Unveiling the role of macranthoin G in the traditional anti-infective properties of Launaea nudicaulis

Klebsiella pneumoniae, a highly prevalent Gram-negative bacterium, is widely known for causing nosocomial infections, leading to various diseases including systemic infections and fever. In traditional medicine, Launaea nudicaulis (L.) Hook. f. (Asteraceae), is often used to alleviate fever caused by bacterial infections. This study aimed to assess the antibacterial efficacy of the key phytochemicals present in the extract of L. nudicaulis against a panel of K. pneumoniae isolates. Three main constituents were isolated from this plant: cichorin (1), methyl-3,5-di-O-caffeoylquinate (syn. macranthoin G) (2), and cynaroside (3). Among these compounds, macranthoin G demonstrated notable antibacterial activity, with minimum inhibitory concentrations ranging from 64 to 256 µg/mL. It was found to inhibit the growth of the tested isolates and significantly affect the integrity of their cell membranes in 65.2 % of cases. Moreover, it increased the permeability of both the inner and outer membranes in 60.87 % and 52.17 % of K. pneumoniae isolates, respectively. Docking studies revealed that it exhibited strong binding scores to LpxC and FabI enzymes, with significant interactions occurring with key amino acids in their active sites. Based on these findings, macranthoin G shows promise as a potential antimicrobial drug, warranting further research to validate its antimicrobial and pharmacokinetic properties.