RESUMO
The aim of the present study was to investigate the antioxidant activity of aqueous extracts of Toona sinensis (TS; 0-100 microg/mL) and gallic acid (0-50 microg/mL), with the purified natural phenolic components evaluated using different antioxidant models. It was found that the TS extracts and gallic acid possess effective antioxidant activity against various oxidative systems in vitro, including the scavenging of free and superoxide anion radicals, reducing power, and metal chelation. However, antioxidant activity in terms of metal chelation was not observed for the gallic acid. Moreover, TS extracts and gallic acid appear to possess powerful antioxidant properties with respect to oxidative modification of human LDL induced by CuSO4, AAPH or sodium nitroprusside, as assessed by the relative electrophoretic mobility, TBARS formation, and cholesterol degradation of oxidized LDL. Furthermore, AAPH-induced oxidative hemolysis, lipid peroxidation, and decline in superoxide dismutase (SOD) activity in human erythrocytes were prevented by both the TS extracts and the gallic acid. Our findings suggest that T. sinensis may act as a chemopreventative agent, providing antioxidant properties and offering effective protection from atherogenesis.
Assuntos
Antioxidantes/farmacologia , Meliaceae/química , Animais , Antioxidantes/química , Compostos de Bifenilo , Quelantes/química , LDL-Colesterol/química , Sulfato de Cobre/química , Ensaio de Desvio de Mobilidade Eletroforética , Eritrócitos/efeitos dos fármacos , Sequestradores de Radicais Livres/química , Ácido Gálico/farmacologia , Hemólise/efeitos dos fármacos , Técnicas In Vitro , Peroxidação de Lipídeos/efeitos dos fármacos , Nitroprussiato/química , Oxirredução , Picratos/química , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Folhas de Planta/química , Superóxidos/química , Substâncias Reativas com Ácido Tiobarbitúrico/químicaRESUMO
Toona sinensis (T. sinensis), well known in Taiwan as a traditional Chinese medicine, has been shown to exhibit antioxidant effects. In this study, therefore, the ability of T. sinensis to induce apoptosis was studied in cultured human premyelocytic leukemia HL-60 cells. Treatment of the HL-60 cells with a variety of concentrations of the aqueous extracts of T. sinensis (TS extracts) (10-75 microg/ml) and gallic acid (5-10 microg/ml), the natural phenolic components purified from TS extracts, resulted in dose- and time-dependent sequences of events marked by apoptosis, as shown by loss of cell viability and internucleosomal DNA fragmentation. Furthermore, apoptosis in the HL-60 cells was accompanied by the release of cytochrome c, caspase 3 activation and specific proteolytic cleavage of poly (ADP-ribose) polymerase (PARP). This increase in TS extracts- and gallic acid-induced apoptosis was also associated with a reduction in the levels of Bcl-2, a potent cell-death inhibitor, and an increase in those of the Bax protein, which heterodimerizes with and thereby inhibits Bcl-2. Interestingly, TS extracts- and gallic acid-induced dose-dependent reactive oxygen species (ROS) generation in HL-60 cells. We found that catalase significantly decreased TS extracts- or gallic acid-induced cytotoxicity, DNA fragmentation, and ROS production, however, slight reduction was observed with vitamins C and E. Our results indicate that TS extracts- or gallic acid-induced HL-60 apoptotic cell death could be due to the generation of ROS, especially H(2)O(2). The data suggest that T. sinensis exerts antiproliferative action and growth inhibition on HL-60 cells through apoptosis induction, and, therefore, that it may have anticancer properties valuable for application in food and drug products.