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Five xanthones from the bark of Garcinia cowa, namely 7-O-methylgarcinone E (1), cowanin (2), cowanol (3), cowaxanthone (4), and beta-mangostin (5), were found to possess in vitro antimalarial activity against Plasmodium falciparum with IC50 values ranging from 1.50 to 3.00 micrograms/ml. Complete 1H- and 13C-NMR assignments of these compounds are also reported.
Three new xanthone glycosides, securixanside A (1), securixanside B (2), and securixanside C (3) were isolated from the stems of Securidaca inappendiculata. These compounds were characterized by spectrometric and chemical methods, including FABMS and one- and two-dimensional NMR experiments.
Three new xanthones, 3, 6-dihydroxy-1, 2, 7-trimethoxyxanthone (2), 3, 7-dihydroxy- 1, 2-dimethoxyxanthone (4) and 1, 2, 7-trihydroxy-3-methoxyxanthone (9), together with seven known compounds were isolated from the roots of Polygala japonica Houtt. Their structures were determined on the basis of spectroscopic data.
Sphingomyelinase is considered to be involved in the regulation of apoptosis and cell growth. In the course of our screening for acidic sphingomyelinase inhibitors we isolated three xanthone compounds, alpha-mangostin, cowanin, and cowanol, from the bark of Garcinia speciosa. These compounds competitively inhibited bovine brain-derived acidic sphingomyelinase with IC(50) values of 14.1, 19.2, and 10.9 microM, respectively and inhibited the acidic sphingomyelinase more effectively than the neutral sphingomyelinase of bovine brain. alpha-Mangostin inhibited the acidic sphingomyelinase in the most selective manner. alpha-Mangostin was chemically modified and its structure-activity relationships are discussed.
A prenylated xanthone has been isolated from the seeds of Symphonia globulifera together with the known compounds sitosterol and oleanolic acid. The structure of the new compound was elucidated by spectroscopic methods.
Two new xanthone derivatives, 1-hydroxy-5,6,7-trimethoxyxanthone and 3-O-methylpaxanthone were isolated from callus of Hypericum perforatum subsp. perforatum together with the known paxanthone, cadensin G, 1-hydroxy-6,7-dimethoxyxanthone, 1,3,6,7-tetrahydroxyxanthone, and 1,3,5,6-tetrahydroxyxanthone. The structures of the new compounds were established by spectroscopic methods.
Two new xanthons, musaxanthone (1) and asmaxanthone (2) were isolated from the leaves of Garciniarigida. The structures were determined by means of spectroscopic analysis.
Reinvestigation of the plant, Swertia decussata resulted in the isolation of four antioxidant xanthones, which were characterized as 1-hydroxy-3,7,8-trimethoxy, 1,8-dihydroxy-3,7-dimethoxy, 1,7-dihydroxy-3,8-dimethoxy and 1,7,8-trihydroxy-3-methoxyxanthones. The structural ambiguity of the first compound was settled by ASIS-NMR and 2D NOESY spectroscopy.
A xanthone derivative, 3,6,7-trihydroxy-1-methoxyxanthone has been isolated from the stem bark of Allanblackia monticola together with other known compounds, 2,6-dihydroxy-1-methoxyxanthone, allanxanthone A, epicathechin and oleanolic acid acetate. The structure of the new compound was elucidated by spectroscopic methods.
This work relates the development and validation of a simple reversed-phase high-performance liquid chromatographic (HPLC) method for the analysis of xanthone (XAN) and 3-methoxyxanthone (3-MeOXAN) in poly(D,L-lactide-co-glycolide) (PLGA) nanocapsule formulations. This method does not require any complex sample extraction procedure. Chromatographic separation is made with a reversed-phase C(18) column, using methanol-water (90:10, v/v) as a mobile phase at a flow rate of 1 mL/min. Identification is made by UV detection at 237 nm. The isocratic system operates at ambient temperature and requires 7 min of chromatographic time. The developed method is statistically validated according to United States Pharmacopoeia 25 and International Conference on Harmonization guidelines for its specificity, linearity, accuracy, and precision. The assay method proposed in this study is specific for XAN and 3-MeOXAN in the presence of nanocapsule excipients. Diode-array analyses confirm the homogeneity of XAN and 3-MeOXAN peaks in stressed conditions. Standard curves are linear (r > 0.999) over the concentration range of 0.4-2.5 and 1.0-5.8 micro g/mL for XAN and 3-MeOXAN, respectively. Recovery from nanocapsules ranges from 99.6% to 102.8% for XAN and 98.8% to 102.4% for 3-MeOXAN. Repeatability (intra-assay precision) is acceptable with relative standard deviation values of 1.2% for XAN and 0.3% for 3-MeOXAN.
1-Hydroxy-3,4,7,8-tetramethoxyxanthone, beta-sitosterol, uvaol-3-palmitate, and sweroside have been isolated from the fresh whole plant of Tripterospermum lanceolatum (Hayata) Haraex Satake (Gentianaceae). Our results on the pharmacological studies of xanthone glycoside and lanceoside suggested that they have a CNS depressant effect.
A series of oxygenated xanthones was prepared so that the antimalarial activity of each compound could be evaluated in vivo, using 4-day suppressive assays against Plasmodium berghei ANKA in BALB/c mice. When given in a dose of 20 mg/kg.day for 4 days, most of the compounds produced significant chemosuppression of parasitaemia. The most active compound was 1,3,6,8-tetrahydroxyxanthone, which reduced the percentage of erythrocytes infected by 70.5%, followed by norlichexanthone (44.3%) and its isomer, 1,3,8-trihydroxy-6-methylxanthone (37.0%). Whereas di-C-allyl-dihydroxyxanthone showed lower but still notable activity (33.4%), 1,3-dihydroxyxanthone was much less active (15.1%). This appears to be the first demonstration of the antimalarial activity of some hydroxyxanthones in vivo.
