Chalcone and flavonol glycosides from Asarum canadense (Aristolochiaceae)

Two chalcone glycosides were isolated, together with seven known flavonol glycosides, from the leaves of Asarum canadense. The structures of the chalcone glycosides were established as chalcononaringenin 2',4'-di-O-glucoside and chalcononaringenin 2'-O-glucoside-4'-O-gentiobioside by chemical, UV, FAB MS, 1H and 13C NMR evidence.     

Efficient synthesis of alpha- and beta-chacotriosyl glycosides using appropriate donors, and their cytotoxic activity

Natural steroidal glycosides containing alpha-L-rhamnopyranosyl-(1-->4)-[alpha-L-rhamnopyranosyl-(1-->2)]-beta-D-glucopyranose (chacotriose) at the oligosaccharide moiety exhibit anti-cancer and anti-herpes activities. To investigate the structure-activity relationships of the aglycone parts of chacotriosides, we developed a synthesis method for chacotriosyl glycosides having various aglycones. In the process, it was revealed that alpha-chacotriosyl glycosides could be obtained mainly by using a trichloroacetimidate donor, while beta-chacotriosyl glycosides were afforded by using phosphite and phosphate donors. In cytotoxicity tests using the A549 and HepG2 cell lines, naturally occurring beta-chacotriosyl diosgenin and cholestanol exhibited higher activities than the corresponding alpha-chacotriosyl glycosides.     

Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure

The aim of this study was to investigate the modifying influence of moderate ultraviolet-B (UV-B) radiation exposure on structurally different flavonol glycosides and hydroxycinnamic acid derivatives during pre-harvest using kale, a leafy Brassica species with a wide spectrum of different non-acylated and acylated flavonol glycosides. Juvenile kale plants were treated with short-term (1 day), moderate UV-B radiation [0.22-0.88 kJ m?2 day?1 biologically effective UV-B (UV-B(BE))]. Twenty compounds were quantified, revealing a structure-specific response of flavonol glycosides and hydroxycinnamic acid derivatives to UV-B radiation. A dose- and structure-dependent response of the investigated phenolic compounds to additional UV-B radiation was found. The investigated quercetin glycosides decreased under UV-B; for kaempferol glycosides, however, the amount of sugar moieties and the flavonol glycoside hydoxycinnamic acid residue influenced the response to UV-B. Monoacylated kaempferol tetraglucosides decreased in the investigated UV-B range, whereas the monoacylated kaempferol diglucosides increased strongly with doses of 0.88 kJ m?2 day?1 UV-B(BE) . The UV-B-induced increase in monoacylated kaempferol triglucosides was dependent on the acylation pattern. Furthermore, the hydroxycinnamic acid glycosides disinapoyl-gentiobiose and sinapoyl-feruloyl-gentiobiose were enhanced in a dose-dependent manner under UV-B. While UV-B radiation treatments often focus on flavonol aglycones or total flavonols, our investigations were extended to structurally different non-acylated and acylated glycosides of quercetin and kaempferol.     

Biotransformations of anthracyclinones inStreptomyces coeruleorubidus andStreptomyces galilaeus

