Glycoalkaloid solanine

Symptoms caused by the glycoalkaloid solanine and its aglycone, solanidine, follow the eating of 4-5 berries. The first symptom is a harsh feeling in the mouth and throat. Then comes vomiting and diarrhoea, spasms and fever. After more severe intoxication, which is very rare, there will be blood in the faeces and urine, paralysis and unconsciousness and respiratory paralysis. 

The two most widely distributed glycoalkaloids, solanine and solason-ine, as well as the less-known solauricine and the alkaloid from Solanum panduraeforme Drege contain as sugar component a trisaccharide, L-rhamnosido-D-galactosido-D-glucose (I), for which the name solanose has been proposed (11, 12, 13, 14, 38, 60, 62). 

Significant toxicity data exist for isolated constituents of a wide variety of commonly available foods, as well as herbs. Potatoes, as a member of the Solanaceae family, contain trace amounts of the toxic glycoalkaloid solanine, especially in green parts of the potato tuber (Turner and Szczawinski 1991). Although the symptoms of solanine poisoning are serious, potatoes themselves are generally considered to be a safe food. While consumption of... 

The fruit of a number of solanaceous plants, including tomato Lycopersicon esculentum), potato Solanum tuberosum) and eggplant Solarium melongena esculentum), have cholinesterase-inhibiting effects (Krasowski et al. 1997). They contain solanaceous glycoalkaloids o-solanine and o-chaconine, which are triglycosides of solanidine, a steroidal alkaloid derived from cholesterol. They are the only plant chemicals known to inhibit both acetlycholinesterase and butyrylcholinesterase, both in vitro and in vivo. 

Glycosides of compounds with a triterpenoid origin include saponins, cardiac glycosides, and glycoalkaloids such as solanine (in potatoes). 

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).

Figure 6.2 A comparison of HPLC separation methods, (a) HPLC of a-chaconine and a-solanine in the flesh and the peel of one variety of potato. Conditions column, Inertsil NH2 (5 xm, 4.0 X 250 mm) mobile phase, acetonitile/20 mM KH2PO4 (80 20, v/v) flow rate, I.OmL/min column temperature, 20°C UV detector, 208 nm sample size, 20 (xL. (b) HPLC chromatogram of approximately 1 xg of each of potato glycoalkaloids and their hydrolysis products 1, solasonine (internal standard) 2, a-solanine 3, a-chaconine 4, P2-solanine 5, pi-chaconine 6, (32-chaconine 7, y-solanine 8, y-chaconine. Conditions column. Resolve Cl 8 (5 (xm, 3.9 x 300 mm) mobile phase, 35% acetonitrile/100 mM ammonium phosphate (monobasic) at pH 3 flowrate, I.OmL/min column temperature, ambient UV detector, 200 nm sample size, (c) HPLC chromatogram of the aglycones solanidine and solasodine. Conditions column Supelcosil C18-DB (3 (xm, 4.6x150 mm) mobile phase, 60% acetonitrile/10 mM ammonium phosphate pH 2.5 flowrate, 1.0 mL/min column temperature, ambient UV detector, 200 nm.

The two potato glycoalkaloids in the potato extract were identified as follows (a) comparison of thin-layer chromatography of standards a-chaconine and a-solanine and of samples of each peak collected from the HPLC column containing the individual glycoalkaloids and (b) HCl hydrolysis of the HPLC samples into sugars and the aglycon solanidine. These were identified by GLC-MS (Kozukue et al., 1999, 2008 Kozukue and Friedman, 2003). 

Carman, A. S. Jr, Kuan, S. S, Ware, G. M.,Francis, O. J. Jr., Kirschenheuter, G. R. (1986). Rapid high-performance liquid chromatographic determination of the potato glycoalkaloids a-solanine and a-chaconine. J. Agric. Food Chem., 34, 279-282. 

Friedman, M., McDonald, G. M., Haddon, W. F. (1993). Kinetics of acid-catalyzed hydrolysis of carbohydrate groups of potato glycoalkaloids a-chaconine and a-solanine. J. Agric. Food Chem., 41, 1397-1406. 

Smith, D. B., Roddick, J. G., Jones, J. L. (2001). Synergism between the potato glycoalkaloids a-chaconine and a-solanine in inhibition of snail feeding. Phytochemistry, 57,229-234. 

Figure 14.3 Potato glycoalkaloids. (a) is tomatine, a spirosolane and (b) solanine, a solanidane.

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]. 

Several glycoalkaloids present in food are of toxicological interest. Solaninc. found in potatoes, tomatoes, apples, eggplant, and sugar beets, has been responsible lor several cases uf moderate to severe poisoning. Solanine is a cholinesterase inhibitor and toxic doses are probably ca 200 mg. Market potatoes contain about 1-5 mg of solanine per 10(1 g fresh weight, The USDA establishes solanine levels of 20 mg/100 g as the limit for safe consumption. 

Solanine is a glycoalkaloid that contains three sugar molecules. In animal models, solanine acts as a cardiac glycoside and inhibits cholinesterase activity. 

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