Abstract
Melaleuca alternifolia essential oil (tea tree oil) is widely used as an ingredient in skin care products
because of its recognized biological activities. The European Scientific Committee
on Consumer Products constantly promotes research and collection of data on both skin
distribution and systemic exposure to tea tree oil components after the application
of topical formulations. This study quantitatively evaluates permeation, skin layer
distribution (stratum corneum, epidermis, and dermis), and release into the surrounding environment of bioactive
tea tree oil markers (i.e., α-pinene, β-pinene, α-terpinene, 1,8-cineole, γ-terpinene, 4-terpineol, α-terpineol) when a 5% tea tree oil formulation is applied at a finite dosing regimen.
Permeation kinetics were studied in vitro on pig ear skin using conventional static glass Franz diffusion cells and cells ad
hoc modified to monitor the release of markers into the atmosphere. Formulation, receiving
phases, and skin layers were analyzed using a fully automatic and solvent-free method
based on headspace solid-phase microextraction/gas chromatography-mass spectrometry.
This approach affords, for the first time, to quantify tea tree oil markers in the
different skin layers while avoiding using solvents and overcoming the existing methods
based on solvent extraction. The skin layers contained less than 1% of each tea tree
oil marker in total. Only oxygenated terpenes significantly permeated across the skin,
while hydrocarbons were only absorbed at trace level. Substantial amounts of markers
were released into the atmosphere.
Key words
Melaleuca alternifolia
- Mirtaceae - tea tree oil - headspace solid phase microextraction - GC-MS -
in vitro permeation kinetics - skin layer distribution
