Sceletium strictum

Sceletium strictum (mesembrine), 364 Sceletium tortuosum (mesembrine),... 

Full details have been published of part of the research on the biosynthesis of the mesembrine alkaloids of Sceletium strictum (Aizoaceae). Some of the work has appeared in a preliminary communicationand has been reviewed. 

Detailed evidence has been published following the preliminary report implicating tyrosine as the progenitor of the C(,-C2 unit of mesembrine (107) in Sceletium strictum on the one hand, and phenylalanine as the source of the unusual, if not unique, Q unit on the other. The results showed that (a) methionine served as the specific precursor of the N- and 0-methyl groups (b) whereas dl-[2 - C]- and DL-[3 - C]-phenylalanine gave inactive alkaloid, DL-[ar-U- " C]phenylalanine specifically labelled the aromatic ring of mesembrine and (c) dl-[3 - C]- and DL-[2 - C]-tyrosine were incorporated. Degradation of the mesembrine after administration of the former tyrosine precursor... 

All four A -methyl compounds 143,144,145, and 146 appear to be metabolized by Sceletium strictum. The products of this metabolism are aberrant metabolites of unknown structure but are known to contain ratios which correspond closely to that of the administered... 

A detailed account concerning the isolation and characterization of the pyrido-mesembran alkaloids A4(7) and iV-formyltortuosamine (8) and the mesembran bases (9 R = H, R = OMe), (10), and (9 R = R = H) from Sceletium namaquense and S. strictum has appeared. Their structures were established by detailed H and... 

Mesembrine (-)-Mesembrine (12) is an octahydroindole alkaloid isolated from certain plants of the Sceletium genus, namely S. namaquense, S. strictum and S. tortuosum The mesembrine sttucture has been established as 12. Mesembrine was synthesized from noncarbohydrate, and its synthesis from D-mannitol has been presented herein. 

Since Ar—C2—N—C2—Cg units are involved in the biosynthesis of many alkaloid families (76), the amide 159 was examined as a possible precursor to the Sceletium bases in S. strictum. Again, no incorporation of radioactivity occurred on feeding a suspension of this compound in 20% Tween solution. Therefore, given the same reservation regarding the effect of high Tween concentrations on this result, it would appear that further studies will be required to determine the fate of iV-methyltyramine and 4 -hydroxy-dihydrocinnamic acid in their biosynthetic conversion to the octahydroindole skeleton of the mesembrine alkaloids. 

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