Abstract:
Eight native Thai plant rarely studied were extracted by using distilled water and 95% ethanol
then were investigated for their total phenolics, free radical scavenging, metal chelating and
five antibacterial capacities. Five bacteria consisted of one gram-negative (Esherichia coli) and
four gram-positive (Stapphylococcus aureus, Stapphylococcus epidermidis, Bacillus cereus
and Bacillus subtilis). Significant difference was observed among solvent extractions used and
the plant species. The aqueous extracts gave higher antioxidant abilities but lower antibacterial
capacities than the ethanol ones. Principle component analysis (PCA) revealed that the free
radical scavenging was correlated to the total phenolics. Among the eight species, S. gratum
extracts showed the strongest free radical scavenging ability, while, C. harmandiana showed
the strongest chelating capacity. The G. cowa extracts were exception in antibacterial capacities
because their activities against all the test bacteria. Some native Thai plant rarely studied could
be used as alternative natural sources for antibacterial and antioxidant substances.