Abstract: The main ingredient of antibacterial compound Fr.5.2 isolated by Artemisia hedinii (A.hedinii) was Artemisinin Derivatives.The antibacterial activity,the integrity of cell membrane,the leakage of intracellular substances,Scanning Electron Microscopy (SEM) observation of bacteria and their spores were determinated to study the antibacterial mechanism of Fr.5.2 and DHA against A.alternate,.The results showed that the minimum bactericidal concentration(MIC) and minimum bactericidal concentration (MBC) of aganist A.alternate were 1.25 mg/mL and 2.5 mg/mL,respectively,while the MIC and MBC was the same 10 mg/mL of DHA aganist A.alternate.The cell integrity of A.alternate decreased and the intracellular nucleic acid macromolecules losed with the time in 0-3 h as the Fr.5.2 and DHA concentration of 1/2 MIC.SEM observation shows that the cell membrane of mycelium was small,concave and hollow and the surface of the spores was also sunken;The Fr.5.2 and DHA can inhibit the synthesis of ergosterol and lead to its content decreasing by 29.77%,28.99%,respectively,comparing to the control group.The number of spores increased,however,the germination rate decreased.These results indicate that Artemisinin Derivatives show antibacterial effect on fungi,and can cause the inhibition of fungal ergosterol synthesis,the cell membrane destroyed,the metabolism of fungal cells hindered and fungal spores germinated.

Key words: Artemisia hedinii, artemisinin derivatives, dihydroartemisinin, antibacterial mechanism