The effect of some Solanum steroidal alkaloids and glycoalkaloids on larvae of the red flour beetle, Tribolium castaneum, and the tobacco hornworm, Manduca sexta

The Potential Functions and Mechanisms of Oat on Cancer Prevention: A Review

Oat is classified as a whole grain and contains high contents of protein, lipids, carbohydrates, vitamins, minerals, and phytochemicals (such as polyphenols, flavonoids, and saponins). In recent years, studies have focused on the effects of oat consumption on reducing the risk of a variety of diseases. Reports have indicated that an oat diet exerts certain biological functions, such as preventing cardiovascular diseases, reducing blood glucose, and promoting intestinal health, along with antiallergy, antioxidation, and cancer preventive effects. At present, cancer is the second leading cause of death worldwide. The natural products of oat are an important breakthrough for developing new strategies of cancer prevention, and their ability to interact with multiple cellular targets helps to combat the complexity of cancer pathogenesis. In addition, the comprehensive study of the cancer prevention activity and potential mechanism of oat nutrients and phytochemicals has become a research hotspot. In this Review, we focused on the potential functions of peptides, dietary fiber, and phytochemicals in oats on cancer prevention and further revealed novel mechanisms and prospects for clinical application. These findings might provide a novel approach to deeply understand the functions and mechanisms for cancer prevention of oat consumption.

Medicinal Plants of Solanum Species: The Promising Sources of Phyto-Insecticidal Compounds

Several medicinal plants have the potential to be a promising alternative pharmacological therapy for a variety of human illnesses. Many insects, including mosquitoes, are important vectors of deadly pathogens and parasites, which in the world's growing human and animal populations can cause serious epidemics and pandemics. Medicinal plants continue to provide a large library of phytochemicals, which can be used to replace chemically synthesized insecticides, and utilization of herbal product-based insecticides is one of the best and safest alternatives for mosquito control. Identifying new effective phyto-derived insecticides is important to counter increasing insect resistance to synthetic compounds and provide a safer environment. Solanum genus (Solanaceae family or nightshades) comprises more than 2500 species, which are widely used as food and traditional medicine. All research publications on insecticidal properties of Solanaceae plants and their phytoconstituents against mosquitoes and other insects published up to July 2020 were systematically analyzed through PubMed/MEDLINE, Scopus, EBSCO, Europe PMC, and Google Scholar databases, with focus on species containing active phytoconstituents that are biodegradable and environmentally safe. The current state of knowledge on larvicidal plants of Solanum species, type of extracts, target insect species, type of effects, name of inhibiting bioactive compounds, and their lethal doses (LC50 and LC90) were reviewed in this study. These studies provide valuable information about the activity of various species of Solanum and their phytochemical diversity, as well as a roadmap for optimizing select compounds for botanical repellents against a variety of vectors that cause debilitating and life-threatening human diseases.

High-Performance Liquid Chromatography-Mass Spectrometry Analysis of Glycoalkaloids from Underexploited Solanum Species and Their Acetylcholinesterase Inhibition Activity

Solanum glycoalkaloids are gaining increased scientific attention due to their bioactive potential in the defense of plants against pests and pathogens. The comprehensive glycoalkaloid profiling from the leaves, stems, and roots of seven underexploited Solanum species (S. caripense, S. melanocerasum, S. muricatum, S. nigrum, S. quitoense, S. retroflexum, and S. sisymbriifolium) was conducted using high-performance liquid chromatography-time-of-flight mass spectrometry. A total of 51 glycoalkaloids were shared among the studied Solanum species, with concentrations ranging from 7 to 5.63 × 105 ng g-1. Based on the glycoalkaloid composition, plants were separated into two clusters, Cluster 1 (S. melanocerasum, S. nigrum, and S. retroflexum) and Cluster 2 (S. caripense, S. muricatum, S. quitoense, and S. sisymbriifolium). The inhibition activity of glycoalkaloid extracts on acetylcholinesterase showed a half-maximal inhibitory concentration (IC50), ranging from 0.4 (S. nigrum stems) to 344.9 µg mL-1 (S. sisymbriifolium leaves), that was not directly correlated to the total glycoalkaloid contents. This suggests that the composition of glycoalkaloids in the plant extract, rather than the total concentration, is a driver of biological activity. The study provides a framework for the bioprospecting of underexploited Solanum species for exploring bioactive glycoalkaloids and other compounds with potential pesticidal activities for the development of green bioformulation. This is the first comprehensive report on the glycoalkaloid profiles of S. retroflexum.

