## 4 Conclusions  
The hydrogenation of limonin, with a variety of reducing agents, was investigated in this paper. Seven hydrogenation products, of which six were unreported new compounds in the literature, were obtained. The planar structures and spatial configurations were identified using HR-ESI-MS, 1D-NMR (\({}^{1}\)H and \({}^{13}\)C), 2D-NMR, and IR analysis. The six hydrogenated limonoid products were evaluated and compared with eight natural limonoid compounds. The study found that the hydrogenated products all showed decent anti-inflammatory activity. Among them, compound **3** had the highest inhibitory ratio on the inflammatory factor TNF-\(\alpha\) released by LPS-induced RAW264.7 cell, reaching 37.8%. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Groups** & \multicolumn{2}{c}{**NO Production \(\pm\) SEM (\% of LPS Group)**} \\ \hline Control & & 3.35\% \(\pm\) 1.54 & \\ Model-LPS (100 ng/mL) & & 100.0\% \(\pm\) 0.00 & \\ Positive control- & & & \\ Resveratrol (20 uM) & & & \\ \hline
**Compounds** & **1 uM** & **Inhibition** & **10 uM** & **Inhibition** \\
**2** & 97.94\% \(\pm\) 6.92 & 2.06\% & 87.40\% \(\pm\) 9.08 & 12.60\% * \\
**3** & 89.73\% \(\pm\) 4.66 & 10.27\% & 88.44\% \(\pm\) 2.32 * & 11.56\% ** \\
**4** & 105.3\% \(\pm\) 5.69 & \(-\)5.30\% & 86.57\% \(\pm\) 6.21 & 13.43\% * \\
**5** & 108.6\% \(\pm\) 6.83 & \(-\)8.60\% & 100.7\% \(\pm\) 2.37 & \(-\)0.70\% \\
**6** & 101.2\% \(\pm\) 5.42 & \(-\)1.20\% & 88.43\% \(\pm\) 3.31 & 11.57\% ** \\
**7** & 93.23\% \(\pm\) 6.16 & 6.77\% & 100.6\% \(\pm\) 9.64 & \(-\)0.60\% \\
**8** & 98.66\% \(\pm\) 8.01 & 1.34\% & 83.84\% \(\pm\) 2.12 & 16.16\% \\
**9** & 87.35\% \(\pm\) 7.08 & 12.65\% & 63.48\% \(\pm\) 7.67 & 36.52\% ** \\
**10** & 103.3\% \(\pm\) 8.02 & \(-\)3.30\% & 54.37\% \(\pm\) 7.30 & 45.63\% ** \\
**11** & 90.78\% \(\pm\) 4.67 & 9.22\% & 83.33\% \(\pm\) 2.68 & 16.67\% ** \\
**12** & 96.51\% \(\pm\) 5.01 & 3.49\% & 85.10\% \(\pm\) 3.98 & 14.90\% ** \\
**13** & 91.37\% \(\pm\) 3.43 & 8.63\% & 36.23\% \(\pm\) 2.93 & 63.77\% ** \\
**14** & 95.47\% \(\pm\) 8.39 & 4.53\% & 64.16\% \(\pm\) 1.56 & 35.84\% *** \\
**15** & 88.40\% \(\pm\) 4.38 & 11.60\% & 81.61\% \(\pm\) 2.55 & 18.39\% ** \\
**16** & 89.86\% \(\pm\) 3.79 & 10.14\% & 67.60\% \(\pm\) 2.33 & 32.40\% *** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The ameliorating effects of compounds on LPS-induced BV2 cell inflammation. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Groups** & \multicolumn{2}{c}{**Cell Viability \(\pm\) SEM (\% of the Control Group)**} \\ \hline Control & & 100.0\% \(\pm\) 0.00 \\ Positive control-Resveratrol (20 uM) & & 57.72\% \(\pm\) 3.21 \\ \hline
**Compounds** & **1 uM** & **10 uM** \\ \hline
**2** & 99.64\% \(\pm\) 4.13 & 95.65\% \(\pm\) 3.70 \\
**3** & 93.14\% \(\pm\) 3.77 & 95.11\% \(\pm\) 3.80 \\
**4** & 94.96\% \(\pm\) 2.83 & 92.97\% \(\pm\) 1.97 \\
**5** & 104.0\% \(\pm\) 4.67 & 101.2\% \(\pm\) 1.69 \\
**6** & 101.4\% \(\pm\) 5.23 & 91.67\% \(\pm\) 0.69 \\
**7** & 96.55\% \(\pm\) 3.49 & 90.20\% \(\pm\) 3.85 \\
**8** & 98.56\% \(\pm\) 2.51 & 91.97\% \(\pm\) 1.14 \\
**9** & 100.4\% \(\pm\) 3.99 & 92.44\% \(\pm\) 3.12 \\
**10** & 102.4\% \(\pm\) 1.65 & 92.73\% \(\pm\) 2.92 \\
**11** & 101.5\% \(\pm\) 2.37 & 88.10\% \(\pm\) 3.68 \\
**12** & 99.00\% \(\pm\) 1.88 & 91.42\% \(\pm\) 1.46 \\
**13** & 101.5\% \(\pm\) 0.90 & 90.74\% \(\pm\) 2.47 \\
**14** & 99.45\% \(\pm\) 2.69 & 96.86\% \(\pm\) 4.92 \\
**15** & 96.98\% \(\pm\) 4.55 & 97.10\% \(\pm\) 1.06 \\
**16** & 97.80\% \(\pm\) 4.53 & 97.63\% \(\pm\) 2.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Cytotoxicity of compounds on BV2 Cells. Among the natural limonoids, compound **13** had the highest inhibition ratio of inflammatory factors, reaching 90%. At a concentration of 10 \(\upmu\)M, among the natural limonoids, compound **13** had the best inhibitory activity on LPS-induced BV2 cell inflammation, with a NO inhibition ratio of 63.77%. However, the inhibition ratios of synthesized limonoid derivatives were generally lower than those of the natural limonoids.