New Antimicrobial Cycloartane Triterpenes from Acalypha communis

Three new cycloartane-type triterpenes, 16α-hydroxymollic (1), 15α-hydroxymollic (2), and 7β,16β-dihydroxy-1,23-dideoxyjessic acids (3), were isolated from the aerial parts of Acalypha communis. The structures of the novel triterpenes were determined by spectroscopic methods as well as chemical derivatization. These compounds were tested for their antimicrobial activity against Gram-positive and -negative bacteria. Compounds 1−3 exhibited moderate antimicrobial activity (MIC 8, 32, 8 μg/mL, respectively) against vancomycin-resistant enterococci. In addition, compound 1 was found to be active against methicillin-resistant staphylococci. In contrast, compounds 1−3 were poorly active against Gram-negative bacteria. Compound 3 was tested in an in vivo model; it did not provide protection to mice infected with Staphylococcus aureus.