Xanthones from three Garcinia species

From the stem bark of three previously uninvestigated Garcinia species a number of xanthones have been isolated including three that appear to be novel. The novel compounds are characterized as isocowanin (8-geranyl-4-(3,3-dimethylallyl)-7-methoxy-1,3,6-trihydroxyxanthone), isocowanol (8-geranyl-4-(3-hydroxymethyl-3-methylallyl)-7-methoxy-1,3,6-trihydroxyxanthone) and nervosaxanthone (4,8-di(3,3-dimethylallyl)-2-(1,1-dimethylallyl)-1,3,5,6-tetrahydroxyxanthone). The chemotaxonomic significance of oxygenation patterns in these xanthones is briefly discussed.     

Xanthone 6-hydroxylase from cell cultures of Centaurium erythraea RAFN and Hypericum androsaemium L

Xanthone 6-hydroxylase activity was detected in the microsomal fractions from two plant cell cultures. The enzyme from cultured cells of Centaurium erythraea (Gentianaceae) exhibited absolute specificity for 1,3,5-trihydroxyxanthone as substrate, whereas xanthone 6-hydroxylase from cell cultures of Hypericum androsaemum (Hypericacaea) preferred the isomeric 1,3,7-trihydroxyxanthone but used 1,3,5-trihydroxyxanthone also to a small extent. Both xanthones were regioselectively hydroxylated in position 6. The xanthone 6-hydoxylases are cytochrome P450 monooxygenases, as shown by their dependence on NADPH and molecular oxygen and their inhibition by carbon monoxide and typical P450 inhibitors. In both cell cultures, xanthone accumulation was preceded by an increase in xanthone 6-hydroxylase activity.     

田基黄(口山)酮成分的研究

采用萃取,硅胶及凝胶柱色谱等方法从田基黄全草中分离得到了7个San酮类化合物,利用UV、IR、^1H NMR、^13C NMR、MS等波谱技术将他们的结构分别鉴定为6-脱氧异巴西红厚壳素(1)、异巴西红厚壳素(2)、1,3,5,6-四羟基San酮(3)、1,3,6,7-四羟基San酮(4),1,3,5,6-四羟基-4-异戊烯San酮(5)、1,3,5-三羟基San酮(6)和bijaponicaxanthone(7),其中化合物3、4和6为首次从该植物中分得的San酮类化合物。     

Polyanxanthone A, B and C, three xanthones from the wood trunk of Garcinia polyantha Oliv

Three xanthones, polyanxanthone A (1), B (2) and C (3) have been isolated from the methanol extract of the wood trunk of Garcinia polyantha, along with five known xanthones: 1,3,5-trihydroxyxanthone (4); 1,5-dihydroxyxanthone (5); 1,3,6,7-tetrahydroxyxanthone (6); 1,6-dihydroxy-5-methoxyxanthone (7) and 1,3,5,6-tetrahydroxyxanthone (8). Their structures were determined by means of 1D- and 2D-NMR techniques. Some of the above compounds were screened for their anticholinesterase activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes.     

Benzophenones and xanthones from Garcinia cantleyana var. cantleyana and their inhibitory activities on human low-density lipoprotein oxidation and platelet aggregation

Three benzophenones, 2,6,3′,5′-tetrahydroxybenzophenone (1), 3,4,5,3′,5′-pentahydroxybenzophenone (3) and 3,5,3′,5′-tetrahydroxy-4-methoxybenzophenone (4), as well as a xanthone, 1,3,6-trihydroxy-5-methoxy-7-(3′-methyl-2′-oxo-but-3′-enyl)xanthone (9), were isolated from the twigs of Garcinia cantleyana var. cantleyana. Eight known compounds, 3,4,5,3′-tetrahydroxy benzophenone (2), 1,3,5-trihydroxyxanthone (5), 1,3,8-trihydroxyxanthone (6), 2,4,7-trihydroxyxanthone (7), 1,3,5,7-tetrahydroxyxanthone (8), quercetin, glutin-5-en-3β-ol and friedelin were also isolated. The structures of the compounds were elucidated by spectroscopic methods. The compounds were investigated for their ability to inhibit low-density lipoprotein (LDL) oxidation and platelet aggregation in human whole blood in vitro. Most of the compounds showed strong antioxidant activity with compound 8 showing the highest inhibition with an IC₅₀ value of 0.5 μM, comparable to that of probucol. Among the compounds tested, only compound 4 exhibited strong inhibitory activity against platelet aggregation induced by arachidonic acid (AA), adenosine diphosphate (ADP) and collagen. Compounds 3, 5 and 8 showed selective inhibitory activity on platelet aggregation induced by ADP.     

