Mesembrine

Planta Med. 2012 Feb;78(3):260-8.

In vitro permeation of mesembrine alkaloids from Sceletium tortuosum across porcine buccal, sublingual, and intestinal mucosa.[Pubmed: 22105579]

Sceletium tortuosum is an indigenous South African plant that has traditionally been used for its mood-enhancing properties. Recently, products containing S. tortuosum have become increasingly popular and are commonly administered as tablets, capsules, teas, decoctions, or tinctures, while traditionally the dried plant material has been masticated.
METHODS AND RESULTS:
This study evaluated the in vitro permeability of the four major S. tortuosum alkaloids (i.e., Mesembrine, mesembrenone, mesembrenol, and mesembranol) across porcine intestinal, sublingual, and buccal tissues in their pure form and in the form of three different crude plant extracts, namely water, methanol, and an acid-base alkaloid-enriched extract. The permeability of Mesembrine across intestinal tissue was higher than that of the highly permeable reference compound caffeine (which served as a positive control for membrane permeability) both in its pure form, as well as in the form of crude extracts. The intestinal permeability of mesembranol was similar to that of caffeine, while those of mesembrenol and mesembrenone were lower than that of caffeine, but much higher than that of the poorly permeable reference compound atenolol (which served as a negative control for membrane permeability). In general, the permeabilities of the alkaloids were lower across the sublingual and the buccal tissues than across the intestinal tissue. However, comparing the transport of the alkaloids with that of the reference compounds, there are indications that transport across the membranes of the oral cavity may contribute considerably to the overall bioavailability of the alkaloids, depending on pre-systemic metabolism, when the plant material is chewed and kept in the mouth for prolonged periods.
CONCLUSIONS:
The results from this study confirmed the ability of the alkaloids of S. tortuosum in purified or crude extract form to permeate across intestinal, buccal, and sublingual mucosal tissues.

Org Lett. 2009 Feb 5;11(3):555-8.

Palladium-catalyzed sequential arylation and allylic alkylation of highly functionalized ketones: a concise synthesis of mesembrine.[Pubmed: 19117400]

METHODS AND RESULTS:
An unprecedented palladium-catalyzed sequential procedure toward arylation and allylic alkylation of highly functionalized cyclohexenones was developed. This new protocol leads to useful building blocks containing a benzylic quaternary carbon in only one step.
CONCLUSIONS:
A concise total synthesis of Mesembrine based on this procedure was achieved in only five steps with 22% overall yield.

J Org Chem. 2013 Apr 5;78(7):3410-5.

Double reduction of cyclic aromatic sulfonamides: synthesis of (+)-mesembrine and (+)-mesembranol.[Pubmed: 23496752]

METHODS AND RESULTS:
The synthesis of (+)-Mesembrine (1) and (+)-mesembranol (2) has been achieved from the monoterpene (S)-(-)-perillyl alcohol. Key transformations include a diastereo- and regioselective Pd-mediated intramolecular Heck reaction, and a double reduction of the resultant cyclic sulfonamide, to afford the cis-3a-aryloctahydroindole skeleton.