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dc.contributor.advisorFerreira, D.
dc.contributor.advisorBrandt, E. V.
dc.contributor.authorPotgieter, Eleonora Deborah
dc.date.accessioned2016-06-08T18:32:40Z
dc.date.available2016-06-08T18:32:40Z
dc.date.issued2007-02
dc.identifier.urihttp://hdl.handle.net/11660/2733
dc.description.abstractEnglish: The profisetinidins are an important class of condensed tannins, or proanthocyanidins. Historically, studies towards the structure and conformation of proanthocyanidins were done on their peracetate and permethyl acetate derivatives. A current upsurge in industrial and biological applications of proanthocyanidins has prompted the present efforts at detailed analysis of the conformational behaviour of the naturally occurring free phenolic oligomeric profisetinidins. Studies towards the structure and conformational analysis of a small number of free phenolic dimeric procyanidins that are 4→8 coupled and only one free phenolic dimeric profisetinidin, fisetinidol-(4α→8)-catechin, have hitherto been reported. This study centres on the use of 1H, 13C, gradient COSY, COSY 45, COSY 90W, NOESY PH and HMQC NMR experiments in different solvents and at different temperatures to assign the hydrogen and some carbon resonances of the free phenolic profisetinidins that are found in commercially important southern hemisphere trees, namely Black Wattle (Acacia mearnsii) and Quebracho (Schinopsis balansae). These results, together with data obtained from CD spectra in methanol, were then used to study the conformations of these compounds. Dimers with 2,3-trans-3,4-trans (2,4-cis) configuration, namely fisetinidol-(4α→8)-catechin, fisetinidol-(4α→6)-catechin, ent-fisetinidol-(4β→8)-catechin and ent-fisetinidol-(4β→6)- catechin all displayed sets of duplicate resonances on 1H NMR spectra, indicating the presence of rotamers on an NMR time-scale at ambient temperatures. The proton resonances of the rotamers of the 4→6 linked dimers displayed insignificant chemical shift differences due to the similar magnetic environments and linear shape of both rotamers. The proton resonances of the rotamers of the 4→8 linked dimers displayed significant chemical shift differences due to the presence of compact and extended rotamers resulting in large changes in magnetic environment due to anisotropic effects. The type of solvent, temperature as well as the relative presence of water or cadmium nitrate had a strong influence on the relative concentrations of the rotamers, the conformations of the heterocyclic C- and F-rings as well as the visibility of hydroxy groups. The F-rings all displayed A/E- conformational exchange with line shapes indicating possible skewed boat conformations in some instances. The C-ring conformations ranged from rings with A/E conformational exchange to preferred E-conformers. The dimers with 2,3-trans-3,4-cis (2,4-trans) configuration, namely fisetinidol-(4β→8)- catechin, fisetinidol-(4β→6)-catechin and ent-fisetinidol-(4α→8)-catechin displayed only one set of resonances on 1H NMR spectra at ambient temperatures. The presence of intramolecular hydrogen bonding and limited conformational exchange was confirmed by the following observations: a) Selective broadening of proton resonances in both the heterocyclic and aromatic regions of 1D NMR spectra. b) Sharpening of resonances in 1D spectra at elevated temperatures. c) The presence of abundant coupling between heterocyclic and aromatic ring protons as observed on 2D spectra. d) Coupling between 2-HC and 4-HC on 2D NMR spectra. The C-rings had preferred A-conformations, with the F-rings displaying A/E conformational exchange with line shapes indicating possible skewed boat conformations in some instances. 2D NMR experiments afforded estimations, in some cases, of the angles between the plane of the B-ring and the 2-CC→2-HC bond, the plane of the D-ring and the 4-CF→4-HF bond as well as the plane of the D-ring and the 4-CC→4-HC. The resonances of 4-CC of the 2,3-trans-3,4-trans dimers displayed significant chemical shift differences (± 41 ppm) compared to 4-CC of the 2,3-trans-3,4-cis dimers (± 31 ppm).This could serve as a possible indicator of the relative configurations of the C-rings of 2,3-trans profisetinidins dimers. CD studies of al seven abovementioned dimers, as well as four trimers from Acacia mearnsii displayed complex curves with a number of strong Cotton effects. Although some trends were observed, it was abundantly evident that the chiroptical characteristics of this class of compounds are too complex to be interpreted in terms of the empirical quadrant rule.en_ZA
