Combretumlignan, a new cyclolignan and others constituents with antibacterial activity from <i>Combretum zenkeri</i> (combretaceae)

A previously undescribed cyclolignan, named Combretumlignan <b>1</b>, was isolated from the methanolic extract of the twigs of <i>Combretum zenkeri</i> together with fifteen known compounds. Their structures were determined by a comprehensive analysis of their spectroscopic data in comparison with those published in the literature. The extract, fractions and compounds <b>1</b>, <b>4</b> and <b>5</b> were evaluated against six Gram-negative and one Gram-positive bacteria strains. The methanol crude extract of twigs of this plant showed good antibacterial activities with MIC values of 31.2 and 62.5 <i>μ</i>g/mL against <i>Staphylococcus aureus</i> and <i>Salmonella enterica</i> respectively. The ethyl acetate fraction showed strong antibacterial activity (MIC = 7.8 μg/mL) against <i>Salmonella typhimurium</i> 19430 while the crude extract and the <i>n</i>-hexane fraction exhibited significant activity (MIC = 31.2 μg/mL) against <i>Staphylococcus aureus</i> 12600 for crude extract, and against <i>Salmonella typhimuriummurium</i> 19430 and <i>Pseudomonas aeruginosa</i> HM801 for the <i>n</i>-hexane fraction. All the tested compounds inhibited the growth of the seven bacterial strains tested with MICs ranging from 3.9─125 µg/mL. Hexadecyl ferulate <b>5</b> displayed the best activity with a MIC value of 3.9 μg/mL against <i>Salmonella typhimurium 19430</i>. Compound <b>1</b> showed moderate activity against <i>Salmonella typhimurium 19430 and Escherichia coli</i> with MIC values of 62.5 μg/mL and 31.2 µg/mL, respectively.