Cascading Effects of Root Microbial Symbiosis on the Development and Metabolome of the Insect Herbivore Manduca sexta L

Root mutualistic microbes can modulate the production of plant secondary metabolites affecting plant-herbivore interactions. Still, the main mechanisms underlying the impact of root mutualists on herbivore performance remain ambiguous. In particular, little is known about how changes in the plant metabolome induced by root mutualists affect the insect metabolome and post-larval development. By using bioassays with tomato plants (Solanum lycopersicum), we analyzed the impact of the arbuscular mycorrhizal fungus Rhizophagus irregularis and the growth-promoting fungus Trichoderma harzianum on the plant interaction with the specialist insect herbivore Manduca sexta. We found that root colonization by the mutualistic microbes impaired insect development, including metamorphosis. By using untargeted metabolomics, we found that root colonization by the mutualistic microbes altered the secondary metabolism of tomato shoots, leading to enhanced levels of steroidal glycoalkaloids. Untargeted metabolomics further revealed that root colonization by the mutualists affected the metabolome of the herbivore, leading to an enhanced accumulation of steroidal glycoalkaloids and altered patterns of fatty acid amides and carnitine-derived metabolites. Our results indicate that the changes in the shoot metabolome triggered by root mutualistic microbes can cascade up altering the metabolome of the insects feeding on the colonized plants, thus affecting the insect development.

Effect of Steroidal Glycoalkaloids on Hatch and Reproduction of the Potato Cyst Nematode Globodera pallida

Steroidal glycoalkaloids (SGAs) are phytoanticipins found in solanaceous crops that act as the first line of chemical defense against pathogen attacks. Solanum sisymbriifolium, a trap crop for potato cyst nematodes, has been shown to effectively reduce populations of Globodera pallida. S. sisymbriifolium contains α-solamargine and other solasodine-type glycoalkaloids that may contribute to plant defenses. This study evaluated the influence of solanaceous SGAs on G. pallida hatch, development, and reproduction. Exposure to α-solamargine and α-solamarine reduced G. pallida hatch by 65 and 87%, respectively. Exposure of G. pallida cysts with the glycoalkaloids α-solamargine and solasodine significantly reduced infection in susceptible potato 'Russet Burbank' by 98 and 94% compared with the control. Exposure of cysts to either solasodine or solamargine significantly reduced reproduction of G. pallida on 'Russet Burbank' by 99% compared with the control. The study demonstrated the deleterious effect of SGAs on G. pallida hatch, infection, and reproduction.

BIOACTIVITY OF EXTRACTS FROM SOLANACEAE AGAINST Zabrotes subfasciatus

The botanical family Solanaceae has many species producing compounds with insecticidal properties, e.g. nicotine and capsaicin, which are used for pest management in agriculture. This fact provides perspectives to identify insecticidal compounds in Brazilian native species of Solanaceae. In this study, we performed a screening with 25 ethanolic extracts from 17 Solanaceae species in order to evaluate their bioactivity against the Mexican bean weevil, Zabrotes subfasciatus(Coleoptera: Chrysomelidae: Bruchinae). The bioactivity of Solanaceae ethanolic extracts (2500 mg kg-1) was tested with residual contact bioassays. Adults ofZ. subfasciatus were exposed to treated bean grains, and adult mortality, oviposition, F1progeny and damages on grains were quantified. Most of the ethanolic extracts from Solanaceae reduced the number of eggs per sample, the egg-adult viability, the F1progeny and the damages on bean grains promoted byZ. subfasciatus, but none of them interfered on its sex ratio. Ethanolic extract from leaves of Solanum lycocarpumA. St.-Hil promoted the most promissory effects on Z. subfasciatus. This ethanolic extracts can be a suitable alternative to control Z. subfasciatus in stored beans, mainly for small farmers and organic farmers. 

