Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In this study, two novel ligands were synthesized and separately two crown ether derivatives were all immobilized onto four different silica substrates. These immobilized ligand systems were used to extract six different metal and metalloid ions in water. The extraction capacity of the different immobilized ligands was compared with each other to determine whether the substrates had any influence on the extraction capabilities of these ligands. After the extraction experiments, recovery of the immobilized ligands was attempted by re-protonating the ligands so as to displace the metal ions. Two free parent ligands, 1,4,7-tris-[(S)-2-hydroxypropyl]-1,4,7-tri-azacyclodecane (THTD) and 1,4,8-tris-[(S)-2-hydroxypropyl]-1,4,8-tri-azacycloundecane (THTUD), were synthesized. Previous formation constant data indicated that THTD and THTUD form very stable complexes with Cd2+ which should make these ligands ideal for the extraction of Cd2+. These two ligands are less symmetric due to the carbon bridges between the nitrogen atoms, which differ in length. This gives the ligands the special feature that they can form five - and six membered rings during complexation with the metal ions. The ligands were fully characterized by NMR, mass spectrometry and elemental analysis. Characterization of the silica substrates was done using BET, low angle X-ray diffraction and FTIR. MCM-41 has the highest surface area, followed by SBA-15, Si gel (60 Å) and HMS. Although MCM-41 has the largest surface area, it was not the best support to use. HMS and Si gel (60 Å) have the smallest and almost identical surface areas. Yet, Si gel (60 Å) was a far better support to use than HMS, and even better than MCM-41. The worst supports were SBA-15 and HMS. A spacer, 3-Glycidyloxypropyl-trimethoxysilane (glymo), was introduced to immobilize the ligands to the silica substrates. Solid state NMR and FTIR analysis confirmed that the spacer could indeed be successfully immobilized on the various silica supports. The immobilized ligands were fully characterized with the use of solid state NMR and FTIR. The thermal stability of the immobilized ligands was determined by means of TGA. The immobilized ligands are stable up to 200ºC where after they started to disintegrate. According to literature, 15-crown-5 and 18-crown-6 are suitable ligands for the extraction of Sr2+ and UO22+. Since these ligands were to be immobilized, (2-aminomethyl)-15-crown-5 and (2-aminomethyl)-18-crown-6 were used because of the amino group that can be used as an anchor for immobilization. To immobilize these ligands onto the activated silica substrates, two methods were used: 1) directly onto the substrate by using the amino groups at the end of the carbon arm and 2) by means of the glymo spacer which connects the (2-aminomethyl)-15-crown-5 and (2-aminomethyl)-18-crown-6 to the silica substrates. The immobilization was confirmed and the ligand-substrate moiety fully characterized by solid state NMR and FTIR. The thermal stability of the immobilized crown ethers was determined by means of TGA as stable up to 200ºC where after they disintegrated. Extraction experiments were conducted at 25ºC and atmospheric pressure. The extractions were done at pH values of 4.5 and 5.9. The extraction capacity of the immobilized ligands was determined by ICP analysis. As expected, the extraction done at pH 5.9 was significantly better than at pH 4.5. Cr6+ was the best-extracted metal ion. The best extraction results were obtained with Si gel (60 Å) as support. It was also noticeable that the extraction capacity increased with a spacer added to the support, except for the extraction of UO22+. Better extraction for the uranyl was obtained using the 15-crown-5 and 18-crown-6 immobilized directly onto the supports, rather than with a spacer added. Recovery of the metal ions and the immobilized ligands was attempted, but without success. This aspect will be examined again in future work. In conclusion, ligands were successfully synthesized and immobilized. These immobilized ligands produced moderate extraction results with a number of metal ions from aqueous solution. / AFRIKAANSE OPSOMMING: Hierdie studie behels die sintetisering van 2 nuwe ligande en die immobilisering daarvan, te same met 2 kroon eters, op vier verskillende silika substrate. Die geïmobiliseerde ligande is gebruik vir die ekstraksie van verskillende metaal - en metaloied ione uit water. Die ekstraksie kapasiteit van die onderskeie geïmobiliseerde ligande is vergelyk om te bepaal of die substrate ‘n uitwerking op die ekstraksie vermoeë van die ligande het. Herwinnings eksperimente is uitgevoer deur die verplasing van die geadsordeerde metaal ione deur middel van reprotonasie van die ligande. Twee nuwe azamakrosikliese basis ligande, 1,4,7-tris-[(S)-2-hidroksipropiel]-1,4,7-tri-azasiklodekaan (THTD) en 1,4,8-tris-[(S)-2-hidroksipropiel]-1,4,8-tri-azasikloundekaan (THTUD), is gesintetiseer. Vormings konstante data dui daarop dat THTD en THTUD uiters stabiele komplekse met Cd2+ vorm wat hierdie ligande dus geskik behoort te maak vir die ekstraksie van Cd2+. Die twee ligande toon ook ‘n mindere mate van simmetrie as gevolg van die verskillende lengtes van die koolstof brûe tussen die stikstof atome. Hierdie eienskap verskaf aan die ligande die moontlikheid om beide vyf- en sesledige ringe vorm tydens kompleksering met die metaal ione. Die ligande is ten volle gekarakteriseer deur middel van KMR-metings, massa-spekstroskopie en element analise. Karakterisering van die