Natural compound Tryptoquivaline K shows promise against TB enzyme

Tuberculosis, caused by Mycobacterium tuberculosis, remains one of the world’s deadliest infectious diseases, ranking second in infectious disease deaths after HIV. A major reason many beta-lactam antibiotics fail against this pathogen is a chromosomally encoded gene, blaC, which produces the beta-lactamase enzyme BlaC; this enzyme can hydrolyse many commonly available beta-lactam antibiotics and render them ineffective. Although existing beta-lactamase inhibitors that contain a beta-lactam ring, such as clavulanate, can be effective, they can also prompt bacteria to evolve inhibitor escape mechanisms. In search of alternatives that might avoid these escape routes, offer fewer side effects and higher bioavailability, and even support environmental sustainability through better bioremediation, researchers led by Immanuel Dhanasingh turned to natural products. They screened a large set of natural compounds drawn from the Natural Products Atlas database of PubChem and ZINC — about 10,000 compounds in total — using molecular docking and Molecular Dynamics (MD) simulations to find molecules that could bind to and inhibit BlaC. The study aims to prioritize natural candidates for further experimental testing rather than to present final drug candidates.

The team performed virtual screening and docking experiments to compare how well each compound might bind BlaC. The top 10 compounds from this screen showed favourable docking scores from -7.59 to -9.63 kcal/mol, outperforming the reference molecule Doripenem, which scored -7.35 kcal/mol. After targeted docking and ADMET analysis, the researchers selected three lead compounds for deeper study: Lecanorafuran A, Tryptoquivaline K, and Deacetylisowortmin A. These three were subjected to Molecular Dynamics (MD) simulations for 100 ns to evaluate the stability of the protein-ligand complexes under simulated physiological conditions. The simulations were analyzed using Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF), Radius of gyration, Solvent Accessible Surface Area, PCA, and FEL analysis. Together with Molecular Mechanics/Poisson-Boltzmann Surface Area (MMPBSA) calculations to assess binding affinity, these analyses showed that Tryptoquivaline K exhibited consistent stability throughout the simulation and had promising binding characteristics, leading the authors to highlight it as a potential BlaC inhibitor.

The findings point to the potential value of non-beta-lactam natural products as a different strategy to target beta-lactam resistance in Mycobacterium tuberculosis. By focusing on molecules without a beta-lactam ring, researchers hope to reduce the chance of bacteria developing inhibitor escape mechanisms that have undermined some existing inhibitors like clavulanate. The apparent advantages noted in the study — fewer side effects, higher bioavailability, and better prospects for bioremediation and environmental sustainability — are presented as additional reasons to pursue natural product leads. Importantly, the study is computational and identifies candidates for follow-up rather than proving clinical utility. The authors emphasize that Tryptoquivaline K, singled out by docking, MD simulation stability measures, and MMPBSA calculations, now warrants further validation through experimental studies to confirm inhibitory activity against BlaC, assess safety, and determine whether it can progress toward therapeutic use or combination strategies to restore the effectiveness of beta-lactam antibiotics against tuberculosis.