Die Pregnanderivate der Samen von Dregea abyssinica (HOCHST.) K. Schum. (Asclepiadaceae). I. Isolierungen Glykoside und Aglykone, 304. Mitteilung

Abstract

AbstractThe seeds of Dregea abyssinica (HOCHST.) K. Schum. are very rich in glycosides. These consist of a complicated mixture of ester glycosides, cardenolides are absent. All these glycosides are derived from only the two known pregnane derivatives drevogenin P and Drevogenin D. In the glycosides the latter are esterified with different acids (acetic, isovaleric, α‐hydroxyisovaleric and tiglic acid) and glycosidically linked to different 2‐deoxy‐sugars which in part carry 3‐O‐methyl‐6‐deoxy‐D‐allose and terminal D‐glucose. After mild acidic hydrolysis 5 crystalline sugars and 6 crystalline aglycones could be isolated. The sugars were identified as D‐cymarose, asclepobiose, pachybiose, drebyssobiose and «sugar T» (formerly found in Dregea volubilis). The following aglycones were obtained: drevogenin A, drevogenin B, and four new compounds called drebyssogenin F, G, J and K. The latter was a mixture of two components (K1 and K2). From the original mixture four genuine glycosides could be isolated (the drebyssosides 1, 2, 3 and 4). Of these the drebyssosides 1 and 3 were obtained crystalline, drebyssoside 2 in amorphous but pure form and drebyssoside 4 as a mixture of mainly two closely related components. The probable structures of the new substances (drebyssobiose, sugar T, the four drebyssogenins and the four drebyssosides) are reported in the following publication.