Alkaloids table

Two general classes of alkaloids are distinguished in ergot amine alkaloids and amino acid alkaloids (table 5.9) (Peroutka 1996). While the amine alkaloids are selective for antagonist effects on serotonin receptors, the amino acid alkaloids are less selective and act upon other monoamine receptors. The constituents of interest for cognitive enhancement are predominantly the amine alkaloids. 

Definition, Typology and Occurrence of Alkaloids Table 1 Main types of alkaloids and their chemical groups... 

Some alkaloids (Table 23) are still used in medicine They... 

Isolation and identification of pyrazine alkaloids (Table III) have been achieved in most cases by a combination of gas chromatography and mass spectrometry (35,36,38,69,97,142). Methyl-, 2,3,6-trimethyl-, and tetramethylpyrazines (23a, 21a, and 22a) from the melon fly are identified by utilizing a solid sampling technique in conjunction with gas chromatography-mass spectroscopy (147). Methylpyrazines show the molecule ion as a base peak. Fragmentation proceeds mainly by the loss of HCN or CH3CN from the molecular ion (141). Eth-... 

As far as land animals are concerned, the amphibians are of most concern. They are rarefying worldwide for obscure reasons (Kiesecker 2001), depriving Earth of their unique alkaloids (Table 16.2.5.1). 

Two major families of compounds that incorporate the tetracyclic ergoline nucleus may be identified the amine alkaloids and the peptide alkaloids (Table 16-6). Drugs of therapeutic and toxicologic importance are found in both groups. 

These alkaloids occur in the genera Evodia, Hortia, and Zanthoxylum, all members of the Rutaceae, and are restricted to only a few species. Most of the other species in these genera that have been examined yield furoquinoline and acridine alkaloids. Table I is a record of the occurrences, along with empirical formulas and melting points, of the quinazolinocarboline alkaloids. They are all optically inactive except evodiamine, [a]i> +352° (acetone), which is easily racemized. Wuchuyine, C10H13O2N, mp 237°, [a]D — 18°, occurring in E. rutaecarpa (1), evidently... 

Because Homo sapiens and domestic animals are to some degree herbivores, a large body of empirical knowledge has accumulated on the toxic properties of alkaloids (Tables I through V) and alkaloid-containing plants. Previously, the toxic properties of alkaloids in vertebrates was part of the definition (as a common denominator) for this group of natural products 38,39). In the following, the toxic or adverse effects of alkaloids are separately discussed for invertebrates (mainly insects) and vertebrates. 

The toxic effects observed with intact animals has its counterpart in the cytotoxic effect, which has been recorded for nearly 180 alkaloids (Table III). These data have been obtained by screening many natural products for anticancer activity. However, an alkaloid that can kill a cancer cell is usually also toxic for normal cells. Therefore, the data shown in Table III are another indication of the general toxicity of alkaloids toward animals. Because this toxicity applies also for herbivores, the production of alkaloids by plants can certainly be interpreted as a potent antiherbivore mechanism. 

Fructosylation of other alkaloids than elymodavine is complicated by the fact that (living) cells of C. purpurea also produce elymodavine, and this alkaloid competes with the introduced alkaloids for the fructosyl transfer. It was found that elymodavine has a higher affinity for the fructosyl transfer than other alkaloids (Table 1). Both the lowered yield and separation problems prevented us from obtaining lysergol and DH-lysergol fructosides. Less reactive alkaloids... 

Recently Tallec and coworkersinvestigated the stereochemistry of electroreductions of l-substituted-2,2-diphenylcyclopropenyl bromides in aqueous media at various pHs and in the presence of strongly adsorbed alkaloids (Table 6). Their study shows that the existence of interaction between the alkyl bromides and nitrogen cations makes the two-electron cleavage of the C-X bond easier (sometimes by up to 400 mV). In general, poor optical yields were obtained in the presence of each of the five alkaloids tested. However, the optical yield went up to 42 % when the alkaloid inducer could act as a proton donor. It was also found that the alkaloids were efficient at low concentrations (10 " to 5 x 10 " m) indicating that the induction is a surface phenomenon. 

Vincent and Engelke carried out an isocratic HPLC separation of the five major opium alkaloids in Papaver sornniferum and of thebaine in P. braeteatum on microparticulate silica gel for a quantitative determination of the alkaloids. A mobile phase consisting of four components n-hexane - dichloromethane - ethanol - diethylamine (300 30 40 0.5) separated the five major opium alkaloids (TABLE 7.7, Fig. 7.12). By altering the ratio dichloromethane - ethanol, the retention of the alkaloids could be varied. Capsular tissue extracts could be analyzed directly. 

S,B,o-C,g-C,D,40HS,PsS,I,V, spermoS,alst,serpentine Separation strychnos alkaloids (Table 8.12) Merckosorb Si60 5 urn 300x2 Et,0-DEA(99 1) Et 0-Me0H(l l) 18... 

Separation eburnane alkaloids (Table 8.14, 8.15) Micropak Si 10 or Lichrosorb Si60 5 un vBondapak CN 250x2 250x4.6 300x3.9 Hexane-CHCl.-ACN-MeOH(55 25 20 3) and various3other ratios Hexane-CHClACN(65 20 15),(7 2 1) (75 20 5) 3 55... 

Only a few data have been published on the HPLC of aconitine type of alkaloids (Table 12.1). Sheu et al. analyzed aconitine in crude drugs on an octadecyl stationary phase using methanol - aqueous phosphate buffer (pH 7.52) (85 15) as mobile phase. The influence of the water -methanol ratio in the mobile phase on the retention of alkaloids, including aconitine, has... 

In summary, to better asses the quality of V. africana seeds, we propose additional standards, such as percent of clusters, density, ashes and total alkaloids (Table III). In Ghana, the seeds are purchased according to their weight. Thus, the seed clusters and seed density ate important parameters to assess the quality of voacanga seeds. 

The list of Strychnos alkaloids (Table II) indicates the following items (1) name, (2) structure, (3) molecular formula, (4) molecular weight,... 

A major breakthrough was achieved with transfer hydrogenation catalysts generated from [Ru(Cl2(arene)] and a semi-AT-sulfonated chiral diamine (e.g., AT-to-syl-l,2-diphenyl-l,2-diaminoethane, N N) [19]. With HCOOH/NEtj as donor, enantioselectivities up to 97% were obtained for substrates of types 7 and 8 (s/c 200-1000 tof 83 h ), providing a new general route to alkaloids (Tables 4 and 5). Furthermore, this catalyst exhibited a high chemoselectivity towards the reduction of C=N vs. C=0 functions. As a consequence, imines of type 7 can even be reduced in acetone with <5% production of 2-propanol. 

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