Investigation of the effect of watery and alcoholic extract of Arnebia euchroma on the growth of Candida species isolated from patients with COVID-19-associated oral candidiasis using microdilution method

 Conventional antifungals used to treat fungal infections are no longer as effective, leading to increased mortality. On the other hand, there is an emergence of multidrug-resistant (MDR) fungal strains and for this reason, finding new treatments or substances that have an antifungal effect is noticeable. Therefore, this study aimed to determine the antifungal effects of extracts of Arnebia euchroma on the growth of Candida species isolated from patients with COVID-19-associated oral candidiasis.

 In the present experimental study, watery and alcoholic extracts of Arnebia euchroma were prepared by the maceration method. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of alcoholic and watery extract of Arnebia euchroma were evaluated against clinical and standard isolates of Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei clinical isolates according to the Clinical and Laboratory Standards Institute document M27-A3 (CLSI M27-A3) broth microdilution protocol.

The results of the present study showed that all the investigated isolates were sensitive to watery and alcoholic extracts of Arnebia euchroma. The MIC and MFC of Arnebia euchroma watery extract for Candida albicans were 512 µg/mL and for Candida glabrata were 1024 µg/m, as well as the MIC and MFC of this extract for Candida tropicalis, Candida parapsilosis, and Candida krusei were 2048 µg/mL. Whereas the MIC and MFC of the Arnebia euchroma alcoholic extract for Candida albicans were 0.015625 µg/mL and for Candida glabrata were 256 µg/mL, also the MIC and MFC of this extract for Candida tropicalis and Candida parapsilosis were 512 µg/mL and for Candida krusei were 1024 µg/mL.

 All the studied Candida isolates were sensitive to both types of Arnebia euchroma root extract, and the alcoholic extract, compared with the watery extract, inhibited the growth of the tested Candida isolates at a lower concentration.