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The leaf essential oils of the seven endemic New Caledonian species of the genus Melaleuca have been examined. Melaleuca sphaerodendra var. microphylla and Melaleuca brevisepala produced oils in which β-caryophyllene (28.8% and 26.8% respectively) was the principal component. α-Pinene (24.8%) and β-caryophyllene (14.1%) were the principal compounds detected in the leaf oil of Melaleuca pancheri. Melaleuca brongniartii produced an oil in which the principal monoterpenes were γ-pinene (23.3%), β-pinene (10.3%) and limonene (19.8%). γ-Terpinene (15.2%), p-cymene (12.8%) and terpinolene (17.5%) were the major components in the leaf essential oil of Melaleuca buseana, whereas the leaf oil of Melaleuca dawsonii contained a-pinene (12.8%) and α-phellandrene (10.3%) as principal components. In Melaleuca gnidioides α-pinene (23.6%), β-pinene (13.6%) and spathulenol (14.7%) were the major components. All of these oils differed from the leaf oil of Melaleuca quinquenervia, an indigenous New Caledonian species also found in Australia and New Guinea. [ABSTRACT FROM AUTHOR]

Melaleuca alternifolia (tea tree) and Thymus vulgaris (thyme) essential oils were tested for their antifungal activity to investigate the possibility of their use for seed treatment. The ability of the two oils to inhibit mycelial growth was studied by in vitro assay on agar medium containing different concentrations of the essential oils (0%, 0.05%, 0.1%, 0.25%, 0.5%, 1% v/v). Seven seed-borne pathogen fungi of large interest Ascochyta rabiei, Colletotrichum lindemuthianum, Fusarium graminearum, F. culmorum, Drechslera avenae, Alternaria radicina and A. dauci were transferred on the modified medium in order to test the oils antifungal activity, by calculating the Percentage of Mycelial Growth Inhibition (%MGI) and the Minimum Inhibitory Concentration (MIC). Results showed that both the oils had a clear reducing effect on fungal growth, that was dose-dependent and it differed depending on the fungal species, confirming what is already reported in literature, with T. vulgaris oil to be one of the most potent agent against fungi. M. alternifolia and T. vulgaris oils can be considered potential alternative natural fungicides to the synthetic chemicals that are currently used to prevent and control seed-borne diseases, and could be used in agriculture for safe and eco-friendly seed-treatments. [ABSTRACT FROM AUTHOR]

The leaf oils of the four species which comprise the Melaleuca minutifolia group have been examined by GC and GC/MS. The leaf oils of M. minutifolia contained a mixture of both mono- and sesquiterpenes, with α-pinene (16-20%) bring the principal monoterpene. The main sesquiterpenes present in the oil were aromadendrene (3-11%), bicyclogermacrene (5-10%) and α-, α- and β-eudesmol (7-11%, 5-7% and 8-12% respectively). Melaleuca monantha produced an oil which was much richer in α-pinene, 20-54% from one site and 66% from a second site accompanied by lesser, though still significant amounts of β-pinene (14-30% from one site and 2-9% from the second site). Melaleuca sylvana produced an oil in which α-pinene (26-62%) was the principal component. The main sesquiterpenes were β-caryophyllene (5-13%), bicyclogermacrene (3-11%). The leaf oil M. uxorum contained α-pinene (5-17%), bicyclogermacrene (6-13%), globulol (8-14%), spathulenol (6-14%) and viridiflorol (3-10%) as the main components. PCA analysis supports the taxonomic distinctness of the four species. [ABSTRACT FROM AUTHOR]

