Fungi are ubiquitous in environments and produce secondary metabolites that are usually low-molecular-weight organic compounds during growth processes. Dust samples containing these fungal secondary metabolites collected from study sites are often stored in certain temperature conditions for an extended period until laboratory analysis resources are available. However, there is little information on how stable fungal secondary metabolites are over time at different storage temperatures. We examined the stability of 27 fungal secondary metabolites spiked into floor dust samples collected from a moisture-damaged office building. Ninety-five dust aliquots were made from the spiked dust; five replicates were randomly assigned to a baseline (time = 0) and each of the 18 combinations of three temperatures (room temperature, 4 °C, or -80 °C) and six time points (2, 12, 25, 56, 79, and 105 weeks). At the baseline and each subsequent time point, we extracted and analyzed the fungal secondary metabolites from the spiked dust using ultra-performance liquid chromatograph-tandem mass spectrometer. To estimate change in concentration over storage time at each temperature condition, we applied multiple linear regression models with interaction effect between storage temperature and duration. For 10 of the 27 fungal secondary metabolites, the effect of time was significantly (p-values <0.05) or marginally (p-values <0.1) modified by temperature, but not for the remaining 17 metabolites. Generally, for most fungal secondary metabolites, storage at room temperature was significantly (p-values <0.05) associated with a larger decline in concentration (up to 83% for 3-nitropropionic acid at about 11 months) than storing at 4 °C (up to 55% for emodin) or -80 °C (55% for asperglaucide). We did not observe significant differences between storage at 4 °C, or -80 °C. Storage temperature influenced degradation of fungal secondary metabolites more than storage time. Our study indicates that fungal secondary metabolites, including mycotoxins in floor dust, quickly degrade at room temperature. However, storing dust samples at 4 °C might be adequate given that storing them at -80 °C did not further reduce degradation of fungal secondary metabolites.

中文翻译：

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储存温度和储存时间对从办公大楼喷入地板粉尘中的27种真菌次生代谢产物浓度的影响。

真菌在环境中无处不在，并产生次级代谢产物，这些代谢产物通常是生长过程中的低分子量有机化合物。从研究地点收集的含有这些真菌次生代谢产物的粉尘样品通常会在一定温度条件下长时间保存，直到获得实验室分析资源为止。但是，关于不同存储温度下真菌次生代谢产物的稳定性如何的信息很少。我们检查了掺入从受湿气损坏的办公楼收集的地板粉尘样品中的27种真菌次生代谢产物的稳定性。从加料的粉尘中分出九十五个粉尘等分试样；将五个重复样本随机分配给一个基线（时间= 0），并将三个温度（室温，4°C，或-80°C）和六个时间点（2、12、25、56、79和105周）。在基线和随后的每个时间点，我们使用超高效液相色谱-串联质谱仪从加标粉尘中提取并分析了真菌次生代谢物。为了估计在每种温度条件下储存时间的浓度变化，我们应用了多个线性回归模型，这些模型具有储存温度和持续时间之间的相互作用。对于27种真菌次生代谢物中的10种，时间的影响被温度显着（p值<0.05）或略有改变（p值<0.1），但对其余17种代谢物没有影响。通常，对于大多数真菌次生代谢产物，在室温下的储存显着（p值<0。05）与在4°C（大黄素高达55％）或-80°C（曲格列脲55％）储存时浓度下降更大（3-硝基丙酸在约11个月时高达83％）有关。我们没有观察到在4°C或-80°C下储存之间的显着差异。储存温度对真菌次生代谢产物降解的影响大于储存时间。我们的研究表明，真菌次生代谢产物（包括地板灰尘中的霉菌毒素）在室温下会迅速降解。但是，将粉尘样品存储在4°C可能就足够了，因为将其存储在-80°C并不能进一步减少真菌次级代谢产物的降解。储存温度对真菌次生代谢产物降解的影响大于储存时间。我们的研究表明，真菌次生代谢产物（包括地板灰尘中的霉菌毒素）在室温下会迅速降解。但是，将粉尘样品存储在4°C可能就足够了，因为将其存储在-80°C并不能进一步减少真菌次级代谢产物的降解。储存温度对真菌次生代谢产物降解的影响大于储存时间。我们的研究表明，真菌次生代谢产物（包括地板灰尘中的霉菌毒素）在室温下会迅速降解。但是，将粉尘样品存储在4°C可能就足够了，因为将其存储在-80°C并不能进一步减少真菌次级代谢产物的降解。