Study on the antibacterial activity of selected natural herbs and their application in water treatment

Abstract. The microbial contamination of water is a world-wide environmental problem. Many traditional methods are being used in various parts of the world to purify the water. According to World Health Organization, 80% of world's population living in rural areas relies on herbal traditional medicines as their primary health care. So the study on properties and uses of medicinal plants are subject to growing interests. An attempt was made to assess the antibacterial properties of certain selected herbs such as Ocimum sanctum (Krishna Tulsi), Ocimum kilimandscharicum (Karpoora Tulsi), Ocimum tenuiflorum (Ram Tulsi), Azadirachta indica (Neem), Simarouba glauca (bitterwood), Caesalpinia sappan (Pathimugam), Cuminum cyminum (Jeerakam), Vetiveria zizanioides (Ramacham), Saraca indica (Ashoka tree) and Murraya koenigii (curry leaves) against different bacteria such as total coliforms, faecal coliforms, Escherichia coli, Bacillus sp. and Serratia sp. The antibacterial activity of the plant extracts was determined by spread plate method, Kirby–Bauer disc diffusion method, most probable number (MPN) method and Petrifilm method. The shelf life of the herbal extract Ocimum sanctum (Krishna Tulsi) was also determined using a UV-visible spectrophotometer. A comparison study of the antibacterial efficiency of the three varieties of Ocimum sanctum, Ocimum kilimandscharicum and Ocimum tenuiflorum was also done. After the complete analysis of the antibacterial activity of different herbs, Ocimum sanctum, the most efficient herb, was selected and treatment methods based on the herb were developed so that it can be used conveniently in various households. Therefore Ocimum sanctum plant can be further subjected to isolation of therapeutic antimicrobial and pharmacological evaluation.