Carbon monoxide (CO) is now well established as one of the signaling molecules in higher organisms, including humans. Due to its physiological roles, CO is now accepted as a potential therapeutic agent. The use of CO gas has been studied in multiple clinical trials. Vasodilation, anti-inflammatory, anti-apoptotic, anti-proliferative and cytoprotective effects are just a few of the pharmacological actions attributed to CO gas in various models of diseases. Use of inhaled CO gas as a therapeutic has many limitations which necessitate the development of a new approach for CO delivery. In order to handle CO safely, compounds that release CO (CO-releasing molecules, CORMs) have been developed. CORMs that release CO only when triggered, and with the ability to target certain tissue sites, are of particular interest. Our lab is developing molecules that release CO only when illuminated with visible light (photoCORMs). These photoCORMs are based on a motif found in naturally-occurring flavonols, which are chemical compounds found in wide variety of foods including fruits, vegetables, tea and dark chocolate. The research presented in this dissertation outlines the results of studies on extended flavonols as CO release agents. The specific studies described herein focus on understanding visible light-induced CO-releasing flavonols in terms of their: a) structure/reactivity relationships, especially in biological environments; b) interactions with metal ions and proteins; c) reaction pathway of CO release; and d) their properties when combined with a CO-sensing motif.

Romulea is a genus with numerous attractive and endangered species with horticultural potential. This genus in the Iridaceae has its centre of diversity in the winter-rainfall zone of South Africa. This thesis uses ecophysiological and biotechnological techniques to investigate the physiology behind the propagation of some species in this genus. The ecophysiological techniques of soil sampling and analysis and germination physiology were used to determine the natural and ex vitro growth and development requirements of these plants, while biotechnological techniques are used to determine the in vitro growth and development requirements of these plants and to increase the rate of multiplication and development. Soil sampling and analysis revealed that R. monadelpha and R. sabulosa, two of the most attractive species in the genus, grow in nutrient poor 1:1 mixture of clay and sandy loam soil with an N:P:K ratio of 1.000:0.017:0.189 with abundant calcium. To investigate the physical properties of the seeds, imbibition rate, moisture content and viability of seeds were determined. The seed coat and micropylar regions were examined using scanning electron microscopy. To test for suitable stimuli for germination, the effect of temperature and light, cold and warm stratification, acid and sand paper scarification, plant growth promoting substances, deficiency of nitrogen, phosphorous and potassium, and different light spectra (phytochromes) on germination were examined. An initial germination experiment showed germination above 65% for R. diversiformis, R. leipoldtii, R. minutiflora and R. flava seeds placed at 15°C; while seeds of other species placed at 15°C all had germination percentages lower than 30%. More extensive germination experiments revealed that R. diversiformis and R. rosea seed germinate best at 10°C, R. flava seed germinates best when cold stratified (5°C) for 21 days and R. monadelpha germinates best at 15°C in the dark. Seeds of R. diversiformis, R. flava, R. leipoldtii, R. minutiflora, R. monadelpha and R. sabulosa seem to all exhibit non-deep endogenous morphophysiological dormancy while seeds of R. camerooniana and R. rosea appear to have deep endogenous morphophysiological dormancy. The suitability of various explant types and media supplementations for culture initiation was examined for various species of Romulea. Both embryos and seedling hypocotyls can be used for R. flava, R. leipoldtii and R. minutiflora in vitro shoot culture initiation. R. sabulosa shoot cultures can only be initiated by using embryos as explants, because of the lack of seed germination in this species. Shoot cultures of R. diversiformis, R. camerooniana and R. rosea could not be initiated due to the lack of an in vitro explant shooting response. Shoot cultures can be initiated on media supplemented with 2.3 to 23.2 M kinetin for all species that showed an in vitro response. The most suitable concentration depended on the species used. Some cultures appeared embryogenic, but this was shown not to be the case. A medium supplemented with 2.5 M mTR is most suitable for R. sabulosa shoot multiplication. BA caused vitrification of shoots in all the experiments in which it was included and is not a suitable cytokinin for the micropropagation of these species. The effect of various physical and chemical parameters on in vitro corm formation and