A Comparative Study of Drying Methods and Extraction Solvents on Antioxidant Properties of Persicaria minor (Huds.) Opiz

Persicaria minor (kesum), a popular Southeast Asian culinary herb, is valued for its health benefits, particularly potent antioxidant flavonoids like quercetin-3-glucuronide (Q3G) and quercitrin. While elite accessions have been identified based on quality and these marker compounds, the preservation of these bioactive compounds is significantly impacted by drying methods and extraction solvents. Aims: Therefore, this study aimed to evaluate the effects of different drying methods and extraction solvents on the antioxidant activity and phytochemical content of a selected elite P. minor accession, MKSM10. Study Design: The study was conducted using a completely randomized design (CRD) with a factorial arrangement of treatments involving two factors: drying temperature and extraction solvent. Place and Duration of Study: The study was conducted at MARDI Headquarters between March 2023 to August 2023. Methodology: The aerial parts of P. minor were dried using oven (40°C, 50°C, 60°C, 70°C), ambient and freeze drying methods, then extracted with 70% methanol and distilled water. Antioxidant activity was assessed using established in vitro assays, while total phenolic content (TPC), total flavonoid content (TFC) and specific marker compounds, Q3G and quercitrin were quantified using spectrophotometry and high performance liquid chromatography (HPLC). Results: Low temperature oven drying at 40°C optimized both the total phytochemical yield and the resulting antioxidant activity, particularly within aqueous extracts. In contrast, freeze drying proved superior for preserving specific key flavonoids, including Q3G and quercitrin, due to its efficacy in retaining heat-sensitive constituents. Conclusion: Both drying techniques and extraction solvents significantly influenced the antioxidant properties of P. minor. These findings provide valuable insights for selecting optimal processing methods to maximize bioactive compound retention, supporting the future development of functional products derived from P. minor.