Characterization of Brazilian green propolis as a photosensitizer for LED light-induced antimicrobial photodynamic therapy (aPDT) against methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-intermediate Staphylococcus aureus (VISA).

Staphylococcus aureus is the primary cause of skin and soft tissue infections. Its significant adaptability and the development of resistance are the main factors linked to its spread and the challenges in its treatment. Antimicrobial photodynamic therapy emerges as a promising alternative. This work aimed to characterize the antimicrobial photodynamic activity of Brazilian green propolis, along with the key bioactive compounds associated with this activity. Initially, a scanning spectrometry was conducted to assess the wavelengths with the potential to activate green propolis. Subsequently, reference strains of methicillin-resistant Staphylococcus aureus (MRSA ATCC 43300) and vancomycin-intermediate Staphylococcus aureus (VISA ATCC 700699) were exposed to varying concentrations of green propolis: 1 µg/mL, 5 µg/mL, 10 µg/mL, 50 µg /mL and 100 µg/mL and were stimulated by blue, green or red LED light. Finally, high-performance liquid chromatography coupled with a diode array detector and tandem mass spectrometry techniques, along with classic molecular networking analysis, was performed to identify potential bioactive molecules with photodynamic activity. Brazilian green propolis exhibits a pronounced absorption peak and heightened photo-responsiveness when exposed to blue light within the range of 400 nm and 450 nm. This characteristic reveals noteworthy significant photodynamic activity against MRSA and VISA at concentrations from 5 µg/mL. Furthermore, the propolis comprises compounds like curcumin and other flavonoids sourced from flavone, which possess the potential for photodynamic activity and other antimicrobial functions. Consequently, Brazilian green propolis holds promise as an excellent bactericidal agent, displaying a synergistic antibacterial property enhanced by light-induced photodynamic effects.