives with halogenated benzyl (4b-4d, 4f-4h) and methoxylated benzyl groups (4e) attached to the butoxy amine substituent were synthesized in this study. The synthesized xanthone derivatives exhibited stronger antioxidant activity against H₂ O₂ scavenging than the standard drug, α-tocopherol, but weaker towards DPPH scavenging and ferrous ion chelation. Besides that, 4b-4d, 4f-4h demonstrated good anti-inflammatory activities through NO production inhibition towards lipopolysaccharide (LPS)-induced RAW 264.7 cells and showed 2-4 times stronger effects than the standard drug, diclofenac sodium. Moreover, compound 4b with two brominated benzyl groups attached to the butoxy amine substituent suppressed the production of pro-inflammatory cytokines, TNF-α and IL-1β, significantly. Structure-activity relationship elucidated that the halogenated benzylamine substituent plays an important role in contributing the antioxidant and anti-inflammatory activities of xanthones. In summary, xanthone 4b was identified as a potential lead compound to be further developed into antioxidant and anti-inflammatory drugs. Thus, further studies on the related mechanisms of action of 4b are recommended.

Mangiferin offers protection against deleterious effects of pharmaceuticals, heavy metals, and environmental chemicals

Mangiferin (MGF) is a polyphenolic C-glucosyl-xanthone extracted from the mango tree (Mangifera indica). MGF has shown diverse effects such as antioxidant, antiapoptotic, radical scavenging, and chelating properties. MGF also has been shown to modulate inflammatory pathways. In this review, we examined and evaluated the literature dealing with the protective effects of MGF against various chemical toxicities. Our literature review indicated that the MGF-induced protective effects against the toxic effects of pharmaceuticals, heavy metals and environmental chemicals were mainly mediated via suppression of lipid peroxidation, oxidative stress (along with enhancement of the antioxidant enzyme), inflammatory factors (TNF-α, IL-6, IL-10, and IL-12), and activation of PI3K/Akt and the MAPK survival signaling pathway.

Garcinia subelliptica Merr. (Fukugi): A multipurpose coastal tree with promising medicinal properties

In this short review, the current knowledge on the botany, ecology, uses, and medicinal properties of the multipurpose Garcinia subelliptica (Fukugi) is updated. As yet, there are no reviews on this indigenous and heritage coastal tree species of the Ryukyu Islands in Japan, which has ethnocultural, ecological, and pharmacological significance. Planted by the Okinawan people some 300 years ago, Fukugi trees serve as windbreaks and accord protection against the destructive typhoons. The species has become a popular ornamental tree, and its bark has been used for dyeing fabrics. It forms part of the food chain for mammals and insects and serves as nesting sites for birds. Endowed with bioactive compounds of benzophenones, xanthones, biflavonoids, and triterpenoids, G. subelliptica possesses anticancer, anti-inflammatory, anti-tyrosinase, trypanocidal, antibacterial, DNA topoisomerase inhibitory, DNA strand scission, choline acetyltransferase enhancing, hypoxia-inducible factor-1 inhibitory, and antiandrogenic activities. Fukugetin and fukugiside are two novel biflavonoids named after the species. The chemical constituents of Fukugi fruits when compared with those of mangosteen yielded interesting contrasts.

c-Jun N-terminal kinase-mediated anti-inflammatory effects of Garcinia subelliptica in macrophages

Garcinia plants have been traditionally used to treat inflammatory diseases, such as skin infections and pain, in many regions including South‑East Asia. Garcinia subelliptica, a plant of the Garcinia species widely distributed from Japan to Thailand, has been reported to contain components similar to other Garcinia plants that exhibit anti‑inflammatory effects. The present study aimed to explore the anti‑inflammatory effects of ethanol extracts of Garcinia subelliptica (EGS) in macrophages, as there are no previous systemic studies that have investigated the effects of Garcinia subelliptica on inflammation. Non‑cytotoxic concentrations of EGS (≤200 µg/ml) were observed to reduce nitric oxide production by modulating iNOS expression in lipopolysaccharide (LPS)‑stimulated RAW 264.7 macrophages. The expression of cyclooxygenase‑2, the enzyme responsible for the production of prostaglandin E2, was notably reduced by EGS. EGS treatment inhibited the production of pro‑inflammatory cytokines, including IL‑6 and IL‑1β, however, not TNF‑α. Reduced production of inflammatory mediators by EGS was followed by reduced phosphorylation of c‑Jun N‑terminal kinase (JNK) however, not of other mitogen‑activated protein kinases and nuclear factor‑κB. These results indicate that EGS selectively inhibits the excessive production of inflammatory mediators in LPS‑stimulated murine macrophages by reducing the activation of JNK, suggesting that EGS is a candidate for modulating severe inflammation.

