Solanine structure

Solangustidine solangustine, 671 Solanidine, 661, 662, 671, 708, 712, 713 dehydrogenation products, 663 heterocyclic residue, 665 proximate derivatives, 664 structure, 665, 667 Solanine, 661... 

The structural features of the solanum alkaloids are based on two primary skeletal configurations solanidane, with or without glycoside functionalities, as featured by the toxic and teratogenic steroidal alkaloids a-chaconine and a-solanine with the indolizidine type E-F ring (Figure 2.7a) and the spirosolane... 

In commercial potatoes (Solanum tuberosum) there are two major glycoalkaloids, a-chaconine and a-solanine, both trisaccharides of the common aglycone solanidine. These two compounds comprise about 95% of the glycoalkaloids in potato tubers. Their hydrolysis products, the p and 7 forms and solanidine, may also be present in relatively insignificant concentrations. The structures of these glycoalkaloids and their hydrolysis products are presented in Figure 6.1. 

Figure 6.1 Structures of potato glycoalkaloids a-chaconine and a-solanine, and hydrolysis products (metabolites).

Potato GAs usually belong to one of two structural types, either solanidanes or spirosolanes (Figure 14.3). Solanine and chaconine, both solanidanes, often comprise upwards of 90% of the total GA complement of domesticated potatoes, with chaconine often more abundant than solanine (Griffiths et al., 1997 Sotelo and Serrano, 2000). 

Steroidal alkaloids These alkaloids have a core steroidal skeleton as part of the molecule, e.g. solanine. There are a number of structural varieties that exist in steroidal alkaloids. Following discussion is just on a few selected steroidal alkaloids. 

The function of these tomatinase in formae speciales that do not pathogenise tomato is unknown. One possible explanation could be the presence of tomatine or similar saponins in their host plant species. However, (i) tomatine has not yet been reported in these plants [2, 7, 9] and (ii) although some of these species contain small amount of tomatine and other saponins structurally related to tomatine (e.g. potato contains a- solanine and a-chaconine [2, 4, 9, 90]), these are inactive as inducers of tomatinase and, moreover, tomatinase cannot use any of these glycoalkaloids as substrate [89]. In addition, it is clear that tomatinase is not required for pathogenicity in these isolates, at least in the case of F. oxysporum f. sp. melonis, where some strains that are fully pathogens on muskmelon lack tomatinase activity [89]. 

Fig. 7 Structure of the glykoalkaloids solanine and chaconine (aglycone solanidine). 

Returning to the question in the title of this section, capsaicin does not fall into any of the three classic types of nitrogen-bearing plant natural products, being neither a true alkaloid, a protoalkaloid, or a pseudoalkaloid. Capsaicin is oflimited distribution in Nature and shows pharmacological activity, but is non-basic, structurally unsophisticated, and not directly derived from an amino acidic precursor. On the other hand, the lack of attributes such as basicity, complexity, and an amino acidic pedigree can also be found in compounds commonly perceived as alkaloids. Thus, colchicine is neutral, ephedrine is structurally unsophisticated, and the nitrogen atom of the potato alkaloid solanine is not derived from an amino acid, but rather incorporated into as non-amino acidic framework by a transamination reaction. For the sake of clarity and consistency, it seems therefore convenient to adopt the modern definition of alkaloids, and consider capsaicin, as well as alkylamides such as piperine (18) and pellitorine (19), as such. 

Periodate oxidation has been used in the proof of structure of melezi-tose, gentianose, and solanine in all cases, the hexa-aldehydes were oxidized to the acids and hydrolyzed to identifiable fragments. Similar reactions were applied to the octa-aldehyde from the oxidation of stachy-ose. ... 

Steroidal alkaloids, such as solanine and tomatine which are present in many members of the Solanaceae, can form complexes with the cholesterol and other lipids present in biomembranes. Important for this interaction is the presence of a lipophilic portion of the molecule (given by the steroidal moiety) and a hydrophilic portion (provided by the sugar side chain). Whereas the lipophilic moiety "dives" into the lipophilic interior of the membrane and interacts with the structurally similar cholesterol, the hydrophilic side chain remains outside and binds to external sugar receptors. Since phospholipids are in a continuous motion (spinning around their axis and horizontal movements), a tension easily builds up which leads to membrane disruption i.e. transient "holes" form in the biomembrane rendering the cell leaky. Since particular steroidal alkaloids can specifically interact with receptors, ion channels or transmitter... 

