Evaluation of Camellia oleifera seed saponins degradation in rice fields by UPLC-MS/MS method

Freshwater snails of the genus Pomacea, have been introduced worldwide with well-documented ecological and economic impacts. In rice, a crucial crop for global food security, apple snails have become a major pest. Chemical molluscicides, the most effective method of control, raise concerns due to their ecotoxicity. Exploring alternative, environmentally friendly plant-derived molluscicides, such as saponins from Camellia oleifera seeds, is therefore necessary. However, quantifying saponins in water remains challenging due to their structural diversity and the lack of reference materials. We developed a UPLC-MS/MS method, including a preconcentration Solid-Phase-Extraction step to improve sensitivity, for the determination of 17 selected saponins present in a commercial Camellia oleifera seed extract (COSE). Then, we investigated their degradation kinetics in rice fields water (16 sampling points in 6 rice fields, twice daily for 4 days, mean daytime water temperature > 25 °C). All saponins exhibited a similar degradation pattern, with concentrations gradually declining to near zero. The results indicate that saponins were readily degradable, with half-life (DT₅₀) ranging from 9.28 to 19.94 h. The maximum observed DT₉₀ (time for 90 % degradation) was 66.24 h. Our findings suggest that sealing rice fields for 96 h (4 days) after COSE application could be an effective method for controlling apple snail infestation while minimizing environmental impact in the Ebro Delta region. The UPLC-MS/MS method is thus a valuable tool for monitoring the fate of saponins in rice fields and the environment, enabling the development of effective saponin application strategies for controlling apple snails in rice fields.