title: Anti-pruritic effect of baicalin and its metabolites, baicalein and oroxylin A, in mice.
abstract: OBJECTIVE
  To explore whether intestinal microflora plays a role in anti-pruritic activity of baicalin, a main constituent of the rhizome of Scutellaria baicalensis (SB).
  
  
  METHODS
  Baicalin was anaerobically incubated with human fecal microflora, and its metabolites, baicalein and oroxylin A, were isolated. The inhibitory effect of baicalin and its metabolites was accessed in histamine- or compound 48/80-induced scratching behavior in mice.
  
  
  RESULTS
  Baicalin was metabolized to baicalein and oroxylin A, with metabolic activities of 40.2+/-26.2 and 1.2+/-1.1 nmol.h(-1).mg(-1) wet weight of human fecal microflora, respectively. Baicalin (20, 50 mg/kg) showed more potent inhibitory effect on histamine-induced scratching behavior when orally administered than intraperitoneally. In contrast, baicalein and oroxylin A had more potent inhibitory effect when the intraperitoneally administered. The anti-scratching behavior activity of oral baicalin and its metabolites was in proportion to their inhibition on histamine-induced increase of vascular permeability with oroxylin A more potent than baicalein and baicalin. In Magnus test using guinea pig ileum, oroxylin A is more potent than baicalein and baicalin in inhibition of histamine-induced contraction. The anti-scratching behavioral effect of oral baicalin was significantly reduced when oral antibiotics were simultaneously administered, whereas the effect of baicalein and oroxylin A were not affected.
  
  
  CONCLUSIONS
  Oral baicalin may be metabolized by intestinal microflora into baicalein and oroxylin A, which ameliorate pruritic reactions through anti-histamine action.
authors.affiliation: Department of Pharmaceutical Science and Department of Life and Pharmaceutical Sciences, Kyung Hee University, 1 Hoegi, Dongdaemun-ku, Seoul, Korea.
authors.forename: Hien-trung
authors.initials: HT
authors.lastname: Trinh
authors.forename: Eun-ha
authors.initials: EH
authors.lastname: Joh
authors.forename: Ho-young
authors.initials: HY
authors.lastname: Kwak
authors.forename: Nam-in
authors.initials: NI
authors.lastname: Baek
authors.forename: Dong-hyun
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D000982:Antipruritics / Q000032:analysis / Q000378:metabolism / Q000627:therapeutic use*; D005243:Feces / Q000382:microbiology; D044950:Flavanones / Q000032:analysis / Q000627:therapeutic use*; D005419:Flavonoids / Q000032:analysis / Q000378:metabolism / Q000627:therapeutic use*; D006168:Guinea Pigs; D006632:Histamine / Q000008:administration & dosage; D006633:Histamine Antagonists / Q000032:analysis / Q000378:metabolism / Q000627:therapeutic use*; D007422:Intestines / Q000382:microbiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008813:Mice, Inbred ICR; D008517:Phytotherapy; D011537:Pruritus / Q000188:drug therapy*; D031364:Scutellaria baicalensis / Q000737:chemistry / Q000378:metabolism; D013307:Streptomycin / Q000008:administration & dosage; D013752:Tetracycline / Q000008:administration & dosage
chemical_list: D000900:Anti-Bacterial Agents; D000982:Antipruritics; D044950:Flavanones; D005419:Flavonoids; D006633:Histamine Antagonists; C038044:baicalin; C006680:baicalein; C080669:5,7-dihydroxy-6-methoxy-2-phenylchromen-4-one; D006632:Histamine; D013752:Tetracycline; D013307:Streptomycin
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