RESUMO
The anti-peroxyl radical quality of two aqueous rooibos infusions and solutions of their most abundant glycosylated polyphenols was evaluated using pyrogallol red and fluorescein-based oxygen radical absorbance ratios. It was observed that the artificial infusions, prepared using only the most abundant polyphenols present in rooibos and at concentrations similar to those found in the natural infusions, showed greater antioxidant quality than the latter infusions, reaching values close to those reported for tea infusions. Additionally, the antimicrobial activity of the natural and artificial infusions was assessed against three species of bacteria: Gram (+) Staphylococus epidermidis and Staphylococcus aureus and Gram (-) Escherichia coli. When compared to the natural infusions the artificial beverages did not demonstrate any bacterostatic/cidal activity, suggesting that the antibacterial activity of rooibos is related to compounds other than the glycosylated polyphenols employed in our study.
Assuntos
Antibacterianos/química , Aspalathus/química , Flavonoides/química , Sequestradores de Radicais Livres/química , Glucosídeos/química , Extratos Vegetais/química , Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Apigenina/química , Apigenina/isolamento & purificação , Apigenina/farmacologia , Bebidas , Chalconas/química , Chalconas/isolamento & purificação , Chalconas/farmacologia , Escherichia coli/efeitos dos fármacos , Flavonoides/isolamento & purificação , Flavonoides/farmacologia , Sequestradores de Radicais Livres/isolamento & purificação , Sequestradores de Radicais Livres/farmacologia , Glucosídeos/isolamento & purificação , Glucosídeos/farmacologia , Testes de Sensibilidade Microbiana , Peróxidos , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/farmacologia , Polifenóis/química , Polifenóis/isolamento & purificação , Polifenóis/farmacologia , Quercetina/análogos & derivados , Quercetina/química , Quercetina/isolamento & purificação , Quercetina/farmacologia , Rutina/química , Rutina/isolamento & purificação , Rutina/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus epidermidis/efeitos dos fármacosRESUMO
Syntheses of the C-glycosyl flavone natural products aspalathin and nothofagin have been accomplished in eight steps from tribenzyl glucal, tribenzylphloroglucinol, and either 4-(benzyloxy)phenylacetylene or 3,4-bis(benzyloxy)phenylacetylene. The key step of the syntheses involves a highly stereoselective Lewis acid promoted coupling of 1,2-di-O-acyl-3,4,6-tribenzylglucose with tribenzylphloroglucinol, which gives rise to the corresponding beta-C-aryl glycoside in 30-65% yields.