## 2 Results and Discussion
### The Structural Elucidation of New Compounds
In the HR-ESI-MS analysis, a molecular ion peak was observed (\(m/z_{\text{obsd}}\) 391.1371 [M + Na]\({}^{+}\); \(m/z_{\text{calcd}}\) 391.1369) that suggested a molecular formula of C\({}_{18}\)H\({}_{24}\)O\({}_{8}\) with 6 degrees of unsaturation. The \({}^{1}\)H NMR spectrum (Table 2) showed three singlet methyl groups (\(\delta_{\text{H}}\) 1.13, 3.90, and 4.00) and three olefinic hydrogen protons (\(\delta_{\text{H}}\) 6.34, 7.10, and 7.92) (Table 2). \({}^{13}\)C NMR and DEPT spectra indicated that the compound contains 18 carbons, which were classified as three methyl groups (including two oxidized methyls at \(\delta_{\text{C}}\) 56.7 and 62.0), four methylene groups (including two oxidized methylenes at \(\delta_{\text{C}}\) 63.2 and 77.0), four methine groups (including one oxidized methane at \(\delta_{\text{C}}\) 76.0), and seven quaternary carbons (including one ester carbonyl carbon at \(\delta_{\text{C}}\) 160.4). From the 1D and 2D NMR spectra, we speculated that compound **3** could be a coumarin with a benzopyran-\(\alpha\)-pyrone core structure. The skeletal carbon signals of **3** are very similar to the known compound (2\({}^{\prime}\)R,3\({}^{\prime}\)R)-7-(2\({}^{\prime}\)3\({}^{\prime}\)-dihydroxy-3\({}^{\prime}\),7\({}^{\prime}\)-dimethylocta-6\({}^{\prime}\)-enyloxy)-6,8-dimethoxycumarin [33], with the difference between these two being that **3** lacks two methyl groups and one double bond. Based on \({}^{13}\)C NMR and HMBC data, we found that the C-6\({}^{\prime}\) of compound **3** was an oxidized methylene group (\(\delta_{\text{C}}\) 63.2, \(\delta_{\text{H}}\) 3.53) (Figure 2), indicating that the 6\({}^{\prime}\)-OH has replaced the original double bond and two methyl substituents. And the calculated ECD curve was consistent with the experimental CD curve of 2\({}^{\prime}\)R, 3\({}^{\prime}\)R, indicating that the absolute configuration of compound **3** was 2\({}^{\prime}\)R, 3\({}^{\prime}\)R (Figure 3). In this way, the structure of **3** was eventually determined, and the compound was named (2\({}^{\prime}\)R,3\({}^{\prime}\)R)-7-(2\({}^{\prime}\)3\({}^{\prime}\),6\({}^{\prime}\)-trihydroxy-3\({}^{\prime}\)-methylhexyloxy)-6,8-dimethoxycium (Figure 1). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Position** & \multicolumn{2}{c}{**Compound 3**} \\ \hline  & \(\delta_{\text{H}}\) (J[Hz]) & \(\delta_{\text{C}}\) \\
2 & - & 160.4, s \\
3 & 6.34, d (9.5) & 115.7, d \\
4 & 7.92, d (9.5) & 144.7, d \\
5 & 7.10, s & 105.6, d \\
6 & - & 150.9, s \\
7 & - & 145.9, s \\
8 & - & 141.8, s \\
9 & - & 143.7, s \\
10 & -Growth Inhibition Activity Screening of Compounds Against X. oryzae pv. oryzae PXO 71A and PXO 86A and P. syringae pv. maculicola ES4326  
Using the two-fold dilution method, the growth inhibitory activities of compounds **1** and **2** against _X. oryzae_ pv. _oryzae_ pv. _oryzae_ PXO 71A and PXO 86A and _P. syringae_ pv. _maculicola_ ES4326 were screened. The results showed that, at a concentration of 512 ug/mL, compound **1** significantly inhibited the growth of PXO 71A and PXO 86A strains, with the highest inhibition rates observed being 52.62 \(\pm\) 2.70% and 62.93 \(\pm\) 11.32%, respectively, following 24 h of treatment. The IC\({}_{50}\) values were found to be 485.85 \(\pm\) 28.26 and 314.16 \(\pm\) 36.76 ug/mL for PXO 71A and PXO 86A strains, respectively (Figure 4A,B). After the ES4326 strain was cultured in compound **1**, the growth of the strain was found to be inhibited from 24 h to 48 h, with the inhibition rate reaching a peak of 52.05 \(\pm\) 1.37% at 48 h at 512 ug/mL of compound **1** (Figure 4). We found that compound **2** exhibited significant growth inhibitory activity against PXO 71A and PXO 86A strains. And as the concentration increases, the inhibitory effects also become more pronounced. When the PXO 71A or PXO 86 strain was cultured for 24 h with compound **2** at a concentration of 512 ug/mL, the inhibition rates were 55.83 \(\pm\) 8.60% or 75.70 \(\pm\) 2.29%, respectively (Figure 4D,E).