Antimicrobial activities of Ipomoea batatas (L.) leaf

The antimicrobial activity of artificially grown sweetpotato [Ipomoea batatas (L.) Lam.] leaves was investigated against both Gram positive and Gram negative bacteria; Escherichia coli O157:H7, Bacillus cereus and Staphylococcus aureus. Three different cultivars, 'Simon 1', 'Kyushu 117' and 'Elegant Summer', were used. The sweetpotato leaves were grown under different temperatures (20, 25 and 30 degrees C) and artificial shading (O, 40 and 80%) conditions. There were some cultivar differences however, the lyophilized leaf powder (100 mg) from all the cultivars in the Trypto Soya Broth cultivation medium (10 ml) strongly suppressed the growth of all the bacteria studied. However, the antibacterial extract of the leaves had no effect on the growth of 5 types of bifidobacteria useful for human health. The main components of the antibacterial extract were polysaccharides (30%) and protein (70%). In the polysaccharide fraction, the relative quantities of natural sugars were xylose > galactose > arabinose > glucose > rhamnose > mannose > fucose. These results suggest that the antibacterial component may be a pectin-like material. Thus, the practical use of sweetpotato leaves to prevent the growth of food-poisoning bacteria is very promising.