Ipomoea purga (Wender.) Hayne - syn. Convolvulus purga Wender. - Convolvulaceae
jalap, Veracruz jalap, Jalape, Mexikanische Purgierwinde, Herbst-Prunkwinde

Evergreen herb, native to Central America; leaves heart-shaped, entire; flowers funnel-shaped, pink to red-violet.

„The root contains convolvulin, which is a powerful cathartic. It is used to prevent diarrhea, but large amounts will induce vomiting.“
http://en.wikipedia.org/wiki/Ipomoea_purga

„The resin of I. purga of strong purgative effect is known as jalapa and consists of two fraction, one insoluble in ether called convolvulin and other soluble called jalapin. Treatment of convolvulin with sodium methoxide has yielded a β-D-quinovoside. It consist of one molecule of D-quinovose glycosidically linked to molecule of methyl 11-hydroxytetradecanoate. Alkaline hydrolysis of jalapin yields volatile acids, tyglic, acetic, propionic, isobutiric, isovaleric, valeric and methylethyl-acetic, beside jalaponic acid. It by acid hydrolysis yields the oses glucose, fucose and rhamnose, as well as, jalapinolic acid or 11-hydroxypalmitic acid.“
[Review of the genus Ipomoea: traditional uses, chemistry and biological activities., Meira, M., Silva, E.P.D., David, J.M., David, J.P., Revista Brasileira de Farmacognosia, Vol.22(3), 2012, 682-713]
http://www.scielo.br/scielo.php?pid=S0102-695X2012005000025&script=sci_arttext

Kohl,F.G., Die officinellen Pflanzen der Pharmacopoea Germanica, t.126 (1891-1895)
http://plantgenera.org/species.php?id_species=557173