Solanine in potatoes

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

The amino-type stationary phase was also used in more recent studies by Bushway 9 10. For the separation of a-chaconine and a-solanine in potato extracts, the mobile phase tetrahydro-furan - acetonitrile - water - methanol (50 25 15.5 9.5) was used, resulting in a considerably reduced analysis time when compared to the previously reported methods. For analysis of the alkaloids and their metabolites, the mobile phase ratio was changed to (55 30 10 5)(Fig.10.7). For separation of the lower glycosides from a-chaconine and a-solanine, a carbohydrate analysis column was used in combination with the mobile phase tetrahydrofuran - water - acetonitrile (55 8 37)(Fig.l0.8)10. 

More elegant analytical methods exploit substances biological or biochemical properties. This is simple for acetylcholinesterase-inhibiting pesticides. Acetylcholinesterase is easy to measure, and the enzyme may be bought from suppliers or extracted from flies, earthworms, or vertebrate nervous tissue. The enzyme may be measured with and without addition of the extract containing the insecticide. Some plant materials may contain natural cholinesterase inhibitors (e.g., solanine in potato) that will interfere with this analysis if not removed. 

The increased formation of solanine in potatoes exposed to light is a familiar fact and occurs over a wide range of wavelengths (20). Its glycoside constitution might appear to offer an explanation of the effect, but the most effective radiation appears to lie in the ultraviolet rather than in the photosynthetically efficient ranges. Conner (21) found 171% increase over controls with wavelengths around 300 m i and relatively little with visible radiation. 

The distribution of glycoalkaloids differs in the various parts of plants. a-Solanine and a-chaconine occur in roughly equal amounts. The largest amount of solanine in potato is present in the flowers (5000mg/kg) and germ (1950-4360mg/kg). The highest concentrations in tubers are in the surface layers. Towards the... 

The main objective of this paper is to briefly describe the fate of potato glycoalkaloids a-chaconine and a-solanine in potato tubers and processed potatoes after harvest. 

Solanine (Fig. 11.8) occurs in potatoes, particularly in peel (to 1.5 mm depth), eyes, and repaired tissue, and in small and immature, and light-exposed... 

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 6.2 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.

GL Science, Japan). The mobile phase was acetonitrile/20 mM KH2PO4 (80 20, v/v). For the aglycon solanidine, the mixture consisted of acetonitrile/2.5 mM KH2PO4 (93 7, v/v). The flow rate was 1 mL/min at a column temperature of 20° C. The concentrations of a-chaconine and a-solanine in the potato extracts were calculated by comparison with the integrated peak areas of known amounts of the standards by a Hitachi chromato-integrator. 

Bodart, P, Kabengera, C., Noirfalise, A., Hubert, P, Angenot, L. (2000). Determination of a-solanine and a-chaconine in potatoes by high-performance thin-layer chromatography/densitometry. J. AOAC Int., 83, 1468-1473. 

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. 

Patel, B. C., Salunkhe, D. K., Singh, B. (1971). Metabolism of solanine and chlorophyll in potato tubers as affected by light and specific chemicals. J. Food Sci, 36,474. 

Many human populations have only encountered some mixtures of NPs relatively recently— the first Europeans to encounter chilli peppers, many beans, pineapples, bananas, tobacco and so forth did so only a few hundred years ago. The solanine alkaloids (and other NPs) in potato or tomato were unknown to Asians, Africans and Europeans until very recently, yet these populations seemed untroubled by these novel chemicals. Tomato fruits were initially considered to be poisonous when introduced to Europe and it was only in the nineteenth century that they became widely adopted as a food plant. 

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. 

A variant on the way the cholesterol side-chain is cyclized can be found in solanidine (Figure 6.126), which contains a condensed ring system with nitrogen at the bridgehead. Solanidine is found in potatoes (Solanum tuberosum), typically as the glycoside a-solanine (Figure 6.126). This condensed ring system appears to be produced by a branch from the main pathway to solasodine/... 

Potato alkaloids. The cultivated potato (Solanum tuberosum L.) contains two major glycoalkaloids, a-chaconine and a-solanine. The two components both contain the C i steroidal aglycone solanidine they differ only in the sugar moieties included in the trisaccharide part. a-Solanine and a-chaconine form up to 95% of the glycoalkaloids present in potatoes. Data on occurrence, chemistry, analysis, and toxicology of the steroidal glycoalkaloids present in potatoes have been comprehensively reviewed (77, 75). 

Solanine and chaconine (the main natural alkaloids in potatoes) are cholinesterase inhibitors and were widely introduced into the hviman diet about 400 years ago with the dissemination of the potato from the Andes. They can be detected in the blood of all potato eaters. Total alkaloids are present in potatoes at a level of 15,000 Vig per 200-g potato, which is only about a six-fold safety margin from the toxic level for hximans ( .) Neither alkaloid has been tested for carcinogenicity. By contrast, the pesticide malathion, the main synthetic organophosphate cholinesterase inhibitor present in our diet (17 ug/day), has been thoroughly tested and is not a carcinogen in rodents. Plant breeders have produced an insect-resistant potato however, it had to be withdrawn from the market because of its acute toxicity to hvunans, a consequence of higher levels of solanine and chaconine. 

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