Polyphenolic extracts (PE) of edible flower of Sesbania grandiflora were tested to evaluate its antimicro-
bial effect against some common pathogenic bacteria and growth promoting property against probiotic
organism Lactobacillus acidophilus. The antimicrobial activity of S. grandiflora flower PE against selected
pathogens was evaluated using both in vitro and in situ methods. In vitro studies suggested that PE has
inhibitory effect against Staphylococcus aureus, Shigella flexneri 2a, Salmonella Typhi, Escherichia coli and
Vibrio cholerae. The gram-positive organism S. aureus was the most sensitive organism to PE and min-
imum inhibitory concentration (MIC) was found to be 0.013 mg/mL where as the MIC of PE against V.
cholerae was the highest (0.25 mg/mL). On the other hand PE showed growth promoting effect on the
common probiotic bacterium L. acidophilus. The major finding was that S. grandiflora PE induced a signif-
icant biomass increase of L. acidophilus grown in liquid culture media. PE showed reduction of S. aureus
growth in food (fish) during storage at 10◦C. High performance liquid chromatography analysis showed
that rutin, a major flavonoid of the PE diminished in the culture medium MRS broth with the growth of
L. acidophilus.