Etude de l’activité antioxydante et anti-inflammatoire d’extraits du lichen Parmotrema hypotropa sur un modèle de dermatite atopique chez la souris.

Abstract

Lichens are organisms consisting of a fungus and algae or cyanobacteria living in symbiosis, they are used in traditional medicine throughout the world to treat many diseases such as respiratory, digestive, gynecological, and cutaneous disorders. Recently, many studies have proven their antioxidant, antibacterial, anti-inflammatory, and anti-tumor effects. This work aims to study the effect of Parmotrema hypotropa lichen extracts on induced atopic dermatitis in mice. Our work begins with a study of the phytochemical and antioxidant properties of extracts, followed by an evaluation of the anti-inflammatory effect in vitro and on an atopic dermatitis model in vivo. The content of polyphenols and flavonoids was determined in the dichloromethane and ethanol extracts according to the methods of Folin Ciocaleu and aluminum chloride respectively. The amount of usnic acid in the extracts was measured by high-performance liquid chromatography (HPLC). The antioxidant activity of the two extracts was evaluated by different methods DPPH, ABTS, β-carotene bleaching, and CUPRAC. The extracts were then tested in vitro, for their anti-inflammatory effect via the denaturation test of bovine serum albumin (BSA), and on the cell line of human keratinocytes (HaCaT) by measuring the intercellular production of ROS (Reactive Oxygen Species) and TNF-α (Tumor necrosis factor-alpha), the effect of dichloromethane extract on atopic dermatitis was evaluated in vivo on a model induced by DNCB. The results show that the dichloromethane extract is richer in polyphenols and usnic acid, and it has a greater antioxidant effect than the ethanolic extract. Both extracts prevent the denaturation of BSA in a dose-dependent manner and reduce the intracellular production of ROS and TNF-α by keratinocytes. The dichloromethane extract tested on a dermatitis model shows a reduction in dermatitis-induced lesion scores. From the histological results, the P.hypotropa lichen leads to skin repair. Based on the different results, the P.hypotropa lichen is a potential source of bioactive compounds with antioxidant and anti-inflammatory effects that can be used as treatment for atopic dermatitis.