Background

Ptaquiloside (PTA) is a natural carcinogen found in bracken ferns. PTA is released from the plants via soil to surface and groundwaters from where humans can be exposed via drinking water. Primary degradation of PTA is due to hydrolysis with formation of pterosin B (PTB). Temperature and pH determine the rate of hydrolysis under pure experimental conditions. To assess the applicability of the experimental model to natural groundwaters, PTA degradation kinetics were examined in a range of natural groundwaters at environmentally relevant conditions.

Results

PTA was quantified by UPLC-MS/MS. Over an 80-day study period, PTA half-lives ranged from 6.5 to 47 days (natural pH; 8.0 °C). The fastest degradation was observed for the most alkaline groundwaters with pH of around 8. Rates of degradation were well predicted using an existing mathematical model for hydrolysis. However, deviations from this model were found, especially at the extremes of the examined pH-range (4.7–8.2). The degree of conversion of PTA to PTB was close to unity around neutral pH. However, at slightly acidic conditions, formation of PTB could only count for 9% of the degraded PTA, indicating formation of other products.

Conclusions

Degradation of PTA in groundwater is determined by pH and temperature, and PTA can prevail for months under slightly acid to neutral pH conditions. The existing laboratory-based model for PTA hydrolysis is generally applicable for groundwaters but needs further validation at high and low pH.

中文翻译：

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天然致癌物帕奎洛甙是否会在地下水中容易降解？

背景

邻苯二酚（PTA）是蕨菜蕨中发现的一种天然致癌物。PTA通过土壤从植物释放到地表和地下水，在这里人类可以通过饮用水接触到PTA。PTA的主要降解是由于水解并形成了蝶呤B（PTB）。温度和pH值决定了纯实验条件下的水解速率。为了评估实验模型对天然地下水的适用性，在环境相关条件下，在一系列天然地下水中检测了PTA降解动力学。

结果

通过UPLC-MS / MS对PTA进行定量。在80天的研究期内，PTA的半衰期为6.5至47天（自然pH； 8.0°C）。对于pH约为8的大多数碱性地下水，观察到最快的降解。使用现有的水解数学模型可以很好地预测降解速率。但是，发现与该模型存在偏差，尤其是在所检查的pH范围（4.7-8.2）的极端值处。在中性pH值附近，PTA转化为PTB的程度接近于1。但是，在弱酸性条件下，PTB的形成仅占降解PTA的9％，表明形成了其他产物。

结论

地下水中PTA的降解取决于pH和温度，在弱酸至中性pH条件下PTA可以持续数月。现有的基于实验室的PTA水解模型通常适用于地下水，但需要在高pH和低pH下进行进一步验证。