Aqueous and ethanol crude extracts from thirteen Thai traditional plants were
screen for their total phenolic contents, antioxidant and antibacterial properties. Folin-Ciocalteu method was used to quantify total phenolic contents. The
antioxidant activities were evaluated using antioxidant assay kit and antimicrobial activities against four indicator strains were tested by disc diffusion and broth
dilution method. The highest total phenolic contents and antioxidant activity
obtained from aqueous crude extracts of Syzygium cumini (L.) Skeels was at 358.250 0.014mgGAE/gdw and 332.425 0.21mMTEAC/gdw, respectively. Piper betle Linn. ethanol crude extracts was found to have the highest phenolic contents of 474.083 0.005mgGAE/gdw. Anacardirm occidentale Linn. ethanol crude
extracts showed the highest antioxidant activity at 411.916 0.05mMTEAC/gdw. Almost plants demonstrated the correlation between total phenolic contents and
antioxidant capacity. The antimicrobial activity was found in seven aqueous crude
extracts and two ethanol crude extracts. Aqueous crude extract of Syzygium cumini (L.) Skeels showed the highest inhibition zone against Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA) at the concentration of 100mg/ml. Minimal inhibitory concentration (MIC) and minimal bacteriocidal concentration (MBC) of Syzygium cumini (L.) Skeels aqueous crude extracts against S. aureus and MRSA were 6.25 and 12.5mg/ml, respectively. Thai
traditional plants, especially Syzygium cumini (L.) Skeels. and Piper betle Linn. were possessed high phenolic contents, antioxidant and antimicrobial activities which demonstrated that all these plants can be potential sources of natural products for side dishes, dietary supplement product and medicinal uses