Extracts of Paullinia pinnata have demonstrated therapeutic effects in monosodium urate (MSU)-induced gout in rats, notably by reducing inflammation and hyperalgesia, as well as enhancing antioxidant activity in vivo. However, their in vitro antioxidant potential and their effects on MSU-stimulated macrophages remain insufficiently explored. This study aims to investigate the in vitro antioxidant properties of P. pinnata, with a particular focus on MSU uptake in stimulated macrophages. The in vitro antioxidant activities of aqueous (AEPP) and methanolic (MEPP) extracts of P. pinnata leaves were evaluated using a range of assays, including DPPH radical scavenging, hydroxyl radical scavenging, nitric oxide inhibition, reducing power, hydrogen peroxide-induced hemolysis of rat red blood cells, hydrogen peroxide-induced brain lipid peroxidation, as well as the determination of total flavonoid and polyphenol content. Peritoneal macrophages isolated from rats were pretreated with AEPP and MEPP (10, 30, and 100 µg/mL) for 1 h, followed by stimulation with MSU (10 mg/dL) for 24 h. Subsequently, cell viability, lactate dehydrogenase (LDH) release, nitric oxide (NO) production, MSU uptake, superoxide dismutase (SOD) activity, and reduced glutathione (GSH) levels were measured in the culture medium. AEPP and MEPP significantly inhibited DPPH radicals, with IC50 values of 59.20 and 13.91 µg/mL, respectively, and also scavenged hydroxyl radicals (IC50: 1.45 and 5.39 µg/mL) and nitric oxide (IC50: 139.60 and 138.20 µg/mL). Both extracts exhibited weak reducing power. Hydrogen peroxide-induced red blood cell hemolysis was inhibited, with IC50 values of 12.29 µg/mL for AEPP and 30.00 µg/mL for MEPP, while H2O2-induced brain lipid peroxidation was also reduced (IC50: 21.82 µg/mL for AEPP and 18.22 µg/mL for MEPP). MEPP contained higher concentrations of flavonoids and polyphenols than AEPP. In peritoneal macrophages, both AEPP and MEPP increased cell viability (P < 0.05 and P < 0.01), inhibited LDH release (P < 0.001), enhanced MSU uptake (P < 0.001), suppressed nitric oxide production (P < 0.001), and elevated SOD activity (P < 0.05 to P < 0.01), but had no significant effect on GSH levels. AEPP and MEPP exhibit in vitro antioxidant activity and enhance MSU uptake by macrophages, suggesting their potential use as adjuvant agents in the management of gout.
Tseuguem et al. (Thu,) studied this question.