川西獐牙菜甙类成分

对川西獐牙菜(Swertia mussotii Franch.)的水溶性成分进行了研究。应用层析方法,分离得到裂环烯醚萜甙,黄酮甙,(口山)酮甙,3类8种单体成分(Ⅰ—Ⅷ)。除先前报道过的芒果甙外(Ⅱ),又分离和鉴定了苦龙甙(Ⅲ),当药黄素(Ⅷ),8-O-β-D-吡喃葡萄糖-1,3,5-三羟基(口山)酮(Ⅶ),8-O-[β-D-吡喃木糖-(1→σ)-β-D-吡喃葡萄糖]-1,7-二羟基-3-甲氧基(口山)酮(Ⅵ)4种已知天然化合物。应用化学和光谱分析方法,测定另外3种新(口山)酮甙的结构为:7-O-[α-L-吡喃鼠李糖-(1→2)-β-D-吡喃木糖]-1,8-二羟基-3-甲氧基咄酮(Ⅰ),7-O-β-D-吡喃木糖-1,8-二羟基-3-甲氧基(口山)酮(Ⅳ),3-O-β-D-吡喃葡萄糖-1,8-二羟基-5-甲氧基(口山)酮(Ⅴ)。芒果甙,苦龙甙和7-O-[α-L-吡喃鼠李糖-(1→2)-β-D-吡喃木糖]-1,8-二羟基-3-甲氧基(口山)酮为川西獐牙菜主要甙类成分。有兴趣的是在已发现的龙胆科植物(口山)酮糖甙中,未见(口山)酮木糖甙,(口山)酮鼠李糖-木糖甙的报道。     

滇黄芩中的两个酮甙

从龙胆科滇黄芩属植物滇黄芩(Veratrilla baillonii Franch.)中分离得到两个新的(口山)酮甙,分别命名为:滇黄芩甙C(I)和滇黄芩甙D(Ⅱ).经各种光谱解析及化学反应证明,其结构推定为:2,3,4,5-四甲氧(口山)酮-1-O-β-D-吡喃葡萄糖基(6←l)-β-D-吡喃木糖甙(I)和3,4,5-三甲氧基(口山)酮-1-O-β-D-吡喃葡萄糖基(6←1)-β-D-吡喃本糖甙(Ⅱ).     

细萼扁蕾的化学成分研究

从细萼扁蕾(Gentianopsis barbata var.stennocaryx H.W.Li ex T.N.Ho)全草中分离得到9种化合物,6种(口山)酮成分,1种黄酮甙,2种三萜酸。经化学和光谱方法,分别鉴定为1-羟基-3,7,8-三甲氧基(口山)酮(Ⅰ),1,7-二羟基-3,8-二甲氧基(口山)酮(Ⅱ),1,7,8-三羟基-3-甲氧基(口山)酮(Ⅲ),1-O-[β-D-吡喃木糖-(1→)-β-D-吡喃葡萄糖]-3,7,8-三甲氧基(口山)酮(Ⅳ),1-O-[β-D-吡喃木糖-(1→6)-β-D-吡喃葡萄糖]-7-羟基-3,8-二甲氧基(口山)酮(Ⅴ),1-O-[β-D-吡喃木塘-(1→6)-β-D-吡喃葡萄糖]-7,8-二羟基-3-甲氧基(口山)酮(Ⅵ),木樨草素-7-O-β-D-葡萄糖甙(Ⅶ),齐墩果酸(Ⅷ)和熊果酸(Ⅸ)。     

花锚的三种新(口山)酮甙

从抗肝炎植物药花锚中分得了三种新天然产(口山)酮双糖甙。经化学反应和光谱分析,化合物Ⅰ和Ⅱ分别被鉴定为1-O-[β-D-木吡喃糖-(1-6)-β-D-葡萄吡喃糖]-2,3,5,7-四甲氧基(口山)酮和1-O-[β-D-木吡喃糖-(1-6)-β-D-葡萄吡喃糖]-2,3,5-三甲氧基(口山)酮。经药理实验证明,该两成分为该植物抗肝炎的主要水溶性活性成分。化合物Ⅲ的结构初步被鉴定为1-0-[β-D-木吡喃糖-(1-6)-β-D-葡萄吡喃糖]-2,3,4,5-四甲氧基(口山)酮。     

