title: Antitrypanosomal activity of aloin and its derivatives against Trypanosoma congolense field isolate.
abstract: BACKGROUND
  There is an urgent need for the development of new, cheap, safe and highly effective drugs against African trypanosomiasis that affects both man and livestock in sub-Saharan Africa including Ethiopia. In the present study the exudate of Aloe gilbertii, an endemic Aloe species of Ethiopia, aloin, aloe-emodin and rhein were tested for their in vitro and in vivo antitrypanosomal activities against Trypanosoma congolense field isolate. Aloin was prepared from the leaf exudate of A. gilbertii by acid catalyzed hydrolysis. Aloe-emodin was obtained by oxidative hydrolysis of aloin, while rhein was subsequently derived from aloe-emodin by oxidation. In vitro trypanocidal activity tests were conducted on parasites obtained from infected mice, while mice infected with T. congolense were used to evaluate in vivo antitrypanosomal activity of the test substances.
  
  
  RESULTS
  Results of the study showed that all the test substances arrested parasites motility at effective concentration of 4.0 mg/ml within an incubation period ranging from 15 to 40 min. Moreover, the same concentration of the test substances caused loss of infectivity of the parasites to mice during 30 days observation period. Among the tested substances, rhein showed superior activity with minimum inhibitory concentration (MIC) of 0.4 mg/ml. No adverse reactions were observed when the test substances were administered at a dose of 2000 mg/kg. Rhein at doses of 200 and 400 mg/kg, and the exudate, aloin and aloe-emodin at a dose of 400 mg/kg reduced the level of parasitaemia significantly (P < 0.05) and improved anaemia.
  
  
  CONCLUSIONS
  The results obtained in this investigation indicate that aloin and its derivatives particularly rhein have the potential to be used as a scaffold for the development of safe and cost effective antitrypanosomal drugs that can be useful in the continuing fight against African trypanosomiasis.
authors.forename: Yitagesu
authors.initials: Y
authors.lastname: Tewabe
authors.forename: Daniel
authors.initials: D
authors.lastname: Bisrat
authors.forename: Getachew
authors.initials: G
authors.lastname: Terefe
authors.affiliation: Department of Pharmaceutical Chemistry and Pharmacognosy, School of Pharmacy, Addis Ababa University, Addis Ababa, Ethiopia. kaleab.asres@aau.edu.et.
authors.forename: Kaleab
authors.initials: K
authors.lastname: Asres
mesh_terms: D000818:Animals; D000880:Anthraquinones / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D004133:Diminazene / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004642:Emodin / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D051379:Mice; D015394:Molecular Structure; D011897:Random Allocation; D014344:Trypanocidal Agents / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology; D014348:Trypanosoma congolense / Q000187:drug effects*; D014353:Trypanosomiasis, African / Q000188:drug therapy* / Q000469:parasitology
chemical_list: D000880:Anthraquinones; D014344:Trypanocidal Agents; C518327:aloe emodin; C003915:diminazene aceturate; D004642:Emodin; C006457:alloin; D004133:Diminazene; C020491:rhein