A new xanthone C-glycoside, polygalaxanthone III (1), and a new acylated sugar, tenuifoliside E (2) were isolated from the roots of Polygala tenuifolia. Their structures were characterized as 4-C-[beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranosyl]-1, 3,6-trihydroxy-7-methoxyxanthone (1) and beta-D-(1-O-acetyl-3-O-feruloyl-6-O-sinapoyl)-fructofuranosy l-alpha-D-(2,4,6- O-triacetyl)glucopyranoside (2), respectively, on the basis of chemical and spectral evidence including two dimensional nuclear magnetic resonance (2D-NMR) studies.
Two new xanthones, garciniaxanthone D (1) containing a dihydrobenzofuran ring and 1,4,5-trihydroxyxanthone (2), have been isolated from Garcinia subelliptica as superoxide anion scavengers. Their structures have been determined mainly by spectroscopic methods and some chemical reactions.
Further study of the methanol extract of the stem bark of Allanblackia monticola STANER L.C. resulted in the isolation of a new prenylated xanthenedione, designated allanxanthone C, together with the five known xanthones, garciniafuran, tovophyllin A, rubraxanthone, norcowanin and mangostin and one saponin, stigmasterol-3-O-beta-D-glucopyranoside. The structure of the new compound was established by detailed spectroscopic analysis to be 1,2-dihydro-3,6,8-trihydroxy-1,1,7-tri(3-methylbut-2-enyl)xanthen-2,9-dione (3-hydroxyapetalinone C). The methanol extract and pure compounds were tested on two strains of Plasmodium falciparum, F32 (chloroquine sensitive) and FcM29 (chloroquine resistant). The IC50 values obtained ranged from 0.6 to 8.9 microg/ml. Their cytotoxicity was estimated on human melanoma cells (A375) and the cytotoxicity/antiplasmodial ratio was found to be between 15.45 and 30.46. The antimicrobial activities against a range of microorganisms of the crude extract and some of these compounds are also reported.
Condensation of 2-hydroxy-1-naphthalenecarboxylic acid with phloroglucinol afforded 9,11-dihydroxy-12H-benzo[a]xanthen-12-one (6). Construction of an additional dimethylpyran ring onto this skeleton, by alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement, gave access to 6-hydroxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (12) and 5-hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (13), which were methylated into 6-methoxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (14) and 5-methoxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (15), respectively. Osmium tetroxide oxidation of 14 and 15 gave the corresponding (+/-)-cis-diols 16 and 17, which afforded the corresponding esters 18-21 upon acylation. Similarly, condensation of 2-hydroxy-1-naphthalenecarboxylic acid with 3,5-dimethoxyaniline gave 11-amino-9-methoxy-12H-benzo[a]xanthen-12-one (23) which was converted into 11-amino-9-hydroxy-12H-benzo[a]xanthen-12-one (24) upon treatment with hydrogen bromide in acetic acid. Alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement afforded 6-amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (25) and 5-amino-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (26). The new benzopyranoxanthone derivatives only displayed marginal antiproliferative activity when tested against L1210 and KB-3-1 cell lines. The only compounds found significantly active against L1210 cell line, 16 and 20, belong to the benzo[a]pyrano[3,2-h]xanthen-7-one series, which possess a pyran ring fused angularly onto the xanthone basic core.
Five metabolites tentatively called GS-1 (1)-5 (5) from Gelasinospora santi-florii, and four tentatively called EQ-4 (6), EQ-6 (7)-8 (9) together with 1-4 from Emericella quadrilineata have been isolated in a screening study on immunomodulatory fungal constituents. Among these nine metabolites, EQ-7 and 8 have been unknown. This time, the structures of GS-4 which has previously been isolated, EQ-7, and -8 have been determined to be (4R,4aS,9aR)-1,9a-dihydronidulalin A (4), (4S,4aR,9aR)-4a-carbomethoxy-1,4,4a,9a-tetrahydro-4,8-dihydroxy-6-methylxanthone (8), and 9-hydroxymicroperfuranone (9), respectively, and the six other metabolites have been identified. On bioassay, a dihydroxanthone, nidulalin A (1), a hexaketide, sordarial (5), and a xanthone, pinselin (7) have displayed significant immunosuppressive activities. The structure-activity relationships of these constituents have also been discussed.
Bioactivity-guided fractionation of the methanol extract from the leaves of Santolina insularis led to the isolation of one new xanthone, (E)-3-(6-[(E)-3-hydroxy-3-oxo-1-propenyl]-9-oxo-9H-xanthen-2-yl)-2-propenoic acid, together with six known flavonoids: hispidulin, nepetin, cirsimaritin, rhamnocitrin, luteolin and luteolin 7-O-beta-D-glucopyranoside. The structures were elucidated by means of 1D-, 2D-NMR spectroscopy and mass spectrometry. The topical anti-inflammatory activity of all isolated compounds and extracts was investigated employing the croton oil-induced dermatitis in mouse ear. The most active compound, luteolin, showed an ID50 of 0.3 micromol/cm(2) and prevented ear oedema more effectively than an equimolar dose of indomethacin within 24 h.