Antibacterial Activity and Chemical Characterization of Peel Essential Oil of <i>Citrus Nagato-Yuzukichi</i> Tanaka and Its Constituents

Background The uncontrolled use of antimicrobial drugs has led to the widespread of drug-resistant microbes such as MRSA, which has been regarded as clinically important problem. The essential oil is that some can be developed as natural antibiotics. Antibacterial activity of the Citrus spp. against the resistant and susceptible strains of S. aureus has been reported. However, to date, information on the phytochemical and bioactive characterization of the of C. nagato-yuzukichi essential oil (CNEO) in scarce. Purpose this study aimed to evaluate chemical composition, antibacterial activity against MSSA, MRSA, and E. coli, of the CNEO and their major components. Additionally, we determined their association with vancomycin and antibiofilm activity against MRSA strain of CNEO and their major components. Study design and Method In this work, the composition of CNEO was determined by GC-MS. Disk diffusion method, agar plate dilution method, MIC, MBC, checkerboard assay, and biofilm growth method were determined to assess their antibacterial activities. Results GC-MS analysis revealed 99.73% of the constituents of CNEO. The major components of CNEO were d-limonene (60.06%), γ-terpinene (8.40%), β-phellandrene (7.31%), α-terpineol (3.14%), and β-myrcene (2.34%). CNEO showed antibacterial activities against MRSA (DIZ: 26.78 mm, MIC: 16 mg/mL), with a similar trend to d-limonene (DIZ: 17.42 mm, MIC: 128 mg/mL) and α-terpineol (DIZ: 19.40 mm, MIC: 2 mg/mL). In combination effect, the results showed the additive interaction of vancomycin with CNEO and α-terpineol on the MRSA (FIC indexes: 0.5 &lt; to ≤1.0). Conclusion The integrated analysis in the present study suggested that CNEO or its major components components may be a promising alternative therapy to antibiotic-resistant bacterial infections.