Antibacterial and Antifungal Properties of New Synthetic Tricyclic Flavonoids

<b>Background/Objectives:</b> The discovery of new molecules to which bacteria have not yet developed resistance is a significant medical priority. Synthetic flavonoids are good candidates for developing new antimicrobials. Our study investigates a series of newly synthesized tricyclic flavonoids with several different substituents on the flavonoid core. <b>Methods:</b> By varying the nature of the substituents on rings <b>A</b> and <b>B,</b> a structure-activity relationship study using different microbial strains has been performed. The antibacterial and antifungal properties of these compounds have been investigated against Gram-positive and Gram-negative bacteria and several <i>Candida</i> strains. <b>Results:</b> All seven tested compounds have been found to exhibit the highest antimicrobial activity against <i>S. aureus</i>, with an inhibition zone of up to 23 mm. The tricyclic flavonoids <b>5c</b>, <b>5e</b>, and <b>5f</b> showed good antifungal properties against <i>C. parapsilosis</i>, with an inhibition zone of around 17 mm. <b>Conclusions:</b> All the data support the idea that flavonoids <b>5</b> are reliable candidates for developing effective antimicrobial agents.