Análise de folatos em hortaliças folhosas por cromatografia líquida de alta eficiência, com detecção por fluorescência

• Ano de defesa: 2009
• Autor(a) principal: Della Lucia, Ceres Mattos
• Orientador(a): Sant ana, Helena Maria Pinheiro
• Banca de defesa: Chaves, José Benício Paes , Martino, Hércia Stampini Duarte
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Ciência da Nutrição
• Departamento: Valor nutricional de alimentos e de dietas; Nutrição nas enfermidades agudas e crônicas não transmis
• País: BR
• Palavras-chave em Português: Hortaliças; Cromatografia líquida de alta eficiência; Vitaminas
• Palavras-chave em Inglês: Vegetables; High performance liquid chromatography; Vitamin
• Área do conhecimento CNPq: CNPQ::CIENCIAS DA SAUDE::NUTRICAO
• Link de acesso: http://locus.ufv.br/handle/123456789/2714

The low intake of folate has been identified as a possible cause of serious diseases that affect man, such as heart disease, cancer and congenital malformations. Information in the literature about the concentration of folate in vegetables are rare and often contradictory, due to difficulties associated with analysis of this vitamin, which are related to its low stability, the presence in small concentrations in biological systems, complex procedures of extraction and variety of forms. This study aimed to optimize a methodology for determining the concentration of different natural forms of folate (tetrahydrofolate - THF, 5-methyl tetrahydrofolate - 5-MTHF and 5-formyl tetrahydrofolate - 5-FTHF) in vegetables of high consumption in Brazil and grown in Viçosa , MG (kale, spinach, mustard, flowers and sheets of broccoli). Also aimed to compare the concentrations of folate between two seasons (winter and spring) and assess its stability to various common culinary cooking practices (steam cooking, cooking on immersion in water and stir frying). The optimized method to prepare the vegetables consisted of homogenization in a buffer system (0.1 M phosphate buffer, pH 6.0), followed by heating and centrifugation, and enzymatic deconjugation of poliglutamate to monoglutamate using conjugase from rat plasma. After the stage of extraction, the extract containing the monoglutamate was purified using ion exchange column. The folate analysis was carried out by high performance liquid chromatography (HPLC) using gradient elution and mobile phase consisting of acetonitrile and phosphate buffer (30 mM, pH adjusted to 2.3 with phosphoric acid). We used a completely randomized design with two seasons (winter and spring), five vegetables and four replications in each season. Analysis of variance (α = 5%) was used to determine differences between the two seasons. To check differences between the concentration of compounds in raw and cooked vegetables it was applied the paired t test, at 5% level of probability, and the vegetables compared two by two (vegetable raw x vegetables cooked). For this analysis, we used eight replicates (four replicates in winter and four replicates in x spring). The average concentration of total folate was 549.67 ± 467.07 μg/100 g in kale; 754.57 ± 564.16 μg/100 g in flowers of broccoli; 731.51 ± 384.01 μg/100 g in leaves of broccoli, 241.04 ± 121.80 μg/100 g in spinach and 568.76 ± 383.20 μg/100 g in mustard. There were no significant differences in the concentration of folate in vegetables analyzed in winter and spring. 5-FTHF was found in greater quantity in vegetables studied, and the flowers of broccoli were considered the best source of this isomer. Spinach was vegetable that had the lowest concentrations. Stir frying preserved the concentration of the three isoforms of folate in kale, spinach and mustard. Furthermore, cooking under immersion in water was the method that less preserved the concentration of 5- FTHF and THF in flowers of broccoli (retention of 17.01% for THF and 57.68% for 5-FTHF). Steam cooking also was not effective in preserving THF in flowers of broccoli (41.83% retention). The optimized methodology showed to be reliable for the simultaneous determination of three major forms of folate (THF, 5-MTHF and 5-FTHF) in raw and cooked leafy vegetables. The stability of folate was strongly dependent on the kind of vegetable, the method of cooking and the isomeric form. All the vegetables were considered good sources of folate, and its consumption by the population should be encouraged.