Weed to wonder: antioxidant and antibacterial investigation of Parthenium hysterophorus L.

Bioactive potential of Parthenium hysterophorus L.

Abstract

The overuse of modern synthetic pesticides for controlling insect-pest and plant diseases has led to environmental pollution, health risks, and the development of resistant bacterial strains, creating an urgent need for sustainable and eco-friendly alternatives. Parthenium hysterophorus, a widely distributed invasive weed, is known for its harmful effects but also contains bioactive compounds such as phenolics, flavonoids, tannins, and alkaloids. This study explores its potential as a natural source of antioxidant and antibacterial agents to address crop protection challenges. Aqueous leaf and flower extracts were analyzed for phytochemicals and bioactivity. Qualitative and quantitative profiling confirmed a high level of phenolics (13.5±9.49 mg GAE/g), flavonoids (22.60±0.52 mg QE/g), tannins (11.26±1.70 mg TAE/g), and alkaloids (717.27±211mg/g) in leaf extracts. Antioxidant evaluation revealed strong radical scavenging activity, with leaf extracts exhibiting lower IC₅₀ values in DPPH (604.88 μg/mL) and ABTS (644.9 μg/mL) assays compared to flower (1,028.74 μg/mL and 900 μg/mL, respectively). Reducing power was higher in leaves (256.92 mg AAE/g) than flowers (210.30 mg AAE/g). Fourier transform infrared spectroscopy (FTIR) revealed a strong broad peak at 4000–400 cm⁻¹, corresponding to O–H stretching, which is characteristic of phenolic and alcoholic compounds, and Gas chromatography mass spectroscopy (GC-MS) exhibited the Dimethyl sulfone as a major bioactive compound in both leaf (24.31%) and flower (32.83%) extracts. Antibacterial activity assessed by agar well diffusion demonstrated significant inhibition against Pectobacterium carotovorum (18 mm at 60 mg/mL) and Ralstonia solanacearum (11mm at 60 mg/mL), outperforming flower extracts. These findings highlight P. hysterophorus as a rich source of bioactive compounds with potent antioxidant and antibacterial properties, supporting its transformation from an invasive weed into a sustainable biocontrol agent for eco-friendly crop protection.