Structural Elucidation of Anti-Pseudomonas Component from <i>Eucalyptus Tereticornis</i>

Abstract

Eucalyptus species is a well-known medicinal plant from ancient times with diverse biological functions, antimicrobial activity being one of them. This study attempts to isolate a secondary metabolite with antibacterial properties from ethanol extracts of Eucalyptus tereticornis leaf by antibacterial - against Pseudomonas aeruginosa - activity-guided procedure. Ethanol extract of the leaf powder was obtained by soxhlation and subjected to liquid-liquid extraction with organic solvents – ethyl acetate, n-hexane, n-butane, and chloroform. The active n-hexane and chloroform extracts were purified by column chromatography, and the components of the active eluant fraction were separated by Thin-layer chromatography (TLC). The purity of the antibacterial compound was checked by high performance liquid chromatography (HPLC), the molecular weight determined by Liquid chromatography-mass spectroscopy (LC-MS) and the structure elucidated and identified by nuclear magnetic resonance (NMR) and by Fourier transform infrared spectrometer (FTIR). TLC of n-hexane extract of liquid-liquid extraction showed a single spot with antibacterial activity. A single major peak was observed on HPLC, and LC-MS revealed that the compound is a formylated phloroglucinol component (FPC) with a molecular weight of 471.3. The NMR and FTIR analysis identified that the isolated compound is Macrocarpal A. This study reveals that the isolated relatively pure anti-Pseudomonas compound from the leaf extracts of E. tereticornis is Macrocarpal A, a flavanoid from FPC.