Antioxidant properties of xanthones from Calophyllum brasiliense: prevention of oxidative damage induced by FeSO₄

Background

Reactive oxygen species (ROS) are important mediators in a number of degenerative diseases. Oxidative stress refers to the imbalance between the production of ROS and the ability to scavenge these species through endogenous antioxidant systems. Since antioxidants can inhibit oxidative processes, it becomes relevant to describe natural compounds with antioxidant properties which may be designed as therapies to decrease oxidative damage and stimulate endogenous cytoprotective systems. The present study tested the protective effect of two xanthones isolated from the heartwood of Calophyllum brasilienses against FeSO₄-induced toxicity.

Methods

Through combinatory chemistry assays, we evaluated the superoxide (O₂^●—), hydroxyl radical (OH^●), hydrogen peroxide (H₂O₂) and peroxynitrite (ONOO^—) scavenging capacity of jacareubin (xanthone III) and 2-(3,3-dimethylallyl)-1,3,5,6-tetrahydroxyxanthone (xanthone V). The effect of these xanthones on murine DNA and bovine serum albumin degradation induced by an OH• generator system was also evaluated. Additionally, we investigated the effect of these xanthones on ROS production, lipid peroxidation and glutathione reductase (GR) activity in FeSO₄-exposed brain, liver and lung rat homogenates.

Results

Xanthone V exhibited a better scavenging capacity for O₂^●—, ONOO^- and OH^● than xanthone III, although both xanthones were unable to trap H₂O₂. Additionally, xanthones III and V prevented the albumin and DNA degradation induced by the OH^● generator system. Lipid peroxidation and ROS production evoked by FeSO₄ were decreased by both xanthones in all tissues tested. Xanthones III and V also prevented the GR activity depletion induced by pro-oxidant activity only in the brain.

Conclusions

Altogether, the collected evidence suggests that xanthones can play a role as potential agents to attenuate the oxidative damage produced by different pro-oxidants.

A new benzoylphloroglucinol derivative with an adamantyl skeleton and other constituents from Garcinia multiflora: effects on neutrophil pro-inflammatory responses

A novel benzoylphloroglucinol derivative, garcimultiflorone D (1), with an unusual adamantyl-caged skeleton was isolated from the fruits of Garcinia multiflora, together with four known compounds. The structure of 1 was determined through extensive 1D/2D-NMR and mass-spectrometric analyses. Garcimultiflorone D (1) exhibited inhibitory activities with IC(50) values of 7.21±1.07 and 6.01±0.37 μg/ml against fMLP/CB-induced superoxide anion generation and elastase release, respectively.

Xanthones from the stem bark of Garcinia bracteata with growth inhibitory effects against HL-60 cells

Five xanthones, 1,4,5,6-tetrahydroxyxanthone (1) and bracteaxanthones III-VI (2-5) together with twenty-six known compounds (6-31), were isolated from the ethanol extract of the stem bark of Garcinia bracteata. Their structures were elucidated via spectroscopic analyses. Growth inhibitory activities of these compounds against the human leukaemic HL-60 cell line were measured in vitro. Compounds 7, 11, and 29 exhibited moderate activities with GI(50) values of 2.8, 3.4, and 3.1 μM, respectively, and a preliminary structure-activity relationship is discussed.

