RESUMO
Plants of the genera Werneria (Asteraceae) and Xenophyllum (genus extracted from Werneria) are used in traditional medicine of Latin America for the treatment of mountain sickness, hypertension and gastrointestinal disorders. Only a small number of species of these genera have been studied, leading to the isolation of compounds belonging to the classes of benzofurans, chromenes, acetophenones, coumarates, diterpenes and pyrrolizidine alkaloids. Some of the plant extracts and/or compounds have shown antimicrobial, anti-HIV, hypotensive and photoprotective activities.
Las plantas de los geÌneros Werneria (Asteraceae) y Xenophyllum (geÌnero extraido de Werneria) son usadas en la medicina tradicional de AmeÌrica Latina para el tratamiento del mal de montanÌa, hipertensioÌn y desoÌrdenes gastrointestinales. Solo un pequenÌo nuÌmero de especies de estos geÌneros ha sido investigado, lograÌndose aislar compuestos que pertenecen a las clases de benzofuranos, cromenos, acetofenonas, cumaratos, diterpenos y alcaloides pirrolizidiÌnicos. Algunos de los extractos y/o compuestos de dichas plantas han mostrado actividades antimicrobianas, anti-HIV, hipotensoras y fotoprotectoras.
Assuntos
Plantas Medicinais/química , Extratos Vegetais/uso terapêutico , Asteraceae/química , Acetofenonas/química , Terpenos/análise , Benzopiranos/química , Flavonoides/química , Ácido Clorogênico/química , Ácidos Cumáricos/química , Alcaloides/química , Doença da Altitude/tratamento farmacológico , Hipertensão/tratamento farmacológico , Medicina TradicionalRESUMO
The rates of oxidation of adenosine and chlorogenic acid by tert-butoxyl radicals (t-BuO-) were studied by measuring the absorbance of adenosine at 260 nm and chlorogenic acid at 328 nm spectrophotometrically. t-BuO- radicals were generated by the photolysis of tert-butyl hydroperoxide (t-BuOOH) in presence of tert-butyl alcohol to scavenge OH. radicals. The rates and the quantum yields() of oxidation of chlorogenic acid by t-BuO-radicals were determined in the absence and presence of varying concentrations of adenosine. An increase in the concentration of adenosine was found to decrease the rate of oxidation of chlorogenic acid, suggesting that adenosine and chlorogenic acid competed for t-BuO. radicals. From competition kinetics, the rate constant of chlorogenic acid reaction with t-BuO- was calculated to be 3.20 109 dm3 mol-1 s-1. The quantum yields (expt) were calculated from the experimentally determined rates of oxidation of chlorogenic acid under different experimental conditions. Assuming that chlorogenic acid acts as a scavenger of t-BuO- radicals only, the quantum yields (cal) were theoretically calculated. expt and cal values suggested that chlorogenic acid not only protected adenosine from t-BuO- radicals, but also repaired adenosine radicals, formed by the reaction of adenosine with t-BuO- radicals.