Chemical composition of the leaf essential oil of grapefruits (Citrus paradisi Macf.) in relation with the genetic origin

The composition of twenty-four samples of essential oil isolated from leaves of Citrus paradisi Macf. growing in a northern area of citrus cultivation in Mediterranean climate (Corsica) was investigated by GC (RI), GC-MS and C-13 NMR. Thirty-six compounds accounting for 94.9-99.3% of the oil composition were identified. The oils contained mainly monoterpene hydrocarbons and specially sabinene (up to 60.2%),(E)-beta-ocimene (up to 15.0%) and punctually gamma-terpinene (up to 56.1%), beta-pinene (up to 30.9%) and p-cymene (up to 12.5%). The twenty-four compositions were submitted to k-means partitioning and principal component analysis, which allowed the distinction of one homogeneous group of twenty-two grapefruits (main compound sabinene, mean = 47.1%). This group included eighteen cultivars derived by mutation from the ancestral grapefruit tree (Duncan) and four cultivars known to be interspecific hybrids. Two out group cultivars were clearly differentiated from others by original chemical compositions, in agreement with their hybrid origin.