## 3 Results
### Effect of Herbal Extracts on LPS-Induced NO Production in RAW 264.7 Cells
In the group stimulated with 100 ng/mL LPS, the NO levels were 18.48 \(\pm\) 1.06 ug/mL, while that in the groups treated with 6.25 uM and 12.5 uM liquiritin was decreased to 17.00 \(\pm\) 0.86 ug/mL and 15.38 \(\pm\) 0.85 ug/mL, respectively; this difference, however, was not significant. In the group treated with 25 uM liquiritin, there was an inhibition (_p_ < 0.05) of the NO levels (14.05 \(\pm\) 1.46 ug/mL) compared to those in the LPS-treated group. In the group treated with 50 uM liquiritin, the NO levels were 10.95 \(\pm\) 0.31 ug/mL. The NO levels were suppressed after treatment with 50 uM (_p_ < 0.001) liquiritin, compared to those in the LPS-stimulated group (Figure 4). No cytotoxicity was observed upon treatment with any concentration of 6-gingerol (6.25, 12.5, 25, and 50 uM), similar to that in the untreated group. In the group stimulated with 100 ng/mL LPS, the NO levels were 18.48 \(\pm\) 1.06 ug/mL, while that in the experimental groups treated with 6.25 uM and 12.5 uM 6-gingerol, was reduced (_p_ < 0.05) to 13.90 \(\pm\) 0.25 ug/mL and 13.90 \(\pm\) 0.88 ug/mL, respectively, compared to those in the LPS-treated group. There was a decrease in the NO levels (_p_ < 0.001) in the groups treated with higher concentrations of 6-gingerol, (i.e., 25 uM and 50 uM), with the NO levels at 11.00 \(\pm\) 0.38 ug/mL and 6.62 \(\pm\) 0.48 ug/mL, respectively, compared to those in the LPS-stimulated group (Figure 4). Liquiritin and 6-gingerol were mixed in a 1:1 ratio to reach the final concentrations of 6.25, 12.5, 25, and 50 uM to evaluate the effect of the mixture on the inhibition of NO production. No cytotoxicity of liquiritin and 6-gingerol was observed at 6.25, 12.5, 25, and 50 uM, similar to that seen in the untreated group. In the group stimulated with 100 ng/mL LPS, the NO level was 18.48 \(\pm\) 1.06 ug/mL, while that in the experimental groups treated with liquiritin and 6-gingerol at 6.25 uM, 12.5 uM, and 25 uM were 14.52.81 \(\pm\) 0.25 ug/mL, 12.24 \(\pm\) 0.42 ug/mL, and 7.43 \(\pm\) 0.44 ug/mL, respectively. In the group treated with 50 uM liquiritin and 6-gingerol, the NO level was 2.24 \(\pm\) 0.19 ug/mL, which was lower (_p_ < 0.001) than that in the LPS-stimulated group (Figure 4). Effects of Liquiritin and 6-Gingerol on LPS-Induced Expression of Mitogen-Activated Protein Kinase (MAPK) Proteins in RAW 264.7 Mouse Macrophages  
RAW 264.7 cells were stimulated with LPS and then treated with 50 uM liquiritin, 20 uM 6-gingerol, or a mixture of 50 uM liquiritin and 20 uM 6-gingerol, following which the expression levels of MAPK proteins were assessed in the cells. In the test on the inhibitory effect of a mixture of liquiritin and 6-gingerol on nitric oxide (NO) production, the most effective concentration of liquiritin was a 1:1 ratio of liquiritin and 6-gingerol, compared with double the concentration at the corresponding concentrations of liquiritin and 6-gingerol alone. The NO concentration in the LPS group was 50 uM, which is approximately 60% of maximum. For Western blot analysis, 20 uM 6-gingerol, which resulted in NO levels that were approximately 60% of those in the LPS group, was selected, and a mixture of 50 uM liquiritin and 20 uM 6-gingerol was tested. The levels of phosphorylated c-Jun NH2-terminal kinase (p-JNK), phosphorylated extracellular signal-regulated kinase (p-ERK), p-p38, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) increased upon LPS treatment. There was a decrease in the protein expression levels of p-JNK, p-ERK, p-p38, COX-2, and iNOS in the groups treated with 50 uM liquiritin alone, as well as 50 uM liquiritin and 20 uM 6-gingerol together, post-LPS stimulation. The protein expression levels of p-JNK, p-p38, COX-2, and iNOS also decreased in the group treated with 20 uM 6-gingerol, post-LPS stimulation. In addition, the group treated with 50 uM liquiritin and 20 uM 6-gingerol together showed a significant decrease in protein expression, compared to that in the LPS-stimulated group (Figure 5).