Chemical Constituents and Antimicrobial Activity of the Halophyte Atriplex leucoclada

Objective The rising crisis of antimicrobial resistance necessitates the discovery of bioactive compounds from natural sources. Plants adapted to extreme environments are promising sources of unique secondary metabolites. This study investigates the chemical composition and antimicrobial potential of Atriplex leucoclada (Amaranthaceae), a halophyte native to the Egyptian desert. Methods The dried aerial parts of Atriplex leucoclada were exhaustively extracted with 80% aqueous methanol. The resulting crude extract was suspended in water and successively partitioned with n -hexane and ethyl acetate. The ethyl acetate-soluble fraction was subjected to multi-step chromatographic purification, including flash chromatography and preparative HPLC. The structures of purified metabolites were elucidated through comprehensive spectroscopic analysis, including nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HRESIMS), and by comparison with literature data. The in vitro antibacterial activity of the extract and isolated compounds was evaluated against Bacillus subtilis and Escherichia coli using agar well diffusion and broth microdilution assays. Results Phytochemical investigation of A. leucoclada led to the isolation of six compounds (1-6) spanning diverse structural classes: three alkaloids— N - trans -caffeoyltyramine ( 1 ), N - trans -feruloyltyramine ( 2 ), N - trans -feruloyl methoxytyramine ( 3 ); the lignan syringaresinol ( 4 ), and the ecdysteroids 20-hydroxyecdysone ( 5 ) and 20-hydroxyecdysone-20,22-monoacetonide ( 6 ). Antimicrobial screening identified N-trans -feruloyltyramine ( 2 ) as the most active compound. The isolated ecdysteroids 5 and 6 are of particular interest as phytoecdysteroids, a class of compounds known for their adaptogenic and proposed anabolic properties. Conclusion This study highlights the halophyte Atriplex leucoclada as a promising source of bioactive compounds. The significant antibacterial activity of compound 2 warrants future studies to elucidate its precise mechanism of action, assess its efficacy against several multidrug-resistant pathogens, and evaluate its therapeutic potential.