[Determination of the solanine content of potato tubers].
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The induction of hepatic ornithine decarboxylase (ODC) activity in rat livers by the potato glycoalkaloids alpha-solanine, alpha-chaconine, and their aglycone solanidine, has been studied. Ip administration of alpha-solanine at 7.5, 15 and 30 mg/kg body weight produced markedly elevated enzyme activity at 4 hr after treatment, with a linear dose response. The increase was four-fold at the lowest dose administered to 12-fold at the highest. ODC activity was measured at 1, 2, 3, 4, 5, 6, 8, and 24hr after alpha-solanine was given. A statistically significant increase in enzyme activity was evident at 3 hr after treatment; maximal activity occurred at 5 hr and was approximately 12 times greater than the dimethylsulphoxide (DMSO) control level. Elevated activities persisted for several hours, decreasing to about one-third of the maximal level at 8 hr. The relative effects of alpha-solanine, alpha-chaconine and solanidine on ODC activities were studied at 4 hr using an equimolar dose of 17 mM/kg body weight. ODC activity induced by alpha-chaconine was higher than that induced by alpha-solanine; the latter activity was two-thirds that of the former. The aglycone solanidine did not induce any increase in activity compared with the DMSO control. ODC activity with dexamethasone, a glucocorticoid, at 4 mg/kg body weight, followed a pattern similar to that of alpha-solanine. However, maximal activity occurred slightly earlier at 4 hr after treatment. The results show that the extent of induced ODC activity depends on the structure of the potato alkaloid.
Eating green potatoes has reportedly led to poisoning attributed to potato glycoalkaloids (PGA), primarily alpha-solanine and alpha-chaconine. Concentrations of PGA increase during the greening of potatoes but are reportedly much higher in potato tops (leaves). As it is known that members of the UK Bangladeshi community consume potato tops, a study of the toxic hazard that may be associated with the consumption of green potato tops has been carried out. PGA in seven potato varieties were determined by HPLC. Tubers protected from light contained 0.05-0.65 mg/100 g alpha-solanine and 0.3-0.63 mg/100 g alpha-chaconine. Concentrations in leaf samples ranged from 0.64 to 22.6 mg alpha-solanine/100 g and 0.06 to 55.7 mg alpha-chaconine/100 g. Aqueous leaf extracts were cytotoxic to Chinese hamster ovary cells and lysed human, rat and hamster blood cells with no difference in sensitivity among species. Oral administration of potato tops to rats, mice and Syrian hamsters had no adverse effects at the highest practicable dose. A mixture of alpha-solanine and alpha-chaconine (1:1, w/w) given orally at doses of up to 50 mg/kg body weight to hamsters had no effect, but a single ip injection of 25 mg/kg body weight or greater was lethal, with bleeding in the gut. High concentrations of cytotoxic PGA were found in some potato tops, but their effect in laboratory animals was minimal. It is concluded that the consumption of moderate quantities of potato tops (2-5 g/kg body weight/day) is unlikely to represent an acute health hazard to humans.
BACKGROUND: Disruption of epithelial barrier integrity is important in the initiation and cause of inflammatory bowel disease (IBD). Glycoalkaloids, solanine (S), and chaconine (C) are naturally present in potatoes, can permeabilize cholesterol-containing membranes, and lead to disruption of epithelial barrier integrity. Frying potatoes concentrates glycoalkaloids. Interestingly, the prevalence of IBD is highest in countries where fried potatoes consumption is highest. OBJECTIVE: To further understand the role of potato glycoalkaloids on intestinal barrier integrity, we examined the effect of varying concentrations of solanine and chaconine on intestinal permeability and function. METHODS: Solanine (0-50 microM), chaconine (0-20 microM), or a 1:1 mixture (0-20 microM) were exposed to T84 cultured epithelial monolayers for varying periods of time to determine concentration response effect on epithelial permeability. Next, a 1:1 mixture (5 microM) of solanine-to-chaconine (C:S) was exposed to sheets of normal murine small intestine, mounted in Ussing chambers, from control and interleukin-10 gene-deficient mice to determine whether glycoalkaloids affected intestine from mice with a genetic predisposition for IBD greater than controls. Finally, the effects of glycoalkaloids on colonic histologic injury were examined in mice orally fed amounts of glycoalkaloids that would normally be consumed in a human diet. RESULTS: Glycoalkaloids embedded and permeabilized the T84 monolayer epithelial membrane bilayer in a concentration-dependent fashion, with C:S > C > S. In vitro Ussing chamber experiments also illustrated a concentration-dependent disruption of intestinal barrier integrity in animals with a genetic predisposition to develop IBD, but not in control animals. Similarly, in vivo oral feeding experiments demonstrated that C:S ingestion, at physiologic concentrations, aggravated histologic colonic injury in mice genetically predisposed to developing IBD. CONCLUSION: Concentrations of glycoalkaloids normally available while eating potatoes can adversely affect the mammalian intestine and can aggravate IBD.
