title: Chemical compositions, chromatographic fingerprints and antioxidant activities of Citri Exocarpium Rubrum (Juhong).
abstract: BACKGROUND
  Citri Exocarpium Rubrum (CER), which is known asJuhongin Chinese, is the dried exocarp ofCitrus reticulataBlanco and its cultivars (Fam. Rutaceae) and is currently used in Chinese medicine to protect the stomach and eliminatedampnessand phlegm. The main aim of this study was to develop a high-performance liquid chromatography ultraviolet mass spectrometry (HPLC-UV-MS) method for determining the chemical compositions and fingerprint of CER. We also evaluated the antioxidant properties of CER based on its 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, ferric ion reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays.
  
  
  METHODS
  Ten CER samples were collected from Hong Kong and mainland China. Each CER sample was extracted using an ultrasonic extraction method. Chromatographic separation was achieved using a conventional Dikma Inspire C18 column with photo diode array detection (190-400 nm). Hesperidin, nobiletin and tangeretin were quantified based on the UV signal observed at 330 nm. The column was eluted with a mobile phase consisting of water and acetonitrile (15-55%) over 55 min. Fingerprints combined with similarity and principal component analyses were used to classify the herbs. The DPPH free radical scavenging activity, FRAP and ABTS properties of the different CER samples were assayed. Bivariate correlation analysis was performed to investigate the correlation between the characteristic peaks and their antioxidant capacities.
  
  
  RESULTS
  Limit of detection (LOD), limit of quantification (LOQ), linearity, inter-day precision, intra-day precision, repeatability, stability and recovery of the developed method were validated, and the method was subsequently used to determine the contents of hesperidin, nobiletin and tangeretin, and to acquire the fingerprints of the CER samples. Seventeen characteristic peaks were found in the fingerprints, and eleven of them were identified. Bivariate correlation analysis revealed correlations between the characteristic peaks and the antioxidant activities of the samples.
  
  
  CONCLUSIONS
  An HPLC-UV-MS method was developed and validated after a detailed investigation on extraction of chemical compounds from CER using different solvents and extraction times. None of the peaks was correlated with the DPPH free radical scavenging activity or ferric reducing capacity. Most of the peaks were correlated well with the ABTS radical scavenging capacity.
authors.affiliation: Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung, 40402 Taiwan.|Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001 China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Nursing, Hsin Sheng College of Medical Care and Management, Taoyuan, 32544 Taiwan.
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Kao
authors.affiliation: Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung, 40402 Taiwan.
authors.forename: Chi-Ren
authors.initials: CR
authors.lastname: Liao
authors.affiliation: Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung, 40402 Taiwan.
authors.forename: Kun-Chang
authors.initials: KC
authors.lastname: Wu
authors.affiliation: Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001 China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Nursing, Hungkuang University, Taichung, 43302 Taiwan.
authors.forename: Yu-Ling
authors.initials: YL
authors.lastname: Ho
authors.affiliation: Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung, 40402 Taiwan.|Chinese Crude Drug Pharmacy, China Medical University Hospital, Taichung, 40402 Taiwan.
authors.forename: Yuan-Shiun
authors.identifier: 0000-0002-8149-2638
authors.initials: YS
authors.lastname: Chang