Three new alkyl substituted anthraquinone derivatives,trivially named as symploquinones A-C (Compounds 1-3) were isolated from Symplocos racemosa.The structures of these compounds were determined on the basis of extensive spectroscopic analyses (UV,IR,Mass,1H-and 13C-NMR,and two-dimensional (2D) NMR techniques).The resulting data were also compared with the reported literature.These compounds were then subjected to antibacterial or antibiofilm testing.Compounds 1 and 3 exhibited good antibacterial activity in the concentration range of 160-83 μg·mL-1 against Streptococcus mutans,methicillin resistant Staphylococcus aureus and Proteus mirabilis.Both compounds were further screened for anti-biofilm activity,which revealed promising activities at sub-MIC concentrations.None of the compounds were found to be active against Klebsiella pneumoniae.