A novel, simple and sensitive high-performance liquid chromatographic method for the determination of the potato glycoalkaloids, alpha-solanine and alpha-chaconine, based on the chemiluminescent reaction of tris(2,2'-bipyridine)ruthenium(III) has been developed. The calibration graph was linear in the range of 5 ng/ml-10 microg/ml for both alpha-solanine and alpha-chaconine. The detection limits of alpha-solanine and alpha-chaconine were 1.2 and 1.3 ng/ml, respectively. This method was successfully applied to a potato tuber sample without cleanup, pre-concentration, and derivatization steps. The recoveries (mean +/- standard deviation, %) of alpha-solanine and alpha-chaconine spiked in tuber pith at 10 microg/g (n = 6) were 101.0 +/- 4.4% and 103.6 +/- 7.1%, respectively.
Steroidal glycoalkaloids (SGAs) are potentially harmful specialty metabolites found in Solanaceous plants. Two tri-glycosylated alkaloids, alpha-chaconine and alpha-solanine accumulate in potato tubers. Expressed sequence tags (ESTs) were identified in the available database by searching for protein homology to the Sgt1 (SOLtu:Sgt1) steriodalalkaloid galactosyltransferase. The EST sequence data was used to isolate Sgt3 cDNA sequences by polymerase chain reaction (PCR) from a wounded potato tuber cDNA library. The resulting 1515bp open reading frame of Sgt3, encodes a predicted SGT3 amino acid sequence that is 18 residues longer than, 45% identical to, and 58% homologous to the SGT1 protein. The amino-terminal region of the Sgt3 cDNA was used to create an antisense transgene under control of the granule bound starch synthase, GBSS6, promoter and the ubiquitin, Ubi3, polyadenylation signal. Analysis of SGA metabolites in selected transgenic tubers revealed a dramatic decrease in the accumulation of alpha-chaconine and alpha-solanine. This decrease was compensated by an increase in beta-solanine and beta-chaconine with minor accumulation of alpha-SGAs. These results allowed the identification of the function for SGT3 as the beta-solanine/beta-chaconine rhamnosyl transferase, the terminal step in formation of the potato glycoalkaloid triose side chains.
alpha-Solanine and alpha-chaconine are two naturally occurring steroidal glycoalkaloids in potatoes (Solanum tuberosum), and solanidine-N-oxide is a corresponding steroidal aglycone. The objective of this research was to screen potential cyto-toxicity of these potato glycoalkaloids using bovine oocyte maturation, in vitro fertilization techniques and subsequent embryonic development as the in vitro model. A randomized complete block design with four in vitro oocyte maturation (IVM) treatments (Experiment 1) and four in vitro embryo culture (IVC) treatments (Experiment 2) was used. In Experiment 1, bovine oocytes (n=2506) were matured in vitro in medium supplemented with 6 microM of alpha-solanine, alpha-chaconine, solanidine-N-oxide or IVM medium only. The in vitro matured oocytes were then subject to routine IVF and IVC procedures. Results indicated that exposure of bovine oocytes to the steroidal glycoalkaloids during in vitro maturation inhibited subsequent pre-implantation embryo development. Potency of the embryo-toxicity varied between these steroidal glycoalkaloids. In Experiment 2, IVM/IVF derived bovine embryos (n=2370) were cultured in vitro in medium supplemented with 6 microM of alpha-solanine, alpha-chaconine, solanidine-N-oxide or IVC medium only. The results showed that the pre-implantation embryo development is inhibited by exposure to these glycoalkaloids. This effect is significant during the later pre-implantation embryo development period as indicated by fewer numbers of expanded and hatched blastocysts produced in the media containing these alkaloids. Therefore, we conclude that in vitro exposure of oocytes and fertilized ova to the steroidal glycoalkaloids from potatoes inhibits pre-implantation embryo development. Furthermore, we suggest that ingestion of Solanum species containing toxic amounts of glycoalkaloids may have negative effects on pre-implantation embryonic survival.
Lysis of human erythrocytes by 20 microM chaconine was reduced by 0.5 mM glucose-6-phosphate (G6P) and NADP. Both compounds caused approximately 50% inhibition of haemolysis at 1 mM. Glucose, glucose-1-phosphate, rhamnose, galactose and galactose-6-phosphate were ineffective; NAD was effective, although not to the extent of NADP. Of the tested sugars, only G6P reduced solanine-induced haemolysis. G6P also reduced the synergistic haemolytic action of solanine and chaconine in combination. G6P and NADP at or above 5 mM antagonised chaconine-induced betanin loss from excised red beet root discs; NADP was more effective than G6P. Disruption of PC/cholesterol liposomes by chaconine and inhibition of acetylcholinesterase by chaconine or solanine, were unaffected by up to 10 mM NADP or 50 mM G6P.
