Total flavonoid and phenolic contents, xanthine oxidase inhibition, antioxidant and anti-inflammatory activities of ethanolic and aqueous extracts of the <i>Ya-Tom-Kae-Ka-Sai-Sen</i> remedy, a traditional Thai medicine

Introduction: Ya-Tom-Kae-Ka-Sai-Sen (KS) is a traditional Thai decoction used for muscle and joint pain relief. This study evaluated the phenolic and flavonoid contents, xanthine oxidase inhibitory, antioxidant, and anti-inflammatory activities of KS extracts. Methods: Five KS extracts were prepared by refluxing with 95% ethanol (KS95ER), 50% ethanol (KS50ER), and water (KSWR), and by maceration with 95% ethanol (KS95EM) and 50% ethanol (KS50EM). Total phenolic and total flavonoid contents were determined. In vitro assays of xanthine oxidase (XO) inhibition, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and nitric oxide (NO) inhibition in lipopolysaccharide (LPS)-induced RAW 264.7 cells were performed. Results: Total phenolic content ranged from 71.45 to 116.57 mg gallic acid equivalent (GAE)/g and total flavonoid content from 317.21 to 442.62 mg quercetin equivalent (QE)/g. The 95% ethanol extracts (KS95ER, KS95EM) showed the highest TFC (P &lt; 0.05). At 1 mg/mL, ethanolic extracts showed superior in vitro XO inhibition (56.85–84.36%) compared to the aqueous extract (35.39%) (P &lt; 0.05). KS95ER exhibited potent XO inhibition with an IC₅₀ of 181.00 µg/mL. Its DPPH scavenging activity (IC₅₀ 37.57 µg/mL) was comparable to ascorbic acid (P &gt; 0.05). KS95ER and KS95EM showed the highest NO inhibition, with IC₅₀ values (90.29 and 78.13 µg/mL, respectively) that were comparable to indomethacin (P &gt; 0.05). Furthermore, all extracts were found to be non-cytotoxic at the tested concentrations. Conclusion: Ethanolic KS extracts, especially KS95ER and KS95EM, show potent XO inhibitory and antioxidant activities and anti-inflammatory effects, supporting their traditional use and warranting further study for developing therapies for gout and inflammation.