Résumé:
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.
