This research aims to search for new potent antibacterial agents. Seventeen compounds including one compound from commercial source, eight compounds isolated from plants, two synthetic compounds and six compounds from natural products research unit were collected and tested for antibacterial activity. All isolated and synthesized compounds were elucidated by 1H NMR spectroscopy. Seven compounds namely 6,8- dibromochrysin, 6,8- diiodochrysin, α- mangostin, mansonone G, allyl ether mansonone G, anacardic acid and usnic acid displayed excellent antibacterial activity against Staphylococcus aureus, Streptococcus mutans and Streptococcus sobrinus with MIC of 0. 98- 125 μM. In addition, in combination with antibiotic tetracycline, 6,8- dibromochrysin and 6,8- diiodochrysin exhibited potent synergistic effect, 8-fold increase of tetracycline, against S. aureus. Furthermore, three compounds namely α- mangostin, mansonone G and usnic acid revealed potent antibacterial activity against methicillin-resistant S. aureus (MRSA) with MIC 7.81-125 μM.
