Antimicrobial Activities of Polysaccharides Isolated from Some Plant Leaves

Abstract

Plant leaves were found to have nutritional quality suitable for food, pharmaceutical and biomedical uses as therapy in medicine. Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli) are responsible for infectious diseases in humans and animals. The present study aims to investigate antimicrobial activity (AMA) of polysaccharides isolated from Parsley (Petroselinum sativum), Spinach (Spinocia oleracea), Watercress (Eruca sativa), Radish (Raphanus sativus) and Lettuce (Lactuca sativa) leaves against Staphylococcus aureus (S.aureus), Escherichia coli (E.coli), Bacillus subtilis (B.subtilis) and (MRSA) at different concentrations using agar diffusion method in vitro. Polysaccharides (PS) were extracted, isolated and purified from different plant leave samples separately. Chromatographic analysis of the purified PS, revealed the presence of different percentages of monosaccharides constituents per each isolated PS from different plants. In vitro study was done to estimate the activities of the obtained PS separately against 4 microbial strains (S. aureus, E. coli, B subtilis and MRSA) using agar diffusion method. PS showed AMA against S. aureus and E. coli more than that of B subtilis and MRSA at 10% concentration and inhibition zones were estimated. Minimal inhibitory concentrations (MIC) of PS against S. aureus, E. coli, B subtilis and MRS were found in the range of 1-5 mg/ml. The result demonstrates the killing effect of PS against S. aureus, E. coli, B subtilis and MRSA at 10% PS within 24 hours. Inhibition zone diameters exhibited different levels of decreases with the PS concentrations decreases against S.aureus, E.coli, B.subtilis and MRSA. Inhibition effects of PS against different microbial strains were found to be depending on PS concentration. However, the lowest concentration of PS produced lower inhibitory activity against S.aureus B.subtilis E.coli and MRSA. Results of all the obtained PS showed higher AMA against S. aureus and E.coli than the other two microbial strains used in the present study. Results indicated that these PS have AMA against both Gram-positive and Gramnegative bacterium at 10% concentration. According to these results the obtained PS consider important sources of antimicrobial agents for treatment of infectious diseases with minimal concentrations (100-500µg/ml).