## 4 Discussion  
The present study investigated the anti-inflammatory potential of SJFE in LPS-stimulated RAW 264.7 cells. SJFE was observed to suppress the release of nitric oxide (NO) [Figure 2] and the expression of genes of inflammation-inducing proteins, specifically iNOS, COX-2, IL-6, and IL-18 [Figure 3] in these cells. IL-18 and IL-6 are principal cytokines expressed in chondrocytes and macrophages [17] during arthritic conditions. These cytokines stimulate iNOS and COX-2, leading to the production of NO and prostaglandin E2 [18,19]. Consequently, regulating these cytokines is associated with therapeutic efficacy for arthritic disorders. Based on the results obtained from the cellular experiments, we proceeded to test the anti-inflammatory properties of SJFE in rats with osteoarthritis (OA) induced by MIA. Our observations revealed that SJFE improved the weight-bearing index of affected knee joints [Figure 4B] and reduced the levels of cartilage-degrading enzymes and degraded products in the serum [Figure 5D, E]. Furthermore, SJFE resulted in a decrease in [PERSON]'s score, an index used to gauge the severity of cartilage damage [Figure 6B]. These findings support the fact that the flower extract also possesses anti-inflammatory properties capable of alleviating the symptoms of arthritis. However, it is uncertain what components in SJFE are responsible for its anti-inflammatory properties. This question was raised by the findings where the main component in SJFE was rutin [Figure 1A], but this glycoside (100 \(\upmu\)g/mL) showed no effect on NO production in LPS-stimulated RAW 264.7 cells, whereas quercetin (10 \(\upmu\)g/mL) reduced the production by 60%. However, we assumed that the components exerting the anti-inflammatory activities were flavonoids, particularly quercetin, based on the following reasons. First, we were able to measure quercetin as a major component and kaempfer and isorhamnetin as minors when SJFE was acid-hydrolyzed [Figure 1B], meaning that these flavonoids is SJFE  
Figure 6: Histology of OA –induced joint tissues in rats and [PERSON]’s score of arthritic joint tissues. Experimental conditions were the same as in Figure 4. On day 28, rats were sacrificed, and tissue sections of knee joints were prepared and stained with H&E for inflammatory status or Safranin O for cartilage status (**A**). Using the histological findings of panel A, the severity of arthritis was evaluated by [PERSON]’s modified scoring (**B**). Data are presented as mean \(\pm\) SD for 8 experiments. \({}^{\#\#}\), \(p\) < 0.01 vs. the sham control (student’s \(t\)-test); \({}^{\star\#}\), \(p\) < 0.01 vs. OA-induced rats treated with vehicle (One-way ANOVA); and $5, \(p\) < 0.01 vs. OA-induced rats treated with vehicle (Student’s \(t\)-test). Abbreviations are the same as in Figure 4.  
exist as glycosides (possibly inactive forms) in SFFE. [Figure 1B]. Thus, rutin administered orally is hydrolyzed to release quercetin in the body [20]. Second, it has been reported that fruits or leaves of _S. japonicum_ contain flavonoids, among which quercetin is the main component [10]. Third, there are the reports demonstrating the anti-inflammatory properties of quercetin on the animal models of inflammatory disorders [21]. In addition, the fruit extract of _S. japonicum_ showed a protective effect on prostate inflammation in rats [22]. The flower bud extract of this plant exhibited the suppression of expression of the proinflammatory proteins in experimentally induced contact dermatitis in mice [23]. In these studies, the observed effects were ascribed to the anti-oxidant activity exerted by flavonoids, including quercetin as a principle component. Furthermore, quercetin-rich extracts of _Tabebuia rosea_[24] or _Erica multiiflora_[25] reduced the expressions and serum levels of pro-inflammatory genes and proteins in diet-induced obesity in rats. All these reports support the fact that the anti-inflammatory properties of SJFE are exerted by flavonoids like quercetin.