Potatoes, solanine

Solanine Toxic bitter chemical produced by green potatoes, eggplants, tomatoes, and peppers as a natural defense mechanism. Exposure to grocery store light causes the potato solanine levels to increase. 

Many studies have reported a link between consumption of sunburned potatoes, ie, those exposed to the sun and having an accumulation of chlorophyll and solanine under the skin, with incidences of teratogenic effects and even death (59—61). Because sunburned potatoes in the commercial marketplace are relatively rare, and because the long-term effects of consumption of potatoes at the maximum estabUshed limits of solanine concentration are uncertain, there is equal uncertainty of the tme incidence of human toxicity (62). 

Among the well-known Solanum species that have been chemically examined are S. nigrum, S. tuberosum (potato) and S. lycopersicum (tomato). From these and other species an alkaloidal glucoside, which was first prepared by Desfosses, has been obtained. This substance has been named solan ine, but it is not certain that all the plants recorded as containing solanine contain the same solanine or that the alkaloid has been obtained in a pure state in each case. 

Firbas stated that at least two of these alkaloidal glucosides occur in young potato shoots, solanine and solaneine, and that these may be accompanied by solanidine, a basic decomposition product of solanine. Solaneine was later shown to be a mixture of solanine and solanidine. 

The name solanine should be sufficient to indicate that the substance referred to is the glucosidal alkaloid first isolated from potatoes. The use of such forms as T-solanine, solanine-t and solanine tuberosum is confusing, as is also the proposed substitution of solatubine for solanine. 

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. 

Air, water, soil, and food are all unavoidable components of the human environment. Each of those elements influences the quality of human life, and each of them may be contaminated. Food is not only the elementary source of nutrients, but may also contain natural chemical substances with toxic properties, e.g., cyanogenic glycosides (many plants), solanine (green parts of potatoes, sprouted potatoes, and potatoes stored in light), industrial pollutants (heavy metals), biogenic amines (fish), or mycotoxins (moldy foodstuffs). 

Lift and leave exposed to dry for a few hours. Store in thick paper sacks, tied or folded loosely at the neck. Potatoes must be stored in the dark to prevent them from turning green and developing high levels of solanine, a toxic alkaloid. Frost protection is essential. Ideal storage temperature is 41-50°F (5-10°C). 

Weltring KM et al (1997) Metabohsm of potato saponins a-solanine and a-chaconine by Gibberella pulicaris. Phytochemistry 46 1005... 

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

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... 

The levels of antifeedants can be raised safely only in plants such as forest trees or fiber crops, not in food plants for humans or livestock. Such problems have arisen inadvertently. For instance, a new insect-resistant potato cultivarhad to be withdrawn from the market because it contained high levels of the carcinogens solanine and chaconine (Renwick etal, 1984). In another example, an insect-resistant celery had 10 times the usual concentration of the carcinogen 8-methoxypsoralen (and related psoralens), which caused dermatitis in produce handlers (Seligman etal, 1987). 

Alkaloids are active bioagents in animal tissues. There is clear scientific evidence of this. Crawford and Kocan" " have tested the toxicity of steroidal alkaloids from the potato Solanum tuberosum), such as a-chaconine, a-solanine, solanidine and solasodine, and Veratrum alkaloid, jervine on fish. The results of Crawford and Kocan s research proved that rainbow trout exhibited a toxic response to chaconine, solasidine and solanine, while medaka only did so to chaconine and solanine. Embryo mortality was observed as an effect of toxicity in both species. Many other alkaloids are known to disturb or cause disorder in animal reproductive systems. For example, gossypol from cotton-seed oil is known as a clear reducer of spermatogenesis and premature abortion of the embryo. 

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.

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. 

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). 

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. 

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. 

Kozukue, N., Tsuchida, H., Friedman, M. (2001). Tracer studies on the incorporation of [2-14C]-DL-mevalonate into chlorophylls a and b, a-chaconine, and a-solanine of potato sprouts. J. Agric. Food Chem., 49, 92-91. 

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. 

---