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Pesquisa de actividade inibitória do enzima acetilcolinesterase em extratos aquosos de várias plantas usadas como infusões:identificação de compostos com maior actividade inibitória
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Neste trabalho foram estudados onze extractos aquosos de infusões de doze plantas usadas na medicina tradicional portuguesa e angolana. Assim sendo, foram usadas infusões das seguintes plantas: Citrus x sinensis L. (flor de laranjeira), Equisetum arvense L.(cavalinha), Ginkgo biloba L., Mentha x piperita L. (hortela-pimenta), Lippia sp. (N'dembi), Pterospartum tridentatum L. (carqueja), Persea americana Mill. (abacateiro), Petroselinum crispum L. (salsa), Tabebuia avellanedeae Mill (pau de arco), Zea mays L. (barba de milho) e, ainda, uma mistura constituida pelas espécies Eucaliptus glóbulus L. e Pinus pinaster Ait (Eucalipto e Pinheiro). Determinou-se a actividade inibitória daqueles extractos sobre o enzima acetilcolinesterase através do método de Ellman e calculou-se o valor da concentração de extracto que origina uma inibição da actividade enzimática em 50% (IC50). Dos extractos estudados, as infusões de Lippia sp. (N'dembi) e de Ginkgo biloba L. apresentaram uma maior percentagem de inibição com valores de IC50 de 0,18±0,02 mg/mL e de 0,25±0,02 mg/mL, respectivamente. A actividade antioxidante das diferentes infusões estudadas foi determinada através do método do DPPH. Para tal, calculou-se o valor da concentração de extracto responsável pela extinção do radical em cerca de 50%, (EC50). O melhor resultado foi obtido com o extracto de Ginkgo biloba, o qual apresentou um valor de EC50 de 2,6}0,3 mg/mL. Quantificou-se os fenóis totais usando o reagente de Folin-Ciocalteu, tendo sido usado como padrão: o pirogalol. Os resultados demonstraram a presençaa de fenóis em todos extractos das plantas estudadas. Os melhores resultados foram obtidos com a Ginkgo biloba (315 µg/mg de extracto) e a Pterospartum tridentatum (307 µg/mg de extracto) e foram expressos em equivalente de pirogalol/mg de extracto. A identificação dos compostos bioactivos, responsáveis pela inibição do enzima acetilcolinesterase, foi feita apenas nos extractos de Ginkgo biloba e Lippia sp., uma vez que estes apresentaram valores de IC50 superiores aos dos restantes extractos estudados. Para a pesquisa dos compostos naqueles extractos recorreu-se às técnicas de HPLC-RP-DAD. Os cromatogramas e os espectros obtidos na região da radiação UV foram comparados com os de diversos padrões, o que permitiu concluir que para o Lippia sp. contém um derivado do ácido cafeíco, ácido rosmarínico e rutina. Para a Ginkgo biloba os picos detectados correspondem a estrutura de flavonóides ou compostos semelhantes como e o caso da epigalocatequina, que foi identificada por MS. Simulou-se in vitro a degradação do extracto aquoso da Ginkgo biloba pelo tracto gastrointestinal usando-se uma solução de suco gástrico e pancreático artificial. Verificou-se que em ambas os casos ocorreu a degradação dos compostos, tendo esta sido mais acentuada pelo suco pancreático
The aim of this work was to study eleven extracts of infusions of twelve plants usually used in traditional medicine of Portugal and Angola. The plants studied were Citrus x sinensis L., Equisetum arvense L., Ginkgo biloba L., Mentha x piperita L., Lippia sp., Pterospartum tridentatum L., Persea americana Mill., Petroselinum crispum L., Tabebuia avellanedeae Mill, Zea mays L., and also a misture of the species Eucaliptus glóbulus L. e Pinus pinaster Ait. The extracts ability to inhibit acetylcholinesterase activity was evaluated using Ellman's method. The concentration of extract which inhibits acetylcholinesterase activity in 50 % (IC50) was determined. The infusions of Lippia sp. and Ginkgo biloba L. were the most efficient, with IC50 of 0.18±0.02 mg/mL and 0.25±0.02 mg/mL, respectively. The antioxidant activity of the different extracts used in this study was investigated using DPHH method. The concentration of extract which extinct DPHH activity in 50 % (EC50) was determined. The extract of Ginkgo biloba L. revealed to be the most