Regioselective oxidative phenol couplings of 2,3′,4,6-tetrahydroxybenzophenone in cell cultures of Centaurium erythraea RAFN and Hypericum androsaemum L.

A crucial step in plant xanthone biosynthesis is the cyclization of an intermediate benzophenone to a xanthone. In cultured cells of Centaurium erythraea RAFN, 2,3′,4,6-tetrahydroxybenzophenone (THBP) was shown to be intramolecularly coupled to 1,3,5-trihydroxyxanthone, whereas in cell cultures of Hypericum androsaemum L. it was coupled to form the isomeric 1,3,7-trihydroxyxanthone. These regioselective cyclizations that occur ortho and para, respectively, to the 3′-hydroxy group of the benzophenone depend on cytochrome P ₄₅₀, as shown by the effectiveness of established P ₄₅₀ inhibitors and blue-light-reversible carbon monoxide inhibition. Furthermore, the reactions absolutely require NADPH and O₂. The underlying reaction mechanism is probably an oxidative phenol coupling that is catalyzed regioselectively by xanthone synthases. These enzymes are proposed to be cytochrome P ₄₅₀ oxidases. The intramolecular cyclizations of THBP to 1,3,5- and 1,3,7-trihydroxyxanthones catalyzed by the two xanthone synthases represent an important branch point in the plant xanthone biosynthetic pathway. Received: 24 March 1997 / Accepted: 28 May 1997     

Two new xanthone glycosides from Tripterospermum lanceolatum

Oleanolic acid, mangiferin, and two new xanthone glucosides, named lanceoside (1,8-dihydroxy-3,7- dimethoxyxanthone- 4-O-β-d-glucoside) and lancerin (C-4-β-d-glucosyl-1,3,7-trihydroxyxanthone), respectively, were isolated from the aerial parts of Tripterospermum lanceolatum.     

Xanthones and 4-phenylcoumarins of Mesua thwaitesii

The constituents of the bark, timber and seeds of Mesua thwaitesii were examined by column chromatography and GC-MS. 1,5-Dihydroxyxanthone, 1,7-dihydroxyxanthone (euxanthone), 1,3-dimethoxy-5-hydroxyxanthone, 1,5,6-trihydroxyxanthone, mammeisin, (4-phenylcoumarin) and sitosterol have been characterized. Nine 4-phenylcoumarins including mammeigin, mesuagin, mammeisin, mesuol, or its isomers, have been identified in the seed extract. One coumarin has not been previously reported.     

The Chemical Constitution of Rubrofusarin,a Pigment from Fusarium graminearum

The zinc dust distillates of rubrofusarin, nor-rubrofusarin, and methylxanthones (1-, 2-, 3-, and 4-methylxanthones and l-methyl-3,6,8-trihydroxyxanthone) have been investigated.

On zinc dust distillation, rubrofusarin and nor-rubrofusarin afforded naphthalene and anthracene in low yield, but did not give methylxanthene expected from the formerly proposed structure of methylxanthone.

Methylxanthones are considered to give the corresponding methylxanthenes in the distillates; and it is true for 2-, 3-, and 4-methylxanthones. However, in the 1-methyl derivatives the main product was not 1-methylxanthene but anthracene. It has been found also that on that condition all methylxanthones examined did not give naphthalene that was a main zinc dust distillate in rubrofusarin.

Thus, we conclude that it is appropriate to assign the structure of naphthalene derivative for rubrofusarin instead of the so far proposed methylxanthone structure.     

