Once structures are identified, we realise further experiments in collaboration with specialised teams to determine their targets and modes of actions and compare their activities with related natural or (semi)-synthetic compounds to assess structure-activity relationships.
We also analysed the possible targets for crude extracts. For example the activity of an extract of Keetia leucantha on different forms of trypanosomas showed a possible effect on glycolysis. We also proved the inhibiting effect of Pterocarpus erinaceus extracts on γ-secretase, an enzymatic complex responsible for A-Beta formation, and the effect of Croton zambesicus or Marrubium vulgare extracts on voltage dependent calcium channels.
Researches on pure isolated compounds allowed us to determine some structure-activity relationships for the vasorelaxant effect of trachylobanes diterpenes (collaboration with N. Morel, IREC). Targets were identified as voltage dependent calcium channels.
Structure-activity relationships for the vasorelaxant activity of trachylobanes
Alkaloids inhibiting topoisomerase I were identified in Cassytha filiformis. Synthetic derivatives were prepared in Spain and were also shown to possess antimalarial properties with a high selectivity index. Structure-activity relationships have been studied.
In the antiparasitic domain, we identified several antitrypanosomal terpenic compounds, some of them inhibiting trypanosomal GAPDH activity, a key enzyme of glycolysis, a process vital for trypanosoma development during its human cycle. We also collaborate with the teams of Prof. J. Palermo (University of Buenos Aires), Profs. J. Poupaert and R. Frédérick (LDRI-CMFA) and Profs. G. Acrombessi and F. Gbaguidi (UAC-Bénin) for the evaluation of the antiparasitic activities of (semi)synthetic compounds and establishment of structure-activity relationships. Some semi-synthetic compounds showed very promising antiplamsodial in vitro activity, in the same range as artemisinin.
Their effects on parasitic cells are now studied by metabolomics using LC-MS and NMR data (in collaboration with M. Frédérch and P. De Tullio from ULiège and B. Govaerts and SMCS from UClouvain) to determine the biochemical pathways modified by these natural pure compounds and identify their targets.
The physico-chemical interactions of natural saponins with cholesterol and biological membranes were studied in collaboration with the team of M.P. Mingeot (TFAR-FACM/LDRI) and new results were obtained which could explain several activities of this class of compounds. We also analyse with Prof. Mingeot the interaction of terpenic compounds with parasites membrane models.