Antioxidant and antipathogenic activities of citrus peel oils

The present study was focused on unexplored Pakistani citrus species viz. sweet oranges (Citrus sinensis Vars. Jaffa, Blood Red and Mosambi), Mandarins (Citrus reticulata Var. kinnow) and grapefruits (Citrus paradisi Var. Shamber) for peel oil yield, chemical composition and antipathogen activities. The chemical composition of citrus peel oil was analyzed through gas chromatographic - mass spectrometric analysis. Six compounds viz. D-limonene, d-carvone, Z-5-nonadecane, thujol, trans-P-mentha-2,8-dienol and heneicosane were commonly present in all cultivars. However, D-limonene (40.9-76%) was a major compound in all citrus peel oils. The high amounts of phenolic compounds were recorded in the peel oil with a maximum amount in grapefruit (8.58 mg/g) and minimum in Kinnow mandarin (5.20 mg/g). Jaffa orange cultivar showed a highest radical scavenging activity (70.14%). Furthermore, peel oils were tested for their antimicrobial activities against five pathogenic bacterial strains viz. Staphylococcus aureus, Eschrichia coli, Salmonella typhi, Proteus vulgaris, Staphylococcus epidermidis and two pathogenic fungal strains viz. Aspergillus flavus and Trichophyton alba. Citrus peel was found effective against all tested micro-organisms and in particular Jaffa orange essential oil was highly effective against all microbial strains growth and Salmonella typhi was the most inhibited strains among all.