Usnic acid has a variety of biological activities, and has been widely studied in the fields
of antibacterial, immune stimulation, antiviral, antifungal, anti-inflammatory and antiparasitic.
Based on this, usnic acid is used as the lead compound for structural modification. In order to enhance
the biological activity and solubility of usnic acid, scholars have carried out a large number of
structural modifications, and found some usnic acid derivatives to be of more potential research value.
In this paper, the structural modification, biological activity and structure-activity relationship of
usnic acid were reviewed to provide reference for the development of usnic acid derivatives.