Background: Prasachandaeng remedy (PC) has long been used for relief of fever and internal heat. It is composed of 12 plants. It is in the National Herbal Drug List of Thailand, but there is no report of antibacterial activity of this remedy.
Objective: To investigate antibacterial activity of ethanolic and aqueous extracts of PC remedy and its plant components.
Material and Method: The extraction methods were the maceration in 95% ethanol and drying by evaporator, and decoction or boiling in water, filtering and drying by lyophilizer. In the primary studies, all extracts were tested for antibacterial activity by disc diffusion against two types of gram positive bacteria; Staphylococcus aureus (ATCC 25923) and Staphylococcus aureus MRSA (DMST 20651), and three types of gram negative bacteria; Escherichia coli (ATCC 25922), Shigella dysenteriae (DMST 151161) and Salmonella typhimurium (DMST 22842). The active plant extracts which showed an inhibition zone were diluted to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)
values.
Results: The 95% ethanol extract of PC showed antibacterial activity against S. aureus MRSA (MIC = 0.312 mg/ml, MBC = 2.5 mg/ml). The inhibition zones of all plant extracts were in the range of 7 to 26 mm. The 95% ethanol and aqueous extracts of Caesalpinia sappan L. stems showed the largest inhibition zone against S.aureus MRSA 26 and 20 mm., respectively. The 95% ethanol extract of Mammea siamensis Kosterm. flowers exhibited the best gram positive bacteria activity against S. aureus MRSA with MIC and MBC values of 0.004 and 0.019 mg/ml., respectively. The 95% ethanol extract of Caesalpinia sappan L. stems exhibited the best inhibitory gram negative bacteria activity against S. dysenteriae with MIC and MBC values of 0.156 and 0.156 mg/ml.
Conclusion: The present study demonstrated that 95% ethanol extracts of PC had antibacterial. The 95% ethanol extract of Mammea siamensis Kosterm. flowers exhibited the best gram positive bacteria activity against S. aureus MRSA and the 95% ethanol extract of Caesalpinia sappan L. stems exhibited the best inhibitory gram negative bacteria activity against S. dysenteriae. The extracts of these two plants should be examined for active antimicrobial compound to be marker for quality control of PC.

Keywords: Prasachandaeng, Thai traditional medicine, Antibacterial activity