The Chemical Compositions, and Antibacterial and Antioxidant Activities of Four Types of Citrus Essential Oils

Abstract

Nanfeng mandarins (<i>Citrus reticulata</i> Blanco cv. Kinokuni), Xunwu mandarins (<i>Citrus reticulata</i> Blanco), Yangshuo kumquats (<i>Citrus japonica</i> Thunb) and physiologically dropped navel oranges (<i>Citrus sinensis</i> Osbeck cv. Newhall) were used as materials to extract peel essential oils (EOs) via hydrodistillation. The chemical composition, and antibacterial and antioxidant activities of the EOs were investigated. GC-MS analysis showed that monoterpene hydrocarbons were the major components and limonene was the predominate compound for all citrus EOs. The antibacterial testing of EOs against five different bacteria (<i>Bacillus subtilis</i>, <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i> and <i>Salmonella typhi</i><i>murium</i>) was carried out using the filter paper method and the broth microdilution method. Kumquat EO had the best inhibitory effect on <i>B</i><i>. subtilis</i>, <i>E</i><i>. coli</i> and <i>S</i><i>. typhi</i><i>murium</i> with MIC (minimum inhibitory concentration) values of 1.56, 1.56 and 6.25 µL/mL, respectively. All citrus EOs showed the antioxidant activity of scavenging DPPH and ABTS free radicals in a dose-dependent manner. Nanfeng mandarin EO presented the best antioxidant activity, with <i>IC</i>₅₀ values of 15.20 mg/mL for the DPPH assay and 0.80 mg/mL for the ABTS assay. The results also showed that the antibacterial activities of EOs might not be related to their antioxidant activities.