Essential oil of citrus fruit waste attenuates LPS-induced nitric oxide production and inhibits the growth of skin pathogens

Citrus is an economically important fruit for Jeju Island, but its peel also is one of the major sources of agricultural waste. Due to its fermentability, this waste causes many economic and environmental problems. Therefore it is worthwhile to investigate ways to make use of this citrus waste generated by the juice industry. The aim of this study was to examine the chemical composition of the essential oil obtained from citrus peel waste by hydrodistillation and to subsequently test the efficacy of this essential oil against a diverse range of microorganisms comprising drug-susceptible and drug-resistant skin pathogens. The chemical composition of the essential oil was analyzed by GC-MS, revealing that a total of 6 compounds comprised 94.5% of the total oil. The oil contained limonene (80.51%), gamma-terpinene (6.80%), cymene (4.02%), beta-myrcene (1.59%), alpha-pinene (1.02%) and alpha-terpinolene (0.56%). The oil exhibited promising antibac terial effects against drug-susceptible and drug-resistant skin pathogens as evidenced by the diameter of zones of inhibition and MIC values. The effects of citrus peel waste essential oil (CPWE) on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages were also examined in this study. The addition of CPWE (100 mug mL-1) to the medium with LPS largely inhibited the production of NO by 42.5%. The number of viable activated macrophages was not altered by CPWE, as determined by MTT assays, indicating that the inhibition of NO synthesis by CPWE was not simply due to cytotoxic effects. In addition CPWE (6.125 to 100 mug mL-1) inhibited NO production in a dose-dependent manner. Based on these results, we suggest the possibility that CPWE may be considered as an antibacterial and anti-inflammatory agent.