Bactericidal principle of the fermented aqueous extract of Stevia rebaudiana Bertoni and a possible use of the Stevia extract as a feed supplemen for prevention of the digestive tract infections.

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We have previously shown that a fermenteds extract from the Paraguayan composite plant, Stevia rebaudiana Bertoni has strong bactericidal activity towards a wide range of food-borne pathogenic bacteria, but it shows no significant killing activity to Bifidobacteria and Lactobacilli. Here we studied bactericidal principle of the fermented extract, and tested the extract for possible use as a feed supplement for prevention of the intestinal tract infections of domestic animals and for promotion of animal growth.1. Fermented aqueous extract of Stevia rebaudiana Bertoni was fractionated by the partition with ethyl acetate, followed by the high performance column chromatography using an ODS (C_<18>) column. Two bactericidal fractions and one enhancer fraction were obtained. Viability of E. coli was reduced from 10^9 cfu/ml to <10^3 cfu/ml when incubated with the bactericidal fractions at 37℃ for 1 h. One bactericidal fraction has the maximal absroption at 280 nm, and it was sensitive to light irradiation. The other bactericidal fraction was identified as lactic acid.2. In the laboratory experiments, oral administration of the Stevia extract to the Salmonella-infected calves reduced viable bacteria in the intestinal tract and bacterial tissue invasion, although not prevented the lethal effect of the bacterium.3. In the field experiments, oral administration of the Stevia extract was effective to the intestinal tract infections of piggys. Many of the animals with early-staged diarrhea were recovered within 3 days after the treatment, and their growth rate was normal threeafter. Oral adminitration of the diluted Stevia extract promoted growth of pigs. Livers of the Stervia-fed pigs were evaluated to be very healthy at the slaughter house. Taste of the pork meat was exellent.