engleski

Visualization of quercetin/europium complex effect on Staphylococcus aureus cell structure using confocal laser scanning microscopy

Quercetin, a protective phenolic compound isolated from plants, exerts antibacterial activity against many strains of bacteria. It is discovered that some positive biological effects of free phenolics can be improved by their chemical derivatization with metals. Thus, we synthesized a complex of the phenolic compound quercetin (Q) with the rare earth metal europium (Eu3+) in a biological buffer, and compared its activity against Staphylococcus aureus cells with that of free Q. While free Q did not show antibacterial activity against S. aureus, its complex with Eu3+ did. Using confocal laser scanning microscope we screened for the ability of Q/Eu3+ complex, free Q and Eu3+ to penetrate into S. aureus cells. Images revealed all the three chemical forms penetrated into S. aureus cells. However, while free Q did not disrupt cell morphology, Q/Eu3+ complex and free Eu3+ caused degradation of cell structure – most of the cells were lysed, their structures were amorphous, and only few cells showed minor fluorescence signal corresponding to the Q/Eu3+ or free Eu3+. Thus, the antibacterial activity of Q/Eu3+ was attributed to degradation of complex and antibacterial effect of released free Eu3+. Confocal laser scanning microscopy was successfully employed for visualization of anti-S. aureus effect of Q/Eu3+ complex.

flavonoid; metal; complex; Staphylococcus aureus; confocal laser scanning microscopy

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