Solvent Fractions of <i>Parthenium hysterophorus</i> leaves from the Borkena River, Ethiopia: Phytochemical Screening and Antibacterial Activity against Gram-Positive and Gram-Negative Human Pathogens

Abstract

Objective Parthenium hysterophorus L. (Asteraceae) is an invasive weed that contains diverse secondary metabolites with reported bioactivities. This study evaluated the phytochemical profile and in vitro antibacterial activity of solvent-fractionated leaf extracts of P. hysterophorus collected from the Borkena River in Kombolcha, Ethiopia. Methods Dried leaf powder (300 g) was macerated in methanol (1.5 L) and concentrated to yield 22.3 g crude extract; the crude extract was partitioned into n-hexane, ethyl acetate and methanol fractions. Antibacterial activity was assessed by agar-well diffusion against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Klebsiella pneumoniae at 50, 100 and 200 mg/mL (controls: 10% DMSO negative, chloramphenicol positive). Results Qualitative screening detected alkaloids, flavonoids, phenols, carbohydrates, glycosides, terpenoids, saponins, steroids and tannins in one or more fractions. The ethyl acetate fraction produced the largest inhibition zones ( E. coli : 15.23 ± 0.22 mm at 100 mg/mL and 17.94 ± 0.80 mm at 200 mg/mL), while methanol fractions showed notable activity against L. monocytogenes (11.36 ± 0.50 mm at 200 mg/mL). Hexane fractions were largely inactive. Conclusion These results indicate that ethyl-acetate–soluble constituents of P. hysterophorus leaves contain antibacterial agents active against both Gram-positive and Gram-negative pathogens. Follow-up work (MIC/MBC determinations, chromatographic profiling, bioassay-guided isolation and structural identification) is recommended to validate and characterize the active principles.