Synthesis,in vitroAntifungal Activity and Molecular Modeling Studies of New Mannich Bases Derived from Lawsone

Abstract

Hydroxynaphthoquinones such as lawsone (2-hydroxy-1,4-naphthoquinone) have proven to be effective antifungal agents. These compounds were tested for antifungal activity against yeast standard and clinical strains by the broth microdilution method. Among the synthetic lawsone derivatives, 2-hydroxy-3-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl)naphthalene-1,4-dione, 2-hydroxy-3-(((4-nitrophenyl)amino)(phenyl)methyl)naphthalene-1,4-dione and 2-hydroxy-3-((2-hydroxyphenyl)((4-nitrophenyl)amino)methyl)naphthalene-1,4-dione showed high activity against Candida albicans ATCC 10231, with minimal inhibitory concentrations (MICs) and minimal fungicidal concentrations (MFCs) ranging from 20 to 330 and from 80 to 330 μg mL -1 , respectively. Moreover, they also showed a mechanism of action on exogenous ergosterol. Therapeutic concentrations (CC 50 ) of 2-hydroxy-3-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl) naphthalene-1,4-dione, 2-hydroxy-3-(((4-nitrophenyl)amino)(phenyl)methyl)naphthalene-1,4-dione and 2-hydroxy-3-((2-hydroxyphenyl)((4-nitrophenyl)amino)methyl)naphthalene-1,4-dione were 52.81, 52.58 and 85.94 μg mL -1 , respectively, which can be considered moderate or low. In addition, docking studies showed that these compounds had similar binding energy to standard ketoconazole, which are recognized as the molecular target by van der Waals interactions. Furthermore, they are under Lipinski's rule of 5 with a druglikeness score better than ketoconazole and nystatin. These findings suggest that 2-hydroxy-3-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl) naphthalene-1,4-dione, 2-hydroxy-3-(((4-nitrophenyl)amino)(phenyl)methyl)naphthalene-1,4-dione and 2-hydroxy-3-((2-hydroxyphenyl)((4-nitrophenyl)amino)methyl)naphthalene-1,4-dione have potential as leading compounds against human fungal infections.

Application of the Mannich reaction in the structural modification of natural products

“…Allochio et al. 72 used lawsone as a lead compound, designed and synthesised a series of lawsone Mannich base derivatives using the Mannich reaction, and evaluated their inhibitory activities against Candida spp ( Table 3 ). Among these, compounds 57 and 58 ( Figure 4 ) showed the highest inhibitory activity against Candida albicans American Tissue Culture Collection (ATCC) 10231, with MIC values ranging 20–330 µg mL −1 .…”