Polyphenolic extracts (PE) of edible flower of Sesbania grandiflora were tested to evaluate its antimicrobial 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 minimum 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 significant 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.

Six different cultivars of banana flowers (Musa paradicicus) (Kathali, Bichi, Shingapuri, Kacha, Champa, and Kalabou) were analyzed for the content of polyphenol expressed as gallic acid equivalent and flavonoid expressed as quercetein equivalent, and the in vitro total antioxidative activities of the flower extracts were compared with standard and expressed as trolox equivalent. The reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•(+)) scavenging activities, inhibition of lipid peroxidation in a linoleic acid emulsion system, and liposome peroxidation system were measured and compared with respective standard antioxidants. Iron-mediated Fenton reaction was carried out to evaluate the protective effect of the extract of banana flower (Kacha cultivar) against H(2)O(2)-induced DNA damage. The Kacha variety contains the maximum amount of polyphenol (11.94 ± 0.03 mg of gallic acid equivalent/g of dry weight) and flavonoid (0.174 ± 0.001 g of quercetin equivalent/g of polyphenol). It also has the highest total antioxidant capacity, DPPH radical scavenging activity, and ABTS•(+) radical scavenging activity with a least EC(50) value of 0.051 mg/mL. Hepatic cell damage in iron-mediated Fenton reaction caused by free radicals is reduced by the banana flower extract. On the basis of the results obtained, the banana flowers are found to be a potential source of natural antioxidants. This is the first report on the antioxidant properties of the extracts from banana flowers. The study suggests that the flowers of M. paradicicus that are found in India and consumed as vegetable can provide valuable functional ingredients that help in the prevention of oxidative stress.