As part of an effort to improve plant-derived foods such as potatoes, eggplants, and tomatoes, the antiproliferative activities against human colon (HT29) and liver (HepG2) cancer cells of a series of structurally related individual compounds were examined using a microculture tetrazolium (MTT) assay. The objective was to assess the roles of the carbohydrate side chain and aglycon part of Solanum glycosides in influencing inhibitory activities of these compounds. Evaluations were carried out with four concentrations each (0.1, 1, 10, and 100 microg/mL) of the the potato trisaccharide glycoalkaloids alpha-chaconine and alpha-solanine; the disaccharides beta(1)-chaconine, beta(2)-chaconine, and beta(2)-solanine; the monosaccharide gamma-chaconine and their common aglycon solanidine; the tetrasaccharide potato glycoalkaloid dehydrocommersonine; the potato aglycon demissidine; the tetrasaccharide tomato glycoalkaloid alpha-tomatine, the trisaccharide beta(1)-tomatine, the disaccharide gamma-tomatine, the monosaccharide delta-tomatine, and their common aglycon tomatidine; the eggplant glycoalkaloids solamargine and solasonine and their common aglycon solasodine; and the nonsteroidal alkaloid jervine. All compounds were active in the assay, with the glycoalkaloids being the most active and the hydrolysis products less so. The effectiveness against the liver cells was greater than against the colon cells. Potencies of alpha-tomatine and alpha-chaconine at a concentration of 1 microg/mL against the liver carcinoma cells were higher than those observed with the anticancer drugs doxorubicin and camptothecin. Because alpha-chaconine, alpha-solanine, and alpha-tomatine also inhibited normal human liver HeLa (Chang) cells, safety considerations should guide the use of these compounds as preventative or therapeutic treatments against carcinomas.
Potatoes (Solanum tuberosum L.) supplemented with increasing amounts of sodium selenate were analyzed for glycoalkaloid (GA) content. GAs were extracted with 5% acetic acid from freeze-dried tubers of two potato cultivars, Satu and Sini, harvested 10 weeks after planting as immature. The GAs alpha-solanine and alpha-chaconine were quantified by reverse-phase high-performance liquid chromatography (RP-HPLC) with diode array detection. Two independent experiments were performed. In the first experiment, the total GA concentration +/- standard error of the tubers ranged between 105 +/- 9 and 124 +/- 10 mg kg(-1) fresh weight in Satu and between 194 +/- 26 and 228 +/- 10 mg kg(-1) fresh weight in Sini. The ratio of alpha-solanine to alpha-chaconine was 0.2 in Satu and 0.5-0.6 in Sini. In the second experiment, the total GA concentration +/- standard error was 75 +/- 4 to 96 +/- 11 mg kg(-1) fresh weight, and the ratio of alpha-solanine to alpha-chaconine was 0.3-0.4 in Satu. A high sodium selenate supplementation (0.9 mg of Se kg(-1) quartz sand) slightly decreased the GA content in Satu, but this decrease was not statistically significant. Furthermore, at this addition level the Se concentration increased to a very high level of 20 microg g(-1) dry weight, which cannot be recommended for human consumption. In both experiments, the Se concentration in tubers increased with increasing sodium selenate application levels. Our results show that acceptable application levels of selenate did not have an effect on the GA concentration in immature potato tubers.
Embryos of two species of fish were evaluated for their suitability as model systems for steroidal alkaloid toxicity, the Japanese rice fish, medaka (Oryzius latipes) and the rainbow trout (Oncorhynchus mykiss). Additionally, the equine neurotoxic sesquiterpene lactone repin, was also tested. A PROBIT program was used to evaluate the EC1, EC50 and EC99 as well as the associated confidence limits. The steroidal alkaloids tested were the Solanum potato glycoalkaloids alpha-chaconine, alpha-solanine, the aglyclones solanidine and solasodine and the Veratrum alkaloid, jervine. Embryo mortality, likely due to structural or functional abnormalities in the early development stages of the embryo, were the only response observed in both species. The rainbow trout exhibited a toxic response to chaconine, solasidine, repin and solanine but the medaka embryos were only affected by the compounds, chaconine and solanine. Rainbow trout may indeed serve as a good lower vertebrate model for studying the toxicity of steroidal alkaloids.
