SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Two new xanthones have been isolated from the EtOAc extract of the roots of Premna microphylla Turcz. Based on spectral and chemical evidences, their structures were elucidated as 1-hydroxy-2,3-methylenedioxy-6-methoxycarbonyl-7-acetylxanthone 1 and 1,3-dihydroxy-2-methoxy-6-methoxycarbonyl-7-acetylxanthone 2. This is the first report on isolation of xanthones from this plant.
A series of xanthone derivatives was synthesized and tested in-vitro for their ability to inhibit aggregation of rabbit washed platelets and human platelet-rich plasma (PRP) induced by various inducers. 2-Prenyloxyxanthone showed the most potent inhibition of rabbit washed platelet aggregation induced by arachidonic acid (1C50 = 10.2 microM). Of the compounds tested in human PRP, 2-[3 (propylamino)-2-hydroxypropoxy]xanthone (4) hydrochloride salt exhibited the most potent inhibition of platelet aggregation induced by adrenaline (IC50 = 4.4 microM), whereas in evaluation of mouse antithrombotic activity, compound 4 exhibited the most potent protection of mice from thrombotic challenge. Compound 4, 2-[3-(isopropylamino)-2-hydroxypropoxylxanthone hydrochloride salt and 2,5 dihydroxyxanthone suppressed the secondary aggregation induced by adrenaline in human PRP. We conclude that the antiplatelet effects of these compounds are mainly due to an inhibitory effect on thromboxane formation.
Three new prenylated xanthones, mangostenones C (1), D (2), and E (3), together with 16 known xanthones 4-19, were isolated from the young fruit (7-week maturity stage) of Garcinia mangostana. The structural elucidation of the new compounds was mainly established on the basis of 1D and 2D NMR and HR-MS spectroscopic analysis. Compound 1 showed cytotoxic properties against three human cancer cell lines, epidermoid carcinoma of the mouth (KB), breast cancer (BC-1), and small cell lung cancer (NCI-H187), with IC50 values of 2.8, 3.53, and 3.72 microg/ml, respectively. Among the isolates, alpha-mangostin (12), the major metabolite, exhibited the most potent effects against the BC-1 cells with an IC50 value of 0.92 microg/ml, an activity greater than that of the standard drug ellipticine (IC50 = 1.46 microg/ml). Compound 12 also showed the highest activity against KB cells, while gartanin (10) displayed the strongest activity against the NCI-H187 cells at the respective IC50 values of 2.08 microg/ml and 1.08 microg/ml.
From the cultures of the spore-derived mycobionts of the lichen Pyrenula japonica, two new xanthones, 1,8-dihydroxy-3-hydroxymethyl-5-methoxyxanthone and 1,2,8-trihydroxy-5-methoxy-3-methylxanthone, were isolated along with 1,7-dihydroxy-3-methylxanthone, 1,5,8-trihydroxy-3-methylxanthone, 1,8-dihydroxy-5-methoxy-3-methylxanthone, emodin and sclerotiorin. Their structures were determined by spectroscopic methods. Sclerotiorin was isolated for the first time from lichen mycobionts. Radical scavenging activities of the isolated xanthones were also studied.
Our previous finding of strong cytotoxic polycyclic xanthones, actinoplanones A (1) and B (2), in the culture broth of Actinoplanes sp. R-304 stimulated us to isolate further five new cytotoxic polycyclic xanthones which were named actinoplanones C (3), D (4), E (5), F (6) and G (7) from the broth. Actinoplanones C (3) and G (7) showed very strong cytotoxicity against HeLa cells at less than 0.00004 microgram/ml dosage (IC50). The structures of 3-7 were varieties of 1 for the N-2 and C-4 substituents. All or several actinoplanones showed strong antimicrobial activities against bacteria and the rice blast fungus. Actinoplanone A (1) was tested for cytotoxicity against various tumor cells and for inhibitory effect on HeLa cell macromolecular synthesis, and 1 exhibited strong cytotoxicity against the cells and inhibitory action on DNA synthesis.
A topological modification of ipriflavone 1, a recent antiosteoporotic drug, is described. The flavone moiety of 1 has been replaced by a xanthone one. Among the new derivatives, the 3,6-diisopropoxyxanthone (2a) has shown significant bone resorption inhibition in in vitro and in vivo tests.
