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Abstract(s)
A própolis é uma substância resinosa recolhida pelas abelhas Apis mellifera em diversas fontes vegetais, e utilizada na colmeia para selar as paredes, para fortalecer as extremidades dos favos ou para embalsamar invasores mortos. A especificidade química da própolis é determinada diretamente pela variabilidade das origens vegetais, e também pelas características geográficas e climáticas do local de proveniência. A própolis de regiões tropicais, em particular a própolis de origem Brasileira, é objeto de muitos estudos científicos devido à sua atividade biológica elevada. Em termos comerciais, a própolis verde, predominante no sudeste Brasileiro, é a mais importante, com uma composição rica em derivados prenilados do ácido p-cumárico, como a artepilina C e ácidos cafeoilquínicos. Estas substâncias estão associadas aos rebentos da planta alecrim-do-campo, Baccharis dracunculifolia.
Este trabalho teve como objetivo a identificação e a quantificação de compostos fenólicos em dezassete amostras de própolis proveniente do sul e sudeste do Brasil e a avaliação da atividade antioxidante por técnicas espectroscópicas e eletroquímicas. Desta forma, foi caracterizada a cor das amostras, pela determinação dos parâmetros CIELAB. Avaliou-se o conteúdo em fenóis totais, flavonas/flavonóis e flavanonas/di-hidroflavonóis por métodos espetrofotométricos. O perfil fenólico e a sua quantificação foi efetuada por cromatografia líquida acoplada a espectrometria de massa (LC-MS) e por cromatografia líquida de alto desempenho com um detetor diode-array (HPLC-DAD). Para avaliar a atividade antioxidante dos extratos foram realizados ensaios da capacidade captadora de radicais livres (DPPH) e avaliação do poder redutor bem como a avaliação do total de compostos electroativos por voltametria de impulso diferencial (DPV). Assim, foi possível determinar dois tipos de própolis através do seu perfil cromatográfico e espectroscópico, um do tipo verde, com origem nos rebentos de Baccharis dracunculifolia, em que os compostos maioritários foram o ácido dicafeoilquínico e o seu isómero, assim como a artepilina C, e o outro com uma composição fenólica similar ao própolis de choupo, presente em apenas uma das amostra (RGS3) e com uma composição rica em pinocembrina, crisina e acetato de 3-O-pinobanksina. As amostras que obtiveram uma maior atividade antioxidante, pertencem à região de Minas Gerais, com níveis de 0.02mg/mL para o DPPH, 0.99 g/g de extrato para o poder redutor e 0.60 mg/mL para a atividade antioxidante avaliadas para as técnicas eletroquimicas.
Propolis is a resinous substance collected by honeybees Apis mellifera in several plant sources and used in the hive to seal the walls, to strengthen the ends of the honeycomb or embalming dead invaders. The chemical specificity of propolis is directly determined by the variability of the plant origins and by geographical and climatic features of the origin site. Propolis from tropical regions, in particular propolis from Brazil, is the subject of many scientific studies due to its high biological activity. In commercial terms, green propolis, predominant in southeast Brazil, is the most important, with a composition rich in caffeoylquinic acids, prenylated p-coumaric acid derivatives, such as artepillin C. These substances are associated with plant shoots of rosemary-of-field, Baccharis dracunculifolia. The aim of this work was the identification and quantification of phenolic compounds in propolis samples from seventeen southern and southeastern Brazil and the evaluation of the antioxidant activity by electrochemical and spectroscopic techniques. Thus, the color of the samples was determined through the evaluation of the CIELAB parameters. Also, the total phenolic content, flavones/flavonols and flavanones/dihydroflavonols were determined by spectrophotometric methods. The study of the phenolic profile and its quantification was achieved by liquid chromatography coupled with mass spectrometry (LC-MS) and high-pressure liquid chromatography with diode-array detection (HPLC-DAD) respectively. To evaluate the antioxidant activity, DPPH free radical-scavenging activity assay, reducing power assay and the evaluation of the total electroactive species by differential pulse voltammetry were performed. Two types of propolis were identified by its chromatographic and spectroscopic profile, a green type, with floral origin in Baccharis dracunculifolia, with dicaffeoylquinic acid and its isomer, as well as artepillin C were the major compounds, and the other with a phenolic profile similar to poplar propolis, present in only one sample (RGS3) and with a composition rich in pinocembrin, chrysin and pinobanksin-3-O-acetate. The samples with a higher antioxidant activity belong to the region of Minas Gerais, with levels between 0.02mg/mL for DPPH, 0.99 g/g of extract for reducing power and 0.60 mg/mL for the antioxidant activity evaluated by electrochemical techniques.
Propolis is a resinous substance collected by honeybees Apis mellifera in several plant sources and used in the hive to seal the walls, to strengthen the ends of the honeycomb or embalming dead invaders. The chemical specificity of propolis is directly determined by the variability of the plant origins and by geographical and climatic features of the origin site. Propolis from tropical regions, in particular propolis from Brazil, is the subject of many scientific studies due to its high biological activity. In commercial terms, green propolis, predominant in southeast Brazil, is the most important, with a composition rich in caffeoylquinic acids, prenylated p-coumaric acid derivatives, such as artepillin C. These substances are associated with plant shoots of rosemary-of-field, Baccharis dracunculifolia. The aim of this work was the identification and quantification of phenolic compounds in propolis samples from seventeen southern and southeastern Brazil and the evaluation of the antioxidant activity by electrochemical and spectroscopic techniques. Thus, the color of the samples was determined through the evaluation of the CIELAB parameters. Also, the total phenolic content, flavones/flavonols and flavanones/dihydroflavonols were determined by spectrophotometric methods. The study of the phenolic profile and its quantification was achieved by liquid chromatography coupled with mass spectrometry (LC-MS) and high-pressure liquid chromatography with diode-array detection (HPLC-DAD) respectively. To evaluate the antioxidant activity, DPPH free radical-scavenging activity assay, reducing power assay and the evaluation of the total electroactive species by differential pulse voltammetry were performed. Two types of propolis were identified by its chromatographic and spectroscopic profile, a green type, with floral origin in Baccharis dracunculifolia, with dicaffeoylquinic acid and its isomer, as well as artepillin C were the major compounds, and the other with a phenolic profile similar to poplar propolis, present in only one sample (RGS3) and with a composition rich in pinocembrin, chrysin and pinobanksin-3-O-acetate. The samples with a higher antioxidant activity belong to the region of Minas Gerais, with levels between 0.02mg/mL for DPPH, 0.99 g/g of extract for reducing power and 0.60 mg/mL for the antioxidant activity evaluated by electrochemical techniques.
Description
Mestrado em cooperação com a Universidade de Salamanca