抱茎獐牙菜的(口山)酮甙和黄酮甙

从龙胆科植物抱茎獐牙菜(Swertia franchtiana H.smith)中分得3种(口山)酮甙,1种黄酮甙和1种三萜酸,通过光谱和化学等方法,分别鉴定为当药醇甙,当药黄素,芒果甙,1-O-[β-D-吡喃木糖-(1-6)-β-D-吡喃葡萄糖]-3,5-二甲氧基咄酮(XI)和齐墩果酸,其中晶 XI 为一新化合物。     

川西獐牙菜(Swertia mussotii Franch)中(口山)酮成分的分离与鉴定

从川西獐牙菜(Swcrtia mussotii Franch)中分离和鉴定了八种咄酮成分,即1,8-二羟基-3,5-二甲氧基(口山)酮Ⅰ,1-羟基-3,5-二甲氧基(口山)酮Ⅱ,1-羟基-3,7,8-三甲氧基咄酮Ⅲ,8-羟基-1,3,5-二甲氧基(口山)酮Ⅳ,1,8-二羟基-3,7-二甲氧基(口山)酮Ⅴ,1,7,8-三羟基-3-甲氧基咄酮Ⅵ,1,7-二羟基-3,4,8-三甲氧基(口山)酮Ⅶ和1,3,8-三羟基-5-甲氧基(口山)酮Ⅷ。其中,1,7-二羟基-3,4,8-三甲氧基(口山)酮为新的天然化合物,命名为藏茵陈(口山)酮(zangyinchenin)。     

斜茎獐牙菜酮成分的分离和鉴定

斜茎獐牙菜(Swertia patens Burk)系龙胆科植物。又名:金沙青叶胆,别名小儿寒,小儿腹痛草,落孺疴(彝族语)。它是云南彝族具有悠久历史的常用草药。最近有人从中分离了獐牙菜苦甙(swertiamarin),但其(口山)酮成分尚未见文献记载。我们从中分离了四个(口山)酮,经UV,IR,~1HNMR,MS证明为:1,8-二羟基-3,5-二甲氧     

花锚的三个新(口山)酮

从花锚(Halenia elliptica D.Don)中又得到三种新的(Ⅵ、Ⅶ、Ⅹ)和两种已知的(Ⅷ、Ⅸ)(口山)酮成分。根据化学反应、光谱数据及其相应衍生物与已知化合物比较,三种新(口山)酮的结构分别确定为1,7-二羟基-2,3,4,5-四甲氧基(口山)酮(Ⅵ),1,5-二羟基-2,3,7-三甲氧基(口山)酮(Ⅶ)及1,2-二羟基-3,4,5-三甲氧基(口山)酮(X)。两种已知(口山)酮分別为1,5-二羟基-2,3-二甲氧基(口山)酮(Ⅷ)和1,7-二羟基-2,3-二甲氧基(口山)酮(Ⅸ)。     

二叶獐牙菜化学成分研究

从二叶獐牙菜(Swertia bifolia Batal.)的全草中分离得到了7个化合物,5种口山酮和2种甾醇类化合物。它们的结构经光谱方法分别鉴定为1-羟基-3,5-二甲氧基口山酮(Ⅰ)、1羟基-3,7,8-三甲氧基口山酮(Ⅱ)、1,8二羟基-3,5二甲氧基口山酮(Ⅲ)、1,8二羟基-3,7-二甲氧基口山酮(Ⅳ)、1,7二羟基-3,8-二甲氧基口山酮(Ⅴ)、β-谷甾醇(Ⅵ)、胡萝卜苷(Ⅶ)。     

