Alkyl ferulic acid esters: Evaluating their structure and antibacterial properties

Area of Science:

• Food Science
• Microbiology
• Organic Chemistry

Background:

• Ferulic acid (FA) possesses natural antioxidant and antibacterial properties.
• FA's limited cell penetration due to polarity and short chain restricts its biological activity.
• Modification of FA into alkyl esters (FCs) aims to improve its antibacterial efficacy.

Purpose of the Study:

• To synthesize four alkyl ferulic acid esters (FCs) with varying alkyl chain lengths (C3, C6, C9, C12).
• To evaluate the antibacterial activity of these FCs against foodborne pathogens, including P. aeruginosa, E. coli, S. aureus, and B. subtilis.
• To investigate the mechanism of action of FCs on bacterial cells, focusing on cell wall integrity, biofilm formation, and membrane permeability.

Main Methods:

• Synthesis of FCs using Novozym 435 catalysis.
• Determination of Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC).
• Assessment of bacterial growth curves, alkaline phosphatase activity, biofilm formation (crystal violet method), cell morphology (SEM), membrane potential, and cell content leakage (PI assay).

Main Results:

• Esterification enhanced FA's antibacterial activity, with optimal efficacy observed for hexyl ferulate (FC6).
• FC6 exhibited potent activity against E. coli (MIC 0.5 mg/ml) and P. aeruginosa (MIC 0.4 mg/ml).
• FCs disrupted P. aeruginosa cell walls, inhibited biofilm formation, caused membrane hyperpolarization, and induced cell content leakage.

Conclusions:

• The antibacterial activity of FCs is dependent on the fatty alcohol chain length.
• FC6 demonstrates significant potential as an antibacterial agent against foodborne pathogens, particularly P. aeruginosa.
• This study provides a basis for utilizing plant-derived ferulic acid derivatives in food preservation and antimicrobial applications.