Antimicrobial activities of ethanol extract and coumestans from Eclipta alba (L.) Hassk (Asteraceae)

Ethanol extract and fractions from aerial parts of Eclipta alba (L.) Hassk (Asteraceae) were screened for the antibacterial and antifungal activities against different species of human pathogenic bacterial ATCC, antibiotic-resistant clinical isolates and strains of the dermatophyte Trichophyton rubrum (wild and mutant for TruMDR2 gene) using a microdilution method. Demethylwedelolactone/wedelolactone (DWL/WL) and only wedelolactone (WL), both in a high homogeneity degree, were efficient to inhibit the ATCC strains of Staphylococus aureus (Minimal Inhibitory Concentration MIC = 75 μg/mL), Staphylococcus epidemidis (MIC = 125 μg/mL) and Escherichia coli (MIC = 125 μg/mL) as well as antibiotic-resistant clinical isolates of Enterococcus spp (MIC = 250 μg/mL) and S. aureus (MIC = 125 μg/mL). Ethanol extract was more effective than the purified fractions against Trichophyton rubrum strains (MIC = 125 μg/mL), suggesting that anti-fungal activity is not only related to demethylwedelolactone and wedelolactone, but also to a synergistic action between these coumestans and other compounds found in that extract. Thus, this work suggests that E. alba possesses a significant antimicrobial activity, including that against multi-drug resistant microorganisms, which could be of relevance for the treatment of infectious diseases. Colegio de Farmacéuticos de la Provincia de Buenos Aires