Лекарственные и ароматические растения
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Characterization and Identification of the Components Extracted from 28 Lichens in Tunisia by High Performance Thin-Layer Chromatography (HPTLC), Morphologic Determination of the Species and Study of the Antibiotic Effects of Usnic Acid

Karima Tabbabi and Tijani Karmous

This aim of this work is to study the isolation of usnic acid found in many lichen species and the evaluation of its antibacterial activity. The study began with a morphological determination of lichens harvested in Tunisia. The corresponding analysis identified 28 species belonging to the following families: Xanthoria, Parmelia, Caloplaca, Ramalina, Diploschistes, Usnea. A chromatographic study of the chemical composition of these lichens highlighted the presence of many compounds belonging to various chemical categories: depsides and depsidones, xanthones, anthraquinones, dibenzofurans, etc. Special attention was given to the components of this last category and particularly to usnic acid which is therapeutically very interesting. This component plays a very important role in fighting the bacteria responsible for numerous urinary and pulmonary infections and also in fighting viruses responsible for certain tumors. Antibacterial activity tests showed that the Staphylococcus aureus and Enterococci strains have certain sensitivity to usnic acid extracted from the Usnea hirta lichen. Given that various fields, and especially medicine, are currently showing considerable interest in vegetable extracts, this study will be continued in the future with the aim to isolate other components with efficient therapeutic effects.