title: In vitro studies on dissolved substance of cinnabar: chemical species and biological properties.
abstract: Cinnabar is one of traditional Chinese medicines widely used in many Asian countries. It is also a medicine with potential toxicity especially when taking overdose. Up to date, studies on the mechanism of the biological activity of cinnabar were still insufficient.
  
  
  OBJECTIVE
  To investigate the possible bioactive species from cinnabar after oral administration, which is the fundamental of biological effects of cinnabar.
  
  
  METHODS
  Under mimetic intestinal and gastric conditions, the chemical components dissolved from cinnabar were analyzed by infrared spectroscopy (IR) and Raman spectroscopy. Furthermore, binding of mercuric species of cinnabar extractions to human serum protein (HSA) was characterized and their intestinal permeability was determined using the Caco-2 cell monolayer. The cytotoxicity of cinnabar extractions was assessed on human kidney-2 (HK-2) cell.
  
  
  RESULTS
  Major dissolved species included mercuric polysulfide (i.e. HgS(2)(OH)(-) and Hg(3)S(2)Cl(2)). The apparent permeability coefficient (P(app)) of mercuric polysulfides was (1.6+/-0.3)x10(-6)cm/s, which is slightly lower than that of mercuric chloride (HgCl(2)). Unlike HgCl(2), mercuric polysulfides exhibited two tightly binding sites to HSA and had little effect on viability of HK-2 cells.
  
  
  CONCLUSIONS
  Mercuric polysulfides, as the major dissolved components, may serve as the active species of cinnabar exhibiting pharmacological and/or toxicological effects.
authors.affiliation: State Key Laboratories of Natural and Biomimetic Drugs and Department of Chemical Biology, Peking University, Beijing 100191, PR China.
authors.forename: Xinrui
authors.initials: X
authors.lastname: Zhou
authors.forename: Kewu
authors.initials: K
authors.lastname: Zeng
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Xiaoda
authors.initials: X
authors.lastname: Yang
authors.forename: Kui
authors.initials: K
authors.lastname: Wang
mesh_terms: D018938:Caco-2 Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D017669:Mercury Compounds / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology
chemical_list: D004365:Drugs, Chinese Herbal; D017669:Mercury Compounds; C034211:cinnabar