2023, Vol. 27 ›› Issue (11): 1765-1771

Effects of carvacrol on osteoblasts and common oral pathogens

Zhang Zihan, Wang Wenli, Li Jinnuo, Li Yourui   

Abstract: BACKGROUND: The natural plant extract carvacrol has the characteristics of broad-spectrum antibacterial activity, low drug resistance and low cytotoxicity, which has become a research hotspot of antibiotic substitutes with a good prospect in recent years.
OBJECTIVE: To determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of carvacrol against Streptococcus mutans and Staphylococcus aureus, two common oral pathogens and to explore the antibacterial activity of carvacrol against these two bacteria and its effect on osteoblast proliferation, thereby providing a new choice for oral disease prevention and treatment.  
METHODS: A microplate reader was used to determine the MIC and MBC values of carvacrol against Streptococcus mutans and Staphylococcus aureus. The antibacterial activity of carvacrol was tested by a zone of inhibition test. Cell counting kit-8 was used to detect the proliferation of MC3T3-E1 cells induced by different concentrations of carvacrol at 1, 4, and 7 days. Alkaline phosphatase activity and Runx2 and osteoprotegerin gene expression levels were detected by alkaline phosphatase and real-time fluorescence quantitative PCR kits at 1, 7, and 14 days, respectively.  
RESULTS AND CONCLUSION: The MIC values of carvacrol against Streptococcus mutans and Staphylococcus aureus were 0.20% and 0.04%, and the MBC values were 0.60% and 0.12%, respectively. In the inhibition zone test, carvacrol showed an obvious antibacterial zone, and the difference was statistically significant (P < 0.05). Cell counting kit-8 assay showed that the proliferation activity of cells treated with carvacrol was significantly increased (P < 0.05). The activity of alkaline phosphatase increased in all carvacrol concentration groups. The increase of alkaline phosphatase activity was more obvious on day 7 and the effect of 1MIC group was the most obvious (P < 0.05). Results from the real-time fluorescence quantitative PCR showed that different genes were highly expressed at the mRNA level after treated with carvacrol and all of them occurred in the 1MIC group (P < 0.05). To conclude, carvacrol has strong antibacterial activity against two common oral pathogens, Streptococcus mutans and Staphylococcus aureus, can improve the osteogenic activity of MC3T3-E1 cells, and promote their proliferation and differentiation.
Key words: carvacrol, minimum inhibitory concentration, minimum bactericidal concentration, osteogenesis, bone tissue engineering