The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
G Galli - One of the best experts on this subject based on the ideXlab platform.
-
rapid evaluation of phenolic component profile and analysis of oleuropein aglycon in olive oil by atmospheric pressure chemical ionization mass spectrometry apci ms
Journal of Agricultural and Food Chemistry, 2000Co-Authors: Donatella Caruso, Roberto Colombo, Rossana Patelli, Flavio Giavarini, G GalliAbstract:Epidemiological studies have linked the Mediterranean diet with a low incidence of cardiovascular diseases. Olive oil, the major fat component of this diet, is characterized by antioxidant properties related to their content in catecholic components, particularly oleuropein aglycon. Therefore quantification of these components in edible oils may be important in determining the quality, and consequently its commercial value. The present method allows us to obtain the profile of the phenolic components of the oil from the methanolic extracts of the crude olive oil. In particular tyrosol, hydroxytyrosol, elenolic acid, deacetoxyligstroside and deacetoxyoleuropein aglycons, ligstroside and oleuropein aglycons, and 10-hydroxy-oleuropein are clearly identified by atmospheric pressure chemical ionization−mass spectrometry (APCI−MS). Moreover, oleuropein and its isomers present in the oil are quantified by APCI−MS/MS analysis of the extracts without preliminary separation from other phenolic compounds. Keywords: ...
Yeo Joon Yoon - One of the best experts on this subject based on the ideXlab platform.
-
One-Pot Combinatorial Biosynthesis of Glycosylated Anthracyclines by Cocultivation of Streptomyces Strains Producing Aglycones and Nucleotide Deoxysugars.
ACS Combinatorial Science, 2017Co-Authors: Myoung-chong Song, Ji Yoon Beom, Jin A Jung, Yeo Joon YoonAbstract:Anthracyclines, such as doxorubicin, are effective anticancer drugs composed of a tetracyclic polyketide Aglycone and one or more deoxysugar moieties, which play a critical role in their biological activity. A facile one-pot combinatorial biosynthetic system was developed for the generation of a range of glycosylated derivatives of anthracyclines. Cocultivation of Streptomyces venezuelae mutants producing two anthracycline Aglycones with eight different nucleotide deoxysugar-producing S. venezuelae mutants that coexpress a substrate-flexible glycosyltransferase led to the generation of 16 aklavinone or e-rhodomycinone glycosides containing diverse deoxysugar moieties, seven of which are new. This demonstrates the potential of the one-pot combinatorial biosynthetic system based on cocultivation as a facile biological tool capable of combining diverse Aglycones and deoxysugars to generate structurally diverse polyketides carrying engineered sugars for drug discovery and development.
-
One-Pot Combinatorial Biosynthesis of Glycosylated Anthracyclines by Cocultivation of Streptomyces Strains Producing Aglycones and Nucleotide Deoxysugars
2017Co-Authors: Eunji Kim, Ji Yoon Beom, Jin A Jung, Myoung-chong Song, Myoun Su Kim, Hang Soo Cho, Yeo Joon YoonAbstract:Anthracyclines, such as doxorubicin, are effective anticancer drugs composed of a tetracyclic polyketide Aglycone and one or more deoxysugar moieties, which play a critical role in their biological activity. A facile one-pot combinatorial biosynthetic system was developed for the generation of a range of glycosylated derivatives of anthracyclines. Cocultivation of Streptomyces venezuelae mutants producing two anthracycline Aglycones with eight different nucleotide deoxysugar-producing S. venezuelae mutants that coexpress a substrate-flexible glycosyltransferase led to the generation of 16 aklavinone or ε-rhodomycinone glycosides containing diverse deoxysugar moieties, seven of which are new. This demonstrates the potential of the one-pot combinatorial biosynthetic system based on cocultivation as a facile biological tool capable of combining diverse Aglycones and deoxysugars to generate structurally diverse polyketides carrying engineered sugars for drug discovery and development
Christopher T Walsh - One of the best experts on this subject based on the ideXlab platform.