efficient, presenting an EC50 value of 2.6}0.3 mg/mL. The total quantity of phenols was determined using the Folin-Ciocalteu reagent and the standard reagent used was pirogalol. These experiences showed the presence of phenols in the eleven extracts studied. The extracts of Ginkgo biloba L. and Pterospartum tridentatum revealed to be the most efficient of all with 315 µg/mg of extract and 315 µg/mg of extract, respectively. The results were expressed in equivalents of pirogalol/mg of extract. The identification of the bioactive compounds which are responsible for the inhibition of acetylcholinesterase activity was done, only, with the extracts of Ginkgo biloba and of Lippia sp. once they exhibit the highest values of IC50. To investigate which compounds were present in these two extracts HPLC-RP-DAD techniques were used. Chromatograms and spectra obtained in the presence of UV radiation were compared with those of various compounds used as standards. So, it can be concluded that Lippia sp. is composed by one compound derivate from caffeic acid, rosmarinic acid and rutine. Otherwise, Ginkgo biloba peaks suggest the presence of flavonoids or similar compounds, such as epigalocatechin which was identified by MS. The degradation of aqueous extract of Ginkgo biloba by gastrointestinal tract was simulated using solutions of gastric and artificial pancreatic juice. It was observed that, in both cases, that compound degradation occurred, although that was higher in the presence of pancreatic juice
The aim of this work was to study eleven extracts of infusions of twelve plants usually used in traditional medicine of Portugal and Angola. The plants studied were Citrus x sinensis L., Equisetum arvense L., Ginkgo biloba L., Mentha x piperita L., Lippia sp., Pterospartum tridentatum L., Persea americana Mill., Petroselinum crispum L., Tabebuia avellanedeae Mill, Zea mays L., and also a misture of the species Eucaliptus glóbulus L. e Pinus pinaster Ait. The extracts ability to inhibit acetylcholinesterase activity was evaluated using Ellman's method. The concentration of extract which inhibits acetylcholinesterase activity in 50 % (IC50) was determined. The infusions of Lippia sp. and Ginkgo biloba L. were the most efficient, with IC50 of 0.18±0.02 mg/mL and 0.25±0.02 mg/mL, respectively. The antioxidant activity of the different extracts used in this study was investigated using DPHH method. The concentration of extract which extinct DPHH activity in 50 % (EC50) was determined. The extract of Ginkgo biloba L. revealed to be the most efficient, presenting an EC50 value of 2.6}0.3 mg/mL. The total quantity of phenols was determined using the Folin-Ciocalteu reagent and the standard reagent used was pirogalol. These experiences showed the presence of phenols in the eleven extracts studied. The extracts of Ginkgo biloba L. and Pterospartum tridentatum revealed to be the most efficient of all with 315 µg/mg of extract and 315 µg/mg of extract, respectively. The results were expressed in equivalents of pirogalol/mg of extract. The identification of the bioactive compounds which are responsible for the inhibition of acetylcholinesterase activity was done, only, with the extracts of Ginkgo biloba and of Lippia sp. once they exhibit the highest values of IC50. To investigate which compounds were present in these two extracts HPLC-RP-DAD techniques were used. Chromatograms and spectra obtained in the presence of UV radiation were compared with those of various compounds used as standards. So, it can be concluded that Lippia sp. is composed by one compound derivate from caffeic acid, rosmarinic acid and rutine. Otherwise, Ginkgo biloba peaks suggest the presence of flavonoids or similar compounds, such as epigalocatechin which was identified by MS. The degradation of aqueous extract of Ginkgo biloba by gastrointestinal tract was simulated using solutions of gastric and artificial pancreatic juice. It was observed that, in both cases, that compound degradation occurred, although that was higher in the presence of pancreatic juice
Descrição
Tese de mestrado, Bioquimica, 2008, Faculdade de Ciências, Universidade de Lisboa
Palavras-chave
Bioquímica Teses de mestrado