Antibacterial and antifungal activities of phenolic compound-enriched ethyl acetate fraction from Cochlospermum regium (mart. Et. Schr.) Pilger roots: Mechanisms of action and synergism with tannin and gallic acid

Cochlospermum regium is a shrub used in folk medicine to treat infection diseases. However, limited information are available regarding the antimicrobial mechanism of action, synergic effect of major phytochemical components this specie, and it antimicrobial spectrum of activity. Here, we aimed to investigate the antimicrobial activity of its ethyl acetate fraction (EtOAc) from roots together with some constituents previously isolated and commercially available, to understand the possible pharmacological interactions between these components. The EtOAc fraction of C. regium, tannin and gallic acid commercially available, alone or in combination, were assessed for antimicrobial activity against eight bacteria and five yeasts. EtOAc fraction showed a broad spectrum of antimicrobial activity and gallic acid had better antifungal activity, while tannin was active against all microorganisms tested. Antibacterial effect was induced to catalase activity inhibition. For yeast, results indicated that the EtOAc fraction and compounds gallic acid and tannic acid bind to the ergosterol of the fungal membrane. Checkerboard assay showed that the combination of EtOAc fraction with tannin result in synergic effect against six microorganisms. Thus, highlight the pharmacological use of C. regium as a tannin-enriched extract for the treatment of infectious diseases. Together, data reveals the antimicrobial potential of C. regium, proving it used in the folk medicine of Brazilian southwestern.