Antimicrobial resistance is a growing global problem and motivates continued exploration of natural products for new therapeutic leads. Traditional medicines remain an important source of candidate compounds, especially in low-resource settings. Rumex abyssinicus is a perennial herb used in Ethiopian ethnomedicine for wounds, diarrhoea, inflammatory disorders and infections. Prior work has reported antioxidant, antimicrobial and anti-inflammatory properties for the species, but comprehensive chemical profiling of root extracts using reverse-phase HPLC-mass spectrometry (RPHPLC-MS) alongside broad antimicrobial testing had not been reported for the study area. This study aimed to determine the in vitro antimicrobial activity of R. abyssinicus root extracts prepared with multiple solvents and to characterize major phytochemical constituents by RPHPLC-MS.
Root samples of R. abyssinicus were collected in Chencha, Arba Minch (Gamo Gofa Zone), southern Ethiopia. The plant was taxonomically authenticated by a botanist and a voucher specimen deposited in the National Herbarium of Addis Ababa University (GG. 28). Collected roots were washed, oven-dried at 40°C, and ground to a fine powder for extraction.
An amount of 100 g of powdered root was extracted separately in 1,000 mL of each solvent for 24 hours on an orbital shaker (100 rpm) at room temperature. Six solvents of differing polarity were used to obtain a range of extract profiles (specific solvent names were reported in the source). Filtrates were concentrated under reduced pressure at 40°C using a rotary evaporator. Residues were weighed and reconstituted to produce stock solutions at 100 mg/mL, then stored at −20°C until testing. For phytochemical profiling, powdered root was refluxed with acetonitrile (1:10 w/v) and the acetonitrile extract was analyzed by reverse-phase HPLC coupled to mass spectrometry (RPHPLC-MS).
Antimicrobial activity was assessed against multiple panels of microorganisms. One panel comprised ATCC standard organisms, including Staphylococcus aureus, Salmonella enterica, Klebsiella pneumoniae and Escherichia coli sourced from the Ethiopian Public Health Institute. A second panel consisted of clinically isolated bacteria, including WHO-priority pathogens (the source text indicates methicillin-resistant Staphylococcus species among the clinical isolates). Fungi were also included in the testing panel. Test organisms were cultured and maintained following standard laboratory procedures described in the study.
Antimicrobial activity of each extract was evaluated using the agar well-diffusion assay. Zones of inhibition produced by extracts were measured to compare activity across solvents and organisms. Minimum inhibitory concentrations (MICs) were determined by the tube dilution method. The study used one-way analysis of variance (ANOVA) with post hoc multiple comparisons to assess differences, with statistical significance set at p < 0.05.
RPHPLC-MS analysis of the acetonitrile root extract identified several major anthraquinone-related constituents and related compounds. The principal compounds and their relative abundances reported in the study were emodin (30%), chrysophanol (18%), physcion (16%), helminthosporin (12%), citreorosein (11%), and emodic acid (8%). These compounds are proposed by the authors to contribute to the chemical defence properties of the extracts against the tested microorganisms.
A one-way ANOVA followed by post hoc multiple comparisons was applied to compare antimicrobial effects across extracts, solvents and concentrations. Differences were considered statistically significant at p < 0.05. The source reports that solvent type and extract concentration influenced susceptibilities, although detailed p-values per comparison are reported in the full manuscript and supporting tables.
Extracts of R. abyssinicus roots produced inhibition zones against bacteria ranging from 11 to 25 mm and against fungi ranging from 9 to 24 mm, depending on the solvent and organism tested. The minimum inhibitory concentrations for active extracts ranged between 12.5 and 100 mg/mL. Overall, the extracts showed enhanced antimicrobial activity against the bacterial panel compared with the fungal panel.
Activity varied by extraction solvent and by extract concentration, indicating that solvent polarity influenced recovery of bioactive constituents. The identification of anthraquinone-type compounds (notably emodin, chrysophanol, and physcion) provides a plausible chemical basis for the antimicrobial effects observed. The authors interpret the combined phytochemical and antimicrobial data as supportive of the traditional topical and medicinal use of R. abyssinicus roots for treating infections and inflammatory conditions in the study region.
Root extracts of R. abyssinicus from southern Ethiopia demonstrated measurable in vitro antimicrobial activity against standard bacterial strains, clinical isolates and fungi, with inhibition zones and MICs indicating dose-dependent effects. RPHPLC-MS profiling of the acetonitrile extract detected several major compounds, led by emodin, that may underlie the observed antimicrobial properties. The results support the plant’s traditional use for treating infectious conditions and provide a phytochemical catalogue to guide further bioassay-guided isolation and evaluation. The study used standard in vitro assays and statistical analysis; details such as full organism lists, specific solvent names and individual statistical values are available in the original manuscript and supporting information.