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Abstract
The composition and antimicrobial activity of the essential oil of leaves and flowers of Pelargonium zonale L. cultivated in Egypt were investigated. Hydrodistillation of the leaves and flowers yielded 0.12% and 0.06% (v/w of fresh plant) of yellowish green essential oils, having a sweet balsamic odor. GC-MS analysis led to identification of 25 and 20 components, based on retention indices and mass spectral data, representing 97.0% and 94.8% of the total oils, respectively. Sesquiterpenoids were predominant in the two oils (73.9 and 81.9% of the constituents) with hydrocarbons as major (51. 8% and 63.5%) followed by oxygenated components constituting 22.1% and 18.3%, respectively. On the other hand, monoterpenoids reached only 7% and 5.8% among which hydrocarbons constituted 7% and 1.67%, respectively, of the total oils; while oxygenated compounds (2.6%) were detected only in the flower sample. The essential oil of the leaves was typified by the presence of β-caryophyllene (24.6%), α-humulene (23.8%), caryophyllene oxide (8.5%) and α-cedrol (8.3%); while that of the flowers was characterized by α-humulene (36.73%). Meanwhile, the major monoterpene hydrocarbon was β-myrecene (7% and 1.6%, respectively) in both oil samples. The antimicrobial activities of the essential oils were evaluated through determination of their zones of inhibition and minimum inhibitory concentrations (MIC) by using clinical bacterial and fungal isolates including: Gram positive (Bacillus subtilis, Staphylococcus aureus, Sarcina lutea and Mycobacterium phlei) and Gram negative (Escherichia coli, Pseudomonas aeruginosa and Helicobacter pylori) bacteria and (Aspergillus niger and Candida albicans) as representative of fungi. The essential oil of the leaves exhibited a significant antimicrobial activity against all tested microorganisms except E. coli, while that of the flowers was relatively less active against most of the tested microorganisms. It is noteworthy to mention that both oils were active against Helicobacter pylori.