红厚壳枝条的化学成分

从红厚壳(Calophyllum inophyllum Linn.)枝条乙醇提取物中分离得到11个化合物,通过光谱分析,鉴定其结构为:6-羟基-2,3-二甲氧基 酮 ( 1 ) ,1,3,7-三羟基 酮 ( 2 ) ,1,3,7-三羟基-8-甲氧基 酮( 3 ) ,7-羟基-1,3-二甲氧基 酮( 4 ) ,伪蒲公英甾醇( 5 ) ,1,3,6-三羟基-5,7-二甲氧基 酮( 6 ) ,2-羟基-1-甲氧基 酮 ( 7 ) ,2-羟基-1,8-二甲氧基 酮 ( 8 ) ,1,3,5-三羟基-2-甲氧基 酮 ( 9 ) ,4-羟基 酮 ( 10 ) ,1,3,5-三羟基 酮 ( 11 ) 。化合物 2 ~ 5 为首次从红厚壳属植物中得到,化合物 6 ~ 8 为首次从该植物中得到,化合物 1 为一新的天然产物。细胞毒活性测试结果表明,化合物 9 对人胃癌细胞(SGC-7901)的增殖显示出生长抑制活性, 其IC₅₀值为1.8×10^-5 mol/L。     

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.     

Hydroxyxanthone as an inhibitor of cAMP-activated apical chloride channel in human intestinal epithelial cell

AimsPrevious investigation showed that polyphenols abundantly found in many plants could inhibit Cl^? secretion. The present study was aimed to investigate the effect of phenol containing xanthone derivatives on cAMP-activated intestinal Cl^? secretion and evaluate potential benefits of these compounds in the treatment of cholera.Main methodsFour hydroxy xanthones were synthesized via oxidative coupling reaction of the corresponding ortho-hydroxybenzoic acids and hydroxyphenols. Short-circuit current and apical Cl^? current measurements across monolayers of human intestinal epithelial (T84) cell and Fisher rat thyroid cells transfected with human CFTR (FRT-hCFTR cell) were performed to determine the effect of hydroxyxanthones on cAMP-activated Cl^? secretion. Intracellular cAMP was measured by immunoassay methods. Anti-diarrheal efficacy was evaluated using closed loop model of cholera.Key findingsAmong the tested xanthones, 1,3,6-trihydroxyxanthone (THX-001) was found to be the most potent derivative in the inhibition of cAMP-activated Cl^? secretion across T84 cell monolayers (IC₅₀ ~ 100 μM). Electrophysiological analysis of T84 cells and FRT-hCFTR cells revealed that THX-001 targeted two distinct cAMP-activated Cl^? channels in the apical membrane of T84 cells, namely, CFTR and inward rectifying Cl^? channel (IRC). In contrast, THX-001 had no effect on intracellular cAMP levels in these cells. Importantly, THX-001 completely abolished cholera toxin-induced Cl^? secretion across T84 cell monolayers and significantly inhibited cholera toxin-induced intestinal fluid secretion in mouse closed loop models.SignificanceThis study revealed that hydroxyxanthone represents another chemical class of polyphenolic compounds that may hold promise as anti-secretory therapy for cholera.     

铜、铅、镉、锌、汞和银离子复合污染对水螅的急性毒性效应

以水螅(Hydrasp)为例,通过单因子静态急性毒性试验方法和等毒性溶液法,分别研究Hg2 、Cu2 、Cd2 、Ag 、Zn2 和Pb2 对其单一和复合毒性效应。单一实验结果表明,它们对水螅毒性大小顺序为Hg2 >Cu2 >Cd2 >Ag >Zn2 >Pb2 。复合毒性实验表明,Zn2 与Cu2 、Hg2 、Pb2 、Ag ;Pb2 与Cu2 ;Hg2 与Ag ;Pb2 与Ag 这些组合对水螅联合急性毒性总体上表现出拮抗作用,Cd2 与Cu2 、Hg2 、Pb2 、Ag 组合总体上则是协同作用,Zn2 与Cd2 、Pb2与Hg2 、Cu2 与Hg2 ,Ag 在不同的浓度水平组合下明显表现出不同的毒性效应。     

Production and characterization of antibodies against HT-2 toxin and T-2 tetraol tetraacetate.

