Secondary Metabolite Profiling and In Vitro Bioefficacy of Retama raetam Extracts Using Bacterial Test Systems

Abstract

The increasing global concern regarding reduced effectiveness of conventional antimicrobial agents has intensified interest in identifying alternative bioactive resources of natural origin. This study evaluated the phytochemical profile and in vitro bioefficacy of Retama raetam crude extracts using selected bacterial test systems, namely Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, and Staphylococcus aureus. Aerial parts of the plant were collected from Al-Zawiya, Libya, shade-dried, and extracted using ethanol, methanol, and distilled water through cold maceration. Extraction yield varied according to solvent polarity, with ethanol producing the highest yield. Qualitative phytochemical screening revealed the presence of alkaloids, flavonoids, tannins, terpenoids, and saponins, with a comparatively higher abundance of bioactive constituents detected in the ethanolic extract. Biological response was assessed using the agar well diffusion assay against standardized inocula (0.5 McFarland). The ethanolic extract demonstrated pronounced inhibitory activity, particularly against P. aeruginosa (40 ± 1.2 mm), while moderate inhibition was observed against S. aureus and E. coli. No detectable inhibition was recorded against Klebsiella spp. Statistical analysis using one-way ANOVA confirmed significant differences among extracts (p ≤ 0.05). The observed bioactivity may be attributed to the synergistic action of phenolic compounds and alkaloids capable of influencing bacterial membrane integrity and metabolic pathways. These findings position R. raetam as a promising reservoir of biologically active secondary metabolites and support further quantitative, mechanistic, and minimum inhibitory concentration investigations to clarify its functional potential