Eremostachys laevigata Bunge responses to different extraction solvents and methods: physiological, biochemical, and antibacterial attributes

Abstract

This study examined the biochemical composition of Eremostachys laevigata Bunge's aerial and underground organs using various solvents (methanol, water, N-hexane, chloroform, and acetone) and their impact on antibacterial activity against eight bacterial strains (Escherichia coli, Staphylococcus aureus, Salmonella enterica, Pseudomonas aeruginosa, Klebsiella pneumoniae, Shigella dysenteriae, Proteus mirabilis, and Bacillus cereus). Soxhlet and maceration extraction methods were used, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the tube dilution method. The study found that N-Hexane and water solvents had the highest total phenol content, while methanol, acetone, and chloroform had the lowest. Additionally, N-Hexane and methanol solvents showed the highest and lowest flavonoid content, respectively. The methanol extract from underground organs using the Soxhlet method exhibited the strongest antibacterial activity, whereas the acetone extract showed the weakest antimicrobial effect. Staphylococcus aureus displayed both the MIC and MBC, and Salmonella enterica showed the highest susceptibility to the well diffusion method, while both Escherichia coli and Staphylococcus aureus were highly susceptible to the disk diffusion method. The underground organs contained 6.87 mg.g^-1 of phenolic compounds and 0.19 mg.g^-1 of flavonoids. Two iridoid glycosides, pholoyoside and sesamoside, were separated from the methanol extract of the underground organs using reversed-phase HPLC. The research highlights E. laevigata Bunge's potential as a natural reservoir of antimicrobial compounds, with phenolic and flavonoid compounds, along with iridoid glycosides, presumed to contribute to its antibacterial properties.