Physicochemical Characterization and Solar-Driven Chromophore Removal of Hydroalcoholic Larrea tridentata Extracts in Aqueous Media

Although plant-derived bioactive compounds are promising sustainable alternatives to synthetic herbicides, their environmental fate and transformation behavior remain poorly understood. This study evaluates the physicochemical stability and solar-driven transformation of phenolic and other complex phytochemical constituents in Larrea tridentata hydroalcoholic extracts (AELT) in aqueous media. Spectroscopic and thermal characterization (TGA/DTG, FTIR, 1H/13C NMR, and GC–MS) revealed a chemically complex phytochemical matrix containing aromatic, phenolic, terpenoid, fatty-acid-derived and other oxygenated constituents, which exhibit a characteristic absorption maximum at 280 nm. Solar-driven oxidation experiments were conducted using TiO2, ZnO, and H2O2. Among the evaluated systems, Solar/ZnO emerged as the most efficient standalone treatment, achieving 89.43% chromophore removal and 88.56% reduction of chemical oxygen demand (COD) after 60 min. The findings demonstrate a clear relationship between the phenolic and other complex phytochemical constituents’ nature of the extract and its high susceptibility to ZnO-assisted solar photocatalysis, which effectively transforms UV-absorbing constituents and reduces the oxidizable organic load. This work establishes a robust framework for assessing the solar treatment of complex phytochemical matrices, supporting the potential application of ZnO-assisted processes for mitigating the organic load of plant-derived formulations in water bodies.