The ability to transorm biologically exogenous daunomycinone, 13-dihydrodaunomycinone, aklavinone, 7-deoxyaklavinone, epsilon-rhodomycinone, epsilon-isorhodomycinone and epsilon-pyrromycinone was studied in submerged cultures of the following strains: wild Streptomyces coeruleorubidus JA 10092 (W1) and its improved variants 39-146 and 84-17 (type P1) producing glycosides of daunomycinone and of 13-dihydrodaunomycinone, together with epsilon-rhodomycinone, 13-dihydrodaunomycinone and 7-deoxy-13-dihydrodaunomycinone; in five mutant types of S. coeruleorubidus (A, B, C, D, E) blocked in the biosynthesis of glycosides and differing in the production of free anthracyclinones; in the wild Streptomyces galilaeus JA 3043 (W2) and its improved variant G-167 (P2) producing glycosides of epsilon-pyrromycinone and of aklavinone together with 7-deoxy and bisanhydro derivatives of both aglycones; in two mutant types S. galilaeus (F and G) blocked in biosynthesis of glycosides and differing in the occurrence of anthracyclinones. The following bioconversions were observed: daunomycinone leads to 13-dihydrodaunomycinone and 7-deoxy-13-dihydrodaunomycinone (all strains); 13-dihydrodaunomycinone leads to 7-deoxy-13-dihydrodaunomycinone (all strains); daunomycinone or 13-dihydrodaunomycinone leads to glycosides of daunomycinone and of 13-dihydrodaunomycinone, identical with metabolites W1 and P1 (type A), or only a single glycoside of daunomycinone (type E); aklavinone leads to epsilon-rhodomycinone (types A and B); aklaviinone leads to 7-deoxyaklavinone and bisanhydroaklavinone (type C); epsilon-rhodomycinone leads to zeta-rhodomycinone (types C, E); epsilon-rhodomycinone leads to glycosides of epsilon-rhodomycinone (types W2, P2); epsilon-isorhodomycinone leads to glycosides of epsilon-isorhodomycinone (types W2, P2); epsilon-pyrromycinone leads to a glycoside of epsilon-pyrromycinone (types W1, P1). 7-Deoxyaklavinone remained intact in all tests. Exogenous daunomycinone suppressed the biosynthesis of its own glycosides in W1 and P1; it simultaneously increased the production of epsilon-rhodomycinone in P1.     

Two chromone-secoiridoid glycosides and three indole alkaloid glycosides from Neonauclea sessilifolia

From the dried roots of Neonauclea sessilifolia, two new chromone-secoiridoid glycosides, sessilifoside and 7"-O-beta-D-glucopyranosylsessilifoside, and three novel indole alkaloid glycosides, neonaucleosides A, B, and C, were isolated along with the main known glycosides, 5-hydroxy-2-methylchromone-7-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, sweroside, loganin, grandifloroside, and quinovic acid 3 beta-O-beta-D-quinovopyranoside-28-O-beta-D-glucopyranoside. The structures of these new glycosides were determined by spectroscopic and chemical means. Neonaucleoside A and its C-3 epimer were prepared from secologanin and tryptamine.     

Bacterial glycolipids. Glycosyl diglycerides in Gram-positive bacteria

1. The lipids of ten Gram-positive bacteria have been isolated and the presence in each of a glycosyl diglyceride was established. 2. The glycolipid fractions were isolated and deacylated to give water-soluble glycosides which were purified by paper chromatography. Partial structures for the glycosides have been deduced from chemical and enzymic studies. 3. Nine of the glycosides were disaccharides glycosidically linked to the 1-position of glycerol: the remaining glycoside contained a trisaccharide similarly linked to glycerol.     

Enzymatic synthesis of spacer-linked divalent glycosides carrying N-acetylglucosamine and N-acetyllactosamine: analysis of cross-linking activities with WGA

Divalent glycosides carrying N-acetyl-d-glucosamine (GlcNAc) and N-acetyllactosamine (LacNAc) were designed and prepared as glycomimetics. First, hexan-1,6-diyl bis-(2-acetamido-2-deoxy-beta-d-glucopyranoside) (GlcNAc-Hx-GlcNAc) and 3,6-dioxaoct-1,8-diyl bis-(2-acetamido-2-deoxy-beta-d-glucopyranoside) (GlcNAc-Doo-GlcNAc) were enzymatically synthesized by transglycosylation of an N,N'N',N'-tetraacetylchitotetraose [(GlcNAc)(4)] donor with a primary diol acceptor, utilizing a chitinolytic enzyme from Amycolatopsis orientalis. The resulting divalent glycosides were further converted to the respective hexan-1,6-diyl bis-[beta-d-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-d-glucopyranoside] (LacNAc-Hx-LacNAc) and 6-(2-acetamido-2-deoxy-beta-d-glucopyranosyl)-hexyl beta-d-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-d-glucopyranoside (LacNAc-Hx-GlcNAc), and respective 3,6-dioxaoct-1,8-diyl bis-[beta-d-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-d-glucopyranoside] (LacNAc-Doo-LacNAc) and 8-(2-acetamido-2-deoxy-beta-d-glucopyranosyl)-3,6-dioxaoctyl beta-d-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-d-glucopyranoside (LacNAc-Doo-GlcNAc) by galactosyltransferase. The interaction of wheat germ agglutinin (WGA) with a series of divalent glycosides and related compounds were studied using a biosensor based on surface plasmon resonance (SPR) and by precipitation analysis. Our results demonstrated that divalent glycosides carrying GlcNAc on both sides and GlcNAc and LacNAc on each side are capable of precipitating WGA as divalent ligands, but that the corresponding monovalent controls and divalent glycosides carrying LacNAc on both sides are unable to precipitate the lectin and bind as univalent ligands.     

