Exploring the Potential of Coumarin as a Potent Antitubercular Agent

Tuberculosis (TB), caused by the Mycobacterium tuberculosis complex, affects nearly 10 million people annually and remains the second-deadliest infectious disease after HIV/AIDS. The rise of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains has reduced the efficacy of existing therapies, underscoring the urgent need for novel therapeutic scaffolds. Coumarins, naturally occurring oxygenated heterocycles with diverse pharmacological activities, have emerged as promising candidates for anti-TB drug discovery due to their structural versatility.

A systematic search was conducted in Scopus, Web of Science, PubMed, Google Scholar, Scielo, and ScienceDirect using terms such as "coumarin anti-tuberculosis," "coumarin MIC," and "coumarin derivatives Mycobacterium." Eligible studies included natural, semi-synthetic, and synthetic coumarin derivatives with structural characterization, drug-likeness, and ADME-Tox compliance. In vitro studies focused on standard and resistant M. tuberculosis strains, while in vivo data were included from healthy animal models under ethical conditions. Clinical studies were considered for adults with confirmed pulmonary TB. Exclusion criteria encompassed unstable, toxic, and poorly soluble compounds, non-compliant animal models, and patients with significant comorbidities or treatment non-adherence.

Natural coumarins such as scopoletin (MIC: 42 μg/mL) and indicanine B (MIC: 18.5 μg/mL) demonstrated moderate inhibition, while ferulenol and murralonginol derivatives showed weaker activity. Semi-synthetic modifications produced moderate improvements in potency, whereas synthetic conjugates exhibited the strongest effects. Coumarin-oxime (MIC: 0.04 μg/mL), pyrimidine (0.05 μg/mL), and thiazoline derivatives (0.09 μg/mL) surpassed isoniazid in vitro. Structural features such as oxime groups, triazole linkages, and halogen or methyl substitutions were associated with enhanced efficacy.

These findings highlight coumarins as valuable scaffolds for novel anti-TB agents. SAR insights provide a roadmap for rational drug design, although limited in vivo and clinical evidence necessitates further validation.

Coumarin derivatives, particularly synthetically optimized conjugates, exhibit potent anti-TB activity and represent a promising platform for combating MDR- and XDR-TB.