Stability of saponin biopesticides: hydrolysis in aqueous solutions and lake waters

• DOI: 10.1039/c9em00012g
• Publication Date: 2019-06-03T15:04:15Z
• Authors: Xiaogang Jiang; Bjarne W. Strobel; Nina Cedergreen; Yi Cao; Hans Chr. Bruun H...
• Keywords: 0303 health sciences; Hydrolysis; Quillaja; Temperature; Flocculation; Hydrogen-Ion Concentration; Saponins; 6. Clean water; Solutions; Kinetics; Lakes; 03 medical and health sciences; Biological Control Agents; Nanoparticles

Saponins form a group of plant-produced glycosides with potential as biopesticide ingredients. The environmental fate saponins has never been fully investigated. In the present study, we use QS-18, specific saponin from Quillaja saponaria an example, to quantify hydrolysis under different conditions pH, temperature and water chemical composition. Saponin in buffer solutions was base-catalyzed followed first-order kinetics. Thus, slow at pH 5.1 half-life 330 ± 220 d (26 °C), which increases 0.06 0.01 10.0. Hydrolysis rates were highly sensitive activation energy 56.9 14.2 kJ mol-1 7.2. strong contrast, lake waters (pH 6.4-8.2) produced patterns fast initial dissipation 25 60% added within first five hours, by extremely reaction 75% unreacted left after times longer than 120 h. hypothesized be attributed sorption and/or flocculation inorganic nanoparticles solutes inactivation due sorption/flocculation. study demonstrates that may hydrolyze slowly acidic cold conditions. addition, it kinetics natural deviate substantially predicted based on laboratory experiments "clean" buffered solutions. This emphasizes need for deeper understanding processes affecting toxins conditions, models derived kinetic data seriously flawed.