Antibacterial activity and synergy of antibiotics with sanguisorbigenin isolated from Sanguisorba officinalis L. against methicillin‐resistant Staphylococcus aureus

The present study evaluated the antibacterial activity and the synergy of the sanguisorbigenin (SGB) from the dried root of Sanguisorba officinalis L. combined with β‐lactam antibiotics against methicillin‐resistant Staphylococcus aureus. A total of six strains of reference strain and clinical isolates were used to determine the antibacterial activity using a broth microdilution assay, and the synergistic effects were determined using a checkerboard assay. To analyse the mechanism of synergy, we conducted the level of penicillin‐binding protein 2a by western blot. In addition, quantitative RT‐PCR was performed to analyse the mecA gene expression. The minimal inhibitory concentration values of SGB against six strains of S. aureus were in the range of 12·5–50 μg ml(−1), and there were synergy, or partial synergy effects when SGB was combined with antibiotics. Furthermore, when treated with SGB, the level of penicillin‐binding protein 2a and the expression of the mecA gene was reduced significantly. In conclusion, this study demonstrated that SGB is a potential natural antibacterial agent against methicillin‐resistant S. aureus that represents a considerable burden on the healthcare system worldwide, and may an exceptionally modulator of β‐lactam antibiotics.