Repurposing old natural compounds to target new pathogens: honokiol and magnolol against Candida auris

Abstract

AIM: Evaluation of the antifungal effect of two phenolic compounds (magnolol and honokiol) from Magnolia officinalis bark against clinical isolates of Candida auris. BACKGROUND: Candida auris is an emerging fungus that gained global attention due to its multidrug-resistance and high crude mortality rate of up to 40% in cases of bloodstream infection. Natural products from all over the world have been highlighted as a promising alternative, due to their long-standing traditional use and increasing scientific recognition. METHOD: The antifungal activity of honokiol and magnolol against C. auris CBS 10913 and 15 clinical isolates was assessed using the EUCAST method E. Def. 7.4. Pure active substances were used to prepare the stock solutions. The minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) values for all isolates were obtained and specific statistical parameters (MIC50, MFC50, MIC90, MFC90) have been calculated. RESULTS: Honokiol and magnolol displayed similar activity against investigated C. auris strains. The MIC50, MFC50, MIC90, and MFC90 have the same value for honokiol – 16 mg/L, and were slightly higher for magnolol - 32 mg/L. Compared to the investigated neolignans, fluconazole was less active against yeast strains: MIC range of 64–128 mg/L indicating resistance. Furthermore, the MFC values revealed that both honokiol and magnolol exhibited fungicidal activity against C. auris. Another important fact is the uniformity of the MICs and MFCs, all clinical isolates exhibiting the same value. CONCLUSION: Our results can be regarded as a starting point in the development of novel therapy strategies against C. auris invasive infections.

Keywords

• Honokiol
• Magnolol
• Candida auris
• funcicidal activity
• Magnolia officinalis