Plant extracts for the control of bacterial growth: efficacy, stability and safety issues for food application

The microbial safety of foods continues to be a major concern to consumers, regulatory agencies and food industries throughout the world. Many food preservation strategies have been used traditionally for the control of microbial spoilage in foods but the contamination of food and spoilage by microorganisms is a problem yet to be controlled adequately. Although synthetic antimicrobials are approved in many countries, the recent trend has been for use of natural preservatives, which necessitates the exploration of alternative sources of safe, effective and acceptable natural preservatives. Plants contain innumerable constituents and are valuable sources of new and biologically active molecules possessing antimicrobial properties. Plants extracts either as standardized extracts or as a source of pure compounds provide unlimited opportunities for control of microbial growth owing to their chemical diversity. Many plant extracts possess antimicrobial activity against a range of bacteria, yeast and molds, but the variations in quality and quantity of their bioactive constituents is the major detriments in their food use. Further, phytochemicals added to foods may be lost by various processing techniques. Several plant extracts or purified compounds intended for food use have been consumed by humans for thousands of years, but typical toxicological information is not available for them. Although international guidelines exist for the safety evaluation of food additives, owing to problems in standardization of plant extracts, typical toxicological values have not been assigned to them. Development of cost effective isolation procedures that yield standardized extracts as well as safety and toxicology evaluation of these antimicrobials requires a deeper investigation.

Acylphloroglucinol and xanthones from Hypericum ellipticum

An acylphloroglucinol, elliptophenone A, and two xanthones, elliptoxanthone A and elliptoxanthone B, were isolated from the aerial portions of Hypericum ellipticum together with three known xanthones, 1,3,7-trihydroxy-8-(3-methyl-2-butenyl)-9H-xanthen-9-one, 1,6-dihydroxy-4-methoxy-9H-xanthen-9-one, and 1,4,5-trihydroxy-9H-xanthen-9-one. Their structures were determined by spectroscopic analyses. The acylphloroglucinol and xanthones were evaluated for cytotoxicity using three human colon cancer cell lines cell lines (HT-29, HCT-116 and Caco-2) and a normal human colon cell line (CCD-18Co).

Cytotoxic polyisoprenyl benzophenonoids from Garcinia subelliptica

Six new polyisoprenyl benzophenonoids, (+/-)-garcinialiptone A (1, 2), garcinialiptone B (3), (-)-cycloxanthochymol (4), garcinialiptone C (5), and garcinialiptone D (6), along with three known compounds, xanthochymol (7), isoxanthochymol (8), and cycloxanthochymol (9), were isolated from the fruits of Garcinia subelliptica. The structures of 1-6 were elucidated by spectroscopic analysis. Biological evaluation showed that all compounds 1-9 exhibited cytotoxic activity against a small panel of human tumor cell lines (A549, DU145, KB, vincristine-resistant KB).

Identification of hydroxyxanthones as Na/K-ATPase ligands

We have screened a chemical library and identified several novel structures of Na/K-ATPase inhibitors. One group of these inhibitors belongs to polyphenolic xanthone derivatives. Functional characterization reveals the following properties of this group of inhibitors. First, like ouabain, they are potent inhibitors of the purified Na/K-ATPase. Second, their effects on the Na/K-ATPase depend on the number and position of phenolic groups. Methylation of these phenolic groups reduces the inhibitory effect. Third, further characterization of the most potent xanthone derivative, MB7 (3,4,5,6-tetrahydroxyxanthone), reveals that it does not change either Na(+) or ATP affinity of the enzyme. Finally, unlike that of ouabain, the inhibitory effect of MB7 on Na/K-ATPase is not antagonized by K(+). Moreover, MB7 does not activate the receptor Na/K-ATPase/Src complex and fails to stimulate protein kinase cascades in cultured cells. Thus, we have identified a group of novel Na/K-ATPase ligands that can inhibit the pumping function without stimulating the signaling function of Na/K-ATPase.

