Antioxidant and Antibacterial Activities of the Essential Oils of Cymbopogon citratus and Citrus sinensis

Aims: The use of essential oils from plants as natural antioxidant and antimicrobial is a field of growing interest. The aim of this study was to investigate the antioxidant and antibacterial properties of the essential oils of Cymbopogon citratus L. (lemongrass) and Citrus sinensis (orange peels) independently.

Methodology: Essential oils extracted by hydrodistillation from Cymbopogon citratus and Citrus sinensis were individually assayed for 1,1 –diphenyl- 2 picrylhydrazyl (DPPH) radical scavenging activity, hydrogen peroxide scavenging, reducing power and metal chelating activity in relation to the total phenolic and total flavonoid content of each essential oil. Antimicrobial analyses were carried out using pour plate method for the determination of the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the oils on pathogenic bacteria Staphylococcus epidermidis and Staphylococcus aureus and non-pathogenic bacteria Lactobacillus casei and Lactobacillus brevis.

Results: The two essential oils possessed antioxidant and antibacterial activities. However, the essential oil of C. citratus showed a higher level of total phenolic (372.81±1.36 µg/ml) and total flavonoid (377.88±1.52 µg/ml) content when compared to the essential oil of C. sinensis which showed a lower total phenolic (262.81±2.66 µg/ml) and flavonoid (79.65±1.44 µg/ml) contents. These resulted in a higher level of DPPH radical scavenging and metal chelating activity of C. citratus compared to C. sinensis. MIC of 212.5 mg/ml oil concentration was obtained for C. citratus against S. epidermidis and less than 106.25 mg/ml against S. aureus while 210 mg/ml oil concentration was obtained for C. sinensis against S. aureus and 850 mg/ml oil concentration against S. epidermidis. MBC was observed for C. citratus at 425 mg/ml while C. sinensis showed MBC at 840 mg/ml oil concentration. None of the oils showed a significant inhibition against the non-pathogenic bacteria compared to the (Gentamycin) negative control.

Conclusion: The essential oils of C. citratus and C. sinensis have potential for use as natural antioxidants and antibacterial agents.