title: Stereoselective metabolism of amygdalin-based study of detoxification of Semen Armeniacae Amarum in the Herba Ephedrae-Semen Armeniacae Amarum herb pair.
abstract: BACKGROUND
  The Mahuang-Xingren (MX) herb pair, the combination of Herba Ephedrae (Mahuang in Chinese) and Semen Armeniacae Amarum (Xingren in Chinese), is a core component of traditional Chinese medicine formulations used to treat asthma and bronchitis. Although Xingren is considered to be toxic, MX is widely used in the clinic and has few adverse effects. The mechanism underlying detoxification of Xingren by Mahuang in MX remains unknown and merits investigation.
  
  
  OBJECTIVE
  To determine the mechanism underlying detoxification of Xingren by Mahuang in MX.
  
  
  METHODS
  Acute toxic effects were evaluated in mice after oral administration of Mahuang, Xingren, and MX aqueous extracts. Synergism, additivity, and antagonism were quantified by determining the CI (combination index) and DRI (dose-reduction index), which were calculated by the median effect method. High performance liquid chromatography analysis of bioactive compounds (ephedrine, pseudoephedrine and amygdalin) in aqueous extracts and data from previous pharmacokinetic studies in rats were combined to explore the potential mechanism of toxicity antagonism by the components of MX. Moreover, the cytotoxic effects of amygdalin and amygdalin activated by β-glucosidase (including different proportions of l-amygdalin and d-amygdalin) were also investigated.
  
  
  RESULTS
  Mahuang prevented and antagonized the acute toxicity of Xingren and allowed escalation of the Xingren dose. Pearson correlation analysis indicated that the proportion of d-amygdalin was closely correlated with the antagonism of Xingren toxicity. The antagonism of its acute toxicity was primarily attributed to stereoselective metabolism of amygdalin. Interestingly, the process was facilitated by Mahuang, which led to reduced levels of the d-prunasin in vivo and thus reduced toxicity. Furthermore, the mechanism was also evaluated by testing the cytotoxicity of amygdalin. Metabolism of d-amygdalin was a major cause of cytotoxicity and no stereoselective metabolism occurred in culture medium.
  
  
  CONCLUSIONS
  A comprehensive study of Xingren detoxification in the context of the MX combination suggested that stereoselective metabolism of amygdalin facilitated by Mahuang may be the crucial mechanism underlying detoxification of Xingren in the MX combination. Therefore, Mahuang acts to enhance and control the effects of Xingren in the MX combination. These results illustrate the rationale behind the combination of Mahuang and Xingren.
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Song
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Qinhai
authors.initials: Q
authors.lastname: Ma
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Qingfa
authors.initials: Q
authors.lastname: Tang
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Feilong
authors.initials: F
authors.lastname: Chen
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Xing
authors.affiliation: Department of Pharmacy, The Renhe Affiliated Hospital to China Three Gorges University, Yichang 443002, PR China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Shenshen
authors.initials: S
authors.lastname: Guo
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Tan
authors.affiliation: School of Traditional Chinese Medical Science, Southern Medical University, Guangzhou 510515, PR China; Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Southern Medical University, Guangzhou 510515, PR China. Electronic address: ljb@smu.edu.cn.
authors.forename: Jiabo
authors.initials: J
authors.lastname: Luo
mesh_terms: D000678:Amygdalin / Q000378:metabolism* / Q000633:toxicity*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004338:Drug Combinations; D004365:Drugs, Chinese Herbal / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D029790:Ephedra sinica; D009570:Nitriles / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D004338:Drug Combinations; D004365:Drugs, Chinese Herbal; D009570:Nitriles; C000612342:Xingren; C019063:prunasin; D000678:Amygdalin
keywords: Detoxification; Ephedrine (PubChem CID: 9294); Herb pair; Mahuang; Pharmacokinetics; Prunasin (PubChem CID: 120639); Pseudoephedrine (PubChem CID: 7028); Xingren; d,l-amygdalin (PubChem CID: 39999); d-amygdalin (PubChem CID: 656495); d-prunasin (PubChem CID: 119033); l-amygdalin (PubChem CID: 441462); l-prunasin (PubChem CID: 91434)