Racemosol Derivatives and Other Metabolites from Bauhinia malabarica Bark with Antibacterial Activity

Racemosol, a natural phenolic compound, is known for its antimicrobial potential, yet experimental studies remain limited. In this study, two new racemosol derivatives (4 and 5) and four known compounds (1-3, 6) were isolated from the bark of Bauhinia malabarica and structurally elucidated using spectroscopic analyses. Most of isolated compounds exhibited notable activity against Gram-positive bacteria, including Staphylococcus aureus, Bacillus subtilis, and Listeria monocytogenes, while showing limited effects on Gram-negative strains. Racemosol (1) and its derivatives (2, 4, and 6) displayed potent antibacterial activity with MIC values of 0.156-0.625 µg/µL and bactericidal properties confirmed by comparable MBCs. Compound 6 exhibited the highest potency, indicating that specific structural modifications enhance activity. These findings provide new insights into the structure activity relationships of racemosol derivatives and highlight B. malabarica as a promising natural source of phenolic antibacterial agents.