Beneficial effect of 3,4,5,6-tetrahydroxyxanthone on dyslipidemia in apolipoprotein E-deficient mice

Previous investigations have shown that decreased expression of angiopoietin-like protein 3 (Angptl3) is protective against dyslipidemia in atherosclerosis. The present study was conducted to test the effect of 3,4,5,6-tetrahydroxyxanthone, a xanthone compound, on dyslipidemia in apolipoprotein E-deficient (ApoE-/-) mice. Forty mice were randomly divided into 4 groups (n = 10): control group (C57BL/6J mice), ApoE-/-mice group, and two groups of ApoE-/- mice treated with 3,4,5,6-tetrahydroxyxanthone (10 or 30 mg/kg per day). Eight weeks after treatment, lipid levels in the blood and liver, expression of hepatic Angptl3, and adipose tissue lipoprotein lipase (LPL) were determined. Treatment with 3,4,5,6-tetrahydroxyxanthone (10 or 30 mg/kg) significantly decreased plasma and hepatic total cholesterol and triglyceride concentrations, increased plasma high-density lipoprotein cholesterol, and significantly downregulated expression of Angptl3 mRNA and protein concomitantly with upregulated expression of LPL mRNA. In addition, T0901317 (a liver X receptor ligand) caused elevated expression of hepatic Angptl3 mRNA and protein, and the effect of T0901317 was also abrogated by 3,4,5,6-tetrahydroxyxanthone in vivo and in vitro. The present results suggest that the beneficial effect of 3,4,5,6-tetrahydroxyxanthone on dyslipidemia may be related to reduced expression of Angptl3.

Analgesic and antioxidant activity of mangiferin and its derivatives: the structure activity relationship

Mangiferin, 2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxy-9H-xanthen-9-one, obtained directly from methanolic extracts of Bombax ceiba leaves in substantial amounts demonstrated strong antioxidant activity (EC(50) 5.8+/-0.96 mug/ml or 13.74 muM) using DPPH assay comparable to rutin, commonly used as antioxidant for medical purposes. The acetyl and cinnamoyl derivatives were found to be less active than mangiferin whereas, methyl and 3,6,7-trimethylether tetraacetate derivatives were inactive implying that for antioxidant activity, free hydroxyl groups and catechol moiety are essential. Moreover, mangiferin showed hepatoprotective activity against carbon tetrachloride induced liver injury further supporting the free radical scavenging property in the in vivo system. Additionally, plant extracts and mangiferin failed to exhibit acute anti-inflammatory activity whereas, it displayed significant analgesic effect in acetic acid-induced writhing and hot plate tests in mice. Using naloxone, it was revealed that plant extracts induced analgesia was independent of opioid receptor, whereas, mangiferin demonstrated significant interaction with it at peripheral site with a slight contribution at the neuronal level.

Prenylated anthronoid antioxidants from the stem bark of Harungana madagascariensis

Two new prenylated anthronoids, harunmadagascarins A and B, were isolated from the stem bark of Harungana madagascariensis along with six known compounds including two anthronoids: harunganol B and harungin anthrone, one benzophenone: methyl 3-formyl-2,4-dihydroxy-6-methyl benzoate and three pentacyclic triterpenes: friedelin, lupeol and betulinic acid. Harunmadagascarins A and B were characterized as 8,9-dihydroxy-4,4-bis-(3,3-dimethylallyl)-6-methyl-2,3-(2,2-dimethylpyrano)anthrone and 8,9-dihydroxy-4,4,5-tris-(3,3-dimethylallyl)-6-methyl-2,3-(2,2-dimethylpyrano)anthrone, respectively. The structures of these secondary metabolites were determined by spectroscopic means and comparison with the published data. Methyl 3-formyl-2,4-dihydroxy-6-methyl benzoate was isolated for the first time from a plant. Harunmadagascarins A and B, harunganol B and harungin anthrone exhibited significant antioxidant activity.

