Phenanthrenes from <i>Juncus articulatus</i> with Antibacterial and Biofilm Formation Inhibitory Activity

Continuing our search for bioactive compounds in species from the Juncaceae family, <i>Juncus articulatus</i> was investigated. Ten previously undescribed phenanthrenes─articulins A-J (<b>1</b>-<b>10</b>)─and ten known compounds─juncuenin B, dehydrojuncuenin B, juncatrin B, ensifolins E, F, H, I, K, juncuenin D, and luzulin A (<b>11</b>-<b>20</b>)─along with other compounds, have been isolated and identified. The isolated compounds were evaluated for antibacterial activity against <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, methicillin-susceptible <i>Staphylococcus aureus</i> (MSSA), and methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). Compounds <b>12</b> and <b>14</b> exhibited the most potent activity against planktonic and sessile MSSA and MRSA with minimum inhibitory concentration (MIC) values of 15.1 μM (<b>12</b> for both bacterial strains) and 15.3 μM (<b>14</b> for both bacterial strains). Compounds <b>15</b>, <b>17</b>, and <b>18</b> also exhibited activity against both strains, although to a lower extent, with MIC values ranging from 30.0 to 56.8 μM. The inhibition of biofilm formation of these compounds was observed at 15.1-114.3 μM. This study elucidates the phenanthrene composition of <i>J. articulatus</i> and the antibacterial effect of these compounds.