Evaluation of the chemical constituents and the antimicrobial activity of the volatile oil of Citrus reticulata fruit(Tangerine fruit peel) from South West Nigeria

The volatile oil of tangerine fruit (Citrus reticulata) was extracted by steam distillation and assessed for antibacterial and antioxidant activity. The volatile oil was tested against some Gram-negative organisms (Escherichia coli ATCC 35218, E. coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella paratyphi, Proteus mirabilis and Citrobacter spp); Gram-positive organisms such as Staphylococcus aureus ATCC 25923, S. aureus, Enterococcus faecalis and a fungus (Candida albicans). The minimum inhibitory concentration (MIC) was determined with concentrations of oil extract ranging from 0.87 to 445 mg/ml. Result of the study showed that the oil has a broad spectrum antibacterial activity. MIC recorded were S. aureus (0.74 mg/ml), S. aureus ATTC 25923 (2.46 mg/ml), E. faecalis (1.26 mg/ml), S. typhi (2.07 mg/ml), K. pneumoniae (0.56 mg/ml), E. coli ATTC 35218 (0.19 mg/ml), E. coli (1.95 mg/ml), P. aeruginosa (0.97 mg/ml), C. albicans (0.68 mg/ml). Antioxidant screening with 2,2-diphenyl-1-picrylhydrazyl (DPPH) was negative. Analysis of the chemical constituent by GC-MS showed the presence of D-limonene as the major constituent. Other constituents found were a-pinene and β-pinene