Coumarins as Potential Antiprotozoal Agents: Biological Activities and Mechanism of Action

Synthesis of new coumarin derivatives and assessment of their antimicrobial efficacy

AIM

Developing new antimicrobial agents in response to the urgent challenge of antimicrobial resistance.

METHODS

Synthesis of the targeted coumarins, elucidation of their structures using spectroscopic tools, and investigation of their antimicrobial activity.

RESULTS

Coumarin-pyrazole 11 with CF3 in the 3-position of the pyrazole ring displayed the lowest minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) with values of 1.95 and 15.6 µg/ml, respectively, against Bacillus pumilis. In addition, it exhibited the best inhibitory activity against Saccharomyces cerevisiae (MIC = 3.91 µg/ml) compared to the rest of the derivatives (7.81-62.5 µg/ml). Surprisingly, coumarin 14 with the S-CH3 group had higher ability to inhibit the Staphylococcus faecalis strain with an MIC value of 1.95 µg/ml, which is twice that of penicillin G (MIC = 3.91 µg/ml). At the same time, compounds 6, 8, 11, 16, and penicillin G showed similar activity with an MIC value of 3.91 µg/ml against Staphylococcus faecalis. Also, the lowest MIC value (3.91 µg/ml) was obtained for S-CH3 derivative 14 against Enterobacter cloacae. Coumarins 14 and 1,3,4-thiadiazine derivative 6 recorded the lowest MBC (15.6 µg/ml) against Escherichia coli.

CONCLUSION

Finally, it can be concluded that some designed coumarins have a high potential to act as potent antimicrobial agents. Some of them displayed higher efficacy than or equal to the reference drug.

Recent advances in the synthesis and antimalarial activity of 1,2,4-trioxanes

The increasing resistance of various malarial parasite strains to drugs has made the production of a new, rapid-acting, and efficient antimalarial drug more necessary, as the demand for such drugs is growing rapidly. As a major global health concern, various methods have been implemented to address the problem of drug resistance, including the hybrid drug concept, combination therapy, the development of analogues of existing medicines, and the use of drug resistance reversal agents. Artemisinin and its derivatives are currently used against multidrug- resistant P. falciparum species. However, due to its natural origin, its use has been limited by its scarcity in natural resources. As a result, finding a substitute becomes more crucial, and the peroxide group in artemisinin, responsible for the drugs biological action in the form of 1,2,4-trioxane, may hold the key to resolving this issue. The literature suggests that 1,2,4-trioxanes have the potential to become an alternative to current malaria drugs, as highlighted in this review. This is why 1,2,4-trioxanes and their derivatives have been synthesized on a large scale worldwide, as they have shown promising antimalarial activity in vivo and in vitro against Plasmodium species. Consequently, the search for a more convenient, environment friendly, sustainable, efficient, and effective synthetic pathway for the synthesis of 1,2,4-trioxanes continues. The aim of this work is to provide a comprehensive analysis of the synthesis and mechanism of action of 1,2,4-trioxanes. This systematic review highlights the most recent summaries of derivatives of 1,2,4-trioxane compounds and dimers with potential antimalarial activity from January 1988 to 2023.

Effective Synthesis and Biological Evaluation of Functionalized 2,3-Dihydrofuro[3,2-c]coumarins via an Imidazole-Catalyzed Green Multicomponent Approach

For the first time, an eco-friendly and efficient one-pot green multicomponent approach has been described to synthesize functionalized trans-2,3-dihydrofuro[3,2-c]coumarins (DHFCs). In this synthesis, imidazole and water were used as the catalyst and solvent, respectively, under mild conditions. Applications of the developed catalytic process in a water medium revealed the outstanding activity, productivity, and broad functional group tolerance, affording a series of newly designed DHFC and derivatives in excellent yields (72-98%). Moreover, the human serum albumin (HSA) binding ability of the synthesized DHFC derivatives has been uncovered through the detailed in silico and in vitro-based structure-activity analysis. The ability to bind HSA, the most abundant serum protein, in the low micromolar ranges unequivocally reflects the suitable absorption, distribution, metabolism, and elimination profile of the synthesized compounds, which may further be envisaged for their therapeutic usage endeavors.