title: [Inhibition of extracts from Synotis erythropappa on tyrosinase].
abstract: OBJECTIVE
  To study the inhibition of extracts from Synotis erythropappa on tyrosinase.
  
  
  METHODS
  The 70% ethanol extracts were extracted by petroleum benzine, ethyl acetate and n-butanol, and the inhibitory activities against tyrosinase of every fraction were determined in vitro and the inhibitory kinetics of ethyl acetate and n-butanol fractions were investigated.
  
  
  RESULTS
  The four fractions extracted all had inhibitory activities on tyrosinase, inhibitory activities of ethyl acetate and n-butanol fraction were higher. Their IC50 were 57.8, 140 microg/ml for monophenol oxidase activity and 41.2, 59.6 microg/ml for diphenol oxidase activity, respectively. The inhibition kinetics analyzed by Hnewaver-Burk plots showed that ethyl acetate fraction was a competitive type inhibitor, and its Ki was determined to be 19.7 microg/ml. n-butanol fraction was an uncompetitive type inhibitor, and its Ki was determined to be 60.7 microg/ml.
  
  
  CONCLUSIONS
  Ethyl acetate and n-butanol fractions of extracts from Synotis erythropappa show potential inhibitory activity on tyrosinase.
authors.affiliation: Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China. xuetaoxu@yahoo.com.cn
authors.forename: Xue-Tao
authors.initials: XT
authors.lastname: Xu
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Zhi-Yun
authors.initials: ZY
authors.lastname: Du
authors.forename: Jie
authors.initials: J
authors.lastname: Zheng
authors.forename: Yan-Xiong
authors.initials: YX
authors.lastname: Fang
authors.forename: Xing-Chuan
authors.initials: XC
authors.lastname: Wei
authors.forename: Su-Qing
authors.initials: SQ
authors.lastname: Zhao
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: Yu
mesh_terms: D000085:Acetates; D001104:Arbutin / Q000494:pharmacology; D019659:Asteraceae / Q000737:chemistry*; D002681:China; D004305:Dose-Response Relationship, Drug; D004365:Drugs, Chinese Herbal / Q000302:isolation & purification / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D000431:Ethanol; D020128:Inhibitory Concentration 50; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010946:Plants, Medicinal / Q000737:chemistry; D013997:Time Factors
chemical_list: D000085:Acetates; D004365:Drugs, Chinese Herbal; D004791:Enzyme Inhibitors; D000431:Ethanol; C007650:ethyl acetate; D001104:Arbutin; D014442:Monophenol Monooxygenase