Antibacterial Prenylated Acylphloroglucinols from the Fern Elaphoglossum yungense

Seven new prenylated acylphloroglucinols, yungensins A−G, were isolated from the diethyl ether extract of the scaly rhizomes and roots of an Argentine collection of the fern Elaphoglossum yungense. All the compounds contained a geranyl group attached to the filicinic acid-type residue. The diethyl ether extract and yungensins A−F displayed antibacterial effects against Staphylococcus aureus and Pseudomonas aeruginosa with MICs ranging from 10 to 200 μg/mL. All tested acylphloroglucinols, except for yungensin D, caused bacteriolysis of S. aureus at MBC or higher doses (50−200 μg/mL). At 10 μg/mL, the ether extract as well as yungensins A, B, and D−F altered the biofilm production in both microoganisms.