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India has a tremendous biodiversity. It has optimum conditions for a number of medicinal plants that
thrive naturally here. Catharanthus roseus also known as Sadabahar or Sadhaphuli by vernacular
names is one among many medicinal plants commonly occurring here. C. roseus has always
remained in limelight for its various anticancerous properties imparted by various alkaloids. In this
research paper, a new microbial susceptibility test method is described, which retains the simplicity
of Epsilometer test for determination of MIC. In this method, organisms can be tested directly for
susceptibility to known concentration of plant extracts and antibiotics in agar well. Ranges of
concentrations are used to determine the minimum inhibitory concentration. Using dried leaves of
C. roseus, organic extracts were prepared in acetone and ethyl acetate solvent using soxhlet
apparatus. MIC values of extracts were determined by E-test method against pathogens like
Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris. MIC values evaluated were 25μg/ml
and 12.5μg/ml for E.coli, 12.5μg/ml for P. vulgaris and 6.25μg/ml and 50μg/ml for K. pneumoniae
in acetone and ethyl acetate extracts respectively. The MIC values obtained by E Test are lower than
those reported in literature using broth dilution method. Modified well diffusion method is efficient,
less time consuming and simpler. C. roseus has a great potential as an antimicrobial agent, which
needs to be explored further intensively.
Keywords: Catharanthus roseus, Modified well diffusion, MIC, Acetone, Ethyl acetate