Three new immunogens which were prepared by conjugation of the carboxymethyl oxime (CMO) derivatives of HT-2 toxin, T-2 tetraol (T-2 4ol), and T-2 tetraol tetraacetate (T-2 4Ac) to bovine serum albumin (BSA) were tested for the production of antibodies against the major metabolites of T-2 toxin. Antibodies against HT-2 toxin and T-2 4Ac were obtained from rabbits 5 to 10 weeks after immunizing the animals with CMO-HT-2-BSA and CMO-T-2 4Ac-BSA conjugates. Immunization with CMO-T-2 4ol-BSA resulted in no antibody against T-2 4ol. The antibody produced against HT-2 toxin had great affinity for HT-2 toxin as well as good cross-reactivity with T-2 toxin. The relative cross-reactivities of anti-HT-2 toxin antibody with HT-2 toxin, T-2 toxin, iso-T-2 toxin, acetyl-T-2 toxin, 3'-OH HT-2, 3'-OH T-2, T-2 triol, and 3'-OH acetyl-T-2, were 100, 25, 10, 3.3, 0.25, 0.15, 0.12 and 0.08%, respectively. Antibody against CMO-T-2 4Ac was very specific for T-2 4Ac and had less than 0.1% cross-reactivity with T-2 toxin, HT-2 toxin, acetyl-T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and deoxynivalenol triacetate as compared with T-2 4Ac. The detection limits for HT-2 toxin and T-2 4ol by radioimmunoassay were approximately 0.1 and 0.5 ng per assay, respectively.     

重金属对油菜种子萌发和胚根生长的影响

分析了Hg2 、Cd2 、Ni2 、Co2 、Zn2 5种重金属离子对油菜种子萌发和胚根伸长的影响,以及金属离子K 、Mg2 和Ca2 与重金属的交互作用。结果表明:(1)重金属对油菜种子萌发的抑制作用依次为Hg2 >Cd2 和Co2 >Ni2 >Zn2 ,而对胚根生长的毒害作用依次为Hg2 >Cd2 >Co2 >Ni2 >Zn2 。(2)萌发率为40%以上时,K 和Ca2 可以提高Ni2 、Zn2 和Co2 胁迫下油菜种子的萌发率,却进一步降低了Hg2 、Cd2 胁迫下种子的萌发;Mg2 可以提高Ni2 、Zn2 、Cd2 和Co2 胁迫下种子的萌发率,但对Hg2 毒害却没有缓解。(3)胚根伸长率达到60%以上时,K 和Mg2 增强了Ni2 、Hg2 、Cd2 和Co2 对胚根生长的抑制,而Ca2 则缓解了Zn2 、Ni2 和Co2 对胚根生长的抑制作用。研究结果对于重金属复合污染土壤中植物种子的萌发和定植具有理论和实践意义。     

Transition metal complexes of diclofenac with potentially interesting anti-inflammatory activity

An overview is given of the results of metal ion-diclofenac interactions. Several complexes have been synthesized at the University of Ioannina. Binuclear complexes, [Cu(L)2(H2O)]2 x 2H2O and [CuL2(S)]2 where S is H2O, EtOH, DMSO, (CH3)2CO and DMF, and mononuclear complexes, [MnL2(H2O)], [FeL2(H2O)2], [CoL2(H2O)2] x 0.5H2O, [CoL2(H2O)], [NiL2(H2O)2] x 2H2O, [NiL2] and [PdL2] x 2H2O, have been characterized by spectroscopy, X-ray crystallography and electrochemical studies. The catalytic activity of these complexes was correlated to the reduction potential. Some of the complexes of diclofenac exhibit very promising anti-inflammatory activity and act as antioxidant compounds, a property that is absent from diclofenac.     

Influence of salicylic acid on H2O2 production, oxidative stress, and H2O2-metabolizing enzymes. Salicylic acid-mediated oxidative damage requires H2O2.