A direct continuous spectrophotometric assay for glycosidases with 3-nitro-2-pyridyl glycosides by tautomerization of 2-hydroxy-3-nitropyridine

Two kinds of 3-nitro-2-pyridyl glycosides were synthesized and evaluated as substrates for continuous spectrophotometric assay for glycosidases. The liberated aglycon, 2-hydroxy-3-nitropyridine, immediately tautomerized to 3-nitro-2(1H)-pyridone, causing an absorption shift of ca. 60 nm even under acidic conditions (pH 3-6). Consequently, the enzymatic hydrolysis of these glycosides was monitored continuously in the acidic to neutral pH range (pH 4-7), the optimum pH for most glycosidases. The absorbance of liberated aglycon increased linearly at 390 nm until 10% consumption of the substrate to enable the initial rate to be determined at once without terminating the reaction. The kinetic parameters for the hydrolysis of 3-nitro-2-pyridyl glycosides were obtained from the slopes of the progress curves and were compared with those obtained from the conventional discontinuous assay using p- and o-nitrophenyl glycosides as substrates. The kinetic parameters indicated that 3-nitro-2-pyridyl glycosides were more activated and specific substrates, but with less affinity to the enzymes than the corresponding nitrophenyl glycosides. Moreover, the absorbance shift by tautomerization should promise further applications to continuous spectrophotometric assays for other enzymes acting under acidic conditions, such as acid proteases and acid phosphatases.     

Membranotropic effect of some triterpene glycosides possessing immunostimulating properties

The peculiarities of the interaction between cell membrane lipids and triterpene glycosides from holothurians Apostichopus japonicus S. and Cucumaria japonica (holotoxin A1 and cucumarioside A2-2, respectively) were studied in comparison with plant saponins from Quillaja saponaria, known as hemolytic, adjuvant, and structure-forming components of immunostimulating complexes. Similar to Quillaja saponins, the sea glycosides, holotoxin A1 and cucumarioside A2-2 were shown to possess a high hemolytic activity (2.6 and 3 microg/ml, respectively) and sterol-depending membranotropic effect mediated by the formation of nonbilayer sterol-lipid-glycoside complexes. At the same time, cucumarioside A2-2 bound exogenic cholesterol only in the presence of membrane lipids, such as phosphatidylcholine or monogalactosyldiacylglycerol, in contrast to Quillaja saponins and holotoxin A1, which bound cholesterol in the molar ratios 1:2 and 1:8, respectively. Moreover, in all cases, tree-component complexes containing cholesterol, lipid, and glycoside exhibited a lower hemolytic activity compared with two-component sterol-glycoside complexes. It was concluded that the hydrophobic medium of cell membranes performs a potentiative role in the effective interaction between triterpene glycosides and "sterol receptors". A method for decreasing the toxicity of membranotropic holothurian glycosides possessing the immunomodulating properties was suggested.     

