Abstract: Objective To study the antibacterial activity and mechanism of extracts from Prunellae Spica against pathogenic organisms of acne. Methods The study was performed by determining bacteriostatic curve of Staphylococcus aureus (S.aureus), Staphylococcus epidermidis (S.epidermidis) and Propionibacterium acnes (P. acnes), the permeability of cell wall, content of peptidoglycan and ion leakage of S. aureus． Results It was found that three extracts from Prunellae Spica could prolong lag phase, inhibit growth of S. aureus, S. epidermidis and P. acnes, significantly affect the permeability of cell wall and increase the efflux of potassium and magnesium ion of S. aureus. The antibacterial activity intensity was shown as： water extract > ethanol extract > ultrasonic extract. Conclusion Prunellae Spica possesses the good antibacterial activity against pathogenic organisms of acne. Its antibacterial mechanism is related to affecting the permeability of cell membrane and cell wall.

Key words: Prunellae Spica, Staphylococcus aureus, Staphylococcus epidermidis, Propionibacterium acnes, antibacterial mechanism