紫红獐牙菜中的酮类成分及其细胞毒活性

采用色谱分离手段对紫红獐牙菜Swertia punicea的乙醇提取物中乙酸乙酯和石油醚萃取部分进行分离纯化,运用1H NMR、13C NMR、HSQC、HMBC和ESI-MS等波谱方法和文献数据对比鉴定化合物结构,从紫红獐牙菜全草中得到8个口山酮类化合物,分别鉴定为1-羟基-2,3,5,7-四甲氧基口山酮(1)、1,2,3,4,5-五甲氧基口山酮(2)、1-羟基-2,3,4,7-四甲氧基口山酮(3)、1-羟基-2,3,5-三甲氧基口山酮(4)、dulcisxanthone C(5)、1-羟基-2,3,7-三甲氧基口山酮(6)、1,5-二羟基-2,3-二甲氧基口山酮(7)、1-羟基-3,4,5-三甲氧基口山酮(8),所有化合物均为首次从该植物中分离得到,化合物1、4、5、7对Hep G-2显现了很好的细胞毒活性。     

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.     

A prenylated xanthone from Allanblackia floribunda

A new prenylated xanthone, named allanxanthone A, was isolated from the stem bark of Allanblackia floribunda in addition to known compounds, 1,5-dihydoxyxanthone, 1,5,6-trihydroxy-3,7-dimethoxyxanthone, stigmasterol and stigmasteryl-3-O-beta-D-glucopyranoside. The structure of the new compound was assigned as 1,3,5-trihydroxy-2-(3-methylbut-2-enyl)-4-(1,1-dimethylprop-2-enyl) xanthone, by means of spectroscopic analysis. The 13C NMR spectral data of 1,5-dihydroxyxanthone is reported here for the first time as well as the in vitro cytotoxic activity of xanthone metabolites against the KB cell line.     

木棉素的分离与晶体结构

从木棉科植物木棉(Gossmpinus malabarica(DC.)Mer)的叶中首次分离纯化得到木棉素(Gossampinusxanthone)。经元素分析、波谱数据和X-射线单晶衍射分析,确认该化合物为1,3,6,7-四羟基-2-β-D-吡喃葡萄糖基口山酮(1,3,6,7-terahydroxy-2-β-D-glucopyanosyl-xanthone)。C19H18O11,M=422.34。晶体属斜方晶系,空间群P21212。晶胞参数a=7.265(5),b=30.086(4),c=8.342(2),V=1822(2)3,Z=4,Dc=1.54g/cm3,F(000)=880。木棉素分子由平面口山酮基和椅式葡萄糖基通过C(2)-C(1′)键连接而成。两基团的两个最小二乘平面间的夹角约为76.5°。存在分子内氢键O┄H…O的同时,也有分子间O┄H…O氢键。     

Xanthone biosynthesis in Hypericum perforatum cells provides antioxidant and antimicrobial protection upon biotic stress

Xanthone production in Hypericum perforatum (HP) suspension cultures in response to elicitation by Agrobacterium tumefaciens co-cultivation has been studied. RNA blot analyses of HP cells co-cultivated with A. tumefaciens have shown a rapid up-regulation of genes encoding important enzymes of the general phenylpropanoid pathway (PAL, phenylalanine ammonia lyase and 4CL, 4-coumarate:CoA ligase) and xanthone biosynthesis (BPS, benzophenone synthase). Analyses of HPLC chromatograms of methanolic extracts of control and elicited cells (HP cells that were co-cultivated for 24 h with A. tumefaciens) have revealed a 12-fold increase in total xanthone concentration and also the emergence of many xanthones after elicitation. Methanolic extract of elicited cells exhibited significantly higher antioxidant and antimicrobial competence than the equivalent extract of control HP cells indicating that these properties have been significantly increased in HP cells after elicitation. Four major de novo synthesized xanthones have been identified as 1,3,6,7-tetrahydroxy-8-prenyl xanthone, 1,3,6,7-tetrahydroxy-2-prenyl xanthone, 1,3,7-trihydroxy-6-methoxy-8-prenyl xanthone and paxanthone. Antioxidant and antimicrobial characterization of these de novo xanthones have revealed that xanthones play dual function in plant cells during biotic stress: (1) as antioxidants to protect the cells from oxidative damage and (2) as phytoalexins to impair the pathogen growth.     

Initial reactions of xanthone biodegradation by an Arthrobacter sp.