The potential induction of terata by solanidanes has been of public health concern since a report in 1972 hypothesized that certain birth defects in humans could be attributed to ingestion of blighted potatoes. The potential teratogenicity of solanidane alkaloids from potatoes and tomatoes in domestic livestock had been considered even earlier. In the present report, oral administration of the steroidal alkaloid glycosides alpha-solanine and alpha-chaconine and their aglycone solanidine is shown to induce craniofacial malformations (exencephaly, encephalocele, and anophthalmia) in Syrian hamsters. All three alkaloids, that were either isolated or obtained by hydrolysis from Solanum tuberosum (var. Kennebec) sprouts, possessed the 22-(R),25(S)-configuration in the indolizidine moiety with no other isomers present. Toxicity constraints precluded administration of dosages high enough to induce statistically significant levels of terata in litters dosed with alpha-chaconine and permitted the attainment of only marginal statistical significance for alpha-solanine. However, malformation induction at p < 0.005 was observed in litters upon dosing both the nontoxic aglycone solanidine and the derivative solanidine N-oxide at higher levels. The relatively high teratogenicity of nontoxic solanidine, compared to the glycosides, demonstrates that terata induction by solanidanes is not due to maternal toxicity nor is the oligosaccharide portion of steroidal alkaloid glycosides required to facilitate passage of the teratogen to the fetus. The teratogenicity of solanidine N-oxide, a putative metabolite, suggests that N-oxidation is not an effective mammalian detoxification pathway. Relative teratogenic potencies (RTP) were assigned to solanidanes by conversion of literature data to equimolar doses compared to the powerful Veratrum teratogen jervine and the nonteratogenic spirosolane tomatidine. RTP values are as follows: jervine (100), 22(S),-25(R)-solanidanes (50), alpha-chaconine (43), alpha-solanine (32), 22(R),25(S)-solanidine (32), solanidine N-oxide (32), 5 alpha,6-dihydrosolanidine (9), and tomatidine (0).
Selected allelochemicals that protect plants from invasion by plant pathogenic fungi were investigated for their activity against the entomopathogenic fungus, Paecilomyces fumosoroseus. The alkaloids tomatine, solanine, and camptothecin; the furanocoumarin, xanthotoxin; and the phenolic, tannic acid were tested for their effects on germination of conidia and blastospores and growth of mycelia. The LC50 values (corresponding to 50% inhibition of germination) for tomatine, solanine, camptothecin, xanthotoxin and tannic acid were 51.6, 95.9, 55.9, 83.0 and 72.8 mg/l respectively. When blastospores were placed on media containing a concentration of the individual allelochemicals that inhibit germination in approximately 50% of conidia, all but blastospores on tomatine had significantly less germination than did aerial conidia. Growth rates of mycelia were slowest in the camptothecin medium, followed by those of tomatine and xanthotoxin and were not significantly different from controls in the media containing solanine and tannic acid. A multitude of biotic and abiotic factors are responsible for specificity and degree of pathogenicity of entomopathogens. The effect of crop plant chemistry on the efficacy of entomopathogens should be quantified further in order to maximize their potential when used concomitantly with resistant plant varieties.
Allelochemicals play important roles in the plant defense against herbivorous insects. They act as feeding deterrents, interfere with digestion and nutrient absorption, and cause production of potentially dangerous oxidative radicals. This study demonstrates that the distributions of oxidative radicals and of the antioxidant enzymes that eliminate them are compartmentalized in the digestive tract of Spodoptera littoralis larvae. Feeding on diets supplemented with the tannic acid (TA), alpha-solanine, and demissidine, respectively, did not affect the rate of food passage through the digestive tract of larvae but 1.25, 2.5, and 5% TA evoked a strong oxidative response. The amount of the superoxide anion in the foregut tissue and content increased up to 70-fold and the titer of total peroxides in the foregut content about 3-fold. This oxidative stress was associated with enhanced carbonyl content in the foregut tissue proteins, indicative of certain tissue deterioration. Extensive foregut damage was probably prevented by elevated activity of the glutathione S-transferase peroxidase. A complex antioxidant response was elicited in the midgut. The activities of superoxide dismutase and catalase increased significantly in the midgut tissue and content, and the activity of ascorbate peroxidase rose in the midgut tissue. The enzymes apparently eliminated oxidative radicals passing to midgut from the foregut with the food bolus and thereby prevented carbonylation of the midgut proteins. We postulate that the generation of oxidative radicals in the foregut and the induction of antioxidant defense in the midgut are controlled processes and that their compartmentalization is an important functional feature of the digestive tract. The glycoalkaloid alpha-solanine and the aglycone demissidine applied at 0.05 and 0.1% concentrations had no effect on any of the examined parameters.