Antiaflatoxigenic and antioxidant activities of Garcinia extracts

The effect of hexane and chloroform extracts from the fruit rinds of Garcinia cowa and Garcinia pedunculata on the growth and aflatoxin production in Aspergillus flavus was studied using peanut powder as a model food system. The growth of A. flavus was completely inhibited by the hexane and chloroform extracts from G. cowa and chloroform extract from G. pedunculata at 3000 ppm concentration, which was considered as the minimum inhibitory concentration (MIC). The MIC for the hexane extract of G. pedunculata was at 4000 ppm. Both the extracts from G. cowa inhibited aflatoxin B1 production upto 100% at a lower concentration of 2000 ppm. It was observed that, at lower concentration of the extracts from G. cowa and G. pedunculata, the degree of inhibition of aflatoxin production was much higher than the inhibition of fungal growth. The hexane and chloroform extracts from G. cowa and G. pedunculata were also studied for their antioxidant capacity by the formation of phosphomolybdenum complex at 100 ppm concentration and reducing power by potassium ferricyanide reduction method at various concentrations. Hexane and chloroform extracts from G. cowa showed higher antioxidant capacity than G. pedunculata extracts. Similarly, both the extracts from G. cowa showed higher reducing power than the extracts from G. pedunculata. The antiaflatoxigenic activities of the extracts from G. cowa and G. pedunculata may be due to their effective antioxidative properties, which could suppress the biosynthesis of aflatoxin.

Antimalarial xanthones from Calophyllum caledonicum and Garcinia vieillardii

The antimalarial activity of 22 xanthones against chloroquino-resistant strains of Plasmodium falciparum was evaluated. Natural caloxanthone C (1), demethylcalabaxanthone (2), calothwaitesixanthone (3), calozeyloxanthone (4), dombakinaxanthone (5), macluraxanthone (6), and 6-deoxy-gamma-mangostin (7) were isolated from Calophyllum caledonicum. 1,6-dihydroxyxanthone (8), pancixanthone A (9), isocudraniaxanthone B (10), isocudraniaxanthone A (11), 2-deprenylrheediaxanthone B (12) and 1,4,5-trihydroxyxanthone (13) were isolated from Garcinia vieillardii. Moreover, synthetic compounds (14-22) are analogues or intermediates of xanthones purified from Calophyllum caledonicum (Oger J.M., Morel C., Helesbeux J.J., Litaudon M., Seraphin D., Dartiguelongue C., Larcher G., Richomme P., Duval O. 2003. First 2-Hydroxy-3-Methylbut-3-Enyl substituted xanthones isolated from Plants: structure elucidation, synthesis and antifungal activity. Natural Product Research 17(3), 195-199; Helesbeux J.J., Duval O., Dartiguelongue C., Seraphin D., Oger J.M., Richomme P., 2004. Synthesis of 2-hydroxy-3-methylbut-3-enyl substituted coumarins and xanthones as natural products. Application of the Schenck ene reaction of singlet oxygen with ortho-prenylphenol precursors. Tetrahedron 60(10), 2293-2300). The relationship between antimalarial activity and molecular structure of xanthones has also been explored. The most potent xanthones (2), (3) and (7) (IC50 = c.a. 1.0 microg/mL) are 1,3,7 trioxygenated and prenylated on the positions 2 and 8.

3,4,5,6-Tetrahydroxyxanthone prevents vascular endothelial cell apoptosis induced by high glucose

Apoptosis of endothelial cells may be an important risk factor contributing to the incidence of vascular complications in diabetes. In the present study, we tested the effect of 3,4,5,6-tetrahydroxyxanthone, a synthetic xanthone derivative, on apoptosis induced in human umbilical vein endothelial cells (HUVEC) by a high glucose concentration. Cell apoptosis was detected using DNA ladder formation and flow cytometric techniques. The expression of Bcl-2 protein was analysed using flow cytometric techniques. Lactate dehydrogenase (LDH) activity and malonyldialdehyde (MDA) content in the medium were measured. Cell viability was assayed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) method. Exposure of HUVEC to a high glucose concentration (30 mM) for 48 h markedly increased LDH release and MDA content in the medium and induced apoptosis and Bcl-2 protein expression in HUVEC. Pretreatment with 3,4,5,6-tetrahydroxyxanthone (1, 3 or 10 microM) or probucol (10 microM) significantly decreased the level of LDH and MDA in the medium, reduced apoptosis and increased the expression of Bcl-2 protein in HUVEC. These results suggest that 3,4,5,6-tetrahydroxyxanthone inhibits high-glucose-induced endothelial cell apoptosis by increasing Bcl-2 protein expression in HUVEC.

