Antibacterial activity of Thai medicinal plants Pikutbenjakul.

Background: Bacterial infections caused by resistant strains have been increased dramatically. Pikutbenjakul, a Thai medicinal plant formula containing Piper longum, Piper sarmentosum, Piper interruptum, Plumbago indica and Zingiber officinale have been widely used in Thai traditional medicine.

Objective: To determine antimicrobial activity of Pikutbenjakul formula and its components in order to develop the medicinal plants for alternative treatment of bacteria causing diarrhea.

Material And Method: Activity of Pikutbenjakul formula and its components was tested using disc diffusion and broth dilution methods against bacteria associated a set of bacteria associated with diarrheal disease including Vibrio cholerae, Vibrio vulnificus, Salmonella, Shigella, Escherichia coli (EIEC, ETEC, EPEC, EAEC and EHEC) and Staphylococcus aureus. The extraction was performed by maceration in 95% ethanol.

Results: The results showed all tested strains were susceptible to P. indica while other components were able to inhibit some strains. P. sarmentosum showed antimicrobial activity against Vibrios with the MIC values between 0.625 to > or =5 mg/ml. P. sarmentosum, P. indica and Pikutbenjakul formulas inhibited the growth of all Vibrios. P. interruptum inhibited V. cholerae serogroups O1 and non-O1/non-O139. P. longum was able to inhibit only two isolates of V. cholerae serogroup O139 (MIC = 1.25 mg/ml) and V. vulnificus (MIC > or =5 mg/ml). The activity of Pikutbenjakul containing Zingiber spp. and Pikutbenjakul containing Z. officinal against Vibrios, Shigella spp. and S. aureus was not significantly different. P. indica could inhibit Salmonella (MIC > or =5 mg/ml), E. coli (MIC > or =5 mg/ml) and S. aureus (MIC = 1.25 mg/ml).

Conclusion: The results support the Thai medicinal plants for treatment of diarrhea caused by these bacteria. This study also provides an insightful knowledge on antimicrobial activity which would lead to further development of an effective formula of Pikutbenjakul for diarrheal disease and other infectious diseases in future.