## 3 Results and Discussion
### Kinetics and Tissue Distribution  
For the in vivo study of the kinetics and tissue distribution, different solvents, i.e., ethanol/water (10/90, \(v/v\)), ethanol/water (20/70, \(v/v\)), ethanol/water (25/75, \(v/v\)), ethanol/water (30/70, \(v/v\)), and ethanol/water (40/60, \(v/v\)), were compared for the solubility of ZEN-14G for administration to rats by gavage. When the percentage of ethanol was no less than 25%, satisfactory solubility (>99%) was achieved, and therefore ethanol/water (25/75, \(v/v\)) was selected (Table S5). After administration by gavage, ZEN-14G could be absorbed and converted into its prototype, ZEN, resulting in additional health risks to humans or animals. Both ZEN and ZEN-14G exhibited similar metabolic trends and reached peak concentrations of 4.4 \(\pm\) 1.2 ug/L and 2.8 \(\pm\) 0.2 ug/L in 10 min, respectively (Table 4). After that, ZEN and ZEN-14G rapidly decreased (Figure 3). The low plasma concentrations of ZEN-14G might be due to its poor absorption (oral bioavailability <10%) [24]. The elimination half-life of ZEN-14G was consistent with that acquired by [PERSON] et al. [24] but was lower than that for ZEN obtained by [PERSON] et al., attributed to the higher polarity of the glycoside's structure [56]. The tissue distribution of ZEN-14G and its metabolite, ZEN, is shown in Figure 4. ZEN-14G was still detectable in the stomach, small intestine, and large intestine 24 h after administration by gavage, and this could be hydrolyzed into ZEN in the digestive tract by the intestinal flora during digestion [57, 58]. Compared with investigations into ZEN-14G in the digestive tract for a short time (55 min) [50], our results suggested that ZEN-14G may be continuously and slowly converted to low levels of ZEN that are absorbed into the plasma and subsequently distributed to various tissues. Relatively higher amounts of ZEN were quantified in all tested tissues. The ranked order was as follows: small intestine > large intestine > liver > stomach > ovary > kidney. The highest concentration detected in the small intestine was 1004.9 \(\pm\) 155.0 ug/L. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Matrix** & **Mycotoxin** & **Spiked Level** & **Recovery** & \multicolumn{2}{c}{**Precision (RSD, \%)**} \\ \cline{3-6}  & & **(\(\mu\)g/L)** & **(Mean \(\pm\) SD, \%)** & **Intra-Day** & **Inter-Day** \\ \hline \multirow{6}{*}{Ovary} & \multirow{3}{*}{ZEN} & LLOQ & 92.7 \(\pm\) 10.3 & 11.8 & 16.5 \\  & & 5 & 95.0 \(\pm\) 3.3 & 3.1 & 5.6 \\  & & 20 & 94.0 \(\pm\) 1.4 & 2.8 & 3.1 \\  & & 50 & 103.9 \(\pm\) 1.7 & 2.4 & 3.1 \\ \cline{2-6}  & & LLOQ & 95.5 \(\pm\) 0.5 & 13.2 & 10.4 \\  & & 5 & 101.3 \(\pm\) 3.1 & 2.8 & 3.9 \\  & & 20 & 100.6 \(\pm\) 4.9 & 3.7 & 4.3 \\  & & 50 & 99.2 \(\pm\) 3.4 & 0.9 & 0.6 \\ \hline \multirow{6}{*}{Urine} & \multirow{3}{*}{ZEN} & LLOQ & 89.5 \(\pm\) 7.7 & 5.7 & 7.8 \\  & & 5 & 105.2 \(\pm\) 0.8 & 9.6 & 10.1 \\ \cline{1-1}  & & 20 & 98.9 \(\pm\) 0.9 & 7.0 & 7.0 \\ \cline{1-1}  & & 50 & 103.0 \(\pm\) 6.2 & 4.5 & 14.1 \\ \cline{1-1} \cline{2-6}  & & LLOQ & 92.8 \(\pm\) 3.2 & 10.2 & 9.7 \\ \cline{1-1}  & & 5 & 95.4 \(\pm\) 7.0 & 10.1 & 8.5 \\ \cline{1-1}  & & 20 & 102.4 \(\pm\) 3.4 & 11.3 & 7.9 \\ \cline{1-1}  & & 50 & 102.3 \(\pm\) 3.2 & 4.6 & 3.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Cont. Both ZEN-14G and its metabolite, ZEN, were detected in the urine (Figure 5). The amounts of urinary ZEN-14G were low and showed a decreasing trend at concentration levels from 43.9 \(\pm\) 11.1 ug/L to 7.6 \(\pm\) 3.0 ug/L within 24 h. These results were consistent with our data in plasma showing that ZEN-14G could be absorbed directly into the plasma in small amounts. Compared with ZEN-14G, ZEN maintained relatively higher levels ranging from 301.4 \(\pm\) 36.7 ug/L to 4801.5 \(\pm\) 424.8 ug/L, with the highest concentration detected at 6-12 h, indicating that ZEN-14G was slowly and continuously cleaved to ZEN, followed by sustainable absorption and excretion (Figure 6).