C27-Steroid Alkaloids

The C27-steroid alkaloids contain two heterocyclic rings attached to a steroid nucleus. Either one or both contain a nitrogen atom. The alkaloids are glycosides with the sugars attached to the hydroxy group in position 3. A well-known representative is oc-tomatine, which contains a branched sugar chain frequently found also with steroid saponins (D 6.4.2). 

The C27-steroid alkaloids occur in some families of higher plants, e.g., Solanaceae and Liliaceae. They are accompanied by steroid saponins (D 6.4.2), but are less widespread than these compounds. 

The C27-steroid alkaloids are probably formed from dihydrokryptogenin (D 6.4.2). Compounds of the solasodine or tomatidine type as well as substances of the demissidine and solanidine (5-dehydrodemissidine) type may be formed after replacement of the keto group at C-22 by an imino group (Fig. 125). 

Steroid alkaloids are poisonous to animals. Demissine, a demissidine glycoside, occurring in the green parts of the potato plant, acts, for instance as feeding repellent for the Colorado beetle Leptinotarsa decemlineata (E 5.5.3). Solasodine is an important raw material in the production of steroid hormones (F 4). 

In Veratrum and Fritillaria (Lihaceae) C-nor-D-homosteroid alkaloids with 27 C-atoms are found. These substances are linked to sugars at the C-3 hydroxy group and many carry acyl residues attached to other OH-groups. Two typical representatives are veratr amine and ver ace vine. 

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C27-Steroid alkaloids a-Tomatine trans alp trans alp trans alp... 

Medium length to long (25-50 m) apolar capillary columns were shown to be best suited for the analysis of these compounds (Van Gelder et al. 1988, 1989). Figure 5 shows a GC separation of C27 steroidal alkaloids. Since different biological activities are associated with structural differences in the sugar moieties, isolation and identification of the glycosides remain necessary to examine toxicity. 

Fig. 5A-C. Gas chromatograms obtained simultaneously by FID (A) and PND (B) for a potato extract spiked with C27-steroidal alkaloids, 5a-cholestane, sterols, and steroidal sapogenins. Attenuation FID 2, PND 2 . Post-analysis reprocessing of the raw data from A and B (subtraction of the FID trace from the PND trace) is shown in C. 1 Octacosane 2 5a-cholestane 3 solanthrene 4 cholesterol 5 solanidine 6 demissidine 7 solasodiene 8 stigmasterol 9 diosgenin 10 tigogenin 11 solasodine 12 tomatidine 13 tetratriacontane 14 jervine. Column fused silica, 50m x 0.22 mm i.d., CP Sil 5cb, film thickness 0.12um. Carrier gas H2, linear velocity 49cms" oven temperature 270°C (Van Gelder et al. 1988)...

In other investigations, radioactivdy labeled (25/l)-26-aminocholesterol (306) administered to S. laciniatum was incorporated to a high extent into solasodine (1), whereas the corresponding 16/S-hydroxy derivatives (25/ )-26-aminocholest-5-ene-3/ ,16jS-diol and its 7V-acetyl derivative (306) show only small incorporations (307). These results suggested that in the biosynthesis of C27 steroid alkaloids the introduction of nitrogen occurs imme-... 

Thus, the C27-steroid alkaloids with C-nor-D-homo [14(13->-12)-abeo] ring system, that is, with a jervane (5) or cevane (6) skeleton, found in Liliaceae but until now not in Solanaceae, are not included they will be described exhaustively in another chapter of this volume by S. M. Kupchan. On the other hand, the tertiary Veratrum bases rubijervine, isorubijervine, and veralobine belong to the solanidanes and will be mentioned briefly in this chapter, but a detailed description of these alkaloids and their derivatives will also be given by S. M. Kupchan. 

Figure 26 shows the formula, conformation, and absolute configuration of veratridine (52). The structure and conformation of the C27-steroidal base is very similar to that determined for zygacine (C32H49N08) another Veratrum alkaloid (53). Variations in the pharmacological effects of Veratrum alkaloids appear to be dependent on the substituents attached to the essentially rigid molecular framework. The numerous intramolecular hydrogen bonds that enhance the molecular rigidity are indicated in Fig. 26. The positions of all the hydrogen atoms have been located for the veratridine molecule and the intramolecular donors and acceptors are identified as...

