Triterpenoids and steroids of some Sapotaceae and their chemotaxonomic significance

Extraction of the bark and timber of four Madhuca and five Palaquium species has yielded β-amyrin, β-amyrin acetate, β-amyrin cinnamate,     

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.     

Distribution of some triterpenes and phenolic compounds in the extractives of endemic dipterocarpaceae species of Sri Lanka

Extractives of bark and/or timber of 11 species belonging to the genera Cotylelobium, Hopea, Shorea, Vateria and Vatica yielded a fatty-acid ester, a sitosteryl ester, β-amyrin acetate, β-amyrin, dipterocarpol, ursolic acetate, lupeol, sitosterol, ursolic acid, betulinic acid, hexamethyl-coruleoellagic acid, tetramethylellagic acid, chrysophanol and scopoletin. The distribution of these compounds in 18 other species was examined by TLC screening.     

杠柳枝皮的化学成分研究(英文)

将杠柳枝皮粉末的乙醇提取物悬浮于水后,依次用石油醚、乙酸乙酯和正丁醇萃取.对乙酸乙酯萃取物采用各种柱层析进行多次分离后得到4个化合物,经波谱分析,鉴定它们的结构分别为β-香树素乙酸酯(1)、β-香树素(2)、periplogenin(3)和perilocoside N(4),其中化合物1和2是首次从该植物中分离得到.     

A coumarin from Perezia coerulescens

The roots of Perezia coerulescens contain ψ-taraxasteryl acetate, β-amyrin acetate, 8-hydroxypereflorin, pereflorin B and a new compound identified as 3,4,8-trimethoxy-5-formyl coumarin.     

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.     

Sterols and triterpenols in latex and cultured tissues of Euphorbia pulcherrima

The sterol and triterpenol constituents of Euphorbia pulcherrima latex and cultured callus tissues were examined by GLC and mass spectrometry. Latex extracts from different varieties contained sitosterol, β-amyrin, germanicol, cycloartenol, β-amyrin acetate, and germanicol acetate. Capillary GC profiles of these varieties indicated that the triterpene content was essentially identical for examined latices. Cultured tissues derived from petioles and stem internodes synthesized only sitosterol in significant quantities, although trace amounts of several sterols that occur in latex were also detected in cultured tissues. This study supports the interpretation that the pattern of triterpene synthesis in the laticifer of the normal plant is a highly controlled and stable phenomenon among varieties of this species.     

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.     

构树皮中三萜类化学成分

对构树皮的化学成分进行进一步研究,通过反复硅胶柱层析从构树皮乙醇提取物的石油醚萃取部位中分离得到六个三萜成分,利用波谱技术及理化性质鉴定其化学结构分别为3β-乙酰氧基-甘遂-7-烯-24S,25二醇(1),3β-乙酰氧基-7,23-甘遂二烯-25-醇(2),羽扇豆醇(3),α-香树脂醇乙酸酯(4),3β,25-二羟基-7,23-甘遂二烯(5)和β-香树脂醇(6)。其中化合物1为新的甘遂烷型三萜,化合物2～5为首次从该植物中分离得到。     

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.     

New alkaloids from Tabernaemontana divaricata

A re-investigation of the root bark of Tabernaemontana divaricata resulted in the isolation of 18 compounds, viz. α-amyrin acetate, lupeol acetate, α-amyrin, lupeol, cycloartenol, β-sitosterol, campesterol, benzoic acid, aurantiamide acetate, coronaridine, coronaridine hydroxyindolenine (1), ibogamine, 5-hydroxy-6-oxocoronaridine (6), 5-oxocoronaridine (9), 6-oxocoronaridine (10), (±)-19-hydroxycoronaridine (11), 3-oxocoronaridine (12) and voacamine. The alkaloids 6, 9, 10 and 11 are new compounds, whereas cycloartenol, campesterol, ibogamine, benzoic acid, aurantiamide acetate and coronaridine hydroxyindolenine are reported from this plant for the first time.     

An Acyl Migration in Acetohalogenoglucosamines

Two triterpenoid alcohols, i.e., α- and β-amyrin have been isolated from the unsaponifiable fraction of the ethereal extract of Ilex latifolia Thunberg (Aquifoliaceae). The ratio of the amyrin contents, i.e., α-amyrin to β-amyrin was about 4:1. Stearic acid has also been isolated from the fatty-acid fraction of the hydrolysates.     

大果大戟的化学成分

从大果大戟的根部首次分离得到11个化合物。利用波谱方法鉴定为β-香树素(1),β-香树素乙酸酯(2),3β-乙酰化羽扇豆烯醇(3),baccatin(4),2个caffeic mters(5a,5b),棕榈酸-1-甘油酯(6),棕榈酸(7),东莨菪内酯(8),β-谷甾醇(9)和胡萝卜甙(10)。其中5a,5b是第一次在大戟属中得到;并对5a,5b的碳谱和氢谱数据进行了全归属。     

CYP716A subfamily members are multifunctional oxidases in triterpenoid biosynthesis

