- Evaluation of bioactive saponins and triterpenoidal aglycons for their binding properties on human endothelin ETA and angiotensin AT1 receptors. Caballero-George, C., Vanderheyden, P.M., Okamoto, Y., Masaki, T., Mbwambo, Z., Apers, S., Gupta, M.P., Pieters, L., Vauquelin, G., Vlietinck, A. Phytotherapy research : PTR. (2004)