Composition of the essential oils ofPelargonium sidoides DC. andPelargonium reniforme Curt.

The essential oils of Pelargonium sidoides DC. and P. reniforme Curt. were obtained by hydrodistillation from the leaves of the plants in 0.52% and 0.71% yields, respectively, related to the dry weight. Their composition was analysed by GLC and GC–MS. About 230 components have been detected in each of the Pelargonium oils, of which 102 (P. sidoides) and 81 (P. reniforme) could be unambiguously identified, accounting for about 65% and 49% of the total peak area, respectively. For both species, sesquiterpenes (approximately 60%) were the dominating components, with caryophyllene (2.3%) and caryophyllene epoxide (13%) as the most abundant compounds of the sesquiterpene fraction of the oil of P. sidoides, and the sesquiterpene hydrocarbons δ-selinene (4.2%) and δ-cadinene (4.0%) as the main representatives of the oil of P. reniforme. Other major groups of the oil of P. sidoides comprised monoterpenes (16%) and phenylpropanoids (9%), the major compounds of the latter group being methyleugenol (4.3%) and elemicin (3.6%). By contrast, only monoterpenes were found in reasonable amounts (4.7%) in the related species P. reniforme. Detection of anacardic acids and furan-type constituents provide a rational explanation for insect deterrency by Pelargonium species.