Skin Retention of Sorbates from an After Sun Formulation for a Broad Photoprotection

Cristina Padula,Patrizia Santi,Leticia Grolli Lucca,Anna Demurtas,Silvia Pescina,Sara Nicoli

doi:10.3390/cosmetics6010014

Abstract

Overexposure to sunlight is widely accepted as the underlying cause of cutaneous melanoma. UV radiation induces the formation of DNA photoproducts that, if unrepaired, can induce carcinogenic mutations. Recent data indicate that sorbates can be useful to widen the protection against UV radiation by acting as a triplet-state quencher in the melanocyte. The aim of the present work was to prepare an after sun formulation containing ethylsorbate or sorbic acid in order to take advantage of the triplet-state quenching activity of these molecules and protect the skin from UV-induced damages. Ethylsorbate and sorbic acid were characterized in terms of solubility and partition coefficient, and their transdermal permeation and skin accumulation were studied in vitro from simple solutions and in the presence of cyclodextrins (alpha and hydroxypropylbeta) as a complexing agent. The goal was to reduce as much as possible sorbates permeation while sustaining their skin levels. The obtained results indicated that the addition of alphacyclodextrins determined a 6-folds (ethylsorbate ) or 4-folds (sorbic acid) reduction of the transdermal permeation. Sorbic acid and alphacyclodextrin (1:1 molar ratio) were then formulated in an after sun vehicle using 1.5% hyaluronic acid (sodium salt) as a thickener and hydrating agent. The addition of hyaluronic acid gave rise to a formulation with good cosmetic properties and good sorbate (0.2–0.3 µmol/cm2) skin levels (stratum corneum + viable epidermis) and thus a potential protection against post-exposure UV damage.

Highlights

Cutaneous melanoma is a very aggressive form of skin cancer originating from melanocytes that become cancerous cells due to aberrant changes at the biochemical level
Overexposure to sunlight is widely accepted as the underlying cause of cutaneous melanoma and it has been estimated that four out of five cases of skin cancer could be prevented, through the limitation of exposure to the mid-day sun and the use of sunscreens [1,2]
“dark cyclobutane pyrimidine dimers (CPD)” and are due to the chemiexcitation of melanin derivatives and the formation of a melanin quantum triplet state that acts as a CPD maker [3]

Summary

Introduction

Cutaneous melanoma is a very aggressive form of skin cancer originating from melanocytes that become cancerous cells due to aberrant changes at the biochemical level. The result is the formation of cyclobutane pyrimidine dimers (CPD), DNA photoproducts that, if unrepaired, can induce carcinogenic mutations. These CPDs form picoseconds after an ultraviolet (UV) photon is absorbed, so they originate only during UV exposure and can be prevented by UV filters. Some researchers demonstrated that in melanocytes, CPDs are continuously generated for hours (at least 3) after exposure to UVA. These CPDs are called “dark CPD” and are due to the chemiexcitation of melanin derivatives and the formation of a melanin quantum triplet state that acts as a CPD maker [3].

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Methods

Results