Jingyu Chen, Joseph Lichwa and Chittaranjan Ray*

Abstract: The chemical composition of the essential oils from the leaves of Araucaria heterophylla (also known as Norfolk Island pine), Casuarina cunninghamian, Eucalyptus citriodora, Psidium cattlenium var. lucidum (also known as strawberry guava), and litters of the first two species were studied using two gas chromatography techniques, one equipped with a mass spectrometer detector (GC/MS) and the other with a flame ionization detector (GC/FID). Six volatile compounds were identified in the leaf oil of A. heterophylla. A substantial increase in the amount of α-pinene, α-terpinene and a decrease in the amount of β-caryophyllene was noticed in the litter oil of A. heterophylla. Three volatile compounds were identified in C. cunninghamian. Another monoterpene, α-terpinene, was observed in the litter oil of C. cunninghamian. Eleven compounds were identified in the leaf oil of P. cattlenium, of which β-caryophyllene (59.0%), α-pinene (13.2%) and myrcene (11.3%) were the major components. Thirteen volatile oil compounds were identified in the E. citriodora leaf oil, of which citronellal (42.8%), citronellol (17.9%) and α-terpinene (11.2%) were the major components.

The relative composition of essential oils from the leaves of tropical plants and their associated litters has rarely been investigated. This knowledge can have significance for the chemistry and microbiology of soils present under these plants. Essential oils from four plants in Hawaii: Araucaria heterophylla (Salisb.) Franco (Norfolk Island pine), Casuarina cunninghamian Miq, Eucalyptus citriodora Hook., Psidium cattlenium Sabine var. lucidum Hort (strawberry guava), and litters of the first two species were chosen to be qualitatively and quantitatively analyzed to understand their dynamics. Although several papers about the chemical composition of the leaf oils of A. heterophylla (1-3), E. citriodora (4-7), P. cattlenium (8-10) have been published, we are not aware of any research on the leaf oil compositions of C. cunninghamian and the litters of A. heterophylla and C. cunninghamian.