IN VITRO ANTIBACTERIAL ACTIVITY OF SELECTED UNDERUTILIZED PLANTS AND CYTOTOXIC PROPERTY OF TERMINALIA CATAPPA

Objective : This study aimed at determining the antibacterial activity of the underutilized plants of Sri Lanka, “Kottamba” ( Terminalia catappa), “Purpurata” (Alpinia purpurata) and “ Harankaha ” (Curcuma zedoaria), against food-borne pathogens. Chemical composition and in vitro cytotxicity of the most active antibacterial plant extract(s) were examined. Methods: Crude rhizome extracts were obtained for all plants whereas in respect of T. catappa, the red pericarp of the fruit was used. The antibacterial activity was determined using the agar disc diffusion and broth dilution assays. Total phenol content, Gas Chromatograph-Mass Spectrometry analysis and cytotoxicity assay were conducted only with the plant which showed the most effective antibacterial activity. Results : T. catappa extract showed significantly (p<0.05) high DIZ (19.6±0.47 mm) against S. aureus 113. A. purpurata showed DIZ (16.3±0.94, 15.0±1.00, 14.3±0.57 mm) against L. monocytogenes V7 (1/2a), S. aureus 25925 and S. aureus MSSASS 25D. The MIC of T. catappa ethanol extract was 10 mg/ml, while MBC was 80 mg/ml for S. aureus 113. The phenolic content of T. catappa ethanol extract was 81.54±1.28 mg GAE/g dry sample and the major compound (31.86 %) was 2, 5-Furandione, 3 methyl. The No-Observed Adverse Effect Concentration (NOAEC) of this extract for COS7 cells was 100 µg/ml whereas for 3T3 it was 300 µg/ml. This indicates that the extract is cytotoxic only at a very high concentration, suggesting that at lower concentrations the extract could be used as a food preservative. Conclusion : The results indicate that T. catappa has potential antibacterial activity as a safe bio-preservative.