Isobavachalcone (IBC) is a natural prenylated chalcone with a broad spectrum of pharmacological properties. In this work, we newly synthesized and investigated the antibacterial activity of IBC against Gram-positive, Gram-negative and mycobacterial species. IBC was active against Gram-positive bacteria, mainly against Methicillin-Susceptible Staphylococcus aureus (MSSA) and Methicillin-Resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentration (MIC) values of 1.56 and 3.12 µg/mL, respectively. On the other hand, IBC was not able to act against Gram-negative species (MIC > 400 µg/mL). IBC displayed activity against mycobacterial species (MIC = 64 µg/mL), including Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium kansasii. IBC was able to inhibit more than 50% of MSSA and MRSA biofilm formation at 0.78 µg/mL. Its antibiofilm activity was similar to vancomycin, which was active at 0.74 µg/mL. In order to study the mechanism of the action by fluorescence microscopy, the propidium iodide (PI) and SYTO9 fluorophores indicated that IBC disrupted the membrane of Bacillus subtilis. Toxicity assays using human keratinocytes (HaCaT cell line) showed that IBC did not have the capacity to reduce the cell viability. These results suggested that IBC is a promising antibacterial agent with an elucidated mode of action and potential applications as an antibacterial drug and a medical device coating.

Fungal infections caused by Candida species has increased significantly in recent years. Additionally, resistance to conventional therapy is an aggravating factor causing high morbidity and mortality, especially in immunocompromised patients or those undergoing treatment with another antimicrobials. During the infection process, Candida species produces metabolites which can self-regulate population density, in addition to controlling several virulence factors and exerting action on other microorganisms. In view of this fact, the present study evaluated the in vitro antifungal activity of the pure culture extract of Candida parapsilosis against Candida albicans, Candida auris and Candida parapsilosis. Fungal culture extracts of C. parapsilosis were prepared in Sabouraud Dextrose Broth, extracted with ethyl acetate and dried in a rotary evaporator. Subsequently, tests were performed to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). The antifungal activity of the extracts against Candida species showed values of MIC ranging between 500 - 2000 µg/mL and a MFC range of 1414 µg/mL - 2000 µg/mL. Future investigations for the identification and composition of this fungal culture extract will provide insights about metabolites are present and involved in the antifungal activity shown here, contributing for the future to new therapeutic approaches in the control of infections caused by Candida.