Optimization of solvent extraction for polyphenols and antioxidant activity from Zanthoxylum acanthopodium leaves using simplex centroid design

Background: Zanthoxylum acanthopodium DC., locally known as andaliman, is an indigenous spice from North Sumatra, Indonesia, recognized for its high antioxidant potential. Despite its bioactive richness, optimization of solvent extraction for phenolic and flavonoid compounds from its leaves remains underexplored, even though these compounds are valuable for food and pharmaceutical applications. The use of solvents such as acetone in analytical extraction contexts is acceptable; however, further purification steps would be required for applications in food and pharmaceutical products. Objectives: The main objective of this study was to optimize solvent combinations – comprising water, ethanol, and acetone – to maximize the extraction of polyphenols and flavonoids, along with antioxidant activity from Z. acanthopodium leaves using simplex centroid design (SCD). Materials and Methods: Extraction optimization was performed by varying the proportions of water, ethanol, and acetone. Total phenolic content (TPC) was quantified using the Folin–Ciocalteu method, total flavonoid content (TFC) was measured using the AlCl3 colorimetric method, and antioxidant activity was evaluated through 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. Model validation was conducted by comparing predicted and experimental values using relative standard error (RSE). Results: The optimal solvent composition of 36.1% water, 1.5% ethanol, and 62.5% acetone yielded a TPC of 35.98 mg gallic acid equivalent (GAE)/g dry weight (DW) and a TFC of 5.16 mg quercetin equivalent (QE)/g DW, alongside high antioxidant activity in both DPPH (1.75 μmol trolox equivalent (TE)/g DW) and FRAP (35.90 μmol TE/g DW) assays. Model validation confirmed high predictive accuracy, with RSE values below 5%. Mixed-polarity solvents demonstrated greater extraction efficiency than single solvents. Conclusion: Statistically optimized solvent composition significantly enhanced the extraction efficiency of phenolic and flavonoid compounds from Z. acanthopodium leaves. While the model showed good predictive accuracy near the optimum, the relatively low predicted R2 for some responses suggests that further validation across broader experimental ranges is needed. These findings provide a practical foundation for scaling up extraction processes to obtain natural antioxidants for industrial applications.