Abstract: Filter paper method and double broth dilution method were used to test optimal proportion and minimum inhibitory concentration (MIC) of mixture of Diospyros kaki leaf and Citrus reticulate peel extracts against three bacteria namely Escherichia coli, Bacillus subtilis and Staphylococcus aureus. Meanwhile,the effect of temperature,pH and UV irradiation on stability of extract mixture was also evaluated.The results showed that D.kaki leaf and C.reticulate peel extracts revealed good inhibitory effect against the three tested strains and the extract mixture showed the in vitro synergistic effect.The optimal combination ratio of extracts was 2:3 (g/g),which exhibited a MIC of 6.25 mg/mL against Escherichia coli and Bacillus subtilis and a MIC of 12.50 mg/mL against Staphylococcus aureus. In addition,this extract mixture (2:3) was stabile between 20-80 ℃ and pH 5-9,but was sensitive to UV irradiation.

Key words: Diospyros kaki leaf, Citrus reticulate peel, mixture, synergy, stability