An allelic variant of GAME9 determines its binding capacity with the GAME17 promoter in the regulation of steroidal glycoalkaloid biosynthesis in tomato

Steroidal glycoalkaloids (SGAs) are cholesterol-derived molecules found in the family Solanaceae. SGA content varies among different plant species and varieties. However, the genetic mechanisms regulating SGA content remain unclear. Here, we demonstrate that genetic variation in GLYCOALKALOID METABOLISM 9 (GAME9) is responsible for the variation in SGA content in tomato (Solanum lycopersicum). During a sequential analysis we found a 1 bp substitution in the AP2/ERF binding domain of GAME9. The 1 bp substitution in GAME9 was significantly associated with high SGA content and determined the binding capacity of GAME9 with the promoter of GAME17, a core SGA biosynthesis gene. The high-SGA GAME9 allele is mainly present in S. pimpinellifolium and S. lycopersicum var. cerasiforme populations and encodes a protein that can bind the GAME17 promoter. In contrast, the low-SGA GAME9 allele is mainly present in the big-fruited varieties of S. lycopersicum and encodes a protein that shows weak binding to the GAME17 promoter. Our findings provide new insight into the regulation of SGA biosynthesis and the factors that affect the accumulation of SGA in tomato.

Phytotoxicity and cytogenotoxicity of hydroalcoholic extracts from Solanum muricatum Ait. and Solanum betaceum Cav. (Solanaceae) in the plant model Lactuca sativa

Plants are rich in biologically active compounds. They can be explored for the production of bioherbicides. In this context, the present work aimed to evaluate the allelopathic effect of hydroalcoholic extracts from two Solanaceae species: Solanum muricatum Ait. and Solanum betaceum Cav. For this end, we conducted phytochemical screening and biological assays, determining the effects of the extracts on germination, early development, cell cycle, and DNA fragmentation in plantlets and meristematic cells of the plant model Lactuca sativa L. (lettuce). The percentage of seeds germinated under effect of S. muricatum extract did not differ from the control, but plantlet growth was reduced at the highest concentrations. For S. betaceum extract, dose dependence was observed for both germination and plantlet development, with the highest concentrations inhibiting germination. The growth curves revealed the concentrations of 2.06 and 1.93 g/L for S. muricatum and S. betaceum extracts, respectively, as those reducing 50% of root growth (RG). At these concentrations, both extracts presented mitodepressive effect, besides inducing significant increase in the frequency of condensed nuclei, associated to DNA fragmentation and cytoplasmic shrinkage. The frequency of chromosome alterations was not significant. We further discuss the mechanisms of action related to the chemical composition of the extracts, which presented organic acids, reducing sugars, proteins, amino acids, and tannins, besides catechins and flavonoids, only found in the extract of S. betaceum.

Trichome Independent Resistance against Western Flower Thrips in Tomato

Western flower thrips (WFT) are a major pest on many crops, including tomato. Thrips cause yield losses, not only through feeding damage, but also by the transmission of viruses of which the Tomato Spotted Wilt Virus is the most important one. In cultivated tomato, genetic diversity is extremely low, and all commercial lines are susceptible to WFT. Several wild relatives are WFT resistant and these resistances are based on glandular trichome-derived traits. Introgression of these traits in cultivated lines did not lead to WFT resistant commercial varieties so far. In this study, we investigated WFT resistance in cultivated tomato using a F2 population derived from a cross between a WFT susceptible and a WFT resistant cultivated tomato line. We discovered that this WFT resistance is independent of glandular trichome density or trichome-derived volatile profiles and is associated with three QTLs on chromosomes 4, 5 and 10. Foliar metabolic profiles of F3 families with low and high WFT feeding damage were clearly different. We identified α-tomatine and a phenolic compound as potential defensive compounds. Their causality and interaction need further investigation. Because this study is based on cultivated tomato lines, our findings can directly be used in nowadays breeding programs.

