In this research we proceeded sequentially in a series of procedures for the crude extracts in n-hexane, dichloromethane and ethanol of the plant species Miconia ligustroides belonging to the Melastomataceae family; extraction of the pure substances ursolic acid and oleanoic acid, present in the dichloromethane extract of M. ligustroides. We then evaluated the antimicrobial activity of the crude extracts and pure substances, and in the final contribution we obtained the semi-synthetic derivatives of ursolic acid in order to optimise the results of the antimicrobial activity evaluation. According to the results obtained, it was possible to achieve promising results, especially in terms of changes made to the structures of the acids studied, as well as, of course, a profound discovery of the author in the scientific world.