New steroidal glycosides from rhizomes of Clintonia udensis

A total of 10 steroidal glycosides, together with three new spirostanol glycosides (6-8), a new furostanol glycoside (9), and a new cholestane glycoside (10), were isolated from the rhizomes of Clintonia udensis (Liliaceae). The structures of the new compounds were determined on the basis of extensive spectroscopic analyses, including 2-D nuclear magnetic resonance (NMR) data, and of hydrolytic cleavage followed by chromatographic or spectroscopic analyses. The isolated glycosides were evaluated for their cytotoxic activity against HL-60 leukemia cells. Spirostanol glycosides 1 and 2, and furostanol glycoside 4 showed cytotoxic activity with IC(50) values of 3.2+/-0.02, 2.2+/-0.12, and 2.2+/-0.06 microg/ml, respectively. Neither the spirostanol and furostanol saponins with a hydroxy group at C-1 (6 and 9) and C-12 (7 and 8) nor cholestane glycosides (5 and 10) exhibited apparent cytotoxic activity at a sample concentration of 10 microg/ml.     

甜菊醇糖苷生物合成关键基因的导入和鉴定分析

甜叶菊（Stevia rebaudiana Bertoni）生产的甜菊醇糖苷因具有高甜度、低热能、不参与人体内代谢兼具保健功能等特点,被誉为最有发展前途的新糖源。从甜叶菊叶片克隆了甜菊醇糖苷生物合成途径中的关键基因SrUGT85C2、SrUGT91D2m和SrUGT76G1,构建植物基因过量表达载体,以单独或组合的形式将这些基因导入到甜叶菊中,获得转基因植株。与野生型对照植株相比,单独导入SrUGT85C2的转基因植株中甜菊醇单糖苷含量提高,总糖苷、莱包迪苷A含量及占比没有明显变化;单独导入SrUGT91D2m的转基因植株中甜菊醇单糖苷含量显著降低,而甜菊醇双糖苷含量显著增加;单独导入SrUGT76G1的转基因植株中,总糖苷含量显著提高,莱包迪苷A含量达到10%以上,比对照提高了2倍,而甜菊糖苷含量减少了一半。3个基因组合同时导入的转基因甜叶菊植株与单独导入SrUGT76G1的转基因甜叶菊植株类似,其总糖苷、莱包迪苷A含量及其占比均显著提高。这些结果为以后通过分子生物学技术来调控甜菊醇糖苷生物合成关键基因的表达,培育莱包迪苷A含量高的高品质甜叶菊新品系提供了理论依据和技术方法。     

Two flavonol glycosides, hexandrasides C and D, from the underground parts of Vancouveria hexandra.

In addition to four known glycosides, icariin, epimedin B, epimedosides A and E, two new glycosides of a flavonol with a gamma,gamma-dimethylallyl group were isolated from the underground parts of Vancouveria hexandra. The structures were determined to be des-O-methyl-anhydroicaritin 3-O-beta-D-xylopyranosyl(1----2)-alpha-L-rhamnopyranoside 7-O-beta-D-glucopyranosyl(1----2)-beta-D-glucopyranoside and anhydroicaritin 3-O-alpha-L-rhamnopyranosyl(1----3)-alpha-L-rhamnopyranoside 7-O-beta-D-glucopyranoside by means of spectral analysis.     

Iridoid glycosides and cucurbitacin glycoside from Neopicrorhiza scrophulariiflora

Three iridoid glycosides, picrorosides A (1), B (2) and C (3), and a cucurbitacin glycoside, scrophoside A (4), were isolated from the rhizomes of Neopicrorhiza scrophulariiflora (Scrophulariaceae), along with two known iridoid glycosides, picrosides I (5) and II (6), and three known cucurbitacin glycosides (7-9). Their structures were elucidated on the basis of both chemical and spectroscopic data.     

