Aqueous and ethanol extracts of leaves (1000 ppm) of four important medicinal plant species, Aegle marmelos (Rutaceae), Albizia amara (Mimosoideae), Cassia auriculata (Caesalpinoideae) and Cissus quadrangularis (Vitaceae) has been tested individually and in combination for their antibacterial activity against Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa,Escherichia coli, Salmonella typhi and Bacillus subtilis. Results showed higher antibacterial activity in combination of extracts of the medicinal plants studied. The aqueous leaf extracts of C. auriculata and ethanolic leaf extracts of C. quadrangularis showed 1.8 and 1.7 cm zone of inhibition (ZI), respectively against E. coli and B. subtilis while tested individually. Whereas, the combination of aqueous leaf extracts of C. auriculata +C. quadrangularis (1:1) showed 2.5 cm ZI against E. coli. Similarly, the highest antibacterial activity of 3.0 cm ZI was observed against B. cereus in combination of aqueous leaf extracts of all the four plants. This study clearly demonstrates the synergistic activity of plant extracts against different bacteria.
Natchimuthu Karmegam, Mani Jayakumar and Subbiah Karuppusamy, 2012. Synergistic Antibacterial Activity of Four Medicinal Plants Collected from Dharapuram Taluk of Tiruppur District, South India. Journal of Plant Sciences, 7: 32-38.