Antimicrobial Activity Studies of Lupeol Isolated from Crinum jagus Rhizome

Abstract

Rhizomes of Crinum jagus were pulverized and successively extracted with n-hexane, dichloromethane, and ethyl acetate, followed by concentration using a rotary evaporator, yielding 3.5 g, 5.0 g, and 7.0 g, respectively. Qualitative phytochemical screening of the ethyl acetate extract revealed the presence of steroids, terpenes, saponins, flavonoids, and alkaloids. The crude extract and the isolated compound were evaluated for antimicrobial activity against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus megaterium, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Candida albicans, Trichophyton rubrum, and Aspergillus niger, with zones of inhibition ranging from 7 to 22 mm. Thin-layer chromatography (TLC) of the ethyl acetate extract revealed eight major spots, one of which exhibited fluorescence with an Rf value of 0.44. The isolated compound showed a single fluorescent spot with the same Rf value, indicating purity. Mass spectrometry revealed a molecular ion peak at m/z 462, consistent with a triterpenoid structure, while fragmentation patterns provided further structural insights. Comprehensive spectroscopic analyses (MS, IR, 1D and 2D NMR) confirmed the isolated compound as lupeol. Molecular docking studies demonstrated that lupeol binds effectively to the 7RJC protein of S. epidermidis, with binding energies of −9.0, −8.6, −7.6, and −7.1 kcal/mol, suggesting strong inhibitory potential. The docking results of lupeol, alongside other secondary metabolites identified in the rhizome, correlate with the observed antimicrobial activity, indicating that Crinum jagus is a promising natural source of antimicrobial agents for the treatment of various infectious diseases.