Flavonoids content and anti-microbial activity of extracts from Trifolium repens

The extracts(petroleum ether, chloroform, ethyl acetate phase and water phase of flavonoids) contents from leaves of Crotalaria pallid were measured, and by taking five bacteria(Escherichia coli, Bacillus subtilis, Proteus, Staphylococcus aureus and Pseudomonas aeruginosa), and five fungi(Cocoa grape cavity fungus, Fusarium oxysporum, Fusarium solani, Corynespora cassiicolaand Colletotrichum acutatum) as the tested materials, the antibacterial activity of extracts was determined with bacteriostatic circle method and inhibited mycelial growth rate method. The flavonoid contents of petroleum ether extract, chloroform extract, ethyl acetate extract and water extract were 12.98 mg/g(12.98%), 13.89 mg/g(13.89%), 7.4 mg/g(7.4%), 1.5 mg/g(1.5%) respectively. The antibacterial activity on Escherichia coli, Bacillus subtilis, Proteus vulgaris, Staphylococcus aureus and Pseudomonas aeruginosa were studied by inhibition zone method and the anti-fungal activity on Botryosphaeria rhodina, Fusarium oxysporum, Fusarium solani, Corynespora cassiicola and Colletotrichum acutatum were studied by hypha growth-inhibiting method. There were no obvious inhibition of the petroleum ether extract to the 5 species bacteria. There were different extent of inhibition of the chloroform extract to Proteus vulgaris and Pseudomonas aeruginosa and the minimal inhibitory concentration(MIC) were 2 mg/m L and 8mg/m L respectively. There were different extent of inhibition of the ethyl acetate extract to Bacillus subtilis, Proteus vulgaris and Pseudomonas aeruginosa and the minimal inhibitory concentrations(MIC) were 4 mg/m L, 4 mg/m L and 8 mg/m L respectively. There was different extent of inhibition for the water extract to the 5 species bacteria. There was no obvious inhibition of the petroleum ether extract and water extract to the 5 species fungi. There were different extent of inhibition of the chloroform extract to the 5 species fungi with the EC50 values of 3.54, 6.42, 8.45, 3.63 and 5.90 mg/m L respectively. The ethyl acetate extract had the strongest inhibition to Corynespora cassiicola with the EC50 values of 2.51 mg/m L and the weakest inhibition to Fusarium oxysporum with the EC50 value was 165.43 mg/m L.