-
aknt is an activating protein for the glycosyltransferase akns in l aminodeoxysugar transfer to the Aglycone of aclacinomycin a
Chemistry & Biology, 2005Co-Authors: Catherine Leimkuhler, Gregory J Gatto, Ryan G Kruger, Markus Oberthu R, Daniel Kahne, Christopher T WalshAbstract:Summary During biosynthesis of the anthracycline antitumor agents daunomycin, adriamycin, and aclacinomycin, the polyketide-derived tetracyclic Aglycone is enzymatically glycosylated at the C 7 -OH by dedicated glycosyltransferases (Gtfs) that transfer L-2,3,6-trideoxy-3-aminohexoses. In aclacinomycins, the first deoxyhexose is predicted to be transferred via AknS action, then subjected to further elongation to a trisaccharide by the subsequent Gtf, AknK. We report here that purified AknS has very low activity in the absence of the adjacently encoded AknT; however, at a 3:1 ratio, AknT stimulates AknS k cat by 40-fold up to 0.22 min −1 for transfer of L-2-deoxyfucose (2-dF) to the Aglycone aklavinone. It is likely that several other Gtfs that glycosylate polyketide Aglycones also act as two-component catalytic systems. Incubations of purified AknS/AknT/AknK with two Aglycones and two dTDP-2-deoxyhexoses produced previously uncharacterized anthracycline disaccharides.
-
tandem action of glycosyltransferases in the maturation of vancomycin and teicoplanin Aglycones novel glycopeptides
Biochemistry, 2001Co-Authors: Heather C Losey, Daniel Kahne, Mark W Peczuh, Zhong Chen, Ulrike S Eggert, Steven D Dong, Istvan Pelczer, Christopher T WalshAbstract:The glycopeptides vancomycin and teicoplanin are clinically important antibiotics. The carbohydrate portions of these molecules affect biological activity, and there is great interest in developing efficient strategies to make carbohydrate derivatives. To this end, genes encoding four glycosyltransferases, GtfB, C, D, E, were subcloned from Amycolatopsis orientalis strains that produce chloroeremomycin (GtfB, C) or vancomycin (GtfD, E) into Escherichia coli. After expression and purification, each glycosyltransferase (Gtf) was characterized for activity either with the Aglycones (GtfB, E) or the glucosylated derivatives (GtfC, D) of vancomycin and teicoplanin. GtfB efficiently glucosylates vancomycin Aglycone using UDP-glucose as the glycosyl donor to form desvancosaminyl-vancomycin (vancomycin pseudoAglycone), with kcat of 17 min-1, but has very low glucosylation activity, ≤ 0.3 min-1, for an alternate substrate, teicoplanin Aglycone. In contrast, GtfE is much more efficient at glucosylating both its nat...
-
tandem action of glycosyltransferases in the maturation of vancomycin and teicoplanin Aglycones novel glycopeptides
Biochemistry, 2001Co-Authors: Heather C Losey, Daniel Kahne, Mark W Peczuh, Zhong Chen, Ulrike S Eggert, Steven D Dong, Istvan Pelczer, Christopher T WalshAbstract:The glycopeptides vancomycin and teicoplanin are clinically important antibiotics. The carbohydrate portions of these molecules affect biological activity, and there is great interest in developing efficient strategies to make carbohydrate derivatives. To this end, genes encoding four glycosyltransferases, GtfB, C, D, E, were subcloned from Amycolatopsis orientalis strains that produce chloroeremomycin (GtfB, C) or vancomycin (GtfD, E) into Escherichia coli. After expression and purification, each glycosyltransferase (Gtf) was characterized for activity either with the Aglycones (GtfB, E) or the glucosylated derivatives (GtfC, D) of vancomycin and teicoplanin. GtfB efficiently glucosylates vancomycin Aglycone using UDP-glucose as the glycosyl donor to form desvancosaminyl-vancomycin (vancomycin pseudoAglycone), with k(cat) of 17 min(-1), but has very low glucosylation activity, < or = 0.3 min(-1), for an alternate substrate, teicoplanin Aglycone. In contrast, GtfE is much more efficient at glucosylating both its natural substrate, vancomycin Aglycone (k(cat) = 60 min(-1)), and an unnatural substrate, teicoplanin Aglycone (k(cat) = 20 min(-1)). To test the addition of the 4-epi-vancosamine moiety by GtfC and GtfD, synthesis of UDP-beta-L-4-epi-vancosamine was undertaken. This NDP-sugar served as a substrate for both GtfC and GtfD in the presence of vancomycin pseudoAglycone (GtfC and GtfD) or the glucosylated teicoplanin scaffold, 7 (GtfD). The GtfC product was the 4-epi-vancosaminyl form of vancomycin. Remarkably, GtfD was able to utilize both an unnatural acceptor, 7, and an unnatural nucleotide sugar donor, UDP-4-epi-vancosamine, to synthesize a novel hybrid teicoplanin/vancomycin glycopeptide. These results establish the enzymatic activity of these four Gtfs, begin to probe substrate specificity, and illustrate how they can be utilized to make variant sugar forms of both the vancomycin and the teicoplanin class of glycopeptide antibiotics.
