Phenolic glycosides from Phagnalon rupestre

Analysis of the butanol-soluble fraction from the methanolic extract of the aerial parts of Phagnalon rupestre (Asteraceae) has led to the isolation of seven phenolic compounds. Three have been identified on the basis of their NMR spectra as new natural compounds: the lignan 7,7'-bis-(4-hydroxy-3,5-dimethoxyphenyl)-8,8'-dihydroxymethyl-tetrahydrofuran-4-O-beta-glucopyranoside (1), the prenylhydroquinone glycoside 1-O-beta-glucopyranosyl-1,4-dihydroxy-2-(3'-hydroxy-3'-methylbutyl) benzene (2) and the acetophenone glycoside 12-O-beta-glucopyranosyl-9beta,12-dihydroxytremetone (3). The known flavonoids apigenin-7-O-beta-glucoside, luteolin-7-O-beta-glucoside, luteolin-7-O-beta-glucuronide and the acetophenone picein were also isolated.     

Glycosides from Phlomis lunariifolia

An aliphatic alcohol glycoside, lunaroside 1-octen-3-yl [O-beta-apiofuranosyl-(1-->6)-O-[beta-glucopyranosyl-(1-->2)]-beta-glucopyranoside, a phenylethanoid glycoside, lunariifolioside 2-(3,4-dihydroxyphenyl)ethylO-beta-apiofuranosyl-(1-->6)-O-[O-beta-apiofuranosyl-(1-->4)-alpha-rhamnopyranosyl-(1-->3)]-4-O-(E)-caffeoyl-beta-glucopyranoside and a flavone glycoside, luteolin 7-O-[4-O-acetyl-alpha-rhamnopyranosyl-(1-->2)]-beta-glucuronopyranoside, were isolated from the aerial parts of Phlomis lunariifolia, in addition to 15 known glycosides. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic interpretation and chemical degradation.     

Lignan, phenolic and iridoid glycosides from Stereospermum cylindricum

A lignan glycoside [(+)-cycloolivil 4'-O-beta-d-glucopyranoside], a phenolic glycoside [3,4-dimethoxyphenyl 1-O-beta-d-xylopyranosyl-(1-->6)-beta-d-glucopyranoside] and a iridoid glycoside (stereospermoside) were isolated from the leaves and branches of Stereospermum cylindricum, together with (+)-cycloolivil, (+)-cycloolivil 6-O-beta-d-glucopyranoside, (-)-olivil, (-)-olivil 4-O-beta-d-glucopyranoside, (-)-olivil 4'-O-beta-d-glucopyranoside, vanilloloside, decaffeoyl-verbascoside, isoverbascoside, 3,4,5-trimethoxyphenyl 1-O-beta-d-xylopyranosyl-(1-->6)-beta-d-glucopyranoside, ajugol, verminoside, and specioside. The structure elucidations were based on spectroscopic evidence.     

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.     

A new 5-deoxyflavone glycoside from the aerial parts of Calea clausseniana

A new 5-deoxyflavone glycoside, identified as 7-O-(alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl)-3',4',7-trihydroxyflavone (1), was isolated from the aerial parts of Calea clausseniana. Its structure was determined by spectral analysis.     

A new secoiridoid glycoside and a new sesquiterpenoid glycoside from Valeriana jatamansi with neuroprotective activity

A new secoiridoid glycoside, isopatrinioside (1) and a new sesquiterpenoid glycoside, valeriananoid F (2), together with nine known compounds, were isolated from the roots of Valeriana jatamansi. Their structures were elucidated on the basis of spectroscopic analysis. Compound 1 was an unusual monocyclic iridoid glycoside ring-opened between C-1 and C-2 produced by the cleavage of the pyran ring. Of the eleven isolates, compounds 1 and 4 exhibited moderate neuroprotective effects against CoCl₂-induced neuronal cell death in PC12 cells.     

Antiviral isoflavonoid sulfate and steroidal glycosides from the fruits of Solanum torvum

The C-4 sulfated isoflavonoid, torvanol A (1), and the steroidal glycoside, torvoside H (3), together with the known glycoside, torvoside A (2), were isolated from a MeOH extract of Solanum torvum fruits. Upon enzymatic hydrolysis with beta-glucosidase, torvoside A (2) and torvoside H (3) yielded the corresponding acetal derivatives 4 and 5, respectively. Torvanol A (1), torvoside H (3) and compound 5 exhibited antiviral activity (herpes simplex virus type 1) with IC(50) values of 9.6, 23.2 and 17.4 microg/ml, respectively. Compounds 1-5 showed no cytotoxicity (at 50 microg/ml) against BC, KB and Vero cell lines.     

