Metal Chelation and Antioxidant Capacities of Helianthus annuus Extracts: A Promising Approach for Green Chelators

This study systematically investigated the iron, zinc and copper chelating capacities, along with the antioxidant potential, of hexane (HE), chloroform (CE), ethyl acetate (EAE), and methanolic (ME) extracts obtained from the leaves, stems, and roots of Helianthus annuus. Metal-chelating activities were evaluated in vitro using the ferrozine assay for iron and the murexide method for zinc and copper, with EDTA serving as the reference chelator, while antioxidant activity was assessed using the DPPH radical-scavenging assay. Among the extracts tested, the hexane stem extract (HSE) exhibited the strongest iron-chelating activity (91%), approaching that of EDTA (97%). Zinc chelation was highest in the chloroform leaf extract (CLE), reaching 55%, which notably exceeded the activity of EDTA (37%). For copper, the chloroform stem extract (CSE) demonstrated substantial chelating efficiency (78%), comparable to EDTA (81%). All extracts showed pronounced DPPH radical-scavenging activity, with the methanolic leaf extract (MLE) achieving a maximum inhibition of approximately 91.3%. Corresponding IC50 values further confirmed the superior antioxidant capacity of methanolic extracts relative to the standard antioxidant, ascorbic acid. Overall, these results indicate that H. annuus extracts possess significant metal-chelating and antioxidant properties, supporting their potential use as natural, plant-based green chelators and antioxidants in food, environmental, and agricultural applications as sustainable alternatives to synthetic agents.