The production of reactive oxygen species (ROS) in normal tissues is associated with side effects of many cancer treatments. This is, in particular, the case for the skin photosensitization experienced by certain patients subjected to PDT based on a systemic administration of photosensitizers (PS). Similarly, the ROS generated in normal tissues during radiotherapies are responsible for the damages induced in various organs, including the skin.

Catechin, a natural antioxidant belonging to the family of flavan-3-ols (or flavanols), is known for its beneficial properties associated with its antioxidant action. Therefore, the main aim of the study reported here is to determine if catechin can reduce certain damages induced by PDT performed with one of the most common photosensitizers, 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX).

Our study was performed on an in vivo model, the vasculature developing in the chick's embryo chorioallantoic membrane, which was treated with a topical administration of a 20 mg/mL ALA solution during 4 hours before PDT. We demonstrated that the topical administration of catechin can significantly inhibit the vascular damages induced by ALA-PpIX-based PDT. Our results strongly suggest that catechin possesses a photoprotective effects against PpIX-PDT as well as other sources of ROS.