ex vitro acclimatization and growth was examined. Low temperature significantly increased corm formation in R. minutiflora and R. sabulosa. A two step corm formation protocol involving placing corms at either 10 or 20°C for a few months and then transferring these cultures to 15°C should be used for R. sabulosa. When paclobutrazol and ABA were added to the medium on which R. minutiflora shoots were placed, the shoots developed corms at 25°C. This temperature totally inhibits corm formation when these growth retardants are not present. BA inhibited corm formation in R. leipoldtii. Corms can be commercialized as propagation units for winter-rainfall areas with minimum temperatures below 5°C during winter. Although an incident of in vitro flowering was observed during these experiments, these results could not be repeated. Although none of the corms or plantlets planted ex vitro in the greenhouse survived, a small viability and an ex vitro acclimatization experiment shows that the corms produced in vitro are viable. One embryo of the attractive R. sabulosa, produces 2.1 ± 0.7 SE shoots after 2 months; subsequently placing these shoots on a medium supplemented with 2.5 μM mTR for a further 2 months multiplies this value by 5.5 ± 1.3 SE. Each of these shoots can then be induced to produce a corm after 6 months. This means that 1 embryo can produce about 12 corms after 10 months or about 65 corms after 12 months (if shoots are subcultured to medium supplemented with 2.5 μM mTR for another 2 months). Embryo rescue can enable wider crosses within this genus. These results can be used for further horticultural development of species in this genus and their hybrids and variants. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Substituted tetrazines have been found to undergo facile inversed electron demand Diels-Alder reactions with “tunable” reaction rates. By varying the substituents on tetrazine, cycloaddition rate variations of over 200 fold have been achieved with the same dienophile. Coupled with the availability of different dienophiles, such as norbornene, the reaction rate difference can be over 14,000 folds. These substituted tetrazines can be very useful for selective labeling under different conditions. This finding paves the way to utilize tetrazine conjugation reactions for not only DNA but also stage labeling work. Carbon monoxide (CO) belongs to the gasotransmitter family of signalling molecules in the mammalian systems with importance on par with that of NO and H2S. Studies have shown that endogenous production of CO has anti-inflammatory, anti-proliferative, and anti-apoptotic effects in mammalian system. Besides of the conventional metal-based carbon monoxide releasing molecules (CORMs) to deliver CO for therapeutic purposes, organic CO prodrugs represent a new direction. Here we report the “click and release” approached to release CO. Unlike the metal-based CORMs, our system does not contain transition metal and liberates CO with controllable manner and possesses potential tunable releasing rate property under physiological conditions.

The role of light and temperature on flowering of South African Watsonia species were evaluated to assess the potential for this genus as a commercial flower crop. Species were selected that represent different climatic regions of South Africa, with the aim of understanding how ecologically distinct species perform under cultivation. The four selected species were W. borbonica and W. tabularis (winter-rainfall area), W. angusta (shared rainfall) and W. pillansii (summer-rainfall area). In order to establish the optimum temperature required for flowering, plants were exposed for 12 weeks to three temperature regimes (12/7 °C, 21/15 °C and 29/21 °C) after attaining their first and/or second leaves. A temperature shift of 12/7 °C was used to assess if the plants had a vemalisation requirement. Controls were maintained under 25 % shade under natural conditions, with an average temperature of 24/7 °C. An elevated temperature of 29/21 °C was detrimental to plant growth. Moderate temperatures of 21/15 °C significantly (P<0.001) increased the height and the number of leaves produced per plant relative to the 12/7 °C treatment. These temperatures significantly (P<0.001) increased the total number of flowers produced per plant compared to low temperatures. However, flowering percentage and quality of flowers were reduced. A low temperature regime of 12/7 °C was efficient in satisfying vernalisation requirements and inducing flowering in four selected species. However, the total number of leaves produced per plant was signifcantly reduced. The summer-rainfall species, W pillansii, displayed a qualitative response to vernalisation, as no flowering was observed in non-vernalised plants. Two winter-rainfall species, W borbonica and W. tabularis, demonstrated a quantitative response to vernalisation. These species flowered at non-vernalising