Antioxidant activity and free radical-scavenging capacity of extracts from guava (Psidium guajava L.) leaves

The objectives of this study were to study the antioxidant activity and free radical-scavenging effects of extracts from guava leaves and dried fruit. The results indicated that 94.4–96.2% of linoleic acid oxidation was inhibited by the addition of guava leaf and guava tea extracts at a concentration of 100 μg/ml. The guava dried fruit extracts exhibited weaker antioxidant effects than did the leaf extracts. The results also demonstrated that the scavenging effects of guava leaf extracts on ABTS+ radicals and superoxide anion increased with increasing concentrations. The guava leaf extracts displayed a significant scavenging ability on the peroxyl radicals. However, the scavenging effects were decreased when the extract concentration was greater than 10 μg/ml. The extracts from leaves of various guava cultivars exhibited more scavenging effects on free radicals than did commercial guava tea extracts and dried fruit extracts. The chromatogram data indicated that guava extracts contained phenolic acids, such as ferulic acid, which appeared to be responsible for their antioxidant activity. Correlation analysis indicated that there was a linear relationship between antioxidant potency, free radical-scavenging ability and the content of phenolic compounds of guava leaf extracts.