Comparative stability of 1-alkoxyalkyl alpha-D-glucosides in the presence of acid or alpha-D-glucosidase from yeast

The aminated 1-alkoxyalkyl glycosides [(S)-2-amino-1-methoxyethyl] 6-amino-6-deoxy-alpha-D-glucopyranoside (3) and [(R,S)-1-ethoxyethyl] 6-amino-6-deoxy-alpha-D-glucopyranoside (4) have been synthesised and characterised. These compounds as well as [(R)-2-amino-1-methoxyethyl] alpha-D-glucopyranoside (1) prepared earlier are resistant against alpha-D-glucosidase (maltase, alpha-D-glucoside glucohydrolase, E.C. 3.2.1.20) from yeast, yet undergo hydrolysis under relatively mild acidic conditions. The kinetic parameters of the interaction with alpha-D-glucosidase and with acid were determined. The relative rates of acid hydrolysis of aminated 1-alkoxyalkyl glycosides compared with aminated ordinary glycosides suggest essential differences in the mechanism of acid-catalysed hydrolysis.     

Acylated flavone glycosides from Veronica

A survey of the flavonoid glycosides of selected taxa in the genus Veronica yielded two new acylated 5,6,7,3',4'-pentahydroxyflavone (6-hydroxyluteolin) glycosides and two unusual allose-containing acylated 5,7,8,4'-tetrahydroxyflavone (isoscutellarein) glycosides. The new compounds were isolated from V. liwanensis and V. longifolia and identified using NMR spectroscopy as 6-hydroxyluteolin 4'-methyl ether 7-O-alpha-rhamnopyranosyl(1"'-->2")[6"-O-acetyl-beta-glucopyranoside] and 6-hydroxyluteolin 7-O-(6"-O-(E)-caffeoyl)-beta-glucopyranoside, respectively. Isoscutellarein 7-O-(6"'-O-acetyl)-beta-allopyranosyl(1"'-->2")-beta-glucopyranoside was obtained from both V. intercedens and V. orientalis and its 4'-methyl ether from V. orientalis only. Complete 1H and 13C NMR spectral assignments are presented for both isoscutellarein glycosides. Two iridoid glucosides new to the genus Veronica (melittoside and globularifolin) were also isolated from V. intercedens.     

Constituents from the bark of Tabebuia impetiginosa

The bark of Tabebuia impetiginosa afforded nineteen glycosides, consisting of four iridoid glycosides, two lignan glycosides, two isocoumarin glycosides, three phenylethanoid glycosides and eight phenolic glycosides. Their structures were determined using both spectroscopic and chemical methods. Iridoid glycosides, phenylethanoid glycosides and lignan glycosides had ajugol, osmanthuside H and secoisolariciresinol 4-O-beta-D-glucopyranoside as their structural elements, respectively, whereas the aglycone moieties of the isocoumarin glycosides were considered to be (-)-6-hydroxymellein. Phenolic glycosides had 4-methoxyphenol, 2,4-dimethoxyphenol, 3,4-dimethoxyphenol, 3,4,5-trimethoxyphenol and vanillyl 4-hydroxybenzoate as each aglycone moiety. Additionally, the sugar chains of these isocoumarin glycosides and phenolic glycosides were concluded to be beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside as well as those of osmanthuside H and above phenylethanoid glycosides.     

Two novel immunosuppressive pregnane glycosides from the roots of Stephanotis mucronata

Two novel pregnane glycosides, together with one new aglycone, were isolated from the roots of Stephanotis mucronata. Their structures were determined by means of chemical evidence and extensive spectroscopic methods including 1D and 2D NMR. The two pregnane glycosides displayed significant immunosuppressive activities in vitro.     

