The transdermal absorption of tea tree oil and potential anti-inflammatory properties

Abstract

Melaleuca alternifolia (Tea tree oil) is commonly used by the general public in the treatment of superficial dermatological conditions. There is a growing body of evidence to support its use as an anti-fungal and anti-bacterial agent. However, there is little evidence of the in vivo penetration of components of the oil through the skin, imperative to ensure its use is directed appropriately and safely. Furthermore the extent of TTO’s ability as an anti-inflammatory agent and its potential mode of action are not know.
This thesis describes the adaption and validation of the method in vivo dermal microdialysis in order to identify and quantify components of tea tree oil present at the dermal epidermal junction following the topical application of 100% TTO. In vitro investigations identified that the addition of hydroxypoply –?-cyclodextrin to the perfusate, the adjustment of flow rate and the use of cuprophan membranes ensured optimal recovery of components. Furthermore tape stripping was utilized to identify components present within the stratum corneum (SC). These methods were coupled with gas chromatography-mass spectrometry and were successful in the identification and quantification of terpinen-4-ol, 115.64±28.1 (ng±SEM) and 1,8 cineole, 15.05±2.6 at the dermal epidermal junction (n=10). Also the presence of 9 hydrophilic and lipid components (overall subjects) were observed within this top layer of epidermis (n=7).
In addition the potential anti-inflammatory action of TTO and its component T-4-ol is investigated in vitro using the HaCaT cell line (model keratinocytes) including exploration of a potential mode of action. An inflammatory action was induced using lipopolysaccharide (LPS) and the cell supernatant analysed using the MSD™ electronchemiluminesence assay. A statistically significant increase in the release of IL1? was observed when non-stimulated HaCaT cells were incubated with TTO (not T-4-ol alone), compared to control (medium alone). Furthermore a statistically significant increase in IL6 was observed when non-stimulated HaCaT cells were incubated with TTO and T-4-ol compared with the incubation of stimulated HaCaT cells with the oil and its component. Investigation into the effect of TTO and T-4-ol on the transcription factor NF?B demonstrated that the oil and its component did not exert its effect by initiation of this pathway.
The findings of this research have implications for clinical practice, particularly in the use of TTO on areas of dermatological inflammation and its use on ‘healthy’ skin.

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ORCID for David Voegeli: orcid.org/0000-0003-3457-7177

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