Triterpenoids of Cnidosculus urens

The ethanol extract of Cnidosculus urens yielded β-amyrin cinnamate and germanicol acetate. Also, using ¹³C NMR spectroscopy, mixtures of β-amyrin, germanicol and lupeol as well as their acetates were identified.     

The biosynthesis,metabolism and translocation of β-amyrin in Sorghum bicolor

The biosynthesis of [¹⁴C] β-amyrin and three other labelled 3β-hydroxypentacyclic triterpenes from [2-^14C] acetate in leaves of Sorghum bicolor was demonstrated. Evidence for the metabolism of [¹⁴C] β-amyrin to the corresponding C-3 ketone (β-amyrone) and for the transport of [¹⁴C] β-amyrin in leaves was also obtained.     

Triterpenoids in epicuticular waxes of Dudleya species

The pentacyclic triterpenoids, β-amyrin acetate and taraxerone, are major components in the epicuticular wax of the genus Dudleya.     

Lanostane triterpenes of Canscora decussata

From the aerial parts of Canscora decussata Schult (Gentianaceae), five triterpenes, viz. gluanone, canscoradione, friedelin, fridelan-3-β-ol, and β-amyrin, three sterols, viz. sitosterol, stigmasterol, and campesterol, besides liberal amount of a mixtures of n-alkanes (C₂₇-C₃₁) and n-alkanols (C₂₆-C₃₂) have been isolated. The identity of the compounds has been established by chemical transformations, spectral evidence, and by direct comparison, where possible, with authentic reference materials. Gluanone and canscoradione have not been encountered before in nature.     

Inheritance of triterpene methyl ethers in Cortaderia (Gramineae)

The distribution of triterpene methyl ethers in several generations of interspecific hybrids of Cortaderia indicates dominant gene control of their synthesis. The hybrid C. richardii × C. toetoe is an exception because synthesis of α- and β-amyrin methyl ethers is suppressed in F₁ and F₂, but is restored in the backcross F₁ × C. toetoe; this backcross generation was heterozygous for genes for the amyrin methyl ethers, and on selfing segregated in a simple Mendelian ratio.     

Varietal similarities and differences in the polycyclic isopentenoid composition of sorghum

The intraspecific similarities and differences among the various polycyclic isopentenoids (sterols and pentacyclic triterpenes) which occur in leaf tissue and surface wax from three varieties of flowering Sorghum bicolor; G499 GBR, BOK 8 and IS 809, have been determined. The three varieties exhibited differences in phenotypic characters (e.g. shoot height) and pest resistance. While sterol and pentacyclic amyroid compositions were similar in the three varieties, significant differences were evident in the qualitative distribution of the migrated hopanoids. One variety, IS 809, which is phenotypically short and resistant, contained a single migrated hopanoid, sorghumol Alternatively, the other two varieties, both phenotypically tall and one-G 499 GBR-resistant, the other-BOK 8-susceptible, contained a mixture of four Δ⁹⁽¹¹⁾-migrated hopanoids, i.e. sorghumol and three of its stereoisomers, and the Δ⁵⁽⁶⁾-migrated hopanoid simiarenol. While ketones corresponding to the Δ⁹⁽¹¹⁾-migrated hopanoids were detected in the three varieties, the ketone of the Δ⁵⁽⁶⁾-migrated hopanoid was apparently absent. In contrast to other graminaceous plants, the predominant C-3 derivatives did not include the C-3 methyl ethers, but did include esters and polar conjugates. Significant differences apparent in amounts of pentacyclic triterpenes were not apparent in the total amount of sterols extracted from the leaves (including surface wax) of the three varieties. Since S. bicolor varietal differences occurred only among the migrated hopanoids (found in mature leaves) it would appear that pentacyclic triterpenes, unlike sterols, have greater applicability as chemotaxonomic indices for intraspecific relationships in sorghum.     

Three new oxygenated triterpenoids of the lupane series from Gymnosporia wallichiana

Two new epimeric triterpenoid acids, gymnosporic acid, 3β-hydroxy-(20R)-lupan-29-oic acid, wallichianic acid, 3β-hydroxy-(20S)-lupan-29-oic acid and a new diol wallichianol, (20S)-lupane-3β,29-diol have been isolated from Gymnosporia wallichiana, in addition to β-amyrin, friedelin, 3β-hydroxy-29-norlupan-20-one and dulcitol.     

Biosynthesis of triterpenoids from amino acids in Pisum sativum. The distribution of the radioactivity in squalene biosynthesized from radioisotopically labelled l-leucine and l-valine

Radioisotopically labelled l-leucine and l-valine were fed to Pisum sativum and incorporated into squalene and β-amyrin. Chemical degradation of the radioactive squalene revealed an equal distribution of the radioactivity in the isopentenyl pyrophosphate(IPP)-derived and the 3,3-dimethylallyl pyrophosphate(DMAPP)-derived moieties of the squalene molecule, unlike the unbalanced distribution in favour of the DMAPP-derived moiety of a monoterpenoid molecule biosynthesized from these amino acids by higher plants.     

Aplotaxene epoxide from Cirsium hypoleucum

Aplotaxene epoxide (11,12-epoxyheptadeca-1,8,14-triene) was isolated from the roots of Cirsium hypoleucum. The pentacyclic tritepenes lupeol, taraxasterol and β-amyrin, and other acetates, were identified in C. hypoleucum, C. canum and C. carolinianum.     