Phytochemical and molluscicidal investigations of Fagonia arabica

The aqueous methanolic extract of the aerial parts of Fagonia arabica L. (family Zygophyllaceae) was successively fractionated using certain organic solvents. From the ethyl acetate fraction, two flavonoid glycosides were isolated and identified as kaempferol-7-O-rhamnoside and acacetin-7-O-rhamnoside. Four triterpenoidal glycosides were isolated from the butanolic layer. Their structures were elucidated on the basis of the spectral and chemical data as 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranoside oleanolic acid (1), 3-O-alpha-L-arabinopyranosyl quinovic acid 28-O-beta-D-glucopyranoside (2), 3-O-[beta-D-glucopyranosyl-(1-->2)]-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinosyl oleanolic acid (3) and 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabino-pyranosyl quinovic acid 28-O-beta-D-glucopyranoside (4). The two monodesmosidic saponins 1 and 3 were found to possess strong molluscicidal activity against Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni in Egypt (LC90 = 13.33 and 16.44 microM), whereas the other two bidesmosidic saponins 2 and 4 as well as the two flavonoid glycosides were inactive up to 50 microM.     

Iridoids from Scutellaria albida ssp. albida

Three iridoid glycosides, 6'-O-E-p-coumaroylgardoside (1), 6'-O-p-E-coumaroyl-8-epi-loganic acid (2) and scutelloside (3) were isolated from the aerial parts of Scutellaria albida subsp. albida, in addition to an anomeric mixture in equilibrium of one iridoid aglycone (4, 4a), nine iridoid glycosides (5-13), four known phenylethanoid glycosides (14-17), and six known phenolic derivatives (18-23).     

不同施肥处理对甜菊生长及糖苷含量和积累量的影响

采用盆栽法,以甜菊( Stevia rebaudiana Bertoni)品种‘中山4号'(‘Zhongshan No.4')当年生扦插苗为研究对象,研究不同形态氮肥(硫酸铵、硝酸钠和尿素)及不同施氮量(纯氮)、施磷量( P2 O5)和施钾量( K2 O)对幼苗生长及糖苷含量和单株积累量的影响。结果显示：随氮肥、磷肥和钾肥施用量的提高,甜菊幼苗的株高、茎粗、叶长、叶宽、单株叶干质量和单株茎干质量均呈先升后降的变化趋势,且总体上与对照无显著差异,仅施磷量300 mg·kg-1处理组的叶长显著高于对照;根据施肥量与单株叶干质量的回归方程,确定硫酸铵、硝酸钠、尿素、磷肥和钾肥的施用量分别为64.87、660.21、735.84、211.54和775.92 mg·kg-1时,幼苗单株叶干质量最高。在硫酸铵处理组中,300 mg·kg-1处理组甜菊叶片中的莱鲍迪苷A( R-A)含量及甜菊苷( St)、R-A和总苷的单株积累量以及600 mg·kg-1处理组的St单株积累量高于对照,多数处理组的St、R-A和总苷含量及单株积累量均低于对照;在硝酸钠处理组中,1200 mg·kg-1处理组的R-A和总苷含量、600和900 mg·kg-1处理组的St单株积累量以及300~900 mg·kg-1处理组的R-A和总苷单株积累量高于对照,其他处理组的St、R-A和总苷含量及单株积累量均低于对照;在尿素处理组中,1500 mg·kg-1处理组的R-A和总苷的含量和单株积累量以及600和900 mg·kg-1处理组的R-A和总苷单株积累量高于对照,其他处理组的St、R-A和总苷含量及单株积累量均低于对照;各施氮处理组中,仅1500 mg·kg-1处理组的R-A含量与对照差异显著,其他指标均与对照无显著差异。在施磷处理组中,100 mg·kg-1处理组的R-A含量以及100和200 mg·kg-1处理组的St、R-A和总苷的单株积累量高于对照,多数处理组的St、R-A和总苷含量及单株积累量低于对照且与对照均无显著差异。在施钾处理组中,各处理组的St、R-A和总苷含量及单株积累量均高于对照,其中仅900 mg·kg-1处理组的St、R-A和总苷含量与对照显著差异。各施肥处理组的St含量占总苷含量的百分率均低于对照、R-A含量占总苷含量的百分率均高于对照,且总体上与对照无显著差异。经过综合分析,建议在甜菊生育期内的施肥量为纯氮600~900 mg·kg-1、P2 O5200~300 mg·kg-1和K2 O 600~900 mg·kg-1,其中氮肥以尿素为宜。