This study examined the catabolism of xanthone by an Arthrobacter sp. (strain GFB100) capable of growth on xanthone as its main source of carbon and energy. An early catabolic intermediate was 3,4-dihydroxyxanthone. This compound was isolated from the growth medium of a mutant strain of the Arthrobacter sp. which lacked the xanthone-inducible dihydroxyxanthone ring-fission dioxygenase of the wild-type strain. Cell extracts from wild-type xanthone-grown cells oxidized 3,4-dihydroxyxanthone to a yellow ring-fission metabolite. The same yellow compound accumulated in xanthone-grown cultures of a spontaneous mutant which lacked an active, xanthone-inducible, NADPH-linked ring-fission metabolite reductase. The yellow ring-fission metabolite appears to be 4-hydroxy-3-(2'-oxo-3-trans-butenoate)-coumarin, based on its nuclear magnetic resonance spectrum and mass spectral fragmentation pattern, indicating that ring cleavage of 3,4-dihydroxyxanthone was by an extra-diol (meta-fission) mechanism. Enzymatic analyses indicated that growth on xanthone induced a complete gentisate pathway: dioxygenase-catalyzed cleavage of gentisate to maleylpyruvate, isomerization of maleylpyruvate to fumarylpyruvate, and hydrolysis of fumarylpyruvate to fumarate and pyruvate. 4-Hydroxycoumarin was thought to be a likely pathway intermediate linking the early xanthone catabolic steps to the gentisate pathway, since 2-hydroxyacetophenone, a byproduct of 4-hydroxycoumarin hydrolysis, was formed when wild-type cells were cultured with xanthone. Chlorinated 2-hydroxyacetophenones were also obtained from specific chloro-substituted xanthones.     

Two new 1,3,5,6,7-pentaoxygenated xanthones from Canscora decussata

One new pentaoxygenated free xanthone and a new pentaoxygenated xanthone-O-glucoside have been isolated and characterized from the flowering top of a fresh batch of Canscora decussata. The structure previously assigned to ‘xanthone 9’ has now been confirmed by application of NOE. The biochemical significance of xanthone formation and glucosidation in plants is appraised.     

On the Xanthone Glycosides and Flavonoid Glucoside from Swertia franchetiana H. Smith

Three xanthone glycosides, a flavonoid glucoside and a triterpen acid have been isolated from Swertia franchetiana H. Smith (Gentianaceae). One of them is a new xanthone glyco- side and its stucture is established as 1-O-[β-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl] 3, 5-dimethoxyxanthone (Ⅺ), Others are identified as swertianolin, swertisin, mangiferin and oleanolic acid by chemical and spectral means, respectively.     

Major xanthones from Garcinia quadrifaria and Garcinia staudtii stem barks

The stem bark of Garcinia quadrifaria has yielded the novel xanthone 1, 3, 5-trihydroxy-4, 8-di(3,3-dimethylallyl)xanthone and the biflavonoids O-methylfukugetin and morelloflavone. The seeds contained the biflavonoids but not the xanthone. G. staudtii stem bark gave rheediaxanthone-A and the polyisoprenylated benzophenone xanthochymol. .     

Novel xanthone-polyamine conjugates as catalytic inhibitors of human topoisomerase IIα

It has been proposed that xanthone derivatives with anticancer potential act as topoisomerase II inhibitors because they interfere with the ability of the enzyme to bind its ATP cofactor. In order to further characterize xanthone mechanism and generate compounds with potential as anticancer drugs, we synthesized a series of derivatives in which position 3 was substituted with different polyamine chains. As determined by DNA relaxation and decatenation assays, the resulting compounds are potent topoisomerase IIα inhibitors. Although xanthone derivatives inhibit topoisomerase IIα-catalyzed ATP hydrolysis, mechanistic studies indicate that they do not act at the ATPase site. Rather, they appear to function by blocking the ability of DNA to stimulate ATP hydrolysis. On the basis of activity, competition, and modeling studies, we propose that xanthones interact with the DNA cleavage/ligation active site of topoisomerase IIα and inhibit the catalytic activity of the enzyme by interfering with the DNA strand passage step.     

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