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1.
Biomolecules ; 7(1)2017 01 31.
Article in English | MEDLINE | ID: mdl-28146121

ABSTRACT

Following our interest in new diterpene glycosides with better taste profiles than that of Rebaudioside M, we have recently isolated and characterized Rebaudioside IX-a novel steviol glycoside-from a commercially-supplied extract of Stevia rebaudiana Bertoni. This molecule contains a hexasaccharide group attached at C-13 of the central diterpene core, and contains three additional glucose units when compared with Rebaudioside M. Here we report the complete structure elucidation-based on extensive Nuclear Magnetic Resonance (NMR) analysis (1H, 13C, Correlation Spectroscopy (COSY), Heteronuclear Single Quantum Coherence-Distortionless Enhancement Polarization Transfer (HSQC-DEPT), Heteronuclear Multiple Bond Correlation (HMBC), 1D Total Correlation Spectroscopy (TOCSY), Nuclear Overhauser Effect Spectroscopy (NOESY)) and mass spectral data-of this novel diterpene glycoside with nine sugar moieties and containing a relatively rare 16 α-linked glycoside. A steviol glycoside bearing nine glucose units is unprecedented in the literature, and could have an impact on the natural sweetener catalog.


Subject(s)
Diterpenes/chemistry , Glycosides/chemistry , Stevia/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Plant Extracts/chemistry
2.
Nat Prod Commun ; 10(7): 1159-61, 2015 Jul.
Article in English | MEDLINE | ID: mdl-26410999

ABSTRACT

In a continued search for novel diterpenoid glycosides, we recently isolated and characterized a Rebaudioside M derivative with a hydroxyl group at position 15 in the central diterpene core from an extract of Stevia rebaudiana Bertoni. Here we report the complete structure elucidation of 15α-hydroxy-Rebaudioside M (2) on the basis of NMR (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D TOCSY, NOESY) and mass spectral data. Steviol glycoside with a hydroxyl group at C-15 in the central diterpene core has not been previously reported.


Subject(s)
Stevia/chemistry , Diterpenes/chemistry , Diterpenes/isolation & purification , Glycosides/chemistry , Glycosides/isolation & purification
3.
Nat Prod Commun ; 10(4): 559-62, 2015 Apr.
Article in English | MEDLINE | ID: mdl-25973475

ABSTRACT

A natural sweetener, Rubusoside (1), subjected to extreme pH and temperature conditions, resulted in the isolation and structural elucidation of one novel rubusoside degradant (7), together with seven known degradants (2-6 and 8-9). ID and 2D NMR spectroscopy (1H, 13C, COSY, HSQC-DEPT, HMBC, and NOESY) and mass spectral data were used to fully characterize the degradant 7.


Subject(s)
Diterpenes, Kaurane/chemistry , Glucosides/chemistry , Hydrogen-Ion Concentration , Molecular Structure
4.
Molecules ; 19(11): 17345-55, 2014 Oct 28.
Article in English | MEDLINE | ID: mdl-25353385

ABSTRACT

To supply the increasing demand of natural high potency sweeteners to reduce the calories in food and beverages, we have looked to steviol glycosides. In this work we report the bioconversion of rebaudioside A to rebaudioside I using a glucosyltransferase enzyme. This bioconversion reaction adds one sugar unit with a 1→3 linkage. We utilized 1D and 2D NMR spectroscopy (1H, 13C, COSY, HSQC-DEPT, HMBC, 1D TOCSY and NOESY) and mass spectral data to fully characterize rebaudioside I.


Subject(s)
Diterpenes, Kaurane/metabolism , Beverages , Food , Glucosides/metabolism , Glucosyltransferases/metabolism , Magnetic Resonance Spectroscopy/methods , Mass Spectrometry/methods , Sweetening Agents/metabolism
5.
Oncotarget ; 3(2): 172-82, 2012 Feb.
Article in English | MEDLINE | ID: mdl-22383402

ABSTRACT

Oncogenic fusion proteins, such as EWS-FLI1, are excellent therapeutic targets as they are only located within the tumor. However, there are currently no agents targeted toward transcription factors, which are often considered to be 'undruggable.' A considerable body of evidence is accruing that refutes this claim based upon the intrinsic disorder of transcription factors. Our previous studies show that RNA Helicase A (RHA) enhances the oncogenesis of EWS-FLI1, a putative intrinsically disordered protein. Interruption of this protein-protein complex by small molecule inhibitors validates this interaction as a unique therapeutic target. Single enantiomer activity from a chiral compound has been recognized as strong evidence for specificity in a small molecule-protein interaction. Our compound, YK-4-279, has a chiral center and can be separated into two enantiomers by chiral HPLC. We show that there is a significant difference in activity between the two enantiomers. (S)-YK-4-279 is able to disrupt binding between EWS-FLI1 and RHA in an immunoprecipitation assay and blocks the transcriptional activity of EWS-FLI1, while (R)-YK-4-279 cannot. Enantiospecific effects are also established in cytotoxicity assays and caspase assays, where up to a log-fold difference is seen between (S)-YK-4-279 and the racemic YK-4-279. Our findings indicate that only one enantiomer of our small molecule is able to specifically target a protein-protein interaction. This work is significant for its identification of a single enantiomer effect upon a protein interaction suggesting that small molecule targeting of intrinsically disordered proteins can be specific. Furthermore, proving YK-4-279 has only one functional enantiomer will be helpful in moving this compound towards clinical trials.


Subject(s)
Indoles/pharmacology , Oncogene Proteins, Fusion/antagonists & inhibitors , Proto-Oncogene Protein c-fli-1/antagonists & inhibitors , RNA-Binding Protein EWS/antagonists & inhibitors , Sarcoma, Ewing/drug therapy , Animals , Caspase 3/metabolism , Cell Line, Tumor , Cell Proliferation , Humans , Rats , Rats, Sprague-Dawley , Stereoisomerism , Transcription Factors/metabolism , Transcriptional Activation , Transplantation, Heterologous
6.
Org Biomol Chem ; 8(6): 1287-9, 2010 Mar 21.
Article in English | MEDLINE | ID: mdl-20204196

ABSTRACT

A concise total synthesis of enantiopure circumdatins E, H and J has been developed using a reductive cyclization of chiral N-prolinoyl-2-nitrobenzamides to construct the core quinazolinone ring.


Subject(s)
Benzodiazepinones/chemistry , Benzodiazepinones/chemical synthesis , Quinazolinones/chemical synthesis , Quinazolinones/chemistry , Stereoisomerism , Substrate Specificity
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