title: Quality control ofLycium chinenseandLycium barbarum cortex(Digupi) by HPLC using kukoamines as markers.
abstract: BACKGROUND
  Lycii Cortex (LyC), composed ofLycium chinenseandLycium barbarum cortexand having the Chinese name Digupi, is used to treat chronic diseases like cough, hypertension, and diabetes in Eastern Asia. However, chromatographic methods, such as TLC and HPLC, to determine the phytochemical composition of LyC have not been included in any official compendiums. This study aims to establish a validated HPLC method for quality control of LyC.
  
  
  METHODS
  Kukoamines A and B (KA and KB, respectively) were selected as markers for the HPLC method. An acetic acid solution was adopted for sample extraction because it facilitated the release of kukoamines and effectively prevented their degradation. Optimal separation of the kukoamine isomers was achieved on hydrophilic ligand-coated C18 columns with a gradient elution of acetonitrile and 0.1% (v/v) trifluoroacetic acid. The average contents and proposed contents for LyC were calculated with attest and an uncertainty test based on 16 batches of authentic samples.
  
  
  RESULTS
  The method was validated with linearity (r2= 0.9999 for both KA and KB), precision (RSD = 1.29% for KA and 0.57% for KB), repeatability (RSD = 1.81% for KA and 0.92% for KB), and accuracy (recovery of 90.03-102.30% for KA, and 98.49-101.67% for KB), indicating that the method could offer reliable results for quality control analysis of LyC. At the 95% confidence level, the calculated content limits were 1.45 mg/g for KA and 4.72 mg/g for KB.
  
  
  CONCLUSIONS
  Compared with conventional morphological identification, the HPLC method involving KA and KB contents offers precise, objective, and quantitative results for quality control of LyC.
authors.affiliation: Research Group for Bioactive Products, Department of Biomedical Sciences, City University of Hong Kong, Hong Kong SAR, China.|System and Translational Science Center, RTI International, Research Triangle Park, NC 27709 USA.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Li
authors.affiliation: Research Group for Bioactive Products, Department of Biomedical Sciences, City University of Hong Kong, Hong Kong SAR, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Di
authors.affiliation: Research Group for Bioactive Products, Department of Biomedical Sciences, City University of Hong Kong, Hong Kong SAR, China.
authors.forename: Wing-Leung
authors.initials: WL
authors.lastname: Hsu
authors.affiliation: Research Group for Bioactive Products, Department of Biomedical Sciences, City University of Hong Kong, Hong Kong SAR, China.
authors.forename: Ye-Qing
authors.initials: YQ
authors.lastname: Huang
authors.affiliation: Research Group for Bioactive Products, Department of Biomedical Sciences, City University of Hong Kong, Hong Kong SAR, China.|Key Laboratory of Biochip Technology, Shenzhen Biotech and Health Centre, City University of Hong Kong, Shenzhen, 518057 China.
authors.forename: Hon-Yeung
authors.initials: HY
authors.lastname: Cheung