Study on Antibacterial Activity and Idenfication of Extract from Guava Leaf

The soxhlet extraction method was used for guava leaf by methanol,ethanol,butanol and ethyl acetate.Through the single factor experiment determined the effects on the extraction rate of the guava leaf extract,such as the solid-liquid ratio and extraction time.The optimum extraction technological conditions are as follows:The solid-liquid ratio of methanol,ethanol and ethyl acetate is 1:16 while the extraction time is 5 h;and the solid-liquid ratio of butanol is 1:18 while the extraction time is also 5 h.6 compounds (gallic acid,4hydroxy acid,chlorogenic acid,caffeic acid,ferulic acid,quercetin) were identified in the guava leaf extract by RP-HPLC analysis at 280 nm.Disc diffusion method was used to assay the bacteriostatic effects of the extract from the guava leaf on 4 strains of common bacteria (Bacillus subtilis,Escherichia coli,Tetracoccus,staphylococcus aureus).The effects were compared to 4 ℃,28 ℃,37 ℃.The extract on 28 ℃ have the most strong bacteriostatic effects,and the ethanol extract have the best antibacterial effect to Bacillus subtilis and Tetracoccus,on which the antibacterial circle diameter were 15.3 mm and 12.4 mm.The ethyl acetate extract has the best antibacterial effect to Escherichia coli and staphylococcus aureus,on which the antibacterial circle diameter were 15.5 mm and 16.8 mm.The concentration of guava leaf extract were divided into 100 %,50 % and 25 %,Tetracoccus and staphylococcus aureus were selected to comparative on 28 ℃.The results showed that 25 % of the extract concentration still inhibits bacteria,which was shown to have fairly strong antibacterial effects.