[Antibacterial Activity of Chemical Constituents Isolated from Fibrous Roots of Bletilla striata].

Objective: To investigate the chemical constituents isolated from the fibrous roots of Bletilla striata, and to research their antibacterial activities.

Methods: The native products were isolated and purified by silica gel, Sephadex LH-20 column chromatography and preparative HPLC. Their structures were elucidated on the basis of various spectroscopic analysis, and their antibacterial activities were tested by microbroth dilution method in a 96-well microtiter plate.

Results: Seven compounds were isolated from the ethanol extract of the fibrous roots of Bletilla striata, and identified as p-hydroxybenzaldehyde( 1),2,7-dihydroxy-4-methoxy-9,10-dihydrophenanthrene( 2),4,5-dihydroxy-2-methoxy-9,10-dihydrohenanthrpene( 3),2-dihydroxy-4,7-dimethoxyphenan-threne( 4), militarine( 5), dactylorhin A( 6) and gastrodin( 7). Among them, compounds 2 ~ 4 showed moderate antibacterial activities against several Gram-positive bacterial strains( MIC 8 ~ 128 μg / m L),such as Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis and Bacillus subtilis.

Conclusion: The fibrous roots and tubers of Bletilla striata contain similar compounds, including glucosyloxybenzyl 2-isobutylmalates,and phenanthrene compounds, which showed antimicrobial activities against Gram-positive bacterial strains. And compounds 3,4 are isolated from Bletilla genus for the first time.