Optimization of total phenolic content, total flavonoid content and anti-gout properties of polyherbal formulation

Objectives: An increase in gout prevalence has drawn attention among society and this situation drives the exploration of more favourable treatment using traditional medicinal plants which are rich in phenolic and flavonoid to avoid the side effects of modern medication. However, there are only few studies regarding the optimization of phytochemicals and anti-gout properties of medicinal plants and their combinations. The objectives of this study were to determine the optimal formulation of Strobilanthes crispus, Orthosiphon stamineus Benth and Stevia rebaudiana with maximum total phenolic and flavonoid contents as well as minimum IC₅₀ of in vitro xanthine oxidase inhibitory activity and to examine their correlations among the formulations. Methods: Plant extracts from hot water infusion were tested for the total phenolic content, total flavonoid content and enzyme inhibition through Folin-ciocalteu assay, aluminium chloride method and xanthine oxidase inhibition assay, respectively. Simplex-centroid mixture design was applied in this study and 13 polyherbal formulations were generated by Design Expert Software. Results: Linear, special cubic and quadratic models were selected to describe the interaction effect between polyherbal formulations and their responses. Low IC₅₀ value (13.90 μg/mL) of xanthine oxidase activity was found in the binary combination of O. stamineus and S. rebaudiana and this probably related to its high phenolic and flavonoid contents as xanthine oxidase inhibition and phytochemicals were correlated. Conclusions: The suggested optimal formulation was comprised of 44.26 % O. stamineus and 55.74 % S. rebaudiana and it could be developed as an alternative treatment for gout.