Die Pyrrolizidin‐Alkaloide aus Senecio alpinus (L.) SCOP., S. subalpinus KOCH und S. incanus L. subsp. carniolicus, (WILLD.) BR.‐BL. Pyrrolizidin‐Alkaloide, 13. Mitteilung

Abstract

Senecio alpinus (L.) SCOP. is very rich in alkaloids. The dried overground parts gave 0,45% crude alkaloid mixture. The main component is seneciphylline (1); small amounts of cristalline jacozine (4) could also be isolated. ‐ Senecio subalpinus KOCH gave 0,368% of crude alkaloid mixture. In contrast to former results only 0,1% of this was present in the form of N‐oxides. The bulk was a ca. 1 : 1 mixture of seneciphylline with senecionine (3). ‐ Senecio incanus L. subsp. carniolicus (WILLD) BRä.‐BL. gave 0,40% of crude alkaloid mixture; from this some pure seneciphylline could be isolated. ‐ In all three plants the presence of integerrimine (2) and other non‐identified alkaloids could be established by thin layer chromatography.

Pyrrolizidine Alkaloids from Onosma erecta

“…Because of the high polarity of the N -oxide functionality and the hydroxy groups attached to the necyl moieties, PA N -oxides have high water solubility, which impedes their partition to organic solvents during extraction and also causes their significant loss on silica stationary phases due to irreversible adsorption. Therefore, reduction to the corresponding amines with zinc dust at low pH is usually carried out, followed by their extraction with CHCl 3 or CH 2 Cl 2 from the alkalinized aqueous layer. − Because of the known susceptibility of esters to undergo hydrolysis at extreme pH and the long reduction times needed when zinc is the reducing agent, we attempted to directly separate PA N -oxides from their original mixture, avoiding the need for the reduction/extraction step. For this purpose microcrystalline cellulose was used as the packing material of choice, giving efficient CC separations, with better recovery of PAs compared to silica, and without high backpressure problems compared to usual finer cellulose packings.…”