Beetles as Model Organisms in Physiological, Biomedical and Environmental Studies - A Review

Model organisms are often used in biological, medical and environmental research. Among insects, Drosophila melanogaster, Galleria mellonella, Apis mellifera, Bombyx mori, Periplaneta americana, and Locusta migratoria are often used. However, new model organisms still appear. In recent years, an increasing number of insect species has been suggested as model organisms in life sciences research due to their worldwide distribution and environmental significance, the possibility of extrapolating research studies to vertebrates and the relatively low cost of rearing. Beetles are the largest insect order, with their representative - Tribolium castaneum - being the first species with a completely sequenced genome, and seem to be emerging as new potential candidates for model organisms in various studies. Apart from T. castaneum, additional species representing various Coleoptera families, such as Nicrophorus vespilloides, Leptinotarsa decemlineata, Coccinella septempunctata, Poecilus cupreus, Tenebrio molitor and many others, have been used. They are increasingly often included in two major research aspects: biomedical and environmental studies. Biomedical studies focus mainly on unraveling mechanisms of basic life processes, such as feeding, neurotransmission or activity of the immune system, as well as on elucidating the mechanism of different diseases (neurodegenerative, cardiovascular, metabolic, or immunological) using beetles as models. Furthermore, pharmacological bioassays for testing novel biologically active substances in beetles have also been developed. It should be emphasized that beetles are a source of compounds with potential antimicrobial and anticancer activity. Environmental-based studies focus mainly on the development and testing of new potential pesticides of both chemical and natural origin. Additionally, beetles are used as food or for their valuable supplements. Different beetle families are also used as bioindicators. Another important research area using beetles as models is behavioral ecology studies, for instance, parental care. In this paper, we review the current knowledge regarding beetles as model organisms and their practical application in various fields of life science.

Sublethal Effects of Solanum nigrum Fruit Extract and Its Pure Glycoalkaloids on the Physiology of Tenebrio molitor (Mealworm)

BACKGROUND

Solanaceae plants produce glycoalkaloids (GAs) that affect various physiological processes of herbivorous insects and they are being tested as potential alternatives for synthetic pesticides. They cause lethal and sublethal effects. Nevertheless, their mode of action remains unclear. Therefore, we examined the effects of Solanum nigrum fruit extracts and pure glycoalkaloids on a model beetle, Tenebrio molitor.

METHODS

Plant extracts or pure alkaloids were added to the food of the larvae for three days. The lipid, glycogen, and protein content in the fat body and the midgut were determined, and the contractility of the heart, hindgut, and oviduct muscles was tested using the video-microscopy technique. Finally, the ultrastructure of the fat body and the midgut was observed using electron microscopy.

RESULTS

No lethal effects were noted. Sublethal changes were observed in the content of biomolecules, malformations of organelles, chromatin condensation, and heart and oviduct contractility. The observed effects differed between the tested glycoalkaloids and the extract.

CONCLUSIONS

Both the extract and pure GAs have a wide range of effects that may result in impaired development, food intake, and reproduction. Some early effects may be used as bioindicators of stress. The effects of the extract and pure alkaloids suggest that the substances produced by the plant may act additively or synergistically.

Insecticidal properties of Solanum nigrum and Armoracia rusticana extracts on reproduction and development of Drosophila melanogaster

Plant-derived substances, because of high biological activity, arouse interest of many scientists. Thus, plant extracts and pure substances are intensively studied on various insects as potential insecticides. In such studies, D. melanogaster is one of the most important model organisms. In our studies, we analysed the contents of two plant extracts and tested the activity of their main components against fruit flies and compared observed effects to effects caused by crude extracts. Then, we assessed the development of the next, unexposed generation. The chemical analysis of extracts revealed the presence of numerous glycoalkaloids and glucosinolates in Solanum nigrum and Armoracia rusticana extracts. These extracts, as well as their main components, revealed lethal and sublethal effects, such as the altered developmental time of various life stages and malformations of imagoes. Interestingly, the results for the extracts and pure main compounds often varied. Some of the results were also observed in the unexposed generation. These results confirm that the tested plants produce a range of substances with potential insecticidal effects. The different effects of extracts and pure main components suggest the presence of minor compounds, which should be tested as insecticides.

