## 4 Discussion  
Our previous studies have shown that TQ-6 potently inhibited LPS-induced inflammatory events in RAW264.7 cells [9] and thrombosis in mice [10]. Moreover, TQ-6 diminishes collagen-induced OH\({}^{\bullet}\) in platelets [10]. This study mainly focused on examining the free radical scavenging mechanism of TQ-6 to its anti-inflammatory action and found that TQ-6 scavenges DPPH, galvinoxyl, superoxide (O\({}_{2}^{-}\)), and OH\({}^{\bullet}\) radicals in cell-free systems. Furthermore, TQ-6 exhibited potent antioxidative activity through induction of the Nrf/HO-1 signaling pathway. Additionally, TQ-6 prevented carrageenanan-induced paw edema in rats. These results have demonstrated that the free radical scavenging properties of TQ-6 may play a role in its cell protective effect. LPS can activate a local or systemic inflammatory response in both immune non-immune cells to initiate the inflammatory events. The LPS-pattern recognition receptor, the Toll-like receptor 4 (TLR4) is widely expressed including cardiomyocytes. Therefore, post- treatment of TQ-6 may not exacerbate specific targets on LPS-induced inflammatory dysfunctions such as LPS induce diversity of makers that were recurrently detected in patients with sepsis and also in animals [24]. Thus, in this study, TQ-6 was pretreated to test its anti-inflammatory function in the LPS-induced macrophage cells. Exogenous and endogenous stimulators induce inflammatory reactions, which are reflected in vascular and cellular events. Inflammation-induced ROS production, such as O\({}_{2}^{-}\), OH\({}^{\bullet}\), hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)), peroxy radicals (ROO\({}^{\bullet}\)), and singlet oxygen (\({}^{1}\)O\({}_{2}\)) induce oxidative stress which may lead to cancer and neurodegenerative diseases [25]. In addition, DPPH and galvinoxyl radicals are largely used as substrates to evaluate the antioxidant activity of a drug or substance. DPPH-electron paramagnetic resonance system has been widely used to detect the radical scavenging activities of hydrophilic and lipophilic antioxidants [26]. Experiments with galvinoxyl allow not only a comparison of the radical scavenging activity between samples but also the determination of the concentration of  
Figure 5: Effects of TQ-6 on carrageenanan-induced rat paw edema. The right paw of Wistar rats was injected with TQ-6, 30 min before the carrageenanan injection. The paw volume was measured before 0 h and after the intervals of 1, 2, 4, 6, and 24 h in carrageenanan injection (\(\Circuit\): vehicle; \(\triangle\): carrageenanan; \(\square\): 5 mg/kg indomethacin; \(\Diamond\): 1 mg/kg TQ-6; \(\triangledown\): 2 mg/kg TQ-6). Data are shown as mean \(\pm\) SEM (\(n=6\)). \({}^{\star}\)\(p<0.05\) compared with the carrageenanan group. antioxidants. A previous study showed that Co(II) complexes had stronger scavenging activity against DPPH than did metenamic acid [27]. Furthermore, [PERSON] et al. [28] used galvinoxyl-radical as a model to study the radical scavenging effect of Co(II) complex and the result showed that this metal significantly inhibited galvinoxyl radicals. In this study, TQ-6 substantially suppressed DPPH free radical production, showing that TQ-6 possesses the capacity to scavenge such free radicals. Xanthine oxidase (XO) produces free radicals in post-ischemic cells and tissues [29], and the X/XO system assay related to an enzymatic reaction which catalyzing the hydroxylation of hypoxanthine to xanthine and then to uric acid which is excreted via kidneys. However, this systemic assay is not appropriate for lipid-soluble antioxidants. [PERSON] et al. [30] showed the inhibitory activity of some metal complexes against XO, of which the cadmium (II) complex was the more potent XO inhibitor than Zn(II) and Mn(II) complexes. This is the first study to demonstrate that even 10 \(\upmu\)M TQ-6 effectively scavenges non-enzymatic, potassium superoxide (KO\({}_{2}\)) system-generated superoxide and was subsequently validated in the X/XO enzymatic system.