Alkaloids of Apocynaceae

Steroid alkaloids were also found in Funtumia and Malouetia. The genus Funtumia comprises tropical trees indigenous to equatorial and West Afrika. Alkaloids found therein belong to types I and II. Many contain only one atom of nitrogen and an oxygen function in positions 3 or 20 in comparison Holarrhena alkaloids exhibit this type of substitution much less frequently. 

The genus Malouetia occurs in both Africa and South America. It is distinguished by the same types of alkaloids as Funtumia and Holarrhena. Of particular interest is the isolation of the quaternary alkaloid malouet-ine with curarizing effect in the African Malouetia, bequaertiana Woods. It is probable that the same effect produced by the Venezuelan drug guachamacd can be attributed to some alkaloids of the South American Malouetia (3). 

The genus Malouetia was described in detail, both from the botanical and chemical point of view, by F. Khuong-Huu-Laine et al. (3). The results of extensive investigations of steroid alkaloids of Apocynaceae have been reviewed in several articles (4-8) and in the excellent monograph by Goutarel (9). 

The mass spectrometric investigation of a series of Holarrhena alkaloids was independently undertaken by two groups (10,11 see also 12, 13). Their work resulted in practically identical conclusions and also demonstrated the immense diagnostic value of mass spectrometry in this field of alkaloid chemistry. 

Depending on the number of iV-methyl substituents of the amino group, the mass spectra exhibit characteristic intense peaks, the masses of which form the homologous series 56, 70, and 84 corresponding to primary, secondary, and tertiary amino functions the intensity of the peaks increases in the same order. This fragmentation was rationalized 

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Chemotaxonomic investigations are useful in cases where natural compounds occur in a very limited number of plant families [e.g., 1200 indole alkaloids in three plant families (143)]. The number of species investigated belonging to one plant family should be very high. In the case of di- and polyamine alkaloids, this ratio is only 1 (plant family) 2 (species) compared with, for example, indole alkaloids of Apocynaceae with a ratio of 1 249. Therefore, we think that at present, chemotaxonomic investigations of di-and polyamine alkaloids may not be useful. 

A histochemical investigation also established the presence of alkaloids in Pachysandra, Sarcococca, and Simmondsia (190). The alkaloids found in Sarcococca and Pachysandra are simple pregnane derivatives lacking the alkyl substitution at C-4 and C-14. The alkaloids isolated from Sarcococca pruniformis Lindley show close similarity in structure to alkaloids typical of pregnane-type alkaloids of Apocynaceae some of them were found in both families. 

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