Review on toxicology and activity of tomato glycoalkaloids in immature tomatoes.

Owing to the lack of selection and limited intelligence in mechanical picking, some immature tomatoes that contain alkaloids are thrown away. Tomatine alkaloids are steroidal alkaloids naturally present in Solanaceae plants, which are distributed in small amounts in immature tomato fruits and decrease as the fruits ripen. Tomato glycoalkaloids are harmful to human health. However, in small quantities, there is some evidence that these compounds might be beneficial, as other non-antioxidant bioactivities. This article considers recent research on the biological effects of tomato glycoalkaloids in immature tomatoes, providing reference value for the potential development of these compounds.

Neurotoxicity of the steroidal alkaloids tomatine and tomatidine is RIP1 kinase- and caspase-independent and involves the eIF2α branch of the endoplasmic reticulum.

Steroidal alkaloids are a class of natural products that occur in several species of the Solanaceae family. In the case of the tomato plant (Lycopersicon esculentum Mill.), tomatine and its aglycone, tomatidine, are the most representative molecules. These steroidal alkaloids have already shown several potentially useful biological activities, from anticancer to anti-inflammatory or antibacterial. In this work, the toxicity of these molecules in neuronal cells, namely in the neuroblastoma cell line SH-SY5Y, was assessed, emphasis being given to the cellular mechanisms underlying the effects observed. The results show that tomatine/tomatidine-induced cell death is caspase- and RIP1 kinase-independent, as cell death is not prevented by the pan-caspase inhibitor Z-VAD.fmk or by RIP1 inhibitor necrostatin-1. Analysis of Ca2+ levels using the fluorescent probe Fura-2/AM indicates that both tomatine and tomatidine have a marked effect upon Ca2+ homeostasis by increasing cytosolic Ca2+, an event that might be associated with their effect upon the endoplasmic reticulum. We show that the toxicity of these molecules require the PERK/eIF2α branch of the unfolded protein response, but not the IRE1α branch. Given the role of the endoplasmic reticulum in proteostasis, the ability of these molecules to inhibit the proteasome was also evaluated. Tomatine was able to inhibit the chymotrypsin-like catalytic core of purified human 20S proteasome, as shown by its ability to prevent degradation of the fluorogenic substrate Suc-Leu-Leu-Val-Tyr-AMC, thus suggesting that interference with proteostasis can be responsible for the toxicity of these steroidal alkaloids. This study is relevant as it sheds a light regarding the toxicity of molecules present in one of the most consumed plants worldwide.

Effects of targeted replacement of the tomatinase gene on the interaction of Septoria lycopersici with tomato plants.

Many plants produce constitutive antifungal molecules belonging to the saponin family of secondary metabolites, which have been implicated in plant defense. Successful pathogens of these plants must presumably have some means of combating the chemical defenses of their hosts. In the oat root pathogen Gaeumannomyces graminis, the saponin-detoxifying enzyme avenacinase has been shown to be essential for pathogenicity. A number of other phytopathogenic fungi also produce saponin-degrading enzymes, although the significance of these for saponin resistance and pathogenicity has not yet been established. The tomato leaf spot pathogen Septoria lycopersici secretes the enzyme tomatinase, which degrades the tomato steroidal glycoalkaloid alpha-tomatine. Here we report the isolation and characterization of tomatinase-deficient mutants of S. lycopersici following targeted gene disruption. Tomatinase-minus mutants were more sensitive to alpha-tomatine than the wild-type strain. They could, however, still grow in the presence of 1 mM alpha-tomatine, suggesting that nondegradative mechanisms of tolerance are also important. There were no obvious effects of loss of tomatinase on macroscopic lesion formation on tomato leaves, but trypan blue staining of infected tissue during the early stages of infection revealed more dying mesophyll cells in leaves that had been inoculated with tomatinase-minus mutants. Expression of a defense-related basic beta-1,3 glucanase gene was also enhanced in these leaves. These differences in plant response may be associated with subtle differences in the growth of the wild-type and mutant strains during infection. Alternatively, tomatinase may be involved in suppression of plant defense mechanisms.

Spirosolane-containing Solanum species and induction of congenital craniofacial malformations.