Two new polyprenylated xanthone epimers were isolated from gamboges of Garcinia hanburyi, and identified by detailed spectroscopic analysis as 30-hydroxygambogic acid (2a) and its (2S)-epimer 30-hydroxyepigambogic acid (2b). Both compounds exhibited significant cytotoxicities against the human leukemia K562/S and the corresponding doxorubicin-resistant K562/R cell lines (Table 2).
The complete 1H and 13C NMR assignments are reported for the new natural products, 7-hydroxy-3-(hydroxymethyl)-1-methoxy-9H-xanthen-9-one (1) and 2,5-dihydroxy-8-methoxy-6-methyl-9-oxo-9H-xanthene -1-carboxylic acid (2). Both of these secondary metabolites were isolated from the fermentation culture of the endophytic fungus Xylaria sp. FRR 5657. 1D and 2D NMR experiments that included 1H, gCOSY, gHSQC and gHMBC were used for the determination of the structure and assignment of these xanthones.
The effect of the xanthone derivative 2-(2-hydroxyethoxy)-6-(1-H-tetrazole-5-yl)xanthen-9-one (BW A440C) on red cells was studied. When added to stored red cells at a concentration of 6 mM, greatly improved preservation of 2,3-diphosphoglycerate (2,3-DPG) was observed. There was no effect on internal pH of the erythrocyte. At a concentration 0.500 mM, many red cell enzyme activities were inhibited completely. At a 0.500 mM concentration, however, inhibition of pyruvate kinase and diphosphoglycerate phosphatase was most striking. Inhibition of either of these enzymes could result in elevation of 2,3-DPG levels. BW A440C in concentrations which elevated 2,3-DPG levels in humans caused a decrease in 2,3-DPG levels in rabbits and markedly impaired the viability of 21-day stored rabbit erythrocytes.
Mitochondrial permeability transition (MPT) is a Ca(2+)-dependent, cyclosporine A-sensitive, non-selective inner membrane permeabilization induced by a wide range of agents or conditions, which has often been associated with necrotic or apoptotic cell death. When mitochondria isolated from livers of rats treated with the natural occurring glucosyl xanthone mangiferin (40 mg/kg body weight) were exposed in vitro to Ca(2+), they underwent CsA, NEM, and ADP-sensitive high amplitude swelling and associated membrane potential dissipation, release of pre-accumulated Ca(2+), oxidation of thiol groups, and depletion of GSH, without changes in the NAD(P)H redox state. The same treatment reduced the phosphorylation rate of mitochondria and the resting respiration by around 4 and 11%, respectively, as well as generation of reactive oxygen species (ROS) by organelle. The in vitro exposure of untreated mitochondria to mangiferin plus Ca(2+) also resulted in oxidation of thiol groups, in the same way that the compound inhibited the Ca(2+)-induced peroxidation of mitochondrial membrane lipids. The spectrum of mangiferin during its oxidation by the H(2)O(2)/HRP system showed a characteristic absorption peak at 380 nm, which decreased immediately after reaction was started; two isosbestic points at around 336 and 412 nm, with a blue shift in the position of the maxima absorption of mangiferin were observed, suggesting their conversion into one oxidation product. Glutathione abolished this decrease of absorbance, suggesting that the oxidation product of mangiferin forms adducts with GSH. We propose that Ca(2+) increases levels of mitochondria-generated ROS, which reacts with mangiferin producing quinoid derivatives, which in turn react with the most accessible mitochondrial thiol groups, thus triggering MPT. It seems probable that the free radical scavenging activity of mangiferin shifts its anti-oxidant protection to the thiol arylation. An interesting proposition is that accumulation of mangiferin quinoid products would take place in cells exposed to an overproduction of ROS, such as cancer cells, where the occurrence of MPT-mediated apoptosis may be a cellular defence mechanism against excessive ROS formation.
The catecholic xanthones and flavonoids 1-13 were isolated from the root bark of Cudrania tricuspidata. Compounds 1 and 3-8 exhibited significant antioxidant activity against low-density lipoprotein (LDL) oxidation in the thiobarbituric acid-reactive substance (TBARS) assay. Among them, prenylated flavonoids 10-12 showed an inhibitory effect on the NO production and iNOS expression in RAW264.7 cells. Also, compounds 1, 2, 5, 7, 9, and 11 preferentially inhibited hACAT-2 than hACAT-1, whereas compounds 3, 4, 6, and 8 showed a similar specificity against hACAT-1 and -2. However, flavonoids 10, 12, and 13 dominantly inhibited hACAT-2, not hACAT-1.
