Comparitive studies on antibacterial activity of Patchouli [Pogostemon cablin (Blanco) Benth] and Geranium (Pelargonium graveolens) aromatic medicinal plants

Solvent (Hexane, Ethanol, Methanol) extracts of Patchouli ( Pogostemon cablin ) and Geranium (Pelargonium graveolens ) were compared for their potential antibacterial activity against four bacterial species using disc diffusion assayed method. DMSO and Chloramphenicol were used as negative and positive controls respectively. The growth inhibitory effect of the various solvents on Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Enterobacter aerogenes were obtained and the most  effective  extract was the hexane extract of Patchouli compared to that of Geranium, which showed a maximum zone of inhibition (18 to 21 mm) against S. aureus . Ethanol and methanol extracts of Geranium showed maximum zone of inhibition (10 to 11 mm) against S. aureus . There was no zone of inhibition for aqueous, ethanol and methanol extracts of patchouli with 20 to 80 µl concentration and no zone of inhibition for aqueous, hexane extracts of Geranium with 20 to 80 µl concentration. The minimum inhibitory concentration (MIC) ranged from 40 to 80 µl for Patchouli hexane extract and MIC ranged from 60 to 80 µl for Geranium ethanol and methanol extracts. The potency of these extracts based on the zones of inhibition and MIC values were higher indicating that leaves have a potential broad spectrum antibacterial activity. The combination of these antimicrobial plant extracts can be used to treat infectious diseases in the near future. Keywords: Patchouli, geranium, plant extracts, disc diffusion, bacterial species, MIC, zone of inhibition, infectious diseases African Journal of Biotechnology , Vol 13(23) 2379-2384