Abstract
Tyrosinase is a target enzyme to be inhibited in order to reduce excessive melanin
production and prevent typical age-related skin disorders. Essential oils are complex
mixtures of volatile compounds, belonging mainly to monoterpenoids and sesquiterpenoids,
which have been relatively little studied as tyrosinase inhibitors. Among the monoterpenoids,
citral (a mixture of neral and geranial) is a fragrance compound in several essential
oils that has shown interesting tyrosinase inhibitory activity. Although citral is
listed as an allergen among the 26 fragrances in Annex III of the Cosmetics Directive
2003/15/EC, it can be safely used for the formulation of topical products in amounts
that are not expected to cause skin sensitization, as shown by various commercially
available products.
The aim of this work was to evaluate two different formulations (oil/water emulsion,
oily solution) containing a new combination of essential oils (Litsea cubeba, Pinus mugo, Cymbopogon winterianus) applied to the skin both in nonocclusive and partially occlusive modes. The blend
is designed to reduce the concentration of citral to avoid potential skin reactions
while taking advantage of the inhibitory activity of citral. Specifically, the amount
of citral and other bioactive compounds (myrcene, citronellal) delivered through the
skin was studied as a function of formulation and mode of application.
The results show that an oil/water emulsion is preferable because it releases the
bioactive compounds rapidly and minimizes their evaporative loss. In addition, semi-occluded
conditions are required to prevent evaporation, resulting in higher availability of
the bioactive compounds in viable skin.
Key words
essential oils - dermal permeation -
Litsea cubeba
- Lauraceae -
Pinus mugo
- Pinaceae -
Cymbopogon winterianus
- Poaceae
