ISOLATION AND IDENTIFICATION OF TRACE CACTUS ALKALOIDS

SUNIBHOND PUMMANGURA, Purdue University

Abstract

On screening of twelve higher plants for alkaloid content, a medicinal plant from the Bahamas, Amyris elemifera, was selected for further alkaloid investigation. A known coumarin, dehydrogeijerin, was isolated from this plant, and certain chemical shifts in nmr spectra were reassigned; this compound gave false-positive tests for alkaloids. One of the cacti screened was Coryphantha missouriensis; hordenine and N-methyltyramine were isolated, and tyramine and N-methyl-3,4-dimethoxy-(beta)-phenethylamine were identified from this previously uninvestigated cactus. The absence of (beta)-hydroxylated-(beta)-phenethylamines in this plant may be a chemical justification for some taxonomic distinctions within this large genus. In a further investigation of the Mexican cactus, Backebergia militaris, the isolation of lemaireocereine, an aromatic substitution isomer of heliamine at m/z 194 (MH('+)), showed that traditional isolation methods vs. MIKE spectrometry are still necessary for the complete structure identification of cactus alkaloids. In addition, 3-methoxytyramine was isolated from this cactus plant. Tehuanine N-oxide, a new cactus alkaloid, was isolated from Pachycereus pringlei. This is the first time that this compound has been reported, and it is the first N-oxide to be identified from cactus species. The structure of a second new N-oxide, deglucopterocereine N-oxide, previously isolated but uncharacterized from Pterocereus gaumeri, was also elucidated. Both N-oxides were identified by physical means and by synthesis of reference compounds; subsequent studies demonstrated that they are natural in the plants and are not extraction artifacts. The structure of one of them, deglucopterocereine N-oxide, was confirmed by chemical reduction of the N-oxide to form the parent tertiary amine (deglucopterocereine). Another new cactus alkaloid, dehydrosalsolidine, was isolated from the saguaro, Carnegiea gigantea, and was proposed to play an important role in the biosynthesis of salsolidine. Dehydrosalsolidine was also demonstrated by MIKES, using a temperature profile technique, to be a natural compound. Also, MIKES showed that there is a thermolabile second source of dehydrosalsolidine in the plant, possibly a carboxylic acid which might play a role as an intermediate in the biosynthesis of such cactus alkaloids. Heliamine was also isolated for the first time from this plant to fulfill the results of previous MIKES screening. In a grafted plant experiment (Trichocereus pachanoi on T. spachianus and vice versa) tlc and gc were used to indicate the presence and absence of mescaline in scion and stalk parts. The samples indicating the presence of mescaline were quantitated by gc using standard methods. The results demonstrated that there was no translocation of mescaline in the grafted plants.

Degree

Ph.D.

Subject Area

Pharmaceuticals

COinS