Antioxidant and antimicrobial activities of ethanol extract from the stem and leaf of Impatiens balsamina L. (Balsaminaceae) at different harvest times.

The aim of this study was to investigate the total phenolic content, total flavonoid contents, antioxidant activity and antimicrobial activity of ethanolic extract from stems (S) and leaves (L) of Impatiens balsamina L. (Balsaminaceae), which were harvested in Korea on March 10, 2011 (S1 and L1), May 14, 2011 (S2 and L2), and July 5, 2011 (S3 and L3), respectively. Our results revealed that the total phenolic (79.55-103.94 mg CE/g extract) and flavonoid (57.43-104.28 mg QE/g extract) contents of leaf extract were higher (p < 0.01) than those of stem extract. Leaf extracts (L1, L2, and L3) exhibited stronger (p < 0.01) free radical scavenging activity (66.06, 63.71, and 72.19%, respectively) than that of the positive control. In terms of antimicrobial activity, leaf extracts showed higher inhibitory effects against microorganisms than those of stem extracts (S1, S2, and S3). Among the leaf extracts at different harvest times, L3 showed the greatest antimicrobial activity against both Gram negative and Gram positive strains. From these results, the leaf extract from I. balsamina L. might be a valuable bioactive resource, and would seem to be applicable as a natural antioxidant in food preservation.