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Estudos da biossíntese das piranocumarinas xantiletina e seselina em laranja pêra (Citrus sinensis (L.) Osbeck) e limão cravo (Citrus limonia Osbeck)
(Universidade Federal de São Carlos, 2017-04-06) Amaral, Jéssica Cristina; Silva, Maria Fátima das Graças Fernandes da; https://lattes.cnpq.br/0457632122660653; https://lattes.cnpq.br/6610572791860659
The present work describes the study of biosynthesis of pyranocoumarins in Citrus sinensis and Citrus limonia. Coumarins, like other phenylpropanoids, have biosynthetic origin in p-hydroxy cinnamic acid and their great structural diversity is mainly due to the incorporation of prenyl units in the benzene ring. To obtain answers on the prenylation reaction, isotopic labeling experiments were performed to confirm the biosynthesis of pyranocoumarins. To verify if the isopentyl diphosphate (IPP) unit used in the prenylation of umbelliferone in C-6 and C-8, leading to the linear and angular pyranocumarins respectively, comes from the mevalonate (MEV) pathway via 2-C-methyl-D-erythritol- 4-phosphate (MEP), or mixed route; the biosynthesis of the terpene portion of xanthyletin and seselin was investigated by the incorporation of glucose-1 [¹³C] into C. sinensis and C. limonia. For the confirmation of the biosynthetic route, the enrichment pattern was determined by comparing the quantitative ¹³C NMR spectra of xanthyletin and seselin isolated from the C. sinensis and C. limonia root cultured in MS basal medium with 100% glucose and of a second experiment with 75% glucose-1 [¹³C]. The results showed that the isoprene portion derives exclusively from the MEP pathway, because only the C-1 and C-5 carbons of the IPP unit, for both C. sinensis and C. limonia xanthyletin and C. limonia seselin were enriched. By analyzing the chemical profile of the plant parts, the presence of the pyranocoumarins was observed only in the roots of both species, indicating that the biosynthesis of the same occurs in the citrus roots. It was also carried out the quantification of pyranocoumarins in roots, to determine a genotype that presented higher production of this class of compounds. In the quantification of pyranocoumarins in the 12 genotypes of C. sinensis and C. limonia grown in vitro in MS basal medium, it was observed that there is a significant decrease in the production of these substances among the genotypes of each of the evaluated species and that the concentration of these compounds in C. limonia is 158,35% higher than in C. sinensis.
Reações cíclicas de oxidação e redução de materiais a base de Ni para geração de hidrogênio
(Universidade Federal de São Carlos, 2017-04-06) Corrêa, João Vítor Soares; Santos, João Batista Oliveira dos; https://lattes.cnpq.br/0285313473901330; https://lattes.cnpq.br/8578196889928435
Hydrogen (H2) is used in several industrial processes, including ammonia production and petroleum refining. Commercially, most of the H2 produced is from methane steam reforming. Although well established industrially, methane steam reforming requires high energy demand and has problems of catalyst deactivation. As an alternative, this work presents the methane conversion to H2 through chemical looping reactions. This process consists in reacting a metal oxide (MeO) with methane (reducing agent) producing CO and H2 in the gas phase and reduced metal (Me) in the solid phase. Then, regeneration of the Mel is carried out with an oxidizing agent (air, for example), again producing MeO. To make this technology viable, the development of oxygen transporting materials that present high activity, selectivity and stability in the two reaction stages is essential. In this work, Ni/NiO based materials supported on different metal oxides were synthesized. The materials were prepared by wet impregnation and characterized by thermogravimetry, X-ray diffraction, programmed temperature reduction, surface area (BET method), pore volume and transmission electron microscopy. Reactive tests were carried out using methane as reducing agent and oxygen as oxidizing agent. In general, the materials showed activity in both stages of reaction and it was verified that the support exerts influence in the behavior of the formation of the products and the characteristics of Ni/NiO particles.