Cl 0 monoterpenes Cl 5 sesquiterpenes C20 diterpenes C30 triterpenes C27 steroids C40 tetraterpenes C(n) polyterpenes Saponins Cucurbitacins Terpenoid alkaloids... 

The steroidal alkaloids have a nucleus based on 21, 24, or 27 carbon atoms (Fig. 44). The C21 alkaloids are pregnane-derived with nitrogen inserted at C-3, at C-20, or at both positions. They are characteristic of the Apocynaceae Funtumia and Holarrhena species) and the Buxaceae Buxus species). The Buxaceae also produces C24 alkaloids based on the cycloartane skeleton. The most interesting alkaloids are those in the Solanaceae and the Liliaceae. These are C27 alkaloids, and examples include solasodine and solanidine many derivatives are glycosylated. The alkaloids from the Liliaceae, such as veratramine of the white hellebore (Veratrum album), were formerly used for cardiac... 

Two main groups of steroid alkaloids are known the compounds such as solasodine (IV) and the Cji alkaloids such as holaphyllamine (V). The C27 com-... 

Steroid alkaloids have been isolated from four families of terrestrial plant sources (Solanaceae, Uliaceae, jPpocynaceae and Buxaceae), two animal sources (Salatnandra and Phjllobates)> and several marine sources. Steroid alkaloids can be classified based on structure and fall into a variety of categories. The spirosolanes contain a C27 cholestane skeleton with a C20 spiroaminoketal moiety, as exemplified by the most abundant members of this class, veramine... 

The above-mentioned types of Solanum alkaloids are derived from the same pathways as most other steroids in plants. For more information on the formation of the various precursors involved, see Chapters 23 and 24. The biosynthesis and metabolism of the C27 sapogenins and alkaloids are closely related (Ripperger and Schreiber, 1981 Gross et al, 1985). Acetate and mevalonate are incorporated into all types of steroid alkaloids. 

Fig. 36.15. Proposed biosynthetic scheme for the origin of steroid alkaloids with unaltered C27 skeletons (modified from Gross et al., 1985).

Thus, the C2 7-steroid alkaloids with C-nor-D-homo ring system, that is, with a jervane or cevane skeleton, with 18-nor-17j8-methylcholestane skeleton (23-27) or other alterations of the C27-carbon skeleton of cholestane, found in Liliaceae but not yet in Solanaceae, are not included. They are described exhaustively in other volumes of this series by Kupuchan and By (28) as well as by Tomko and Voticky (29). On the other hand, some Veratrum bases, for instance, teinemine and baikeine, belong to the 5o/amim-type alkaloids and are mentioned in this chapter. 

Nitrogen-Free Steroid Sapogenins (Spirostanou) and Related Compounds in Solanum Species and Other Plants Containing C27-STER01D Alkaloids ... 

This chapter presents a survey of newly isolated Veratrum and Solanum alkaloids between 1974 and 2014. These alkaloids generally possess a C27 cholestane carbon skeleton with five or six carbocyclic or heterocyclic rings they occur as glycosides, aglycones, or esters with various acids. Following lUPAC recommendations, these alkaloids are organized on the basis of their carbon framework into isosteroidal alkaloids and steroidal alkaloids. The former—sometimes designated as Veratrum alkaloids—are... 

Pollinastanol (9p,19-cyclopropane-/C27-type), 5a-cholest-8-en-3P-ol, and isofucosterol (substituent at C-24 =C-CH3 ci g) were accumulated in discs of potato tubers when treated with synthetic inhibitors of the steroidal alkaloid biosynthesis (Bergenstraahle et al. 1996). 

Steroid alkaloids are plant constituents having a C27 steroid skeleton and nitrogen content. Solanaceae contain these compounds, their occurrence in potatoes being the most interesting from a food chemistry point of view. 

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