Comparison by GC analysis of purified alkaloid extracts of Solanum species revealed no measurable free solasodine, other spirosolanes, or any non-spirosolane steroidal alkaloid aglycones in unhydrolyzed total alkaloid fractions of fruit of Solanum elaeagnifolium Cav. (silverleaf nightshade), Solanum sarrachoides (S. villosum Lam.--hairy nightshade), Solanum dulcamara L. (European bittersweet nightshade) or Solanum melongena L. (eggplant). All alkaloidal material was apparently present as glycoside. Conversely, sprouts of Solanum tuberosum L. (potato) contained 67% of its alkaloids as glycosides, which was freed only upon hydrolysis with the remaining 33% present as free solanidine. GC/MS analysis of hydrolysates of purified extracts of the test Solanum species revealed that solasodine was a principal or sole aglycone of the alkaloid glycosides in each of the test species except Solanum tuberosum. In the latter, solanidine was the sole aglycone. Among the test species, exclusive of S. tuberosum, only S. dulcamara contained aglycones other than solasodine. In addition to solasodine, S. dulcamara contained appreciable amounts of an unknown spirosolane, an aglycone provisionally identified as soladulcidine. The induction of congenital craniofacial malformations in hamsters by high oral doses of the four Solanum species that contained mainly solasodine glycosides--S. elaeagnifolium, S. dulcamara, S. sarrachoides and S. melongena was compared to inductions of malformations by Solanum tuberosum, that contained mainly solanidane glycosides. Compared to controls, Solanum elaeagnifolium and Solanum dulcamara fruit both induced a high percentage incidence of deformed litters (20.4 and 16.3, respectively) that was statistically significant (P less than 0.001 level) while percentage incidence of deformed litters induced by Solanum sarrachoides and Solanum melongena fruit (9.5 and 7.6 respectively) were both higher than controls (3.4%), in neither case was the incidence statistically significant (P less than .05). Deformed litter incidence induced by sprouts of Solanum tuberosum was 24.0%, (P less than 0.001).

Toxic effect of the glycoalkaloids solanine and tomatine on cultured neonatal rat heart cells.

The toxic effects of the glycoalkaloids, alpha-solanine and tomatine, were studied in beating heart cell cultures from 1--2-day-old rats. After addition of alpha-solanine (80 microgram/ml) and tomatine (40 microgram/ml) to the culture medium, the cells ceased beating within a few minutes. At a concentration of 40 microgram/ml alpha-solanine and 20 microgram/ml tomatine, both compounds caused a pronounced increase of the contraction frequency, lasting for at least 2h. K-strophantin, a reference heart glycoside, caused arrhythmic beating at 20 microgram/ml and complete cessation of contractions at 160 microgram/ml.

Effect of feeding solanidine, solasodine and tomatidine to non-pregnant and pregnant mice.

The aglycone forms of three steroidal glycoalkaloids-solanidine (derived by hydrolytic removal of the carbohydrate side chain from the potato glycoalkaloids alpha-chaconine and alpha-solanine), solasodine (derived from solasonine in eggplants) and tomatidine (derived from alpha-tomatine in tomatoes)-were evaluated for their effects on liver weight increase (hepatomegaly) in non-pregnant and pregnant mice and on fecundity in pregnant mice fed for 14 days on a diet containing 2.4 mmol/kg of aglycone. In non-pregnant mice, observed ratios of % liver weights to body weights (%LW/BWs) were significantly greater than those of the control values as follows (all values in % vs matched controls+/-S.D.): solanidine, 25.5+/-13.2; solasodine 16.8+/-12.0; and tomatidine, 6.0+/-7.1. The corresponding increases in pregnant mice were: solanidine, 5.3+/-10.7; solasodine, 33.1+/-15.1; tomatidine, 8.4+/-9.1. For pregnant mice (a) body weight gains were less with the algycones than with controls: solanidine, -36.1+/-14.5; solasodine, -17.9+/-14.3; tomatidine, -11.9+/-18.1; (b) litter weights were less than controls: solanidine, -27.0+/-17.1; solasodine, -15.5+/-16.8; tomatidine, no difference; (c) the %LTW/BW ratio was less than that of the controls and was significant only for solasodine, -8.7+/-13.7; and (d) the average weight of the fetuses was less than the controls: solanidine, -11.2+/-15.2; solasodine, -11.4+/-9.4; tomatidine, no difference. Abortion of fetuses occurred in five of 24 pregnant mice on the solanidine and none on the other diets. To obtain evidence for possible mechanisms of the observed in vivo effects, the four glycoalkaloids (alpha-chaconine, alpha-solanine, solasonine and alpha-tomatine) mentioned above and the aglycones solanidine and tomatidine were also evaluated in in vitro assays for estrogenic activity. Only solanidine at 10 microM concentration exhibited an increase in the MCF-7 human breast cancer cell proliferation assay. Generally, the biological effects of solanidine differ from those of the parent potato glycoalkaloids. Possible mechanisms of these effects and the implication of the results for food safety and plant physiology are discussed.