Interspecific variation in leaf wax of Dudleya

The distribution of the pentacylic triterpenoids, β-amyrin acetate and taraxerone, in the glaucous epicuticular wax of Dudleya subgenus Dudleya is correlated with both the geographic distribution and corolla tube length of a particular species. This is significant in a genus with many systematic problems.     

A hydroxygermacrene and other constituents from Pseudobrickellia brasiliensis

Pseudobrickellia brasiliensis afforded, in addition to known compounds, a new germacradiene derivative and a hydroxy-α-amyrin.     

The stereospecificity of biosynthesis of squalene and β-amyrin in Pisum sativum

The distribution of deuterium in squalene and β-amyrin, biosynthesized from mevalonic acid-6,6,6-d₃ in Pisum sativum, has been examined b     

Aided-efflux and high production of β-amyrin realized by β-cyclodextrin in situ synthesized on surface of Saccharomyces cerevisiae

As a plant-derived pentacyclic triterpenoid, β-amyrin has been heterogeneously synthesized in Saccharomyces cerevisiae. However, β-amyrin is intracellularly produced in a lower gram scale using recombinant S. cerevisiae, which limits the industrial applications. Although many strategies have been proven to be effective to improve the production of β-amyrin, the intracellularly accumulation is still a challenge in reaching higher titer and simplifying the extraction process. To solve this problem, the amphiphilic β-cyclodextrin (β-CD) has been previously employed to aid the efflux of β-amyrin out of the cells. Nevertheless, the supplemented β-CD in the medium is not consistent with β-amyrin synthesis and has the disadvantage of rather high cost. Therefore, an aided-efflux system based on in situ synthesis of β-CD was developed in this study to enhance the biosynthesis of β-amyrin and its efflux. The in situ synthesis of β-CD was started from starch by the surface displayed cyclodextrin glycosyltransferase (CGTase) on yeast cells. As a result, the synthesized β-CD could capture 16% of the intracellular β-amyrin and improve the total production by 77%. Furthermore, more strategies including inducing system remodeling, precursor supply enhancement, two-phase fermentation and lipid synthesis regulation were employed. Finally, the production of β-amyrin was increased to 73 mg/L in shake flask, 31 folds higher than the original strain, containing 31 mg/L of extracellular β-amyrin. Overall, this work provides novel strategies for the aided-efflux of natural products with high hydrophobicity in engineered S. cerevisiae.     

朱砂藤根化学成分的研究

首次从朱砂藤根中人离并鉴定了β－香树脂醇乙本能酯,蒲公英醇,β－谷甾醇,另有两个结晶尚在鉴定中,将另文报道。     

Iguesterin,a new quinonoid triterpene from Catha cassinoides

β-Amyrin, sitosterol, celastrol, pristimerin, tingenone and a new hydroxymethylene quinonoid dinor-triterpene iguesterine were isolated from the root bark of Catha cassinoides. The structure of iguesterine was determined spectroscopically and by synthesis from tingenone. Tentative assignments are given for the chemical shifts of the methyl groups of iguesterin, tingenone and some of their derivatives.     

Molecular Cloning and Functional Characterization of Oxidosqualene Cyclases from Panax vietnamensis

Panax vietnamensis is a valuable medicinal resource with promising preclinical applications. Ginsenosides, which are triterpenoids, are the primary active components in P. vietnamensis. Oxidosqualene cyclases (OSCs) catalyze the formation of the basic skeleton of triterpenes from 2,3-oxidosqualene, which is a crucial step in the biosynthesis of triterpenoids. The OSCs involved in triterpenoid biosynthesis in P. vietnamensis have not yet been characterized. Four OSC genes (PvOSC1–4) were cloned from P. vietnamensis and functionally characterized via heterologous expression in yeast. Transgenic yeast expressing PvOSC1, PvOSC3, and PvOSC4 produced the corresponding products β-amyrin, cycloartenol, and dammarenediol-II, respectively. PvOSC1, PvOSC3, and PvOSC4 are monofunctional OSCs. In this study, we characterized three PvOSC genes, providing a better understanding of the biosynthesis of triterpenoids in P. vietnamensis and the multiple choices of plant OSCs for metabolic engineering in yeast and other hosts.     

Chemical Composition and Antimicrobial Effect of Western Ethiopian Propolis

Propolis or bee glue is commonly named as a natural resinous mixture produced by honeybees (Apis mellifera) from substances collected from parts of plants, buds, and exudate. The result of the ethyl acetate - methanol (3 : 2) volume by volume fraction yielded a total of two compounds namely betulinic acid and β-amyrin isolated from Bodji Dirmaji and Fincha'a district propolis, respectively. The crude ethanolic extract was portioned with the different solvent systems by increasing the polarities in the following order of hexane, ethyl acetate, and methanol. Column chromatographic method on normal silica gel was used to isolate the compounds. The structures of the compounds were characterized using 1D NMR techniques. The study revealed that western Ethiopian propolis was rich in saponins, tannins, flavonoids, steroids, triterpenes, and glycosides. The antibacterial activity for the isolated compound (betulinic acid) showed the highest inhibition for S. aureus (11.2±1.6), E. coli (17.7±1.1), and A. niger (12.6±1.2) mm.