Kornkanok Ingkaninan - One of the best experts on this subject based on the ideXlab platform.
-
lc esi qtof ms based screening and identification of isomeric jujubogenin and pseudojujubogenin Aglycones in bacopa monnieri extract
Journal of Pharmaceutical and Biomedical Analysis, 2016Co-Authors: Nitra Nuengchamnong, Sontaya Sookying, Kornkanok IngkaninanAbstract:Abstract Bacopa monnieri (L.) Wettst. (Scrophulariaceae) is an Ayurvedic medicinal plant used as a memory enhancer. Its major chemical constituents are Bacopa saponins consisting of jujubogenin and pseudojujubogenin glycosides. These two Aglycones are isomers different at the positions of prenyl substitution i.e. , at C-23 for jujubogenin and at C-22 for pseudojujubogenin. In this study, we demonstrate the rapid and comprehensive characterization of saponin glycosides in B. monnieri using liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometer (LC-ESI-QTOF-MS). This shows that ESI-QTOF-MS in positive-ion mode, jujubogenin and pseudojujubogenin glycosides could be discriminated by the peak abundance ratio of m / z 455 [Aglycone + H-H 2 O] + to m / z of 473 [Aglycone + H] + . Furthermore, the sequence of sugar moieties can be observed. In a similar manner, the isomeric saponins; deoxyjujubogenin and deoxypseudojujubogenin glycosides can be distinguished using the m / z 437[Aglycone + H-H 2 O] + and m / z 455[Aglycone + H] + peak ratio. Use of the negative-ion mode with MS/MS fragmentation can provide information about the type of sugar linked to the Aglycone i.e. , at m / z 633 (Aglycone + glucose) or at m / z 603 (Aglycone + arabinose). With our method, 62 chemical constituents in B. monnieri including saponin glycosides, flavonoids, and alkaloids were identified. This is the first systematic study in structural characterization on isomeric saponins and other metabolites in B. monnieri using ESI-QTOF-MS.
Seppo Auriola - One of the best experts on this subject based on the ideXlab platform.
-
high performance liquid chromatography with electrospray ionization mass spectrometry and diode array ultraviolet detection in the identification of flavonol Aglycones and glycosides in berries
Journal of Chromatography A, 1998Co-Authors: Sari Hakkinen, Seppo AuriolaAbstract:High-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) was used to study flavonol Aglycones and glycosides in berries. For the identification of Aglycones, photodiode-array detection (DAD) was also used. The HPLC-ESI-MS technique is highly valuable in the identification of flavonol Aglycones and glycosides from berry extracts. This ionization technique provides information on the structure of the Aglycones and glycosides without time-consuming pre-purification or derivatization steps. Quercetin Aglycone was identified with both ESI-MS and DAD in all of the berries studied. Myricetin Aglycone was identified with both techniques in three berries. Hexose, deoxyhexose-hexose and pentose derivatives of quercetin were the most abundant flavonol glycosides identified. Two glycosides of myricetin and one glycoside of kaempferol were identified in blackcurrant. To confirm the data obtained using the HPLC-ESI-MS procedure, fractions of the glycosides from four berries were separated, hydrolyzed, silylated and the sugars were analyzed using gas chromatography-mass spectrometry.