In vitro antibacterial and cytotoxic activity of Laurobasidium lauri extracts

Abstract

Background: Plants and mushrooms have been used as medicines for many years, as a source of antibiotics, antineoplastics, among others [1]. Research have been conducted on the medicinal uses of Portuguese plants, however, the therapeutic potentials of some of these plants used in traditional medicine, has remained unexploited. Objective: This study aims to evaluate antibacterial and cytotoxic activities, in vitro, of Laurobasidium lauri, a well-known fungus used in folk medicine on Madeira Island. Methods: An experimental study was performed using two extracts (aqueous and ethanolic 55% (V/V)) of the fungus isolated and in combination with three medicinal plants (Parietaria judaica, Polygonum aviculare, and Peperomia galioides). The antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus, through disc diffusion and broth microdilution methods. Cytotoxicity was evaluated using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. Results: Regarding the disc diffusion method E. coli was not susceptible to any of the extracts, except for the antibiotic (41.0 ± 1.0 mm). However, S. aureus, when subjected to 10 mg/ml of the ethanolic extracts of L. lauri (isolated and in combination) exhibited an inhibition with a diameter of 16,3 ± 2,5 mm and 12,0 ± 1,7 mm, respectively, when compared to the control, ciprofloxacin (24,0±1,0 mm). Also, the ethanolic extract of the isolated fungus had the best value of minimum inhibitory concentration (MIC) for S. aureus (MIC = 0.078125 mg/mL). The ethanolic extract of the fungus in combination with medicinal plants showed greater cytotoxic action on lung cancer cells A549 (IC₅₀ = 48.3±1.0 µg/mL). Conclusions: The fungus presented cytotoxic and antibacterial potential, and the results observed may be related to some bioactive compounds (e.g., costunolide and dehydrocostuslactone, two natural sesquiterpene lactones present in Laurus trees, where the fungus grows) [2]. However, more research is needed to confirm these biological activities and mechanisms of action.