Extraction and evaluation of antimicrobial activities of essential oils from orange peel (Citrus nobilis) grown in Can Tho City, Vietnam

This study determined the extraction conditions, chemical composition, and antimicrobial activities of the essential oils of Citrus nobilis. The results illustrated that soaking in the 9% (w/v) NaCl solution for 2 h with a sample and solvent ratio of 1:3 (w/v) and a subsequent extraction time of 45 min yielded the highest extraction efficiency, reaching 3.66% (w/w). The main chemical components of the essential oils were limonene (90.42%), beta-myrcene (4.7%), and alpha-pinene (1.22%). The minimum inhibitory concentration (MIC) at the density of 5x10(4), 5x10(5), and 5x10(6) cells/mL of Escherichia coli were 100, 125, and 125 mg/mL, respectively; for Staphylococcus aureus were 75, 100, and 125 mg/mL, respectively; and for Bacillus cereus were 50, 75, and 100 mg/mL, respectively. The minimum bactericidal concentration (MBC) at densities of 5x10(4), 5x10(5), 5x10(6) cells/mL of E. coli were 175, 225, 225 mg/mL, S. aureus were 150, 200, 225 mg/mL, and B. cereus were 125, 175, 200 mg/mL, respectively. The inhibitory activities of Aspergillus flavus of orange essential oils according to the agar dilution method at concentrations of 0.025-0.1%) on the 5th day were 8.84-30.61%.