dc.description.abstractAfrikaans: Die profisetinidiene vorm ‘n belangrike klas van gekondenseerde tanniene, oftewel proantosianidiene. Die oorgrote meerderheid studies om die struktuur en konformasie van hierdie verbindings te bepaal, is op hulle perasetaat en metieleterasetaat derivate gedoen. Die toename in industriële en biologiese toepassings van proantosianidiene het gelei tot die huidige studies om ‘n gedetailleerde analise van die konformasionele gedrag van vry fenoliese oligomeriese profisetinidiene te doen. Slegs etlike vry fenoliese dimeriese prosianidiene wat 4→8 gekoppel is en slegs een vry fenoliese dimeriese profisetinidien, naamlik fisetinidol-(4α→8)-katesjien, is tot op hede bestudeer. Hierdie studie behels die gebruik van 1H, 13C, gradient COSY, COSY 45, COSY 90W, NOESY PH en HMQC KMR eksperimente in verskillende oplosmiddels en by verskillende temperature om die waterstof en sommige van die koolstof resonanse van die dimeriese profisetinidiene gevind in die kommersiëel belangrike Swart Wattel (Acacia mearnsii) en Quebracho (Schinopsis balansae). Beide hierdie bome kom in die suidelike halfrond voor. Hierdie resultate, tesame met die data wat verkry is van SD spektra in metanol, is gebruik om die konformasies van hierdie verbindings te bestudeer. Dimere met 2,3-trans-3,4-trans- (2,4-cis-) konfigurasie, naamlik fisetinidol-(4α→8)-katesjien, fisetinidol-(4α→6)-katesjien, ent-fisetinidol-(4β→8)-katesjien en ent-fisetinidol-(4β→6)- katesjien vertoon almal stelle gedupliseerde resonanse in 1H KMR spektra, wat op die teenwoordigheid van twee rotamere op ‘n KMR tydskaal by kamertemperatuur dui. Die proton resonanse van die dimere wat 4→6 gekoppel is, het geen betekenisvolle chemiese verskuiwings getoon nie. Dit kan toegeskryf word aan die soortgelyke magnetiese omgewings van die rotamere, asook hulle liniêre oriëntasie. Die proton resonanse van die dimere wat 4→8 gekoppel is, het betekenisvolle chemiese verskuiwings getoon wat toegeskryf kan word aan die teenwoordigheid van kompakte en verlengde rotamere, met beduidende verskille in magnetiese omgewings as gevolg van anisotropiese effekte. Die tipe oplosmiddel, temperatuur, asook die teenwoordigheid van water en kadmium nitraat, het ‘n sterk invloed op die relatiewe konsentrasies van die rotamere, die konformasies van die heterosikliese C- en F-ringe asook die sigbaarheid van hidroksie groepe gehad. Die konformasies van die F-ringe het almal op A/E-konformasionele uitruiling gedui, met lynvorm analise wat ook moontlike skewe boot konformasies aandui. Die konformasies van die C-ringe het gestrek van A/E konformasionele uitruiling tot voorkeur Ekonformere. Dimere met 2,3-trans-3,4-cis- (2,4-trans-) konfigurasie, naamlik ent-fisetinidol-(4α→8)- katesjien, fisetinidol-(4β→6)-katesjien en fisetinidol-(4β→8)-katesjien het slegs een stel resonanse op 1H KMR spektra getoon by kamertemperatuur. Dit kan verklaar word aan die hand van waterstofbindings wat konformasionele uitruiling beperk, en is bevestig deur die volgende waarnemings: a) Selektiewe verbreding van sommige proton resonanse in beide die heterosikliese en aromatiese areas van 1H KMR spektra. b) Resonansverskerping by verhoogde temperature. c) Die oorvloedige teenwoordigheid van koppeling tussen heterosikliese en aromatise protone soos waargeneem op 2D spectra. d) Koppeling tussen 2-HC en 4-HC op 2D spektra. Die C-ringe het almal voorkeur A-konformasies getoon en die F-ringe A/E konformasie uitruiling met lynvorm analise wat ook moontlike skewe boot konformasies in sommige gevalle aandui. Beraamde skattings kon in sommige gevalle van die hoeke tussen die vlak van die B-ring en die 2-CC→2-HC binding, die vlak van die D-ring en die 4-CF→4-HF binding asook die vlak van die D-ring en die 4-CC→4-HC binding vanaf 2D KMR eksperimente gedoen word. Die resonanse van 4-CC van die 2,3-trans-3,4-trans dimere het beduidende chemiese verskuiwingsverskille getoon (±41 ppm) in vergelyking met 4-CC van die 2,3-trans-3,4-cis dimere (± 31 ppm). Dit kan as ‘n moontlike indikator van die relatiewe konfigurasies van die C-ringe van 2,3-trans profisetinidien dimere dien. CD studies van al sewe bogenoemde dimere, asook vier trimere vanuit Acacia mearnsii het komplekse kurwes tot gevolg gehad wat elk ‘n aantal hoë amplitude Cotton effekte vertoon het. Alhoewel sommige algemene neigings waargeneem is, is dit baie duidelik dat die chiroptiese eienskappe van hierdie klas verbindings nie in terme van die empiriese kwadrantrëel geïnterpreteer kan word nie.af
dc.description.sponsorshipCentral Research Fund of the University of the Free Stateen_ZA
dc.description.sponsorshipResearch Committee of the Port Elizabeth Technikon, now the Nelson Mandela Metropolitan University
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectTrimeric Profisetinidinsen_ZA
dc.subjectFlavan-3-olsen_ZA
dc.subjectConformational analysisen_ZA
dc.subjectFree phenolic profisetinidinsen_ZA
dc.subjectDimeric profisetinidinsen_ZA
dc.subjectTrimeric profisetinidinsen_ZA
dc.subjectNuclear magnetic resonanceen_ZA
dc.subjectCircular dichroismen_ZA
dc.subjectAcacia mearnsiien_ZA
dc.subjectSchinopsis balansaeen_ZA
dc.subjectThesis (Ph.D. (Chemistry))--University of the Free State, 2007en_ZA
dc.subjectTanninsen_ZA
dc.subjectFlavonoidsen_ZA
dc.titleConformational analysis of oligomeric profisetinidinsen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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