## 2 Results and Discussion
### The Structural Elucidation of New Compounds
The IC\({}_{50}\) values of compound **2** against PXO 71A and PXO 86A strains were 354.09 \(\pm\) 23.75 and 274.12 \(\pm\) 67.19 \(\mu\)g/mL, respectively. \begin{table}
\begin{tabular}{c c c} \hline
**Position** & \multicolumn{2}{c}{**Compound 3**} \\ \hline
1\({}^{\prime}\) & 4.08, dd (10.3, 8.3); 4.54, dd & 77.0, t \\
2\({}^{\prime}\) & 3.80, dd (8.3, 2.6) & 76.1, d \\
3\({}^{\prime}\) & - & 73.3, s \\
4\({}^{\prime}\) & 1.55, m; 1.68, m & 36.6, t \\
5\({}^{\prime}\) & 1.65, m & 27.3, t \\
6\({}^{\prime}\) & 3.53, m & 63.2, t \\
7\({}^{\prime}\) & 1.13, s & 22.8, q \\
6-OMe & 3.90, s & 56.7, q \\
8-OMe & 4.00, s & 62.0, q \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 4: The growth inhibitory activity of compounds **1** and **2** against agricultural invasive bacteria. (**A–C**) represent the results of the inhibitory activity screening of compound **1** against the bacteria _Xanthomonas oryzae_ pv. _oryzae_ PXO 71A, PXO 86A, and _Pseudomonas syringae_ pv. _maculicola_ ES4326. (**D–F**) represent the results of the inhibitory activity screening of compound **2** against the bacteria PXO 71A, PXO 86A, and ES4326. An independent samples _t_-test was used to compare the experimental and control groups, where \(p\) \(<\) 0.05 was _”_, \(p\) \(<\) 0.01 was _”_, and \(p\) \(<\) 0.001 was _”_. Meanwhile, compound **2** also exhibited a certain inhibitory effect on the growth of the ES4326 strains. When the ES4326 strain was treated with 256 \(\mathrm{\SIUnitSymbolMicro g}\)/mL of compound **2** for 48 h, the inhibition rate was found to be 49.04 \(\pm\) 3.06% (Figure 4F). The inhibition rate of 4 \(\mathrm{\SIUnitSymbolMicro g}\)/mL kanamycin (positive control) against the PXO 71A strain after co-culturing for 24 h was 85.67 \(\pm\) 3.25%. The PXO 86A strain was treated with streptomycin (positive control) for 24 h with an IC\({}_{50}\) of 21.15 \(\pm\) 2.38 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, and the inhibition rate of 4 \(\mathrm{\SIUnitSymbolMicro g}\)/mL kanamycin against the ES4326 strain after treatment for 24 h was 82.27 \(\pm\) 3.25% (Figure S31). Meanwhile, the double dilution method was used to screen compounds **13**, **15**, and **17** for antimicrobial activity against the PXO 71A, PXO 86A, and ES4326 strains. Compound **13** exhibited a weak inhibitory effect against the PXO 71A, PXO 86A, and ES4326 strains. Compound **15** had almost no effect on the growth of the ES4326 strain but exhibited weak inhibitory effects against the PXO 71A and PXO 86A strains. Culture of PXO 71A and PXO 86A for 36 h with 512 \(\mathrm{\SIUnitSymbolMicro g}\)/mL of compound **15** resulted in inhibition rates of 22.38 \(\pm\) 2.67% and 31.22 \(\pm\) 2.29%, respectively. However, compound **17** only exhibited a weak inhibitory effect against PXO 86A (28.24 \(\pm\) 2.71% after treatment with compound **17** at 256 \(\mathrm{\SIUnitSymbolMicro g}\)/mL for 24 h (Figure S2). _A. altissima_ exhibits remarkable biological activities and is recognized as a versatile tree. For example, its leaves possess antibacterial properties, its bark demonstrates neuroprotective effects, and its seeds and branches exhibit notable anti-inflammatory activity [34]. According to previous studies, the leaves of _A. altissima_ are abundant in polyphenols, sesquiterpenes, and triterpenoids, among which the phenolic composition of leaf extracts exhibits excellent antibacterial activity against _Escherichia coli_ and _Candida albicans_[35]. In addition, the triterpenoid compound ailanthone extracted from _A. altissima_ leaves can significantly inhibit the growth of garden cress and radish when its concentration is 7.5 mg/L, and the inhibition rate can reach up to 95% after 30 days of treatment [36]. In this study, two new steroidal compounds, ailanstigol A (**1**) and ailanstigol B (**2**), a new coumarin (2\({}^{\prime}\)R,3\({}^{\prime}\)R)-7-(2\({}^{\prime}\),3\({}^{\prime}\),6\({}^{\prime}\)-trihydroxy-3\({}^{\prime}\)-methylhexyloxy)-6,8-dimethoxyocyanin (**3**), and 18 known compounds were isolated from _A. altissima_ leaves.