Studies on Antibacterial Stability and Antioxidant Activity of Essential Oils from Cymbopogon citratus

Objective: To study the chemical components and antioxidant activity of Cymbopogon citratus essential oil and to and to investigate the effect of processing and storage conditions on its antibacterial stability. Methods: The essential oil was extracted by steam distillation, and its chemical components were analyzed by GC-MS. The effects of temperature, ultraviolet rays, pH, and CaCl₂ on the antibacterial activity were determined by filter-paper method and the antioxidant activity was determined by the ABTS+·,DPPH· and O₂⁻· radical-scavenging assay and the reducing capacity for Fe³⁺. Results: A total of 49 compounds were identified, and 12 compounds with contents greater than 1%, accounting for 88.11%, with citral (26.73%), neral (18.57%), and β-myrcene (9.30%) as the main components. The essential oil of Cymbopogon citratus showed strong antibacterial activity. The inhibitory effect against Staphylococcus aureus (25.43±0.24 mm) was better than that of Escherichia coli (23.54±0.67 mm) and Bacillus subtilis (18.33±0.03 mm) (P<0.05). The antibacterial activity of the essential oil were stable under ultraviolet rays, but were unstable under different temperature and pH. The antibacterial activity was stronger at low temperatures and acidic conditions, and CaCl₂ could increases the antibacterial effect. The essential oil showed good antioxidant activity, the scavenging ability of ABTS⁺·, DPPH·, O²⁻· and the reducing ability of Fe³⁺ increased with the concentration of essential oil（P<0.05）, the IC₅₀ of ABTS⁺·, DPPH·, O²⁻· were 4.36, 7.09, 3.13 mg/mL, respectively, which were 6.92, 10.58 and 5.05 times of ascorbic acid. Conclusion: The essential oil of Cymbopogon citratus has good antibacterial activity and antioxidant activity, high temperatures and alkaline conditions should be avoided during storage and processing.