Plant-Derived Substances Used Against Beetles-Pests of Stored Crops and Food-and Their Mode of Action: A Review

Plants are sources of numerous active substances that are used to protect crops. Currently, due to the limitations of using synthetic insecticides, plant products have attracted increasing attention as possible pesticides. In this review, we discuss some of the most interesting plant products (for example, Solanaceae, or Asteraceae extracts, Artemisia absinthium or Citrus spp. essential oils, and single compounds like α-chaconine, or α-solanine) that exhibit insecticidal activity against beetles that are pests of stored food products. Next, we describe and discuss the mode of action of these products, including lethal and sublethal effects, such as antifeedant or neurotoxic activity, ultrastructural malformation, and effects on prooxidant/antioxidant balance. Furthermore, the methods of application of plant-derived substances in food storage areas are presented.

Ultrastructural and developmental toxicity of potato and tomato leaf extracts to beet armyworm, Spodoptera exigua (lepidoptera: noctuidae)

Beet Armyworm, Spodoptera exigua is a herbivorous moth and a serious pest of many economically important plants, which are used as food sources. Because of rigorous standards of food quality, usage of synthetic insecticides in crop protection, against pests, is limited. Solanaceae plant extracts may be a relatively cheap source of efficient natural insecticides that can limit usage of synthetic substances. Their biological activity is not fully known. In particular, ultrastructural studies, using transmission electron microscopy, are not usual. In the present article we describe the effects of sublethal concentrations of tomato and potato leaf extracts against S. exigua. Acute lethal effects were not observed. Both extracts exerted similar effects within midgut and fat body cells. Midgut cells were not significantly altered while fat body cells showed prominent swelling of nuclear envelope and endoplasmic reticulum, vacuolization of mitochondria and fusion of fat droplets. These changes were much more intensive within groups exposed to potato than tomato extracts at highest concentration at least. Light microscopy was used to observe and document developmental alterations of S. exigua exposed to potato and tomato leaf extracts. Potato leaf extracts significantly decreased hatching success and caused morphological malformations of imagoes. Among them, malformations of wings were the most prominent. Interestingly, these effects were not observed within populations exposed to tomato extracts at highest concentration at least.

Solanum tuberosum and Lycopersicon esculentum Leaf Extracts and Single Metabolites Affect Development and Reproduction of Drosophila melanogaster

Glycoalkaloids are secondary metabolites commonly found in Solanaceae plants. They have anti-bacterial, anti-fungal and insecticidal activities. In the present study we examine the effects of potato and tomato leaf extracts and their main components, the glycoalkaloids α-solanine, α-chaconine and α-tomatine, on development and reproduction of Drosophila melanogaster wild-type flies at different stages. Parental generation was exposed to five different concentrations of tested substances. The effects were examined also on the next, non-exposed generation. In the first (exposed) generation, addition of each extract reduced the number of organisms reaching the pupal and imaginal stages. Parent insects exposed to extracts and metabolites individually applied showed faster development. However, the effect was weaker in case of single metabolites than in case of exposure to extracts. An increase of developmental rate was also observed in the next, non-exposed generation. The imagoes of both generations exposed to extracts and pure metabolites showed some anomalies in body size and malformations, such as deformed wings and abdomens, smaller black abdominal zone. Our results further support the current idea that Solanaceae can be an impressive source of molecules, which could efficaciously be used in crop protection, as natural extract or in formulation of single pure metabolites in sustainable agriculture.

A Review of Bioinsecticidal Activity of Solanaceae Alkaloids

Only a small percentage of insect species are pests. However, pest species cause significant losses in agricultural and forest crops, and many are vectors of diseases. Currently, many scientists are focused on developing new tools to control insect populations, including secondary plant metabolites, e.g., alkaloids, glycoalkaloids, terpenoids, organic acids and alcohols, which show promise for use in plant protection. These compounds can affect insects at all levels of biological organization, but their action generally disturbs cellular and physiological processes, e.g., by altering redox balance, hormonal regulation, neuronal signalization or reproduction in exposed individuals. Secondary plant metabolites cause toxic effects that can be observed at both lethal and sublethal levels, but the most important effect is repellence. Plants from the Solanaceae family, which contains numerous economically and ecologically important species, produce various substances that affect insects belonging to most orders, particularly herbivorous insects and other pests. Many compounds possess insecticidal properties, but they are also classified as molluscides, acaricides, nematocides, fungicides and bactericides. In this paper, we present data on the sublethal and lethal toxicity caused by pure metabolites and crude extracts obtained from Solanaceae plants. Pure substances as well as water and/or alcohol extracts cause lethal and sublethal effects in insects, which is important from the economical point of view. We discuss the results of our study and their relevance to plant protection and management.

