Potencial antibacteriano de cordiaquinonas obtidas de Cordia polycephala

Abstract

Bacterial infections are a leading cause of death, especially in developing countries, and resistance to antibiotics, plus the ability to form biofilms contribute to make those infections a major public health problem. One strategy when searching for agents to treat bacterial infections is the use of natural products, among them, the different types of quinones. Cordiaquinones are naphthoquinones obtained from plants of genus Cordia that have several biological activities reported in literature, such as antifungal, larvicidal and antitumor. Therefore, the aim of this study was to evaluate the antibacterial activity of cordiaquinones B, E, L, N and O against different strains of bacteria, including Methicillin resistant strains. Thus, the minimum inhibitory (MIC) and bactericidal concentration (MBC) were determined following CLSI recommendations. To evaluate if these cordiaquinones can inhibit biofilm formation 1/2, 1/4 and 1/8 of MIC was used and the percentage of inhibition was measured. Atomic force microscopy (AFM) was performed to identify alterations in bacterial cells morphology. The majority of Gram positive tested strains were susceptible to cordiaquinones B, E, L and N. The lowest MIC value was 7.8 μM (2.53 μg/mL) of Cordiaquinone L against S. saprophyticus. Cordiaquinones B and E showed the lowest MBC value, 62.5 μM (20.25 μg/mL), against the same strain. Cordiaquinones B and E inhibit biofilm formation of S. aureus ATCC 29213 and S. aureus Med 55 (clinical specimen resistant to Methicillin) in about 90%. Among the morphological changes observed by AFM, it was observed that the treatment with cordiaquinone L reduced mean size of S. saprophyticus cells. The results presented in this work suggest that cordiaquinones have an antibacterial potential, since they can inhibit the growth of both sensitive and resistant to Methicillin bacteria, besides, they can inhibit biofilm formation, an important aggravating factor of bacterial infections.