Alkaloids which inhibit acetylcholine esterase, monoamine oxidase and catechol-O-methyltransferase are tabulated in Table 11. Potent ACE blocker are indole alkaloids of the physostigmine type (e.g., eseramine, geneserine, physovenine, eserine), protoberberine alkaloids (e.g., berberine, columbamine, coptisine, jatrorrhizine, palmatine), steroidal alkaloids (leptine I, solanine, solamargine, and tomatidine), galanthamine and others. A plausible structure-function relationship is not apparent, except that all these alkaloids have a quaternary N under physiological conditions, and that an oxygen can be traced 2 to 4 carbons adjacent to the N, similar to the situation in acetylcholine. 

Other alkaloids that appear to have effects on ion chanels may, more accurately, be general disrupters of membrane structure. For example alpha-solanine and alpha-chaconine affect ion channels, but are well-established as having general effects on membranes [531, 532]. 

Structures of the steroidal alkaloids whose relative teratogenic potencies are listed in Table 2 and whose embryolethality and teratogenicity is recorded in Table 3 are provided as follows jervine (1), cyclopamine (2), tomatidine (4), and solasodine (6) are listed in the text. Structures for 22/ , 255-solanidine, a-solanine, and ct-chaconine are provided in Fig. (10). In solanidine-N-oxide, the electron pair on the nitrogen atom of solanidine in Fig. (10) is replaced by an oxygen atom. Dihydrosolanidine refers to solanidine with a reduced C-5, C-6 linkage. Dihydrojervine refers to the jervine structure (1) with the C-12, C-13 bond saturated and tetrahydrojervine has both C-5, C-6 and C-12, C-13 linkages saturated. Dihydrosolasodine is shown as structure 6 having C-5, C-6 saturated. 

Figure 1. Molecular structure of solanin, 1, the poisonous compound in green potatoes recently proven to exhibit a SmA phase [63, 64].

An example for such a compound is solanin (1, the structure in Fig. 1) which for many years has been reported to possess two different melting points [631. Only recently was it shown that these two temperatures are the melting and clearing points of a smectic liquid crystal [64]. 

A large plant family may produce several groups of structurally diverse alkaloids. One example is the plant family the Solanaceae. Therefore, if a classification based on a Solanaceae alkaloid is used, solanine, isolated from the bud of potato Solamm tuberosum), the tropane alkaloids, are grouped... 

The steroidal alkaloid solasonine is isolated from the fruit of Solanum aviculare and Solanum sodomeum [3,4]. The sugar moiety of this alkaloid is equivalent to that of a-solanine, whereas the aglycone is different [5]. The aglycone of solasonine is known as solasodine and possesses an oxo-azaspi-rodecane structure. 

Rubijervina 12a-hydroxysolanidine solanid-5-ene-3p,12a-diol, a Veratrum alkaloid of the jervera-trum type. M, 413.65, m. p. 242"C, [ajp -h 19 (ethanol). It occurs in hellebore (Veratrum album, V. nigrum and V. viride) and differs structurally from solanidine (see a-Solanine) by the presence of a 12a-hydroxyl group. Rubisco see Ribulose huphosphate carboxylase. 

Fig. 7.22 The six most frequent glycoalkaloids of the genus Solanum further solanaceous detections solasonine in Cestrum parqui, solanine in Capsicum annuum, tomatine in Lycianthes ran-tonnetii. Dotted lines separate the structures given together with their trivial names above) from related congeners (below)...

The main compounds in the potato tuber are a-solanine (Formula 17.23) and a-chaconine, which differs from the former compound only in the structure of the trisaccharide (substitution of galactose and glucose with glucose and rham-nose). a-Solanine and a-chaconine and their aglycone solanidine have a bitter/buming taste (Table 17.18) and these sensations last long. The taste thresholds have to be determined in the presence of lactic acid due to a lack of water... 

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