Total flavonoid and phenolic contents, xanthine oxidase inhibition, antioxidant and anti-inflammatory activities of ethanolic and aqueous extracts of the Ya-Tom-Kae-Ka-Sai-Sen 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 ۹۵% ethanol (KS۹۵ER), ۵۰% ethanol (KS۵۰ER), and water (KSWR), and by maceration with ۹۵% ethanol (KS۹۵EM) and ۵۰% ethanol (KS۵۰EM). Total phenolic and total flavonoid contents were determined. In vitro assays of xanthine oxidase (XO) inhibition, ۲,۲-diphenyl-۱-picrylhydrazyl (DPPH) radical scavenging activity, and nitric oxide (NO) inhibition in lipopolysaccharide (LPS)-induced RAW ۲۶۴.۷ cells were performed. Results: Total phenolic content ranged from ۷۱.۴۵ to ۱۱۶.۵۷ mg gallic acid equivalent (GAE)/g and total flavonoid content from ۳۱۷.۲۱ to ۴۴۲.۶۲ mg quercetin equivalent (QE)/g. The ۹۵% ethanol extracts (KS۹۵ER, KS۹۵EM) showed the highest TFC (P < ۰.۰۵). At ۱ mg/mL, ethanolic extracts showed superior in vitro XO inhibition (۵۶.۸۵–۸۴.۳۶%) compared to the aqueous extract (۳۵.۳۹%) (P < ۰.۰۵). KS۹۵ER exhibited potent XO inhibition with an IC₅₀ of ۱۸۱.۰۰ µg/mL. Its DPPH scavenging activity (IC₅₀ ۳۷.۵۷ µg/mL) was comparable to ascorbic acid (P > ۰.۰۵). KS۹۵ER and KS۹۵EM showed the highest NO inhibition, with IC₅₀ values (۹۰.۲۹ and ۷۸.۱۳ µg/mL, respectively) that were comparable to indomethacin (P > ۰.۰۵). Furthermore, all extracts were found to be non-cytotoxic at the tested concentrations. Conclusion: Ethanolic KS extracts, especially KS۹۵ER and KS۹۵EM, 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.