A comparative study of antioxidant potentials and phenolic acid and flavonoid profiles of <i>Amaranthus spinosus</i> leaf, stem and root extracts

Oxidative stress has been identified as a contributing factor in the onset of several illnesses and disorders. This has led to the adoption of multiple studies in recent years aimed at improving clinical outcomes by increasing antioxidant levels. The plant studied, Amaranthus spinosus, has been used in tribal cultures worldwide for its ethnomedicinal properties. Here, the present investigation characterises the phenolic acids and flavonoids in the methanolic extracts of A. spinosus from the leaf (ASLE), stem (ASSE), and root (ASRE) using High-performance liquid chromatography (HPLC). Additionally, a comparative evaluation of their antioxidant activity was conducted both in vitro and in vivo. ASLE exhibited high levels of rutin (12.93±0.06 μg/mg) and syringic acid (8.84±0.09 μg/mg), while ASSE was rich in gallic acid (3.39±0.03 μg/mg) and protocatechuic acid (2.05±0.004 μg/mg). In vitro antioxidant assays demonstrated comparable radical scavenging activities among the extracts, despite differences in phytochemical profiles. Also, in vivo experiments on thioacetamide-induced oxidative stress in mice (Mus musculus) demonstrated considerable antioxidant capabilities among all extracts. Administration of extracts restored catalase and SOD enzyme activity, elevated glutathione levels, and decreased lipid peroxidation in liver homogenates, indicating their therapeutic value. Therefore, the presence of important phenolic acids (e.g., syringic and chlorogenic acids) and flavonoids (e.g., rutin and quercetin) might explain the observed effectiveness. However, there were no significant variations in in vivo antioxidant activity amongst the extracts. This study highlights the therapeutic potential of A. spinosus, which supports its traditional use in combating oxidative stress. However, further research is necessary to identify the specific phytochemical combinations responsible for its antioxidant properties and their underlying mechanisms.