Abstract: Antibioticsubstance of Loropetalum Chinese var. rubrum leaves were extracted by the ethanol in orthogonal test. The optimum extracting conditions are: 60% ethanol , 45℃ and 3h. Extract acted on Staphylococlus aureus, Shigella dysenteroae and Escheichia coli, the MIC was 12.5 mg/ml, 50 mg/ml and 25 mg/ml respectively. Extracting solution was not steady in the alkaline environment, but was steady in the hi-temp. Antibioticsubstance could be extracted by the ethyl acetatehe three bacteriostatic active composition were isolated with silica gel chromatography and thin-layer chromatography (TLC) in the extract of ethyl acetate. The result of chemical reaction and the examination of UV showed that extracts are hydrolysablet annin.

Key words: Loropetalum Chinese var. rubrum leaves, bacteriostatic activity, column chromatography, TLC, hydrolysablet annin