Impacts of heavy metal, high temperature, and UV radiation exposures on Bellis perennis L. (common daisy): Comparison of phenolic constituents and antioxidant potential (enzymatic and non-enzymatic)

Bellis perennis L., common daisy, is a beneficial medicinal plant used in folk medicine to treat skin diseases, wounds, sore throats, common colds, inflammation, and rheumatism. The objective of this study was to determine the effect of 4 different abiotic stress applications [mercury chloride (HgCl₂), copper sulfate (CuSO₄), high temperature (45 °C) and ultraviolet radiation (UV)] on individual phenolic constituents, non-enzymatic antioxidant activities (free radical scavenging activity, total phenol-flavonoid content, and proline level), and enzymatic antioxidant activities [superoxide dismutase (SOD) and catalases (CAT)] in common daisy callus cultures. Quantification of the 21 phenolic substances was performed using LC-ESI-MS/MS analysis and all applied stress applications increased specific phenolic constituents comparing with control (no exposure to any stress). Heavy metal stresses (HgCl₂ and CuSO₄) and high temperature application enhanced the quantity of the selected phenolic substances more than UV-radiation stress. The most noticeable increased quantities were observed with high temperature stress in p-coumaric acid (51.74-fold), and with CuSO₄ stress in luteolin (17.76-fold) and apigenin (15.62-fold). Chlorogenic acid was the most prevalent phenolic compound in all tested callus extract including control. Although the first highest total phenol content was obtained with HgCl₂ exposure and then followed by high temperature stress, the first highest total flavonoid content was obtained with high temperature stress and then UV radiation. The antioxidant capacity was significantly enhanced (2.11 fold increase) with CuSO₄ stress application. Stress-related enzymatic antioxidant activity (SOD and CAT) was elevated the most with HgCl₂ stress. Similarly, the highest proline content was obtained with HgCl₂ treatment. These findings showed the ability of the phenolic compounds to protect common daisy against harmful heavy metals, high temperature and UV-radiation stresses. The adaptation of the callus under abiotic stress conditions developed here may be useful for the production of optimized phenolic compounds of common daisy and the exploitation of other medicinal species of interest.