[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.

Antibacterial Biphenanthrenes from the Fibrous Roots of Bletilla striata.

Four new 9',10'-dihydro-biphenanthrenes, including an unprecedented 1,2'-linked biphenanthrene, 4,7,3',5'-tetramethoxy-9',10'-dihydro(1,2'-biphenanthrene)-2,7'-diol (1), a new 1,3'-linked biphenanthrene, 4,7,7'-trimethoxy-9',10'-dihydro(1,3'-biphenanthrene)-2,2',5'-triol (2), and two new 1,1'-linked biphenanthrenes, 4,7,4'-trimethoxy-9',10'-dihydro(1,1'-biphenanthrene)-2,2',7'-triol (3) and 4,7,3',5'-tetramethoxy-9',10'-dihydro(1,1'-biphenanthrene)-2,2',7'-triol (4), as well as two known biphenanthrenes (5, 6), were isolated from a 95% ethanol extract of the fibrous roots of Bletilla striata. Their structures were determined by spectroscopic and spectrometric methods. Atropisomerism of these compounds was considered based on their chiral optical properties and potential energy surface scans at the ab initio HF/3-21G level, which revealed their racemic mixture form. Compounds 2-6 showed potent antibacterial activities against six Gram-positive bacterial strains.