Coumaroyl triterpene lactone, phenolic and naphthalene glycoside from stem bark of Diospyros angustifolia

From the ethanolic extract of stem bark of D. angustifolia three new compounds, a coumaroyl triterpene lactone, diospyrosooleanolide (1), a phenolic glycoside, diospyrososide (2) and a naphthalene glycoside, diospyrosonaphthoside (3) were isolated along with five known compounds (4-8). The structures of these compounds were established on the basis of spectroscopic and chemical evidences.     

A trinorsesterterpene glycoside from the North American fern Woodwardia virginica (L.) Smith

A new trinorsesterterpene glycoside was isolated from the ethanol extract of the American fern Woodwardia virginica having a 3-[6-(4,8-dimethyl-nona-1,3,7-trienyl)-4-hydroxy-2,6-dimethyl-cyclohex-1-enyl]-3-hydroxypropionic acid, as the aglycone and a saccharide moiety linked at C-4 to glucoses, xylose or arabinofuranose. The structure was elucidated using extensive spectroscopic analysis (1D and 2D NMR, MS, IR and UV) including determination of absolute stereochemistry by means of the MTPA and PGME derivatives and also by chemical methods.     

LC-ESI/MS determination of xanthone and secoiridoid glycosides from in vitro regenerated and in vivo Swertia chirayita

A rapid analytical method has been developed to determine xanthone and secoiridoid glycoside in in vitro and in vivo Swertia chirayita extracts. Ultra performance liquid chromatography–electrospray ionization mass spectrometry (LC-ESI/MS) was applied and validated for the analysis of xanthone and secoiridoid glycoside a potential active component isolated from methanolic extracts of in vitro and in vivo Swertia chirayita plantlets. Chromatographic separation was achieved on a RP-C18 column using gradient elution. Mangiferin (Xanthone), Amarogentin and Swertiamarin (Secoiridoid glycosides) were identified in both the extracts. In the LC/ESI-MS spectra, major [M + H] ⁺ and [M + Na] ⁺ ions were observed in positive ion mode and provided molecular mass information. An ultra-performance liquid-chromatography in combination with electrospray ionization tandem mass spectrometry involving metal cationisation was successfully utilized for the rapid identification of xanthone and secoiridoid glycosides. This method is suitable for the routine analysis, as well as for the separation and identification of known and novel secoiridoid glycoside and xanthone.     

The structural basis of substrate recognition in an exo-beta-D-glucosaminidase involved in chitosan hydrolysis

Family 2 of the glycoside hydrolase classification is one of the largest families. Structurally characterized members of this family include enzymes with β-galactosidase activity (Escherichia coli LacZ), β-glucuronidase activity (Homo sapiens GusB), and β-mannosidase activity (Bacteroides thetaiotaomicron BtMan2A). Here, we describe the structure of a family 2 glycoside hydrolase, CsxA, from Amycolatopsis orientalis that has exo-β-d-glucosaminidase (exo-chitosanase) activity. Analysis of a product complex (1.85 Å resolution) reveals a unique negatively charged pocket that specifically accommodates the nitrogen of nonreducing end glucosamine residues, allowing this enzyme to discriminate between glucose and glucosamine. This also provides structural evidence for the role of E541 as the catalytic nucleophile and D469 as the catalytic acid/base. The structures of an E541A mutant in complex with a natural β-1,4-d-glucosamine tetrasaccharide substrate and both E541A and D469A mutants in complex with a pNP-β-d-glucosaminide synthetic substrate provide insight into interactions in the + 1 subsite of this enzyme. Overall, a comparison with the active sites of other GH2 enzymes highlights the unique architecture of the CsxA active site, which imparts specificity for its cationic substrate.     

Crystal structure of exo-inulinase from Aspergillus awamori: the enzyme fold and structural determinants of substrate recognition

