Studies on Stability and Antibacterial Activity of Aqueous Extracts of Some Indian

Kshama M. Chavan¹, Vrushali S. Tare²⁺ and P. P. Mahulikar¹*

¹School of Chemical Sciences, North Maharashtra University, Jalgaon- 425 001 (India) ²Division of Entomology, National Chemical Laboratory, Pune- 411 008 (India)

Four different types of aqueous extracts viz., cold, hot, and their corresponding sterilized extracts of leaves of four Indian medicinal plants, namely Datura strammonium, Nerium indicum, Vitex trifolia and Ricinus communis were prepared and evaluated for their antibacterial activity against four test bacteria species, namely Pseudomonas putida, Bacillus mecarium, Escherichia coli and Bradyrhizobium japonecum with an interval of a week to check the stability and efficacy of the prepared extracts. All types of extracts of D. strammonium exhibited better antibacterial potency and efficacy from four to five weeks. The hot extract of R. communis was more potent than the cold extract. It's sterilized hot extracts gave better antibacterial efficacy in fourth week against B. japonecum followed by E. coli. The sterilized hot extract of V. trifolia was found to be good antibacterial agent against all test bacterial species in fifth week directly, however, hot extract became active on seventh week. The sterilized hot extract of N. indicum reflected good antibacterial action against all bacterial species in fourth week, however, remaining three extracts exhibited activity against B. mecarium and B. japonecum only. The increase in activity with fermentation for four weeks might be due to the hydrolysis of ether, ester and ether linkages in secondary compounds present in plants to alcoholic, phenolic, carboxylic, amino etc. functionalities; which could confer the increased activity. Furthermore, the decrease in activity after four weeks could be due to degradation and decomposition of parent secondary compounds followed by hydrolysis into less or non-active products. The antibacterial activity was found to be independent of the concentration of plant extracts.

Botanicals; Aqueous extraction; Stability; Sterilization; Antibacterial potency; Integrated Pest Management (IPM)