Quality assessment and stoichiometric analysis of fresh Citrus reticulata ‘Chachi’ peels based on flavonoids spectrum, bioactivity, and ultra high performance liquid chromatography-fingerprint analysis

The dried and matured pericarp of Citrus reticulata 'Chachi' (CRC), also known as Pericarpium Citri Reticulatae Chachiensis, is a traditional Chinese medicine renowned for its expectorant properties and extensively studied for its efficacy in alleviating cough and asthma symptoms. Ensuring the quality control of fresh CRC is crucial for its efficacy and safety. This study evaluated the quality and efficacy of CRC from the main production areas in Xinhui District. First, multi-wavelength fusion technology was employed to establish ultra high performance liquid chromatography (UHPLC) fingerprint analysis. Second, the in vitro antioxidant activity of fresh CRC peel samples was assessed using DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)) scavenging assays. Additionally, grey relational analysis (GRA) and partial least squares (PLS) modeling were used to correlate fingerprint patterns with efficacy parameters. Eleven major flavonoid compounds and total flavonoids were quantified across 26 samples. Finally, technique for order preference by similarity to ideal solution (TOPSIS) analysis comprehensively evaluated the overall quality of fresh CRC peels from these production areas. The results demonstrated a high degree of similarity among the 26 samples, ranging from 0.850 to 0.997. Notably, 21 peaks were identified as significant contributors (variable importance in the projection (VIP) > 0.7), including hesperidin, didymin, 3′-demethylnobiletin, and demethylnobiletin. Furthermore, TOPSIS and entropy weight analysis indicated that Gujing, Daze, and Luokeng exhibited superior overall quality. This study provides scientific evidence to support quality control and efficacy evaluation of fresh CRC peels.