temperatures. W angusta behaved like the winter-rainfall species in terms of flowering. Overall, a vernalisaton treatment marginally reduced days to flower while flowering percentage was increased compared to other temperature regimes. However, there was no increase in the total number of flowers produced per plant. Low temperatures were not only effective for flower induction, but also for releasing corm dormancy, thus synchronising growth. Storing corms at either 4 or 10 QC resulted in 100 % sprouting within 4-6 weeks. The role of daylength in flowering of Watsonia plants was established by subjecting plants to long days (LO) of 16 h light and 8 h dark and to short days (SO) of 8 h light and 16 h dark. The number of leaves and flowering were significantly (P<0.01) promoted under the LO regime. However, there was strong temperature and daylength interaction in terms of flowering potential, as at low temperatures flowering was induced irrespective of daylength. In W. pillansii, flowering was obtained under both regimes (LO and SO) applied at the second leaf stage. Flowering in W. borbonica and W. tabularis was only observed under the LO regime at the second leaf stage. In both species, flowering was also obtained in SD-treated plants, provided treatment occurred after the formation of the third leaf. However, the total number and quality of flowers were reduced. To examine the effect of light intensity on flowering, plants at different developmental stages (first and/or second or beyond the third leaf stage) were exposed to photosynthetically active radiation (PAR) of 150 jJmol m-2s-1 or 39.5 jJmol m-2s-1 for 7 weeks. Exposure to low light intensity at either developmental stage compromised leaf quality. No flowering was observed following low light intensity treatment during the first to third leaf stages, even though plants were exposed to low temperature and LO regimes, both of which promoted flowering. Observation of the shoot apical meristem revealed that the second leaf stage was critical as the anatomical transition to flowering occurred at this level. When beyond the third leaf stage, low light intensity did not prevent flowering. However, the number of flowers produced per plant was reduced compared to plants maintained at 150 jJmol m-2s-1. Thus, light intensity played a role in both plant morphogenesis and flowering. LDs were effective in promoting vegetative growth whereas high light intensity and low temperature regimes played pivotal roles in flower induction. This makes them useful horticulture tools to produce desirable Watsonia plants for commercialisation. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Tesis por compendio / [ES] El uso de Colocasia esculenta (L.) Schott y Xanthosoma sagittifolium (L.) Schott como materia prima en forma de almidón o harina es una alternativa sostenible y nutritiva al trigo y otros granos. Esta alternativa permite a los agricultores minimizar las pérdidas después de su cosecha y garantizar la seguridad alimentaria ya que sus propiedades nutricionales, digestivas y saludables son reconocidas por la comunidad científica. Sin embargo, la información existente sobre este rizoma dirigida a su aplicación es bastante limitada. Esta tesis expone la caracterización funcional y tecnológica de los almidones obtenidos a partir de cormos y cormelos de Xanthosoma sagittifolium (L.) Schott. Asimismo, se evaluó tecnológicamente el efecto de la combinación de enzimas, hidrocoloides, almidón de patata, harina pregelatinizada sobre la harina de los cormelos de la Colocasia esculenta (L.) Schott en el desarrollo de un pan sin gluten. Además, se evaluaron las propiedades tecnológicas y digestivas de una fórmula básica para puré desarrollada a partir de harina de cormelos de Xanthosoma spp. y Colocasia spp. Además, la revisión bibliográfica realizada permitió poner en contexto los efectos saludables demostrados clínicamente de esta materia prima y sus componentes. Se demostró que existen diferencias significativas entre el almidón de cormos y cormelos de la misma especie. Se concluyó que la harina de Colocasia esculenta (L.) Schott es una buena opción para incrementar el valor nutricional de los panes sin gluten. Entre las estrategias probadas, el pan elaborado a partir de la mezcla con almidón de patata resultó la menos aconsejable. Además, todas las estrategias aplicadas originaron panes con menor índice glucémico que sus homólogos sin gluten reportados en otros estudios. Por primera vez, este trabajo recomienda el uso de harina de cormelos de Xanthosoma sagittifolium (L.) Schott y Colocasia esculenta (L.) Schott y para desarrollar purés con un valor nutricional agregado. La revisión bibliográfica realizada permitió recopilar los efectos demostrados clínicamente, concretamente antihiperglucémicos, antihepatotóxicos, antihipertensivos, hipoglucemiantes, anticancerosos, hipolipidémicos y prebióticos, entre otros, de los compuestos bioactivos presentes en