Isorhamnetin as a promising natural bioactive flavonoid: in vitro assessment of its antifungal property

Isorhamnetin (3’-methylquercetin) is an important flavonoid produced as a secondary metabolite from medicinal and aromatic plants due to its pharmacological and therapeutic properties. Thus far, the anticancer, antiallergic, antiinflammatory, antioxidant, antiviral, and antimicrobial properties of isorhamnetin have been evaluated in indirect studies conducted with isorhamnetin found in plant extracts or essential oils or direct studies performed with pure isorhamnetin. However, this is the first study in the literature on the antifungal activity of 97% pure isorhamnetin against C. tropicalis, C. albicans, C. krusei, and C. parapsilosis using two assays including agar dilution and broth microdilution methods. This study showed that isorhamnetin has a significant inhibitory effect against all Candida species used. The minimum inhibitory concentration (MIC) value of isorhamnetin against C. tropicalis, C. albicans, C. krusei, and C. parapsilosis was 1.875 mg/mL, the same for all yeast strains. These results have opened a new horizon regarding the usability of isorhamnetin as a pharmacological therapeutic antifungal agent.