The present study investigated the antifungal activity of the 70% ethanol extracts of the leaves (IGL), stem bark (IGSB) and roots (IGR) of Irvingia gabonensis against multidrug‐resistant Candida albicans and Candida glabrata strains and clinical isolates. The inhibitory activities of extracts against biofilm formation and mature biofilms were also investigated. Furthermore, the effects of the combinations of I. gabonensis extracts with amphotericin B, ketoconazole, voriconazole, nystatin and caspofungin, against the resistant Candida strains and isolates were evaluated using the checkerboard assay. Qualitative and quantitative assessments of the phytoconstituents in the plant extracts, as well as their antioxidant activities, were then analysed. IGSB displayed considerable anti‐ Candida activity with minimum inhibition concentrations (MICs) of 15.63 μg/mL–500 μg/mL, while IGR showed MICs of 125 μg/mL–1000 μg/mL. IGL demonstrated limited activity with MICs of 500 μg/mL–> 2000 μg/mL. IGSB also exerted significant antibiofilm activity against the drug‐resistant C . albicans and C . glabrata strains and isolates with SMIC 90 of 31.25 μg/mL–1000 μg/mL and 125 μg/mL–2000 μg/mL against the formation of biofilms and mature biofilms, respectively. In the checkerboard assay, IGSB recorded the most synergistic interactions with the conventional antifungal drugs producing median FICI values that ranged between 0.35 to 0.61 and 0.30 to 0.68, and synergistic action that ranged between 50% to 66.67% and 55.56% to 100%, against the MDR C. albicans and C. glabrata isolates, respectively. The extracts displayed strong antioxidant activities, which correlated with their total phenol, flavonoid and tannin contents. The presence of phytochemicals such as glycosides, coumarins and triterpenoids was also detected in I. gabonensis extracts. The study findings have demonstrated that I. gabonensis , particularly its stem bark, is a potential source of bioactive compounds that could be developed into novel antifungal agents.
Harley et al. (Thu,) studied this question.