Study on antioxidant and antimicrobial activities of essential oils extracted from leaves of differnt citrus varieties

Abstract

Essential oils are natural compounds containing an amount of complex mixtures of volatile compounds. This study was carried out to determine the antioxidant and antimicrobial activities of essential oils extracted from leaves of different citrus varieties. Essential oils of Long An lime (Citrus aurantifolia Swingle), Xoan orange (Citrus sinensis Osbeck) and Tan Trieu pomelo (Citrus grandis Osbeck) were extracted by hydro-distillation method. The antimicrobial activities were tested by diffusion method and dilution method. Essential oil of pomelo leaves was the strongest among all with big zones of inhibition (25.38 ± 0.38mm, 24.41 ± 0.38mm, 24.17 ± 0.29mm) and low minimum inhibitory concentration (21.5mg/ml, 21.5mg/ml, 10.75mg/ml) against Staphylococcus aureus, Samonella typhimurium and Bacillus cereus. On the other hand, essential oil of orange leaves was considered as the weakest one because of no inhibition against Pseudomonas aeruginosa. The antioxidant activities of these essential oils were determined by 2,2-diphenyl–1-picrylhydrazyl (DPPH) assay and Ferric Thiocyanate (FTC) assay. The antioxidant activities of essential oil of pomelo leaves, in contrast to antimicrobial activities, were reported to be the weakest among all (with 2.142 ± 0.003mg/ml and 36.84 ± 0.22mg/ml of half inhibition concentration). Essential oil of lime leaves was found to be the strongest in antioxidant activities (with 1.209 ± 0.003mg/ml and 30.34 ± 1.03mg/ml of half inhibition concentration). According to the results, essential oils extracted from leaves of different Citrus varieties may have different antimicrobial and antioxidant activities. Key words: essential oil, Citrus leaves, hydro-distillation, antimicrobial activities, antioxidant activities