Triterpene methyl ethers of Chionochloa (Gramineae)

The leaf wax of twenty species of Chionochloa was examined for triterpene methyl ethers; twelve species gave positive yields. The known pentacyclic methyl ethers arundoin, miliacin, lupeol methyl ether and β-amyrin methyl ether were identified and the methyl ethers of the tetracyclic alcohols, cycloartenol and parkeol are reported as new natural products. Arundoin and miliacin occur in many species while the remaining compounds may be suitable chemotaxonomic markers.     

水青树茎皮的化学成分研究

水青树(TetracentronsinenseOliv.)系水青树科水青树属植物,是我国特有的单种属珍稀濒危古老孑遗植物,主要分布于陕西南部、云南、四川、湖北、湖南等省〔1〕。在漫长的地质年代变迁过程中,为适应生存,其自身体内生理、生化过程也发生多次调整,结果必然伴随多种类型的次生代谢产物的形成,而有关其化学成分的研究迄今为止国内外未见报道,为此,我们对它进行了化学成分研究,这对人们充分认识并开发利用和更好地保存它将有着重要的意义。笔者从鄂西产水青树茎皮中初步分离得到7个化合物,经鉴定,化合物1为β-谷甾醇、6为β-胡萝卜甙、7为长链脂…     

Molecular cloning and expression in yeast of 2,3–oxidosqualene– triterpenoid cyclases from Arabidopsis thaliana

A vast array of triterpenes are found in living organisms in addition to lanosterol and cycloartenol, which are involved in sterol biosynthesis in non–photosynthetic and photosynthetic eukaryotes respectively. The chemical structure of these triterpenes is determined by a single step catalysed by 2,3–oxidosqualene–triterpene cyclases. The present study describes cloning and functional expression in yeast of several OS–triterpene cyclases. Three Arabidopsis thaliana cDNAs encoding proteins (ATLUP1, ATLUP2, ATPEN1) 57%, 58% and 49% identical to cycloartenol synthase from the same plant were isolated. Expression of these cDNAs in yeast showed that the recombinant proteins catalyse the synthesis of various pentacyclic triterpenes. Whereas ATLUP1 is essentially involved in the synthesis of lupeol, ATLUP2 catalyses the production of lupeol, – and –amyrin (in a 15:55:30 ratio). ATLUP2 is therefore a typical multifunctional enzyme. Under the same conditions, ATPEN1 did not lead to any product. Systematic sequencing of the Arabidopsis genome has led to genomic sequences encoding proteins identical to the above triterpene synthases. ATLUP1 and ATLUP2 are representative of a small subfamily (A) of at least five genes, whereas ATPEN1 is representative of a subfamily (B) of at least seven genes. The number of introns is characteristic of each subfamily. Whereas genes of family A possess 17 exons and 16 introns, genes of the subfamily B contain 14 exons and 13 introns. The size of each exon is remarkably conserved within each subfamily whereas that of each intron appears to be highly variable. Organization of the genes, sequences and functions of the deduced proteins are discussed in evolutionary terms.     

Chemical Constituents of Lac Host,Acacia suma

Six crystallin compounds were isolated from the stem bark of Acacia surna BuchHam. ex. Wall. Based on spectral and chemical evidences, four of them were demonstrated as triacontanol, β-sitosterol, daucosterin and lupeol heptylate. All were firstly reported from the plant. Among them lupeol heptylate was a new compound.