Exo-inulinases hydrolyze terminal, non-reducing 2,1-linked and 2,6-linked beta-d-fructofuranose residues in inulin, levan and sucrose releasing beta-d-fructose. We present the X-ray structure at 1.55A resolution of exo-inulinase from Aspergillus awamori, a member of glycoside hydrolase family 32, solved by single isomorphous replacement with the anomalous scattering method using the heavy-atom sites derived from a quick cryo-soaking technique. The tertiary structure of this enzyme folds into two domains: the N-terminal catalytic domain of an unusual five-bladed beta-propeller fold and the C-terminal domain folded into a beta-sandwich-like structure. Its structural architecture is very similar to that of another member of glycoside hydrolase family 32, invertase (beta-fructosidase) from Thermotoga maritima, determined recently by X-ray crystallography The exo-inulinase is a glycoprotein containing five N-linked oligosaccharides. Two crystal forms obtained under similar crystallization conditions differ by the degree of protein glycosylation. The X-ray structure of the enzyme:fructose complex, at a resolution of 1.87A, reveals two catalytically important residues: Asp41 and Glu241, a nucleophile and a catalytic acid/base, respectively. The distance between the side-chains of these residues is consistent with a double displacement mechanism of reaction. Asp189, which is part of the Arg-Asp-Pro motif, provides hydrogen bonds important for substrate recognition.     

The Structure of Remsamabilinin B

A new cucurbitacin glycoside, named hemsamabilinin B (2), was isolat-ed from Hemsleya amabilis Diels. 2 was hydrolyzed by enzyme on acid to produce 23,24-dihydrocucurbitacin F (3) or D-glucose respectively. On the basis of the spectrosco-pic data of 2 and its acetate (4) (1H NMR, 13CNMR and MS), the structure of 2 wasassigned as 2-0-β-D-glucopyranoside of 3.     

Rebaudioside F, a diterpene glycoside from Stevia rebaudiana

The sweet diterpenoid glycoside, rebaudioside F, was isolated from leaves of a high rebaudioside C producing line of Stevia rebaudiana, and its structure was established by chemical and spectral studies.     

α-Bisabolol β-d-fucopyranoside from Carthamus lanatus

A sesquiterpene glycoside has been isolated from the aerial parts of Carthamus lanatus and identified by its spectroscopic and chemical properties as α-bisabolol β-d-fucopyranoside.     

O(3)-(2-Acetylamino-2-deoxy-β-d-glucopyranosyl)-oleanolic acid,a novel triterpenoid glycoside from two Pithecellobium species

A new triterpenoid glycoside containing an amino sugar moiety has been isolated from Pithecellobium cubense and P. arboreum and identified as O(3)- (2-acetylamino-2-deoxy-β-d-glucopyranosyl)oleanolic acid. β-d-Glucopyranosyl-α-spinasterol was also obtained from P. cubense.     

Steroidal glycosides from the fruits of Solanum abutiloides

Four steroidal glycosides, named abutilosides L, M and N, these being 22S,25S-epoxy-furost-5-ene type glycosides, and abutiloside O, a 20-22 seco-type steroidal glycoside, were isolated from the fresh fruits of Solanum abutiloides. Their structures were determined by 2D NMR spectroscopic analysis and chemical evidence.     

Chemical constituents from the root of Damnacanthus officinarum Huang

The present phytochemical investigation on Damnacanthus officinarum Huang led to the isolation of a new anthraquinone glycoside named digiferruginol-11-O-β-gentiobioside, along with six known compounds, including anthraquinone glycosides, iridoid glycoside and etc. In the study, compounds (2–7) were isolated for the first time from D. officinarum Huang and Damnacanthus genus. The found of compounds (1–4, 6 and 7) indicate a close relationship between D. officinarum Huang and Morinda officinalis, which may be as chemotaxonomic markers for the tribe Morindeae     

Pinocembrin 7-neohesperidoside from Nierembergia hippomanica

A flavanone glycoside isolated from Nicrembergia hippomania was characterized by spectroscopic methods as pinocembrin 7-neohesperidoside. The structure was confirmed by total synthesis of the glycoside.     

Function and Structure Studies of GH Family 31 and 97 α-Glycosidases

A huge number of glycoside hydrolases are classified into the glycoside hydrolase family (GH family) based on their amino-acid sequence similarity. The glycoside hydrolases acting on α-glucosidic linkage are in GH family 4, 13, 15, 31, 63, 97, and 122. This review deals mainly with findings on GH family 31 and 97 enzymes. Research on two GH family 31 enzymes is described: clarification of the substrate recognition of Escherichia coli α-xylosidase, and glycosynthase derived from Schizosaccharomyces pombe α-glucosidase. GH family 97 is an aberrant GH family, containing inverting and retaining glycoside hydrolases. The inverting enzyme in GH family 97 displays significant similarity to retaining α-glycosidases, including GH family 97 retaining α-glycosidase, but the inverting enzyme has no catalytic nucleophile residue. It appears that a catalytic nucleophile has been eliminated during the molecular evolution in the same way as a man-made nucleophile mutant enzyme, which catalyzes the inverting reaction, as in glycosynthase and chemical rescue.