silika substrate [Si gel (60 Å), MCM-41, SBA-15, and HMS] sluit in BET, lae hoek X-straaldiffraksie en FTIR. MCM-41 het die grootste oppervlakte, gevolg deur SBA-15, Si gel (60 Å) en HMS. Ten spyte van die feit dat MCM-41 die grootste oppervlakte het, was dit egter nie die beste subtraat om te gebruik nie. Die interne areas van die uiters groot porie-oppervlaktes van MCM-41 is nie toeganklik vir immobilisering nie a.g.v. die uiter klein porie-openinge. Si gel (60 Å) en HMS het die kleinste oppervlak areas. Si gel (60 Å) is ‘n baie beter substraat om te gebruik as HMS, en selfs ook beter as MCM-41 aangesien die totale oppervlakte van die Si gel (60 Å) gebruik kan word. Die mees ongeskikte substrate was SBA-15 en HMS. Die alreeds klein oppervlak areas word verder “verklein” a.g.v. die klein porie openinge wat die interne oppervlekte van die porieë ontoegangklik maak. ‘n Verbinder, 3-Glysidieloksipropiel-trimetoksisilaan (glymo) is gebruik om die ligande op die silika substrate te immobiliseer. Vaste toestand KMR en FTIR analise het bevestig dat die verbinder suksesvol geïmmobiliseer is op die onderskeie silika substrate. Die geïmmobiliseerde aza makrosikliese ligande is ten volle gekarakteriseer deur vaste toestand KMR en FTIR. Die termiese stabiliteit is bepaal d.m.v GTA en die geïmmobiliseerde ligande is stabiel tot 250ºC. Die basis ligande 15-kroon-5 an 18-kroon-6 is uiters geskik vir die ekstraksie van Sr2+ en UO22+. Om hierdie kroon eters te immobiliseer, is (2-aninometiel)-15-kroon-5 en (2-aninometiel)-18-kroon-6 gebruik. Die amino groep dien as anker vir die immobilisering. Twee metodes van immobilisering op silika is gebruik: 1) direkte immobilisering op die substraat en 2) immobilisering d.m.v. die glymo verbinder. Die immobilisering is bevestig en die ligand-substraat funksionel groep is gekarakteriseer d.m.v. vaste toestand KMR en FTIR. Die termiese stabiliteit van die geïmmobiliseerde kroon eters is bepaal d.m.v. GTA en is stabiel tot 200ºC. Ekstraksie eksperimente is uitgevoer by 25ºC en atmosferiese druk. Die ekstraksies is uitgevoer by pH waardes van 4.5 en 5.9. Die adsorpsie kapasiteit van die geïmmobiliseerde ligande is bepaal d.m.v. IGP analise. Soos verwag is die ekstraksie by pH 5.9 beter as by pH 4.5. Cr6+ ekstrksie was die hoogste met al die die ligande geïmmobiliseerd op die onderskeie substrate. Si gel (60 Å) was die beste substraat om te gebruik. Die ekstraksie kapasiteit van al die metaal ione het verbeter met die toevoeging van ‘n verbinder, behalwe vir UO22+. Beter ekstraksie van die UO22+ is verkry met die gebruik van die kroon eters wat direk op die substrate geïmmobiliseer is, eerder as met ‘n verbinder toegevoeg. Herwinning van die metaal ione en die ligande is probeer deur standard filtrasie. Na die filtrasie is die geïmmobiliseerde ligande en substrate met water gewas. Die filtreerpapier en ligande is met HNO3 behandel, maar van die metaal ione het egter op die filtreer papier agter gebly en die IGP resultate het ‘n hoër herwinning getoon as wat tydens die ekstraksie verkry is. Hierdie aspek sal weer in die toekoms ondersoek moet word. Die ligande is suksesvol gesintetiseer en geïmmobiliseer. Hierdie geïmmobiliseerde ligande toon gemiddelde ekstraksie resultate met ‘n aantal metaal ione uit waterige medium by ‘n pH van 5.9.

Oxidative stress is the major driving force behind the aging process and many age-related diseases. However, direct experimental evidence of whether antioxidants, such as ascorbate (AA) and lipoic acid (LA) can slow the progression of aging process and/or reduce risks of developing degenerative disease is largely absent. This suggests a better understanding of the precise mechanism of how dietary micronutrient affect parameters of involved in cellular redox balance and aging are warranted. In this dissertation, young and old rats were used as our model to understand potential pro-oxidant events that contribute to increases in oxidative stress in various tissues and how antioxidants such as ascorbate and lipoic acid influence these events. Our major findings are that the age-related impairment of mitochondria and increased deposition of iron contribute significantly to heighten levels of oxidative stress, as evidenced by the resultant increases in the rates of oxidant appearance and in the levels of oxidative damage to DNA, lipids and proteins. We find that AA and LA strongly protected against transition metal-ion dependent increases in oxidative stress. AA effectively inhibited transition metal-mediated lipide peroxidation in human plasma. LA in its reduced form effectively binds iron and copper in a redox inactive manner and reversed chronically elevated levels of iron in the brain without removing enzyme bound transition metal ions. LA also significantly attenuated the age-related increase in oxidative stress associated with mitochondrial decay in the heart, as evidenced by the improvements in AA levels and glutathione redox status. The declines in tissue GSH levels in aged rats were strongly associated with the diminished γ-GCL activity (in parallel with decreased expression of the catalytic and modulatory subunits), and lowered Nrf2 expression and binding to ARE sequence in rat liver. Remarkably, all these events were effectively reversed by the administration of LA, modulating the parameters to return to the observed in young animals. The implications of this work open new avenues not only for further understanding of the aging process but also for possible strategies in its modulation by the micronutrients. / Graduation date: 2004