Identification of Antibacterial Compounds from Lantana Camara Leaves through Bioassay-Guided Fractionation, TLC-Bioautography, and GC-MS/MS

Abstract

Lantana camara L. is a highly adaptable shrub renowned for its ecological resilience and invasive nature, particularly in semi-arid regions. While its crude extracts are known to possess antimicrobial properties, the specific bioactive molecules responsible remain under-characterised. This study aimed to systematically identify the antibacterial compounds from L. camara leaves collected from the environmental stressor conditions of the Todgarh-Aravalli Forest margin in Rajasthan, India. Extraction efficiency was optimised by comparing hot methanolic Soxhlet extraction with cold poly-solvent maceration. The cold extract demonstrated superior bulk yield and broad-spectrum antibacterial efficacy against four multi-drug resistant (MDR) strains (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus), indicating the presence of thermolabile defensive metabolites. Subsequent liquid-liquid partitioning revealed that the antibacterial activity was overwhelmingly concentrated in the non-polar n-hexane fraction. Direct TLC-bioautography of this fraction against P. aeruginosa successfully isolated a highly active bio-zone spanning an Rf of 0.63-0.78. Chemical profiling of this bioactive eluate via GC-MS/MS putatively identified ten distinct compounds, predominantly branched-chain alkanes (24.6% peak area), alongside the fatty acid amide oleamide, which has documented membrane-interacting potential and the diterpenoid thunbergol. These findings confirm that the robust antibacterial defense mechanism of L. camara relies primarily on lipophilic secondary metabolites, highlighting its potential as a valuable botanical resource for novel therapeutics against antibiotic-resistant pathogens.