Demethylbellidifolin preserves endothelial function by reduction of the endogenous nitric oxide synthase inhibitor level

The present study examined the anti-oxidation and protective effects of demethylbellidifolin (DMB), a xanthone compound extracted from swertia davidi Franch, on endothelium. The relationship between the protective effects of DMB on endothelium and the level of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, was also determined in the present study. DMB significantly inhibited Cu(2+)-induced low-density lipoprotein (LDL) oxidation and scavenged DPPH radicals. DMB significantly attenuated the inhibition of endothelium-dependent vasodilator responses, induced by lysophosphatidycholine (LPC) in vitro and LDL in vivo, and increased release of lactate dehydrogenase induced by LDL in cultured endothelial cells. DMB significantly attenuated the increased concentration of malondialdehyde and ADMA, and the decreased level of nitric oxide induced by LDL in vivo and in cultured endothelial cells. DMB also significantly reduced the decreased activity of dimethylarginine dimethylaminohydrolase (DDAH) induced by LDL in cultured endothelial cells. In summary, the present results suggest that DMB protects endothelial damage induced by LPC in vitro and LDL in vivo or in endothelial cells, and the protective effect of DMB on the endothelium is related to reduction of ADMA concentration via an increase of DDAH activity by inhibition of lipid peroxidation.

Antioxidant xanthones from Garcinia vieillardii

Two new xanthones, 6-O-methyl-2-deprenylrheediaxanthone B (1) and vieillardixanthone (2), were isolated from the stem bark of Garcinia vieillardii, as were four known compounds (4-7). The structures of 1 and 2 were determined by means of spectroscopic analysis and chemical derivatization. Each isolate was tested for its antioxidant properties based on a scavenging activity study using the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical.

Trypanocidal Constituents in Plants 2. Xanthones from the Stem Bark of Garcinia subelliptica

The constituents of the stem bark of Garcinia subelliptica (Guttiferae) were investigated based on its trypanocidal activity against epimastigotes of Trypanosoma cruzi, the etiologic agent for Chagas' disease. As the active components, nine xanthones were isolated including two new ones, 4-hydroxybrasilixanthone B and 1,3,5,6-tetrahydroxy-4,7,8-tri(3-methyl-2-butenyl)xanthone. Their structures were determined by spectroscopic analysis. Trypanocidal activity against trypomastigotes, an infectious form of T. cruzi, was also estimated as well as cytotoxic activity. Fukugetin, the major component of the bark, showed no activity.

Antimicrobial, antioxidant, antitumour-promoting and cytotoxic activities of different plant part extracts of Garcinia atroviridis griff. ex T. anders

Crude extracts (methanol) of various parts, viz. the leaves, fruits, roots, stem and trunk bark, of Garcinia atroviridis were screened for antimicrobial, cytotoxic, brine shrimp toxic, antitumour-promoting and antioxidant activities. The crude extracts exhibited predominantly antibacterial activity with the root extract showing the strongest inhibition against the test bacteria at a minimum inhibitory dose (MID) of 15.6 microg/disc. Although all the extracts failed to inhibit the growth of most of the test fungi, significant antifungal activity against Cladosporium herbarum was exhibited by most notably the fruit (MID: 100 microg), and the leaf (MID: 400 microg) extracts. None of the extracts were significantly cytotoxic, and lethal towards brine shrimps. The root, leaf, trunk and stem bark extracts (except for the fruits) showed strong antioxidant activity exceeding that of the standard antioxidant, alpha-tocopherol. Antitumour-promoting activity (>95% inhibition) was shown by the fruit, leaf, stem and trunk bark extracts.

Dulxanthones F-H, three new pyranoxanthones from Garcinia dulcis

Three new pyranoxanthones, dulxanthones F-H (1-3), have been isolated from the leaves of Garcinia dulcis. Their structures have been determined on the basis of extensive NMR studies.

A benzophenone and a xanthone from Garcinia Subelliptica

A new benzophenone derivative, 2',3',6-trihydroxy-2,4-dimethoxybenzophenone and a new xanthone, 1,6-O-dimethylsymphoxanthone have been isolated from the wood of Garcinia subelliptica. Their structures have been determined by analysis of the spectroscopic data and comparison of the NMR data with those of the compounds previously reported.