Studies on the Leaf Oils of Citrus Species

Leaf oil samples of four different citrus species were prepared from young leaves and the detailed composition of each leaf oil was investigated using gas chromatography, thin-layer chromatography and infrared spectrometry. The following components were identified: α-pinene, α-thujene, β-pinene, limonene, γ-terpinene, p-cymene, p-α-dimethylstyrene, β-humulene, β-selinene, trans-2-hexen-l-al, cis-3-hexen-l-ol, trans-2-hexen-l-ol, linalool terpinen-4-ol and α-terpineol. In addition, camphene, sabinene, β-myrcene, α-terpinene, β-elemene, caryophyllene, neral, geranial, nerol and geraniol were tentatively identified. Most of the components were found to be contained in common in the leaf oils of four different citrus species, but the relative contents of some of the components such as limonene, γ-terpinene, p-cymene, linalool, neral and geranial were distinctly different from species to species. Thus, gas chromatographic analyses of leaf oils seemed to be useful for the identification of citrus species.