In vitro antimicrobial potential and phytochemical analysis of root extracts of Rumex abyssinicus from southern Ethiopia

The escalating challenge of antimicrobial resistance require a continuous search for novel compounds with therapeutic potential. The approach of linking traditional practices and knowledge with evidence-based preclinical studies can help minimize the resource-intensive process of drug screening. Rumex abyssinicus is an important plant species used in Ethiopian traditional medicine, and this study aims to conduct a phytochemical analysis of root extracts of R. abyssinicus and determine its antimicrobial activity. R. abyssinicus roots were extracted in six solvents of different polarities. Agar well-diffusion assays of the extracts were performed against type culture bacterial strains, clinically bacterial isolates, and fungi, while the tube dilution method was used to determine the minimum inhibitory concentration of the extracts. The ground root powder was refluxed with acetonitrile (1:10 w/v) and analyzed using reverse-phase high-performance liquid chromatography combined with mass-spectrometry. A one-way analysis of variance followed by post hoc multiple comparisons was performed, and differences were considered statistically significant at p < 0.05. The root extract of R. abyssinicus showed antimicrobial activity against type culture bacteria and clinical isolates, and fungi. Extraction with different solvents yielded extracts with varying antimicrobial activities. The extracts showed a varied range of antimicrobial activities against the test organisms, with inhibition zones of 11-25 mm for bacteria and 9-24 mm for fungi. The MIC range fell between 12.5 and 100 mg/mL. The phytochemical analysis revealed the presence of major compounds such as emodin (30%), chrysophanol (18%), physcion (16%), helminthosporin (12%), citreorosein (11%) and emodic acid (8%) which are envisaged to have functional roles in chemical defense against the tested organisms. The susceptibilities of the tested bacteria and fungi varied depending on the type of solvent used for extraction and extract concentration. Enhanced antimicrobial activities were observed against the entire panel of bacteria compared to those against the test fungi. The results support the traditional use of R. abyssinicus for treating infectious diseases.