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Two germacradienols, 4-β-hydroxygermacra-1(10),5-diene (β-germacrenol) and 6-α-hydroxygermacra-1(10), 4-diene (kunzeaol) were identified in the solvent extracts of members of the family Myrtaceae. Acid solvolysis associated with steam distillation or leaf ageing causes these germacradienols to rearrange to a mixture of (+)-δ-cadinene, α-cadinol, τ-cadinol, α-muurolol, τ-muurolol and associated sesquiterpenoids. Copyright © 2001 John Wiley & Sons, Ltd.

The sesquiterpenoids (+)-δ-cadinene, epicubenol and cubenol in the essential oils of the Myrtaceae are by-products of the acid-solvolysis of the sesquiterpene alcohols cubebol and epicubebol. This solvolysis can occur during leaf ageing or steam distillation. Significant proportions of these compounds can be found in many members of the Myrtaceae, most notably commercial tea tree (Melaleuca alternifolia and M. linariifolia). Copyright © 2000 John Wiley & Sons, Ltd.

The steam distillates of the family Myrtaceae are often found to contain the three isomeric sesquiterpene alcohols, β-, β- and γ-eudesmol. Associated with these alcohols but not steam-distilled with them are two hydrates of eudesmol, cryptomeridiol and 4-epicryptomeridiol, compounds which have not been previously reported in the Myrtaceae. These five alcohols are the major by-products of the hydrolysis of hedycaryol, which can occur during leaf ageing or distillation. The use of H218O during distillation implicated the presence of hedycaryol prior to distillation by trapping the eudesmyl-carbocation formed during the hydrolysis. Copyright © 2000 John Wiley & Sons, Ltd.

The minimum inhibitory concentrations (MIC) of 60 terpenoids against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Candida albicans have been determined. Hierarchical cluster analysis was used to group the compounds into five groups according to their activity patterns against the four microorganisms. K-Means cluster analysis was then used to confirm these groupings and to show the differences in the activity patterns of the groups. Ten molecular properties of the terpenoids, either calculated via molecular modelling or determined by direct measurement, were then used as variables in a forward stepwise discriminant analysis to identify which variables discriminated between groups. Low water solubility of Group IV compounds, mainly hydrocarbons and acetates, was found to be associated with their relative inactivity. The remaining groups, all containing oxygenated terpenoids, showed characteristic but distinct activity patterns towards the four test organisms. Hydrogen bonding parameters were found to be associated with antimicrobial activity in all cases. Activity against Gram-negative E. coli and P. aeruginosa was associated with a combination of a hydrogen bonding and size parameters. This was not found to be the case for the Gram-positive S. aureus or the yeast C. albicans. Copyright © 1999 John Wiley & Sons, Ltd.

A hydrodistilled oil obtained from the leaves of Leucas milanjiana Gurke (Lamiaceae) was analysed by capillary GC and GC-MS. The leaf volatile oil contained 30 components, out of which 26 were identified. The predominant components were found to be β-cubebene (38.15%), α-pinene (19.71%), trans-caryophyllene (7.41%) and α-terpinolene (5.34%). The results are qualitatively and quantitatively at variance with data on other Leucas species and may therefore be of some chemotaxonomic significance for the genus. Copyright © 2006 John Wiley & Sons, Ltd.