Quality assessment of differentially processed Rubi Fructus (Rubus chingii Hu.) using near-infrared spectroscopy and HPLC

Rubi Fructus (RF), a traditional Chinese herb derived from the dried immature fruit of Rubus chingii Hu., exhibits chemical composition and economic value that are significantly influenced by processing methods. Comparative analysis using HPLC fingerprinting and near-infrared spectroscopy (NIRS) revealed significant differences between infiltration-and-redrying (IAR) processed RFs and one time direct dried (OTDD) samples, indicating that IAR processing induces substantial chemical changes. The ellagic acid concentration demonstrated a time-dependent pattern during infiltration, initially increasing before subsequently decreasing. Notably, IAR RFs showed increased ellagic acid content by up to 61.76 % than OTDD control. Partial least squares discriminant analysis (PLS-DA) of NIRS data effectively distinguished IAR samples, with the multiple scattering-corrected model achieving R²Y and Q² values of 0.8280 and 0.6220, respectively. Quantitative analysis demonstrated that the Savitzky-Golay (SG) smoothed PLS model provided optimal accuracy for calculating ellagic acid and kaempferol-3-O-rutinoside (KR) content. Subsequent synergy interval PLS (si-PLS) treatment further enhanced model performance, getting test set correlation coefficients (Rp²) of 0.9930 and 0.7954 for the respective compounds.