The leaf oils of the 11 recorded Western Australian species of the broombush complex of the genus Melaleuca have been examined by a combination of GC and GC/MS. Melaleuca atroviridis produced a monoterpenic leaf oil with α-pinene (11.0%) and 1,8-cineole (73.2%) being the principal components. Melaleuca concreta showed the presence of three chemotypes, one of which was rich in terpinen-4-ol (35.4%), while a second was rich in 1,8-cineole (58-81%). A third chemotype contained significant amounts of α-pinene (16.7%), 1,8-cineole (28.4%) and globulol (11.3%). Melaleuca exuvia produced a monoterpenic oil, which appeared to exist in two chemotypes, which contained α-pinene (13-23%), 1,8-cineole (56-67%), terpinen-4-ol (0.1-2%) and α-terpineol (3-7%) in one form and α-pinene (5-7%), 1,8-cineole (28-38%), terpinen-4-ol (11-17%) and α-terpineol (3-4%) in the second form. Melaleuca hamata produced a leaf oil that was dominated by monoterpenes. There appeared to be two chemotypes present, one in which terpinen-4-ol (41.6%) was the major component and a second chemotype in which 1,8-cineole (40.0%) and linalool (33.9%) were the principal components. Melaleuca interioris (from one population) contained a mixture of mono- and sesquiterpenes, in which sesquiterpenes predominated. Melaleuca osullivanii gave a leaf oil in which sesquiterpenes predominated, the principal component being spathulenol (10-18%). Melaleuca scalena produced a leaf oil dominated by monoterpenes, with α-pinene (25-31%) and 1,8-cineole (43-55%) being the principal components. Melaleuca stereophloia was dominated by monoterpenes of which the principal component was 1,8-cineole (78-83%). Melaleuca uncinata sens. strict. existed in a variety of forms one of which had major amounts of 1,8-cineole (44-56%), while a second contained major amounts of terpinen-4-ol (21-31%), γ-terpinene (10-14%) and α-terpinene (6-8%). Melaleuca vinnula appeared to exist in two chemotypes, one of which was rich in α-pinene (65.3%), while the second chemotype was rich in 1,8-cineole (60.6%). Melaleuca zeteticorum produced a leaf oil that was overwhelmingly monoterpene in character, the principal component being 1,8-cineole (63-68%). [ABSTRACT FROM AUTHOR]

Variations in the chemical composition and concentration of foliar essential oils of Melaleuca ericifolia from throughout the natural range of the species in southeastern Australia have been studied. The principal aim was to identify seed sources that had abundant oil with relatively high proportions of linalool in combination with relatively low proportions of 1,8-cineole for establishment of pilot plantations. Oil yield (w/w% DW ± SD) was greatest amongst NSW populations (3.2% ± 0.95) and poorest amongst the populations from western Victoria and northwestern Tasmania (0.6% ± 0.3). Oil composition varied quantitatively throughout the species range rather than qualitatively in an apparent association with latitude of occurrence. Linalool and linalool oxide were abundant in the oils from the north of the species range in New South Wales with a gradual southerly decline in these compounds to central Victoria with concomitant increase in the proportions of 1,8-cineole, á-terpineol and limonene. The most southerly populations sampled in southern Victoria and Tasmania gave oils containing relatively high proportions of 1,8-cineole (mean 34.5% ± SD 6.6) and low proportions of linalool (3% ± 4.5). Four populations from the Central Coast of NSW (Coopernook, Hawks Nest, The Entrance and Tuggerah Lake) provided the greatest opportunity of identifying seed trees that combine the attributes required for plantation development. The tree that had the best combination of oil traits (DL 3116 from Hawks Nest) had an oil yield of 4.5%, a linalool content of 60% and a 1,8-cineole content of 16%. [ABSTRACT FROM AUTHOR]

The essential oil of the previously un-investigated leaves and twigs of Melaleuca teretifolia End1. (Myrtaceae), growing wild in Western Australia, was investigated by GC and GC/MS. One oil, which yielded 0.2% on a fresh weight basis, was found to be rich in 1,8-cineole (84.0%), with α-pinene (1.8%), β-pinene (1.2%), limonene (3.1%), terpinen-4-ol (1.8%) and α-terpineol (3.3%) as the only other significant constituents. The lemon form gave a much higher yield (1.5%) of an oil rich in neral (29.1%), geranial (38.8%), and myrcene (9.8%), with significant concentrations of limonene (1.0%), citronellal (1.0%), terpinen-4-ol (3.4%), geraniol (2.1%), nerol (1.1%), (Z)-isocitral (1.6%) and (E)-isocitral (2.4%). This form has the potential to compete with commercial citral oils. [ABSTRACT FROM AUTHOR]