The Leaf Essential Oils of Eucalyptus miniata and Its Allies

Abstract

The leaf oils of Eucalyptus chartaboma Nicolle, Eucalyptus miniata Cunn. Shauer and E. gigantangion L. Johnson et K. Hill have been analyzed by a combination of GC and GC/MS. Eucalyptus chartaboma has been found to exist as two chemotypes that are determined by the number of aryl ketones contained in the leaf oil. Chemotype 1 contained isobaeckeol (1-(6-hydroxy-2, 4-dimethoxy-3-methylphenyl)-2-methylpropan-1-one) and homoisobaeckeol (1-(6-hydroxy-2, 4-dimethoxy-3-methylphenyl)-2-methylbutan-1-one), each accounting for approximately 25% of the oil. Chemotype 2 contained nine aryl ketones: apodophyllone (1-(2,4,6-trimethoxy-3, 5-dimethylphenyl)-2-methylpropan-1-one), isotorquatone (1-(2,4,6-trimethoxy-3,5-dimethylphenyl)-2-methylbutan-1-one), torquatone (1-(2,4,6-trimethoxy-3,5-dimethylphenyl)-3-methylbutan-1-one), chartabomone (1-(6-hydroxy-2,4-dimethoxy-3,5-dimethylphenyl)-2-methylbutan-1-one), isobaeckeol, miniatone (1-(6-hydroxy-2,4-dimethoxy-3,5-dimethylphenyl)-3-methyl-butan-1-one), baeckeol methyl ether, homoisobaeckeol and homobaeckeol methyl ether, which together accounted for approximately 50% of the oil. In both cases, the remainder of the oil consisted of terpenes, with α-pinene being by far the major component. Eucalyptus miniata contained only one chemotype, which contained all nine of the above aryl ketones in similar proportions to those in chemotype 2 of E. chartaboma. E. gigantangion did not contain any aryl ketones in its leaf oil, which was composed entirely of terpenes, with α-pinene (45%), limonene (5%), α-terpineol (8%) and borneol (5%) being the principal components.