Abstract:

In this study, petroleum ether-phase, ethyl acetate-phase and n-butanol-phase fractions of ethanol extract of sisal flower and polysaccharides extracted from the ethanol extraction residue were prepared and then their antioxidant activities were evaluated by measuring the scavenging rates to DPPH radical (DPPH·), hydroxyl radical (·OH) and superoxide anion radical (O2·) respectively . The results showed that the three fractions of ethanol extract all have certain activity to scavenge DPPH·, ·OH and O2· with dose-dependent manner. Furthermore, compared to the other two, the ethyl acetate-phase fraction of ethanol extract at the concentration of more than 600 μg/ml presents the highest scavenging rate to DPPH·, which is much lower than that of TBHQ and BHT. At the concentration of not less than 64μg/ml, the ethyl acetate-phase fraction exhibits the highest ·OH scavenging rate, followed by the other two fractions having similar ·OH scavenging rate to TBHQ and BHT, and the polysaccharides in turn. At the concentration of 600 μg/ml, the n-butanol-phase fraction exhibits the highest O2· scavenging rate, which is much lower than that of TBHQ and BHT, while the O2· scavenging rate of the polysaccharides is significantly lower than that of the three fractions of    ethanol extract.

Key words: sisal flower, extract, antioxidation, radical scavenging rate