Optimization of Xanthine Oxidase Activity, Phytochemical Screening, Toxicity Assay, and Antigout Activity of Spatholobus littoralis Hassk. Extract

Introduction: A medicinal plant from Central Kalimantan, Spatholobus littoralis Hassk., with a local name bajakah tampala, has long been used to treat gout or uric acid disease. This study aimed to develop the optimum conditions of xanthine oxidase (XO) activity, phytochemical screening, and to obtain the antigout activity of S. littoralis Hassk. Methods: Before performing the phytochemical screening, we performed a simplicia maceration with water and 70% ethanol solvents. The development of the optimum conditions for XO was carried out using the Response Surface Methodology (RSM) combined Box-Behnken Design (BBD). Toxicity assay (LC₅₀) on both extracts was assessed by BSLT (Brine Shrimp Lethality Test). The two extracts were then evaluated for antigout activity. Results: The yield of 70% ethanol extract (11.24%) was higher than the aqueous extract (7.29%). The phytochemical screening on the simplicia and the two extracts positively contained steroids, flavonoids, saponins, and tannins. The optimum conditions of XO activity were temperature of 20 ℃, pH of 8.0, and xanthine concentration of 1.40 mM. The toxicity of the 70% ethanol extract (LC₅₀ 662.25 mg/L) was stronger than the aqueous extract (LC₅₀ 774.68 mg/L). Moreover, the 70% ethanol extract (IC₅₀ 224.14±8.62 mg/L) showed higher XO inhibition than the water extract (IC₅₀ 348.83±4.85 mg/L). Lineweaver-Burk plot analysis showed that 70% ethanol and water extracts inhibited XO competitively with the inhibition constant (KI) of 272.68 mg/L and 378.44 mg/L, respectively. Conclusion: This preliminary study can be a reference that S. littoralis Hassk. is potentially an antigout.