α-Tomatine suppresses invasion and migration of human non-small cell lung cancer NCI-H460 cells through inactivating FAK/PI3K/Akt signaling pathway and reducing binding activity of NF-κB.

α-Tomatine, isolated from Lycopersicon esculentum Linn., is a naturally occurring steroidal glycoalkaloid in immature green tomatoes. Some reports demonstrated that α-tomatine had various anticarcinogenic properties. The purpose of this study is to investigate the anti-metastatic effect of α-tomatine in NCI-H460 human non-small cell lung cancer cells. First, the results showed that α-tomatine significantly suppressed the abilities of the adhesion, invasion, and migration of NCI-H460 cells under non-cytotoxic concentrations. Molecular data also showed α-tomatine could inhibit the activation of focal adhesion kinase (FAK) and phosphatidylinositol 3-kinase (PI3K)/Akt signal involve in the downregulation the enzyme activities, protein and messenger RNA levels of matrix metalloproteinase-7 (MMP-7). Next, α-tomatine also strongly inhibited the degradation of inhibitor of kappaBα (IκBα) and the nuclear levels of nuclear factor kappa B (NF-κB). Also, a dose-dependent inhibition on the binding ability of NF-κB by α-tomatine treatment was further observed. Furthermore, α-tomatine significantly decreased the levels of phospho-Akt and MMP-7 in Akt1-cDNA-transfected cells concomitantly with a marked reduction on cell invasion and migration. Presented results indicated α-tomatine might be further application for treating cancer metastasis.

Evaluation of novel aggregate structures as adjuvants: composition, toxicity studies and humoral responses.

Adjuvants are compounds that, when combined with an antigen, potentiate an immune response in an immunized species. There are numerous pathogens for which there are no protective vaccines and since alum is the only adjuvant licensed for use in humans, there is a clear need for more effective adjuvant preparations. In this study we describe the immunopotentiating properties of three novel molecular aggregate formulations based on tomatine (RAM1), a glycosylamide lipid (RAM2) and a fifth generation dendrimeric polymer (RAM3) respectively. These formulations were evaluated for their ability to augment antigen-specific antibody responses when administered with a soluble protein antigen. All three adjuvants were shown to be nontoxic to mice and elicited antigen-specific antibody responses. Of the three formulations, RAM1 was found to induce the highest titers of antibody; these were substantially higher than those induced by reference control adjuvants. RAM1 elicited antibodies of the IgG1 and IgG2a subclasses indicating, indirectly, that this adjuvant can stimulate Th2 and Th1 type immunity.

Pharmacology and toxicology of chaconine and tomatine.

The pharmacological responses produced by alpha chaconine and tomatine on guinea pig ileum, on the isolated electrically stimulated frog ventricle, and recordings of EEG, ECG, respiration and blood pressure in the rabbit showed no essential differences from those produced by alpha solanine. The LD50 values of chaconine and solanine in the mouse and rabbit are also similar and suggest that compounds other than these are probably responsible for the predominant toxic effects of certain hybrid potatoes in man and animals. The failure of the three glycoalkaloids to produce a significant teratological effect in the chick embryo lends no support to the hypothesis that they may be the teratogens responsible for certain congenital malformations in man.