Aurantii Fructus Immaturus(AFI) is a traditional Chinese herbal medicine with multiple origins from Citrus aurantium and its legally cultivated variants. With advancements in agricultural biotechnology, many new cultivated varieties have sprung up,leading to an abundance of AFI adulterants and chaos in the herbal medicine markets. This study developed a specific identification method for AFI and its closely related adulterants by examining the appearance trait, content of extract, and multiple ingredients,involving indicators such as the ratio of pulp capsule to cross section diameter(Pc/Cs ratio), the content of extract, and the profile of 11 ingredients. The research finds that:(1) Pc/Cs ratio can conveniently identify adulterants such as Poncirus trifoliata, Ju, and Babagan from the genuine AFI.(2) The extract content can be used to identify adulterants originated from C. wilsonii with C. aurantium.(3) The contents of synephrine in all the samples were in accordance with the Chinese Pharmacopoeia except for the adulterants from P. trifoliata, C. wilsonii, C. aurantium 'Changshanhuyou' and orah mandarins. The synephrine content was high as 1. 40% in some C. sinensis varieties. The mass fraction of hesperidin was over 10. 00% in C. sinensis, while it was below 2. 50% in C. aurantium. C. aurantium contained high levels of naringin(3. 96%-15. 21%) and neo-hesperidin(9. 38%-21. 93%).(4) The compositions of adulterants from P. trifoliata and C. wilsonii were more similar to that of C. aurantium 'Daidai', but with significantly lower neo-hesperidin content(0. 03%-0. 14%) than that in C. aurantium, and they lacked hesperetin and tangeretin. C. maxima(originating from C. maxima) showed closer composition to Choucheng and hybrid originated from Citrus aurantium × Poncirus trifoliata, but had higher hesperidin content(3. 13%) than that in C. aurantium. Ju was closely related to C. sinensis and neither contained naringin nor neo-hesperidin. Hesperidins in Babagan and orah mandarins were similar to that in C. sinensis, with none containing rhoifolin. These quality indicators in combination can accurately distinguish between C. sinensis, C. aurantium, and their closely related adulterants(P. trifoliata, C. wilsonii, C. maxima, orah mandarins and C. reticulata), which are expected to provide a systematic method for quality control of AFI.
Keywords: Aurantii Fructus Immaturus; Aurantii Fructus Immaturus adulterants; Citrus; cluster analysis; difference analysis; fingerprint; high-performance liquid chromatography; identification.