esta planta. / [CA] L'ús de Colocasia esculenta (L.) Schott i Xanthosoma sagittifolium (L.) Schott com a matèria primera en forma de midó o farina, és una alternativa per a minimitzar les perdues després de la seua collita i garantir la seguretat alimentària ja que les seues propietats nutricionals, digestives i saludables són reconegudes per la comunitat científica. Aquesta tesi exposa la caracterització funcional i tecnològica dels midons obtinguts a partir de corms i cormelos de Xanthosoma sagittifolium (L.) Schott. D'una banda és va avaluar tecnològicament l'efecte de la combinació d'enzims, hidrocol·loides, midó de creïlla, farina pregelatinitzada sobre la farina dels cormelos de la Colocasia esculenta (L.) Schott en el desenvolupament d'un pa sense gluten. D'altra banda, es van avaluar les propietats tecnològiques i digestives d'una fórmula bàsica per a puré desenvolupada a partir de farina de cormelos de Xanthosoma spp. i Colocasia spp. que es pot destinar a poblacions vulnerables amb afeccions gastrointestinals, diabètics, celíacs, entre altres. A més, es va realitzar una revisió on s'exposen els efectes saludables demostrats clínicament, dels seus components. Es va demostrar que existeixen diferències significatives entre el midó de corms i cormelos de la mateixa espècie. Per tant, es va concloure que la farina dels cormelos de la Colocasia esculenta (L.) Schott és una bona opció per a incrementar el valor nutricional dels pans sense glútens i entre les estratègies provades, el pa elaborat a partir de la mescla amb midó de creïlla va resultar la menys aconsellable, però tots van mostrar menor índex glucèmic que els seus homòlegs sense glútens reportats en altres estudis. A més, per primera vegada es va recomanar l'ús de farina cormelos de Xanthosoma sagittifolium (L.) Schott i Colocasia esculenta (L.) Schott per a desenvolupar purés amb un valor nutricional agregat. La revisió bibilogràfica realitza va permetre recopilar el efectes demostrats clínicament, en concret antihiperglucémic, antihepatotóxic, antihipertensiu, hipoglucemiant, anticancerós, hipolipidémic i prebiòtic, entre altres, dels compostos bioactius presents en aquest rizoma. / [EN] The use of Colocasia esculenta (L.) Schott and Xanthosoma sagittifolium (L.) Schott as a raw material in form of starch or flour is a nutritious and sustainable alternative to wheat and other grains. This alternative allows farmers to minimize losses after harvest and guarantee food safety since its nutritional, digestive and healthy properties are recognized by the scientific community. Nevertheless, there is still scarce information about these rhizomes that limit their application. This thesis illuminates the functional and technological characterization of the starches obtained from corms and cormels of Xanthosoma sagittifolium (L.) Schott. Likewise, the effect of the combination of enzymes, hydrocolloids, potato starch, pregelatinized flour on Colocasia esculenta (L.) Schott cormels flour toward the development of a gluten-free bread was technologically evaluated. Furthermore, the technological and digestive properties of a basic formula for pastes developed from cormels flour of Xanthosoma sagittifolium (L.) Schott and Colocasia esculenta (L.) Schott was evaluated. In addition, a review was conducted and the health effects clinically demonstrated are exposed. It was shown that there are significant differences between the starch of corms and cormels of the same species. It was concluded that the flour from Colocasia esculenta (L.) Schott cormels is a good option to increase the nutritional value of gluten-free breads. Among the strategies tested, the bread made from mixtures with potato starch was the least desirable, but all strategies tested gave breads with lower glycemic index than gluten-free counterparts reported in other studies. For the first time, this works recommends the use of cormels flour from Xanthosoma sagittifolium (L.) Schott and Colocasia esculenta (L.) Schott was recommended to develop pastes to nutritional value to gluten-free products. In addition, the bibliographic review carried out allowed the compilation and analysis of the clinically demonstrated effects, especifically, antihyperglycemic, antihepatotoxic, antihypertensive, hypoglycemic, anti-cancer, hypolipidemic and prebiotic effects, among others, of the bioactive compounds present in these plants. / Authors acknowledge the financial support of the Spanish Ministry of Science, Innovation and Universities (RTI2018-095919-B-C21), Spanish Ministry of Economy and Competitiveness (Project AGL2014-52928-C2-1-R), the European Regional Development Fund (FEDER) and Generalitat Valenciana (Project Prometeo 2017/189). Tropical Food Research Institute from Cuba provided the rhizomes. / Calle Domínguez, J. (2021). Properties of Malanga Flours and their Use in Pastes and Gluten Free Breads [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/168396 / Compendio