AIM: To choose at least one kind of better derivate from 81 novel compounds for further structure-function relationship researches by contrast study on antibacterial activity of three kinds of derivates developed from decanoyl acetaldehyde, a certain kind of ethnodrug and pure synthetics. METHODS: Three quality control strains, staphylococcus aureus ATCC25923, bacillus coli ATCC25922 and bacillus aeruginosus ATCC27853 were used in the preliminary screening in vitro. Some active derivates were selected to carry out the minimal bactericidal concentration test, killing curve test, and the effect of cultivation parameters on minimal inhibitory concentration on clinical separated staphylococcus aureus and MRSA. Acute toxicity test of a few promising derivates were tested preliminarily by intragastric administration to mice. RESULTS: There were significant differences of the antibacterial activity for the three different kinds of derivatives compared to the quality control groups. Results shown that 15 percent of the 53 compounds developed from decanoyl acetaldehyde had special activity of inhibiting staphylococcus aureus ATCC25923. Some optimized derivatives had better activity to clinical separated staphylococcus aureus and MRSA compared to the positive control drug decanoyl acetaldehyde. And the derivates showed stronger inhibitive action to the staphylococcus aureus in basylous circumstance than in acid circumstance. Meanwhile, among 20 derivates developed from a certain kind of ethnodrug, there were 90 percents shown fairly strong and broad antibacterial activity to staphylococcus aureus ATCC25923 and bacillus coli ATCC25922 with high toxicity in mice. And 8 samples of pure synthetics showed weak antibacterial activity. CONCLUSION: The derivates developed from natural products showed fairly well antibacterial activity. And the derivates related to decanoyl acetaldehyde had lower toxcity than that of derivates obtained from the ethnodrug. The pure synthetic compounds had weak activity. It is preferable to do the structure-function relationship research of the derivates related to decanoyl acetaldehyde, and the exploratory study for ethnodrug derivates should be continued if experimental condition permitted. This research has optimized the lead compounds and the result is underway of applying national patent. This study does benefit to the innovative antibacterial drug research that has intellectual property rights. The in-depth systematic researches are continuing. AIM: To choose at least one kind of better derivate from 81 novel compounds for further structure-function relationship researches by contrast study on antibacterial activity of three kinds of derivates developed from decanoyl acetaldehyde, a certain kind of ethnodrug and pure synthetics. METHODS: Three quality control strains, staphylococcus aureus ATCC25923, bacillus coli ATCC25922 and bacillus aeruginosus ATCC27853 were used in the preliminary screening in vitro. Some active derivates were selected to carry out the minimal bactericidal concentration test, killing curve test, and the effect of cultivation parameters on minimal inhibitory concentration on clinical separated staphylococcus aureus and MRSA. Acute toxicity test of a few promising derivates were tested preliminarily by intragastric administration to mice. Results sh own that 15 percent of the 53 compounds developed from decanoyl acetaldehyde had special activity of inhibiting staphylococcus aureus ATCC 25923. Some optimized derivatives had better activity to clinical separated staphylococcus aureus and MRSA compared to the positive control drug decanoyl acetaldehyde. And the derivates failed stronger inhibitive action to the staphylococcus aureus in basylose circumstance than in acid circumstance. Meanwhile, among 20 derivates developed from a certain kind of ethnodrug, there were 90 percents showing strong and broad antibacterial activity to staphylococcus aureus ATCC25923 and bacillus coli ATCC25922 with high toxicity in mice. And 8 samples of pure synthetics showed weak antibacterial activity. CONCLUSION: The derivates developed from natural products showed fairly well antibacterial activity. And the derivates related to decanoyl acetaldehyde had lower toxcity than that of derivates obtained from the ethnodrug. The pure synthetic compoundshad weak activity. It is preferable to do the structure-function relationship research of the derivates related to decanoyl acetaldehyde, and the exploratory study for ethnodrug derivates should be continued if experimental condition permitted. This research has optimized the lead compounds and the result is underway. of applying national patent. This study does benefit to the innovative antibacterial drug research that has intellectual property rights. The in-depth systematic researches are continuing.