Nov 24, 2022 · Prior to UPLC analysis, all solutions were stored at 4°C and filtered through 0.22 μm nylon micropore membranes. The method was validated for linearity, precision, repeatability, stability, and recovery rates following the International Conference on Harmonization (ICH) guideline (ICH Q2(R1), 2005). 2.5 The content of flavonoids and tannins