Triterpenoids are a diverse group of secondary metabolites that are associated with a variety of biological activities. Oleanolic acid, ursolic acid and betulinic acid are common triterpenoids in plants with diverse biological activities, including antifungal, antibacterial, anti-human immunodeficiency virus (HIV) and/or antitumor activities. In the present study, using the gene co-expression analysis tool of Medicago truncatula, we found a strong correlation between CYP716A12 and β-amyrin synthase (bAS), which encodes the enzyme responsible for the initial cyclization of 2,3-oxidosqualene to β-amyrin (the basic structural backbone of most triterpenoid saponins). Through an in vitro assay, we identified CYP716A12 as a β-amyrin 28-oxidase able to modify β-amyrin to oleanolic acid (through erythrodiol and, possibly, oleanolic aldehyde). We also confirmed its activity in vivo, by expressing CYP716A12 in transgenic yeast that endogenously produce β-amyrin. In addition, CYP716A12 was evaluated for its potential α-amyrin- and lupeol-oxidizing activities. Interestingly, CYP716A12 was able to generate ursolic acid (through uvaol and, possibly, ursolic aldehyde) and betulinic acid (through betulin). Hence, CYP716A12 was characterized as a multifunctional enzyme with β-amyrin 28-oxidase, α-amyrin 28-oxidase and lupeol 28-oxidase activities. We also identified homologs of CYP716A12 in grape (CYP716A15 and CYP716A17) that are involved in triterpenoid biosynthesis, which indicates the highly conserved functionality of the CYP716A subfamily among plants. These findings will be useful in the heterologous production of pharmacologically and industrially important triterpenoids, including oleanolic acid, ursolic acid and betulinic acid.     

Triterpene functional genomics in licorice for identification of CYP72A154 involved in the biosynthesis of glycyrrhizin

Glycyrrhizin, a triterpenoid saponin derived from the underground parts of Glycyrrhiza plants (licorice), has several pharmacological activities and is also used worldwide as a natural sweetener. The biosynthesis of glycyrrhizin involves the initial cyclization of 2,3-oxidosqualene to the triterpene skeleton β-amyrin, followed by a series of oxidative reactions at positions C-11 and C-30, and glycosyl transfers to the C-3 hydroxyl group. We previously reported the identification of a cytochrome P450 monooxygenase (P450) gene encoding β-amyrin 11-oxidase (CYP88D6) as the initial P450 gene in glycyrrhizin biosynthesis. In this study, a second relevant P450 (CYP72A154) was identified and shown to be responsible for C-30 oxidation in the glycyrrhizin pathway. CYP72A154 expressed in an engineered yeast strain that endogenously produces 11-oxo-β-amyrin (a possible biosynthetic intermediate between β-amyrin and glycyrrhizin) catalyzed three sequential oxidation steps at C-30 of 11-oxo-β-amyrin supplied in situ to produce glycyrrhetinic acid, a glycyrrhizin aglycone. Furthermore, CYP72A63 of Medicago truncatula, which has high sequence similarity to CYP72A154, was able to catalyze C-30 oxidation of β-amyrin. These results reveal a function of CYP72A subfamily proteins as triterpene-oxidizing enzymes and provide a genetic tool for engineering the production of glycyrrhizin.     

Three triterpenes and other terpenoids from Catha cassinoides

The investigation of stems and leaves of Catha cassinoides afforded, in addition to sitosterol, β-amyrin, ursolic acid, lup-20(29)-en-3β,30-diol and friedelin, three new pentacyclic triterpenes: 30-hydroxyfriedelan-3-one, 29-hydroxyfriedelan-3-one and 3-oxo-friedelan-29-oic acid. The structures ofthese were determined by spectral studies and correlations, and were confirmed by X-ray analysis of 29-hydroxyfriedelan-3-one acetate.     

The mechanism of operation of climatic factors in the biogenesis of tea flavour

The relative amounts of chlorophyll, leucine, α-alanine and α-ketoisocaproic acid in tea leaves, and those of carotenoids, β-ionone, dihydroactinidiolide, theaspirone, β-amyrin, acetate, trans-2-hexenal and phenlacetaldehyde in processed black tea have been found to vary with climatic conditions, and indicate the mechanism of flavour development in tea. These variations are related to the degree of CO₂ fixation, and the extent of intra- as compared with extra- chloroplastidic biosynthetic reactions. Evidence is discussed that extra-chloroplastidic biogenesis of terpenoid compounds from leucine leads to the development of tea flavour, whereas intrachloroplastidic fixation of CO₂, and the consequent derivation of terpenoids from acetate results in the production of teas without flavour. The leucine pathway for terpenoid biogenesis operates in conditions of climatic stress which limit CO₂ fixtation in the leaf, whereas the acetate pathway predominates in conditions of vigorous growth.     

大头艾纳香化学成分的研究

利用硅胶柱色谱、Sephadex LH-20柱色谱等手段从大头艾纳香(Blumea megacephala(Randeria)Chang etTseng)全草中分离得到13个化合物,根据化合物的理化性质和光谱数据分别鉴定为无羁萜(1)、小麦黄素(2)、豆甾醇二十六烷酸酯(3)、豆甾醇十八烷酸酯(4)、α-香树脂醇(5)、α-香树脂醇乙酸酯(6)、β-香树脂醇乙酸酯(7)、β-谷甾醇(8)、豆甾醇(9)、β-胡萝卜苷(10)、二十七烷醇(11)、十六烷酸(12)和二十四烷酸(13)。所有化合物均为首次从大头艾纳香中分离得到。     

Epicuticular wax constituents of North American and European Euphorbia esula biotypes

The epicuticular leaf wax of four North American and one Austrian Euphorbia esula biotypes was examined as a potential source of chemotaxonomic information relative to intraspecies classification. Analysis (GC and GC/MS) shows general similarity of wax constituent character among all biotypes but differences in specific component yields between the North American and Austrian biotypes. Distinctive variation in occurrence of five triterpenes (α- and β-amyrin, δ-amyrenone, 24-methylenecycloartenol and lupeyl acetate) was observed between the North American and Austrian biotypes.