Anti-trypanosomal and cytotoxic effects of extracts from commiphora swynnertonii burtt 1935

PhD-Thesis

Application of trypanocides both curatively and prophylactically is a key component of beset with many problems including drug toxicity and treatment failure due to widespread resistance ofthe parasites. Given little progress in vaccine development, there is a pressing need for discovery of new alternative trypanocidal molecules that can further be developed into trypanocidal drugs. Plants are one such source from which alternative trypanocidal molecules could be obtained. Commiphora swynnertonii is a member of the family Burseraceae which is reported to possess a number of compounds active against protozoa. This thesis provides Commiphora swynnertonii extracts, and its potential as a source of lead molecules for development of alternative trypanocidal drug for trypanosomosis control. The main results are presented in two published papers and one submitted manuscript. The first paper presents the in vitro trypanocidal activity of Commiphora swynnertonii extracts on Trypanosoma congolense in which, the motility of T. congolense was evaluated after incubation for 20 minutes with ethanolic stem-bark and resin extracts at concentration of2 mg/ml and 4 mg/ml. In the second study, T. congolense was incubated with the extracts at concentrations of 0.4 mg/ml and 2 mg/ml for 36 - 56 min after which 0.08 ml of the aliquots were inoculated intraperitoneally into mice to assess infectivity. In both studies, negative (phosphate buffered saline with glucose without the extract) and positive (diminazene diaceturate) controls were used. The findings showed that C. swynnertonii ethanolic stem bark extract caused complete cessation of T. congolense motility in 30 minutes at the concentration of 4 mg/ml. Resin extract had a delayed effect on the cessation of T. congolense motility observed after 90 and 100 minutes of incubation at concentrations of 4 mg/ml and 2 mg/ml respectively. The drug incubation showed that ethanolic stem bark extract reduced significantly (P=0.000) the infectivity of T. congolense at concentration of 2 mg/ml compared to negative control and was not significantly (P=0.S97) different from the positive control. It was concluded that, C. swynnertonii ethanolic stem bark extract possesses in vitro trypanocidal activity. The second paper presents the results ofin vivo activity of C. swynnertonii ethanolic stem bark extract on T. congolense parasitaemia and its effect on immunological components in mice. Groups of mice infected with T. congolense were treated with the stem bark extracts at 1000 mg/kg, 1500 mg/kg and 2000 mg/kg, twice a day in one set and thrice a day in another setting for three days consecutively, and parasitaemia monitored. In the other setting, uninfected mice randomized in five groups were treated with the extract that was categorized as thorough mixed extract (TME) and supernatant extract (SE)) each at 500 mg/kg and 1500 mg/kg, in 8 hourly intervals respectively for three days consecutively. The groups that received the extracts (1000 mg/kg and 2000 mg/kg) at eight hourly intervals had drastically reduced parasitaemia (P<0.05). It was concluded that C. swynnertonii ethanolic stem bark extract possesses in vivo trypanocidal activity. On the other hand, SE at the dose of 1500 mg/kg significantly (P<0.05) reduced the percentage of peripheral lymphocytes. Both doses (500 mg/kg and 1500 mg/kg) of TME significantly (P<0.05) reduced lymphocytes percent while neutrophils and monocytes percent increased significantly (P<0.05). Histopathology of the spleen in the mice treated with 1500 mg/kg of SE and TME showed apoptosis of lymphocytes around the marginal zone and lymphoid follicles. Hence, it was concluded that C. swynnertonii ethanolic stem bark extract within anti-trypanosomal therapeutic dose range possesses cytotoxic effect on lymphocytes. The submitted manuscript provides the results on anti-trypanosomal activities of fractions and sub-fractions of C. swynnertonii ethanolic stem bark extract against T. congolense. Negative (phosphate buffered saline with glucose without the extract) and positive (diminazene diaceturate) controls were used. In addition, chromatographic techniques were employed to determine bioactive molecules in the sub-fractions. The findings indicated that anti-trypanosomal activity in the fractions of aqueous, dichloromethane and petroleum ether were decreasing in that order. In this study, four terpenoids (bomeol, geranylgeraniol, coronopilin and 4,8,13-duvatriene-l,3-diol) were detected and were considered to be likely responsible for trypanocidal activity of Commiphora swynnertonii ethanolic stem bark extract. Further studies to evaluate the in vivo trypanocidal potential are recommended. As a general conclusion, this study has shown that C. swynnertonii stem bark extract possesses in vitro and in vivo trypanocidal activity. The in vivo trypanocidal activity is probably affected by cytotoxic effect on lymphocytes at the therapeutic dosage. It was further found that bomeol, geranylgeraniol, coronopilin and 4,8,13-duvatriene-l,3-diol could be responsible for observed trypanocidal efficacy of C. swynnertonii stem bark extract. Further studies to determine their therapeutic trypanocidal potentials are recommended

Tanzania Commission for Science and Technology