A comparison between the extraction yields of xanthones and flavanones from the root bark of the Maclura pomifera by solid-liquid extraction (SLE), matrix solid phase dispersion (MSPD), and an alternative method using sea sand as a sample disruptor, is presented here. Two extraction solvents were used for all extraction techniques, dichloromethane and methanol:water, (9:1, v/v). The extraction procedures were reproducible as the R.S.D. values were less than 5% for almost all compounds. A recovery above 80% was obtained for macluraxanthone using the sea sand extraction procedure. Statistical treatment, ANOVA-single factor, was used to evaluate the different extraction procedures, and homogenization of plant material with sand followed by elution with dichloromethane provided the most efficient and rapid extraction method.
The earlier work carried out in our laboratory led to the identification of a novel rat liver microsomal enzyme termed as acetoxy drug: protein transacetylase (TAase), catalyzing the transfer of acetyl group from polyphenolic acetates (PA) to functional proteins. In this paper, we have reported the comparison of the specificities of acetoxy derivatives of coumarins, biscoumarins, chromones, flavones, isoflavones and xanthones with special reference to the phenyl moiety/bulky group on the pyran ring of PA. The results clearly indicated that compounds having phenyl moieties, when used as the substrates, resulted in a significant reduction of TAase catalyzed activity. The alteration in TAase catalyzed activation of NADPH cytochrome c reductase and inhibition of benzene-induced micronuclei in bone marrow cells by PA were in tune with their specificities to TAase.
Two xanthones, namely virgataxanthone A and B, have been isolated from the stem bark of Garcinia virgata, together with two formylated tocotrienols and the known delta-tocotrienol, griffipavixanthone and 2,6-dihydroxy-4-methoxybenzophenone (cotoin). Their structures were mainly established using one and two-dimensional NMR and mass spectroscopies. When sufficient material was available, the antioxidant activities of the crude extracts as well as the isolated compounds were evaluated.
Xanthones, 1,3-dihydroxy-5-methoxyxanthone-4-sulfonate and 1,3-dihydroxy-5-O-beta-D-glycopyranosylxanthone-4-sulfonate, together with nine known compounds were obtained from H. sampsonii. This is the first report of sulfonated xanthonoids. Furthermore, compounds 1 and 2 exhibited significant cytotoxicity against the P388 cancer cell line.
Two new xanthones, smeathxanthone A (1) (2-(3,7-dimethyl-2,6-octadienyl)-1,3,5,8-tetrahydroxyxanthone) and smeathxanthone B (2) (5,7,10-trihydroxy-2-methyl-2-(4-methylpent-3-enyl)[2H, 6H]pyrano[3,2-b]xanthen-6-one), have been isolated from the stem bark of Garcinia smeathmannii, and their structures elucidated on the basis of 1D and 2D NMR experiments. 1,3,5-Trihydroxyxanthone and 1,5-dihydroxyxanthone were also obtained. The compounds showed only modest activity against a range of bacteria and yeasts.
Chemical investigation of the roots of Cratoxylum formosum has resulted in the isolation and characterization of xanthones: three new, named formoxanthone A-C and three known together with three known anthraquinones. Their structures were established on the basis of analysis of spectroscopic evidence. In addition, antibacterial and cytotoxic activities of the isolates were also evaluated.
A phytochemical investigation of the constituents of the roots of Vismia laurentii has resulted in the isolation of two xanthone derivatives named laurentixanthone A (1) (6-hydroxy-3,3-dimethyl-11-(3-methylbut-2-enyl)pyrano[2,3-c]xanthen-7(3H)-one) and laurentixanthone B (2) (1-hydroxy-5,6,7,8-tetramethoxyxanthone), along with 11 known compounds: 1,7-dihydroxyxanthone, vismiaquinone, vismiaquinone B, bivismiaquinone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone, O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol, 6-deoxyisojacareubin, 1,8-dihydroxy-6-methoxy-3-methylanthraquinone, kaempferol, friedelin and stigmasterol. The structures of compounds were established by means of spectroscopic methods. Furthermore, the compounds were screened for antimicrobial activities in vitro.