Abstract:

Based on the determination of minimum inhibition concentrations (MICs) of 8 food preservatives against Escherichia coli in vitro, the structural optimization and vibrational frequency analysis were carried out for these food preservatives with density functional theory B3LYP in Gaussian 98 program, and the stable structures were acquired. Meanwhile, the frontier molecular orbital (FMO) and Mulliken population of these antimicrobial molecules were also investigated. Results showed that carboxyl, phenolic hydroxyl or carbonyl, including aldehyde group, comprised the active sites of these antimicrobial molecules. The antimicrobial activity of preservatives could be improved when carbon-carbon double bond, alternate carbon-carbon double bonds or phenyl was linked to the active sites. There was a close correlation between FMO energy and antimicrobial activity of preservatives, which could be described by the following formula: Y ＝ －4.4506－1.8819X1＋2.9969X2 [Y represents MIC (μmol/ml) of preservatives, andX1 and X2 represent EHOMO(eV) and ELUMO(eV), respectively] with a standard error of 0.6256 and a significance level, α = 0.05, a correlation coefficient (R) of 0.929, and a determination coefficient of 0.863.

Key words: food preservative, quantum chemistry, structure-activity relationship