Title

Synergistic Antibacterial and Antibiofilm Activities of 3- and 6-Shogaol Against Staphylococcus aureus

Authors List

Ngai Peng Lau¹, Shawn Kai Jie Leong¹, Yee Ling Yong¹, Lu Syeun Lim¹, Yun Khoon Liew², Yoon Yee Then³, Lai Chun Wong³

¹School of Pharmacy, IMU University, 57000 Kuala Lumpur, Malaysia

²Department of Life Sciences, School of Pharmacy, IMU University, 57000 Kuala Lumpur, Malaysia

³Department of Pharmaceutical Chemistry, School of Pharmacy, IMU University, 57000 Kuala Lumpur, Malaysia 

Background

Staphylococcus aureus poses a great clinical challenge due to its multidrug resistance and biofilm-forming ability. These traits greatly limit treatment efficacy and contribute to persistent infections. Hence, it is important to find new therapies to combat this bacterium. This study evaluated the antibacterial and antibiofilm activities of 3- and 6-shogaol against Staphylococcus aureus.

Method

3- and 6-shogaol were synthesized via a modified literature method and characterized using FTIR and NMR spectroscopy. Minimum inhibitory concentrations against Staphylococcus aureus ATCC 43300 were determined, and combination effects with methicillin, oxacillin, amoxicillin, and gentamicin were assessed via checkerboard assay. Biofilm inhibition was evaluated against Staphylococcus aureus ATCC 35556 (strong biofilm producer) and ATCC 43300 (moderate biofilm producer) using the crystal violet assay. 

Results

The minimum inhibitory concentrations were 64 μg/mL for 3-shogaol and 1024 μg/mL for 6-shogaol, and 16, 64, 32 and 256 μg/mL for methicillin, oxacillin, amoxicillin, and gentamicin, respectively. Combination therapy revealed synergistic effects with all tested antibiotics, reducing the antibiotic concentration required for inhibition. Both shogaols significantly inhibited biofilm formation by ATCC 35556 (P<0.05), with 3-shogaol showing greater activity than 6-shogaol. No measurable biofilm inhibition was observed for ATCC 43300 due to its moderate biofilm production. 

Conclusion

3- and 6-shogaol exhibited potent antibacterial activity and significant biofilm inhibition against a strong biofilm-producing Staphylococcus aureus strain. Their synergistic interactions with antibiotics indicate potential to reduce antibiotic dosage requirements and slow the emergence of resistance. These results support the potential of shogaols as promising candidates for the treatment of Staphylococcus aureus infections.