Metabolite profiling, antifungal, biofilm formation prevention and disruption of mature biofilm activities of Erythrina senegalensis stem bark extract against Candida albicans and Candida glabrata

The antifungal activity of the 70% ethanol stem bark extract of Erythrina senegalensis (ESB) against different strains and drug resistant clinical isolates of Candida albicans and Candida glabrata were evaluated in the study. The effect of ESB on biofilms as well as its activity in combination with fluconazole, nystatin or caspofungin against the Candida strains were also evaluated. We then evaluated the antifungal activity of a microemulsion formulation of ESB against planktonic and biofilms of the Candida species. UPLC-QTOF-MS(2) analysis was then undertaken to identify the phytoconstituents of the extract and UPLC fingerprints developed for the routine authentication as part of quality control measures. ESB exerted strong antifungal activities against C. albicans ATCC 10231 and SC5314 strains, and C. glabrata ATCC 2001 strain with minimum inhibitory concentration (MIC) values from 3.91 to 31.25 μg/mL and minimum fungicidal concentrations (MFCs) that ranged from 62.5 to 250 μg/mL. It also exhibited potent antifungal activities (MIC = 4–64 μg/mL) against a collection of C. albicans and C. glabrata clinical isolates that were resistant to either nystatin or azole antifungals. The formulated ESB demonstrated higher antifungal potency against the C. albicans and C. glabrata strains with MIC values of 3.91–31.25 μg/mL which was the same as the MFC values. The extract and its microemulsion formulation were active against biofilms of the strains of the Candida species inhibiting their biofilm formations (SMIC(50) = 16–64 μg/mL) and their preformed biofilms (SMIC(50) = 128 –>512 μg/mL). ESB also exhibited synergistic antifungal action with fluconazole and nystatin against C. albicans ATCC 10231 and C. glabrata ATCC 2001 strains in the checkerboard assay. Chemical characterization of the extract revealed the presence of phenolic compounds such as flavonoids and their prenylated derivatives, anthracene glycosides and alkaloids. UPLC Fingerprints of the extract was also developed and validated for routine identification and authentication of the stem bark of E. senegalensis. The study findings have demonstrated that the stem bark of E. senegalensis is as a potential source of bioactive compounds that could be developed as novel antifungal agents.