Bean, calabar

First obtained from Physosligma venenosum (Calabar bean) and is readily isolated from many plant sources where it often co-occurs with sitosterol. It has served as a starting substance for the synthesis of steroid hormones. 

Eseramine, C43H25O3N4, was first obtained by Ehrenberg, and its occiurence in Calabar beans was confirmed by Salway. It forms colourless needles, m.p. 245° (dec.) and is sparingly soluble in ether, chloroform or benzene, but readily in hot alcohol. 

Cacalia hastata, 601 Cacotheline, 566 Cactaceae, 154 Cadaverine, 518 Calabar bean alkaloids, 539 Calabarine, 540 Calabash curare, 373 alkaloids, 380... 

Physostigmine (eserine) is a carbamate found in the calabar bean (Physostigma benenosum), which acts as an anticholinesterase. It was used in West Africa in witchcraft trials by ordeal. It has also been used in human medicine. Insecticidal carbamates are structurally related to it and also act as anticholinesterases (Ballantyne and Marrs 1992). 

The chemical and biological properties of carbamate insecticides (CBs) are described in some detail in the texts of Kuhr and Borough (1976) and Ballantyne and Marrs (1992). An early model for their development was physostigmine, a natural product found in Calabar beans. Many CBs came into use during the 1960s, sometimes as substitutes for banned OC insecticides. 

The alkaloid physostigmine found in the calabar bean is another classic milestone molecule in total synthesis. Metrics for thirteen plans to this molecule are summarized in Table 4.25. 

Node and Fuji have developed a new chiral synthesis of various alkaloids using chiral nitroalkene, (S)-(-)-2-methyl-2-(2 -nitrovinyl)-S-valerolactone. Scheme 8.11 shows a total synthesis of (-)-physostigmine, a principal alkaloid of the Calabar bean.53 The key nitroalkene is prepared by asymmetric nitroolefination of a-methyl-8-lactone using a chiral enamine (see... 

Traditionally, plants are a rich source of AChE inhibitors. People from the Caucasus used bulbs of snowdrops Galanthus sp.) to treat forgetfulness [25]. The active compound in this plant has been isolated and called galanthamine. Other plant-derived AChE inhibitors used for treatment of Alzheimer s disease include Huperzine A from Huperzia serrata and Rivastigmine (Excelon). The latter is a derivative from physostigmine isolated from the calabar bean, Physos-tigma vmmosum. 

The classic cholinesterase inhibitor is the alkaloid physostigmine (6)/ eserine (7). It was first isolated from the calabar bean, the seeds of Physostigma venenosum. Many novel natural products with AchE-inhibifing properties have shown promise as therapeutics for AD. Some examples of such products (pure compounds/plant extracts or formulations) are briefly reviewed here. 

Physostigmine (14) Physostigma venenosum Balfour (Calabar bean) Cholinergic (parasympathomimetic)... 

The classic cholinesterase inhibitor is the alkaloid physostigmine (33), also called eserine. Investigations carried out in the nineteenth century on the ordeal poison esere, which consisted of an extract of the Calabar Bean, the seeds of Physostigma venenosum Balf, resulted in the isolation of (33)... 

The toxic effects of Calabar Bean extract were found to be due to excessive cholinergic stimulation giving rise to symptoms such as increased salivation, nausea, bradycardia, muscle cramps and respiratory failure, as well as CNS effects such as agitation. The cholinergic excess was found to be... 

It is a tertiary ammonium alkaloid obtained from the Calabar bean, the dried ripe seed of Physostigma venenosum, which... 

Clinical anticholinesterases are mainly carbamates which have use for the treatment of conditions in which Ach stores are depleted or are ineffective. One, physostigmine, is a natural compound used in ancient judgement rituals in West Africa. To judge the veracity of an accused person, he was made to drink a brew made from the Calabar bean. If he got sick and vomited, thus eliminating the poison, he was innocent. If the stuff stayed down and he died, he was, of course, guilty. Physostigmine has an in vivo duration of inhbition of 3 to 4 hours. 

Takano S and Ogasawara K (1989) Alkaloids of the calabar bean. The Alkaloids, Chemistry and Pharmacology (ed Brossi A) Vol 36. Academic, San Diego, pp 225-251. 

In the mid-19th century the Calabar bean was sent to Scotland and the two principal alkaloids were extracted in a number of European laboratories. There the formulae were determined and toxic and medicinal properties intensively studied. By the early 20th century the formula for physostigmine and the presence of two... 

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