Antioxidant Activity of Pot Marigold (Calendula officinalis L.) in Response to Metal(loid) Induced Oxidative Stress from Fly Ash Amended Soil

The present study aimed to investigate the variation in the metal(loid)s composition, phytochemicals, enzymatic and nonenzymatic antioxidants activity of pot marigold grown in different treatments of soil and fly ash (FA), i.e., control (soil 100% + 0% FA), 20% FA (soil 80% + 20% FA), 40% FA (soil 60% + 40% FA), 60% FA (soil 40% + 60% FA), 80% FA (soil 20% + 80% FA), and 100% FA (soil 0% + 100% FA). The plant leaves from each treatment were harvested and screened for various metal(loid)s concentrations (Fe, Cu, Mn, Ni, Co, Zn, Cd, Mg, Ca, and As). Further, the harvested leaf samples were extracted using three solvents (ethanol, methanol, and water), and their extract yield percentage, total flavonoid, and phenolic profile, total antioxidants (1,1-Diphenyl-2-picrylhydrazyl (DPPH) assay, ABTS (2,2'-Azinobis-(3-Ethylbenzthiazolin-6-Sulfonic Acid), Ferric reducing power assay ( FRAP)), and antioxidant enzymatic activity (Superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and catalase (CAT)) were determined. The results revealed that a high accumulation of Fe, Cu, Ni, Co, Zn, and Cr with bioaccumulation factor (BAF > 1) was detected at 40% FA treatment. Furthermore, the phenolic and flavonoid content were increased by 35.44 and 160.13% respectively whereas, DPPH and ABTS activity (with low IC50) was decreased by 82.67 and 31.87% in ethanolic leaf extract at 60% FA application compared to the control. Additionally, at high FA application (100% FA), the parameters such as FRAP value, SOD, CAT, APX, and POD activity were increased by 42.42%, 313.98%, 388.76%, 415.11%, and 177.54% with respect to control soil. The findings suggested that FA application ( up to 60%) in soil induced increased production of secondary metabolites, and total antioxidant activity compared to control soil. [GRAPHICS] .