Evaluation of cytotoxic, antifungal, and larvicidal activities of different bis-sulfonamide Schiff base compounds

Schiff bases (imines or azomethines) are versatile ligands synthesized from the condensation of amino compounds with active carbonyl groups and used for many pharmaceutical and medicinal applications. In our study, we aimed to determine the cytotoxic, antifungal and larvicidal activities of biologically potent bis-sulfonamide Schiff base derivatives that were re-synthesized by us. For this aim, 16 compounds were re-synthesized and tested for their cytotoxic, antifungal and larvicidal properties. Among this series, compounds A1B2, A1B4, A4B2, A4B3, and A4B4 were shown to have cytotoxic activity against tested cancer lung cell line (A549). The most potent antifungal activity was observed in compounds A2B1 and A2B2 against all fungi. A1B1 showed the strongest larvicidal effect at all concentrations at the 72nd h (100% mortality). These obtained results demonstrate that these type of bis-substituted compounds might be used as biologically potent pharmacophores against different types of diseases.

Miconazole and terbinafine induced reactive oxygen species accumulation and topical toxicity in human keratinocytes

There are an estimated 1 billion cases of superficial fungal infection globally. Fungal pathogens form biofilms within wounds and delay the wound healing process. Miconazole and terbinafine are commonly used to treat fungal infections. They induce the accumulation of reactive oxygen species (ROS) in fungi, resulting in the death of fungal cells. ROS are highly reactive molecules, such as oxygen (O₂), superoxide anion (O₂•-), hydrogen peroxide (H₂O₂) and hydroxyl radicals (•OH). Although ROS generation is useful for killing pathogenic fungi, it is cytotoxic to human keratinocytes. To the best of our knowledge, the effect of miconazole and terbinafine on HaCaT cells has not been studied with respect to intracellular ROS stimulation. We hypothesized that miconazole and terbinafine have anti-wound healing effects on skin cells when used in antifungal treatment because they generate ROS in fungal cells. We used sulforhodamine B protein staining to investigate cytotoxicity and 2',7'-dichlorofluorescein diacetate to determine ROS accumulation at the 50% inhibitory concentrations of miconazole and terbinafine in HaCaT cells. Our preliminary results showed that topical treatment with miconazole and terbinafine induced cytotoxic responses, with miconazole showing higher cytotoxicity than terbinafine. Both the treatments stimulated ROS in keratinocytes, which may induce oxidative stress and cell death. This suggests a negative correlation between intracellular ROS accumulation in keratinocytes treated with miconazole or terbinafine and the healing of fungi-infected skin wounds.

Efficacy of Novel Schiff base Derivatives as Antifungal Compounds in Combination with Approved Drugs Against Candida Albicans

BACKGROUND

The increasing incidence of fungal infections, especially caused by Candida albicans, and their increasing drug resistance has drastically increased in recent years. Therefore, not only new drugs but also alternative treatment strategies are promptly required.

METHODS

We previously reported on the synergistic interaction of some azole and non-azole compounds with fluconazole for combination antifungal therapy. In this study, we synthesized some non-azole Schiff-base derivatives and evaluated their antifungal activity profile alone and in combination with the most commonly used antifungal drugs- fluconazole (FLC) and amphotericin B (AmB) against four drug susceptible, three FLC resistant and three AmB resistant clinically isolated Candida albicans strains. To further analyze the mechanism of antifungal action of these compounds, we quantified total sterol contents in FLC-susceptible and resistant C. albicans isolates.

RESULTS

A pyrimidine ring-containing derivative SB5 showed the most potent antifungal activity against all the tested strains. After combining these compounds with FLC and AmB, 76% combinations were either synergistic or additive while as the rest of the combinations were indifferent. Interestingly, none of the combinations was antagonistic, either with FLC or AmB. Results interpreted from fractional inhibitory concentration index (FICI) and isobolograms revealed 4-10-fold reduction in MIC values for synergistic combinations. These compounds also inhibit ergosterol biosynthesis in a concentration-dependent manner, supported by the results from docking studies.

CONCLUSION

The results of the studies conducted advocate the potential of these compounds as new antifungal drugs. However, further studies are required to understand the other mechanisms and in vivo efficacy and toxicity of these compounds.