MsrA Efflux Pump Inhibitory Activity of Piper cubeba L.f. and its Phytoconstituents against Staphylococcus aureus...

Area of Science:

• Microbiology
• Pharmacology
• Natural Products Chemistry

Background:

• Macrolide resistance in Staphylococcus aureus is a growing concern, often mediated by efflux pumps like MsrA.
• ATP-binding cassette (ABC) transporters, including MsrA, play a crucial role in conferring antibiotic resistance.
• Piper cubeba fruit is a source of various bioactive compounds with potential medicinal properties.

Purpose of the Study:

• To isolate phytoconstituents from Piper cubeba fruit methanol extract.
• To investigate the potential of these isolated compounds as efflux pump inhibitors against the S. aureus MsrA pump.
• To elucidate the mechanism of action of these inhibitors.

Main Methods:

• Phytochemical isolation from Piper cubeba fruit methanol extract.
• Determination of minimum inhibitory concentration (MIC) of erythromycin in combination with isolated compounds.
• Real-time fluorometry-based ethidium bromide (EtBr) efflux and accumulation studies.
• Assessment of post-antibiotic effect (PAE) of erythromycin.

Main Results:

• Four compounds (pellitorine, sesamin, piperic acid, tetrahydropiperine) were isolated.
• Combinations of isolated compounds with erythromycin showed a 2-8 fold reduction in MIC against S. aureus RN4220.
• Pellitorine and sesamin demonstrated an 8-fold reduction in erythromycin MIC.
• Efflux studies confirmed reduced EtBr efflux and enhanced uptake, indicating MsrA pump inhibition.
• Pellitorine exhibited a significant post-antibiotic effect for erythromycin.
• Compounds were found to impair steady ATP production.

Conclusions:

• Piper cubeba fruit-derived phytoconstituents, particularly pellitorine and sesamin, are effective inhibitors of the S. aureus MsrA efflux pump.
• These compounds enhance erythromycin efficacy by reducing antibiotic efflux and potentially through ATP production impairment.
• The findings suggest a potential therapeutic strategy for combating macrolide-resistant S. aureus infections using natural product-based efflux pump inhibitors.