UV-B Radiation Triggers Phenolic Accumulation and Oxidative Stress Response in Lamiaceae Species: From Plant Defense to Green Dye Remediation.

The present study explores the impact of UV-B radiation on biochemical traits and phenolic profile of in vitro cultures (IC) and micropropagated plants (MP) of Lavandula viridis L'Hér and Thymus lotocephalus G. López and R. Morales. Two UV-B treatments were applied: a single 4 h exposure (UV-B 1) and repeated exposure over four consecutive days (UV-B 4). Additionally, the potential of phenolic-rich extracts loaded into alginate-based hydrogels for dye removal was also evaluated. UV-B exposure triggered oxidative stress in both species, particularly in MP, increasing hydrogen peroxide levels and lipid peroxidation, and affecting chlorophyll and carotenoid content. Both species responded by accumulating soluble sugars and phenolic compounds as a defense mechanism. Rosmarinic acid, the predominant phenolic compound, increased significantly under UV-B radiation in IC and MP. IC showed higher concentrations after UV-B 1 exposure, with L. viridis reaching 50.1 mg/g and T. lotocephalus 32.3 mg/g, increases of 16% and 41%, respectively, over the control. Polyphenol-loaded hydrogels showed high methylene blue adsorption efficiency, highlighting their potential as eco-friendly materials for wastewater treatment and environmental remediation. Optimal adsorption conditions were determined using Box-Behnken design and Response Surface Methodology, demonstrating the applicability of these natural hydrogels as sustainable and efficient materials for dye removal from contaminated wastewater.