Flavones and Their Biological Activities from the Leaves of Callistemon salignus

The chemical constituents from Callistemon salignus were isolated and purified by silica gel and Sephadex LH-20 column chromatographies. Their structures were elucidated on the basis of spectral data and physicochemical property analyses. The antioxidant and antimicrobial activities of isolates were also evaluated. Two flavones were obtained from C.salignus and their structures were identified as 5-hydroxy-6, 8-dimethy-7, 4′-dimethoxy flavone and 5-hydroxy-6-methyl-7, 4′-dimethoxyflavone. The last two exhibited significant antioxidant with IC₅₀=20.0 μg/mL, and the antibacterial activity against Escherichia coli (ATCC 25922) with MIC=62.5 μg/mL.