We investigated how salicylic acid (SA) enhances H2O2 and the relative significance of SA-enhanced H2O2 in Arabidopsis thaliana. SA treatments enhanced H2O2 production, lipid peroxidation, and oxidative damage to proteins, and resulted in the formation of chlorophyll and carotene isomers. SA-enhanced H2O2 levels were related to increased activities of Cu,Zn-superoxide dismutase and were independent of changes in catalase and ascorbate peroxidase activities. Prolonging SA treatments inactivated catalase and ascorbate peroxidase and resulted in phytotoxic symptoms, suggesting that inactivation of H2O2-degrading enzymes serves as an indicator of hypersensitive cell death. Treatment of leaves with H2O2 alone failed to invoke SA-mediated events. Although leaves treated with H2O2 accumulated in vivo H2O2 by 2-fold compared with leaves treated with SA, the damage to membranes and proteins was significantly less, indicating that SA can cause greater damage than H2O2. However, pretreatment of leaves with dimethylthiourea, a trap for H2O2, reduced SA-induced lipid peroxidation, indicating that SA requires H2O2 to initiate oxidative damage. The relative significance of the interaction among SA, H2O2, and H2O2-metabolizing enzymes with oxidative damage and cell death is discussed.     

Production and characterization of antibodies against HT-2 toxin and T-2 tetraol tetraacetate

Three new immunogens which were prepared by conjugation of the carboxymethyl oxime (CMO) derivatives of HT-2 toxin, T-2 tetraol (T-2 4ol), and T-2 tetraol tetraacetate (T-2 4Ac) to bovine serum albumin (BSA) were tested for the production of antibodies against the major metabolites of T-2 toxin. Antibodies against HT-2 toxin and T-2 4Ac were obtained from rabbits 5 to 10 weeks after immunizing the animals with CMO-HT-2-BSA and CMO-T-2 4Ac-BSA conjugates. Immunization with CMO-T-2 4ol-BSA resulted in no antibody against T-2 4ol. The antibody produced against HT-2 toxin had great affinity for HT-2 toxin as well as good cross-reactivity with T-2 toxin. The relative cross-reactivities of anti-HT-2 toxin antibody with HT-2 toxin, T-2 toxin, iso-T-2 toxin, acetyl-T-2 toxin, 3'-OH HT-2, 3'-OH T-2, T-2 triol, and 3'-OH acetyl-T-2, were 100, 25, 10, 3.3, 0.25, 0.15, 0.12 and 0.08%, respectively. Antibody against CMO-T-2 4Ac was very specific for T-2 4Ac and had less than 0.1% cross-reactivity with T-2 toxin, HT-2 toxin, acetyl-T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and deoxynivalenol triacetate as compared with T-2 4Ac. The detection limits for HT-2 toxin and T-2 4ol by radioimmunoassay were approximately 0.1 and 0.5 ng per assay, respectively.     

Measurement of gluconeogenesis by deuterated water: the effect of equilibration time and fasting period

Fasting gluconeogenesis (GNG) is often quantified using the 2H2O technique, which is based on plasma 2H2O enrichment and ensuing enrichment of plasma glucose at the C5 and C2 positions. Fractional (fr)GNG can be calculated using the ratio of C5 to C2 enrichment or the ratio of C5 to plasma 2H2O enrichment. For the latter, equilibration of 2H2O and C2 is required. The optimal equilibration period of 2H2O and C2 remains to be elucidated. In six healthy male subjects fasted for 18 h, we studied the effects of 3-, 5-, and 15-h 2H2O incubation periods on 1) the equilibration of plasma 2H2O and C2 glucose enrichment, 2) the measurement of frGNG, and 3) C5 labeling of hepatic glycogen after 1 mg of glucagon administration. After 3-h 2H2O incubation, plasma 2H2O and C2 were not equilibrated, frGNG C5/2H2O and C5/C2 were also different as was gluconeogenesis calculated with C5/2H2O and C5/C2. After 5- and 15-h 2H2O incubation, plasma 2H2O and C2 were equilibrated, and frGNG C5/2H2O and C5/C2 were similar, as was GNG calculated with C5/2H2O and C5/C2. After glucagon administration, no difference of C5 enrichment was found between 3, 5, and 15 h of 2H2O incubation. In conclusion, for reliable measurement of GNG in healthy subjects with C5/2H2O incubation periods longer than 3 h are required. After 5- and 15-h 2H2O incubation, GNG can be reliably measured with C5/2H2O. Gluconeogenetic labeling of glycogen did not affect the results after 3, 5, or 15 h of 2H2O incubation.