S. Grant Wyllie

The role of structure and molecular properties of terpenoids in determining their antimicrobial activity

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

Determining the Antimicrobial Actions of Tea Tree Oil

Research into the mode of action of the essential oil of Melaleuca alternifolia (Tea tree oil) is briefly reviewed. Its mode of action is interpreted in terms of the membrane-toxicity of its monoterpenoid components and different approaches for determining cell membrane damage are discussed.

Determination of octanol-water partition coefficient for terpenoids using reversed-phase high-performance liquid chromatography.

Octanol-water partition coefficients (Kow) for 57 terpenoids were measured using a RP-HPLC method. Sample detection was achieved with standard UV and refractive index detectors and required no special column treatment. Measured log Kow values for the terpenoids ranged from 1.81 to 4.48 with a standard error of between 0.03 and 0.08 over the entire range. Partition coefficients determined by the RP-HPLC method were compared against shake flask, atom/fragment contribution, fragment and atomistic methods. The HPLC values were found to give the best correlation with shake flask results. Log Kow values calculated by the atom/fragment contribution method gave the best correlation with the HPLC values when compared to fragment and atomistic methods.

The use of HPLC protein profiles in fish species identification

Abstract A method for the rapid identification of fish species by high performance liquid chromatographic (HPLC) analysis of water-soluble sarcoplasmic protein extracts is described. The method relies on the visual comparison of a star-symbol plot constructed from the samples HPLC profile with those obtained from the mean profile data of morphologically identified species. A library of plots is presented for 15 common edible marine fish species from eastern Australian waters, but any suitable data can be used for star construction. The data presented are applicable to the identification of samples from any season or location, whether they are raw, gamma-irradiated, or dried with infra-red radiation. The procedure involves a single 10 min extraction followed by a 60 min analysis, without the use of an internal standard.

Incorporation of oxygen-18 into terpinen-4-ol from the H218O steam distillates of Melaleuca alternifolia (tea tree)

ABSTRACT Steam distillation of young leaves of Melaleuca alternifolia in 18O-labelled water resulted in the 180-labelling of the principal oxygenated p-menthanes, terpinen-4-ol and α-terpineol. The p-methanes; terpinen-4-ol, γ-terpinene, α-terpinene, terpinolene and p-cymene, found in M. alternifolia oil are primarily formed from cis-sabinene hydrate and to a lesser extent from trans-sabinene hydrate and sabinene. The pattern of the p-menthanes and the enantiomeric composition of terpinen-4-ol found in young and old leaves, regardless of the isolation process are similar to those formed during the acid catalyzed transformations of sabinene or sabinene hydrate. The incorporation of 180 into terpinen-4-ol during steam distillation in H2 18O supports the formation of terpinen-4-ol and the other p-menthanes from the terpinen-4-yl cation, generated from the hydration of sabinene and/or sabinene hydrate. This same mechanism appears to operate during leaf aging. Around 60% of the terpinen-4-ol obtained from the ...

Effects of season and location of catch on the fatty acid compositions of some Australian fish species

Abstract Fatty acid compositions and lipid contents of five common table species of marine fish from temperate Australian waters were determined for samples taken during two seasons (four species) and three locations of markedly differing latitude (one species). Variabilities in total lipid extract and phospholipid fatty acid compositions were assessed between samples of each species, as well as between individuals of the same sample. These were then compared with data obtained for the other species analysed. The highest n3 polyunsaturated fatty acid (PUFA) content lipids were found in fish from colder waters (southern locations and spring season catches). The leaner species were found to have much more stable lipid characteristics with changes in the water temperature at sampling.

Effects of preservation by gamma-irradiation on the nutritional quality of Australian fish

Abstract Gamma-irradiation preservation of two species of Australian marine fish (Black Bream and Redfish) resulted in no significant changes in their fatty-acid compositions, even when performed at up to three times the commonly recommended maximum dose for fish. Vitamin E loss was evident in some fillets but could not be correlated with the treatment dosage. All irradiated fillets were found to have vitamin E contents above the levels believed to be desirable for human consumption, relative to the amounts of accompanying polyunsaturated fatty acids.

The origin of terpinen-4-ol in the steam distillates of Melaleuca argentea, M. dissitiflora and M. linariifolia

Abstract The presence of terpinen-4-ol in the steam distillates from Melaleuca argentea, M. dissitiflora and M. linariifolia can be linked to high levels of (+)-sabinene and cis- and trans-sabinene hydrate in the leaf material. Incorporation of 18O into the terpinen-4-ol from steam distillates performed in H2 18O confirms the generation of the terpinen-4-yl carbocation intermediate from (+)-sabinene and cis- and trans-sabinene hydrate. This same mechanism is also operating during leaf aging.

Rearrangement of p-menthane terpenes by Carboxen during HS-SPME

The commercially available 75 μm Carboxen-Polydimethylsiloxane (PDMS) fibre for solid phase microextraction (SPME) has been shown to rearrange some monoterpenoids to p-cymene during headspace (HS)-SPME analysis. Ten commonly encountered monoterpenoids varying in structural and/or functional group were used as test compounds. The p-menthane hydrocarbons α- and γ-terpinene, α-phellandrene, and terpinolene were the only analytes rearranged by the Carboxen-PDMS coating with p-cymene/analyte ratios determined to be higher than those obtained by the 100 μm PDMS-coated fibre used for comparison. The much higher (>10 times) level of moisture adsorbed by the Carboxen-PDMS coating when compared to the PDMS coating is considered to be one of the factors responsible for the rearrangement process.

THE SEPARATION OF STEREOISOMERS FROM OLIGOMERS OF LOW MOLECULAR WEIGHT POLYSTYRENE ON A CARBON CLAD ZIRCONIA COLUMN USING A REVERSED PHASE MULTIDIMENSIONAL HPLC SYSTEM

The two dimensional separation of low molecular weight polystyrene oligomers and stereoisomers was achieved using a liquid chromatographic system designed for ‘heart-cutting’ multidimensional chromatography. The first separation process incorporated a C18 column and a methanol mobile phase to separate the oligomers, whilst the second separation process utilised the change in selectivity associated with a carbon clad zirconia stationary phase and an acetonitrile mobile phase for the separation of the isomers. The two dimensional separation that was achieved using this automated system was comparable to the individual separations following manual sample manipulation in each individual separation step. Furthermore, the multidimensional LC system was shown to be highly reproducible in routine continuous operation over an eight hour period.