Peptide Alkaloids from Higher Plants

Peptide alkaloids have mainly been isolated from the families Rhamna-ceae, Sterculiaceae, Pandaceae, Rubiaceae, Urticaceae, Hymenocardia-ceae, and Celastraceae (6,7). They have been defined as cyclopeptide alkaloids embodying an ansa structure, in which a 13-, 14-, or 15-membered ring is formed either between the 1- and 3-positions or between the 1- and 

4-positions of a benzene ring, as shown in Fig. 1. In the continuing expansion 

Schmidt et al. have reviewed peptide alkaloids in a volume of this series 

In this chapter we describe cyclopeptide alkaloids, spermine and spermidine alkaloids, long-chain acid amides, and the cyclic oligopeptides isolated from higher plants since 1985. 

From Zizyphus sativa (Rhamnaceae), discarine-related 13-membered cyclopeptide alkaloids, sativanines C (1) (14), D (57), E (2), F (3) (15-17), and G (4) (18) have been isolated. Ilie bark of Z. sativa is used to heal ulcers and wounds. Extensive chromatography of the crude bases furnished a further, previously unknown, 13-membered cyclopeptide alkaloid sativan-ine H (5) (79). Sativanine K (6) has been obtained from the powdered bark of Z. sativa. This is the first 13-membered cyclopeptide alkaloid to contain an JV-formyl group as well as a short side chain (20). A new, minor 

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Fig. 1. The characteristic types of peptide alkaloids from higher plants.

Another observation of similar importance is the first isolation of an alkaloid of the peptide type from higher plants. Ergosine (20) (and ergosinine) as well as agroclavine were found in Ipomoea argyrophylla Vatke (21). 

Antitumor compounds, among them cyclic peptides, terpenoids, and alkaloids isolated from higher plants 99YZ529. 

In this chapter, cyclic peptide alkaloids are discussed in Section II and cyclic oligopeptides from higher plants are discussed in Section III. 

Peptides in higher plants can be divided into two major categories. Some have unique structures and functions, whereas others are involved in the synthesis or degradation of proteins (Higgins and Payne, 1982). In this treatment, emphasis will be given the former type. There are limited data concerning peptides of either type from plants, A series of peptides known as phytochelatins has been shown to chelate heavy metals. A number of plants, including those of certain members of the Celastraceae, Euphorbiaceae, and Rhamnaceae, contain peptide alkaloids which are discussed under Peptide and Macrolide alkaloids (Chapter 37). A num-... 

Biosynthesis. In Claviceps purpurea, and presumably also in higher plants, E.a. are biosynthesized from tryptophan and isopentenylpyrophosphate (see Terpenes). Synthesis proceeds via 4-dimethylallyl-tiyptophan, which is converted into the alkaloid chanoclavine (by hydroxylation, methylation, decarboxylation and formation of a new C-C bond). All the other clavine alkaloids and the lysergic acid derivatives are derived from chanoclavine. The peptide moieties of the ergotamine and ergotoxin alkaloids are formed by a multienzyme complex (Fig. 2). E.a. are prepared from the sclerotia of rye, previously inoculated with Claviceps and they are also produced by culture of the fungus on artificial growth media. 

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