Steroidal Saponins in Oat Bran

Saponins are one type of widespread defense compound in the plant kingdom and have been exploited for the production of lead compounds with diverse pharmacological properties in drug discovery. Oats contain two unique steroidal saponins, avenacoside A, 1, and avenacoside B, 2. However, the chemical composition, the levels of these saponins in commercial oat products, and their health effects are still largely unknown. In this study, we directly purified 5 steroidal saponins (1-5) from a methanol extract of oat bran, characterized their structures by analyzing their MS and NMR spectra, and also tentatively identified 11 steroidal saponins (6-16) on the basis of their tandem mass spectra (MS(n), n = 2-3). Among the five purified saponins, 5 is a new compound and 4 is purified from oats for the first time. Using HPLC-MS techniques, a complete profile of oat steroidal saponins was determined, and the contents of the two primary steroidal saponins, 1 and 2, were quantitated in 15 different commercial oat products. The total levels of these two saponins vary from 49.6 to 443.0 mg/kg, and oat bran or oatmeal has higher levels of these two saponins than cold oat cereal. Furthermore, our results on the inhibitory effects of 1 and 2 against the growth of human colon cancer cells HCT-116 and HT-29 showed that both had weak activity, with 2 being more active than 1.

α-Tomatine inhibits growth and induces apoptosis in HL-60 human myeloid leukemia cells

α-tomatine is a glycoalkaloid that occurs naturally in tomatoes (Lycopersicon esculentum). In the present study, the effects of α-tomatine on human myeloid leukemia HL-60 cells were investigated. Treatment of HL-60 cells with α-tomatine resulted in growth inhibition and apoptosis in a concentration-dependent manner. Tomatidine, the aglycone of tomatine had little effect on the growth and apoptosis of HL-60 cells. Growth inhibition and apoptosis induced by α-tomatine in HL-60 cells was partially abrogated by addition of cholesterol indicating that interactions between α-tomatine and cell membrane-associated cholesterol may be important in mediating the effect of α-tomatine. Activation of nuclear factor-κB by the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate failed to prevent apoptosis in HL-60 cells treated with α-tomatine. In animal experiments, it was found that treatment of mice with α-tomatine inhibited the growth of HL-60 xenografts in vivo. Results from the present study indicated that α-tomatine may have useful anti-leukemia activities.

Development and validation a liquid chromatography mass spectrometry for determination of solasodine in rat plasma and its application to a pharmacokinetic study

Solasodine is a poisonous alkaloid chemical compound that occurs in plants of the Solanaceae family. A simple and selective liquid chromatography mass spectrometry method for determination of solasodine in rat plasma was developed and validated over the range of 3-1,000 ng/mL. Chromatographic separation was achieved on a C18 (2.1 mm×50 mm, 3.5 μm) column with acetonitrile-0.1% formic acid in water as mobile phase with gradient elution. The flow rate was set at 0.4 mL/min. After addition of midazolam as internal standard (IS), liquid-liquid extraction by ethyl acetate was used as sample preparation. An electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring mode was used for quantification with target ions m/z 414 for solasodine and m/z 326 for IS. Mean recoveries of solasodine in rat plasma were in the range of 87.6-94.1%. Matrix effects for solasodine were between 94.9% and 102.3%. Coefficient of variation of intra-day and inter-day precision were both <13%. The accuracy of the method ranged from 94.4% to 105.3%. The method was successfully applied to a pharmacokinetic study of solasodine after oral administration of 20mg/kg in rats.

The influence of dietary α-solanine on the waxmoth Galleria mellonella L

Plant allelochemicals are nonnutritional chemicals that interfere with the biology of herbivores. We posed the hypothesis that ingestion of a glycoalkaloid allelochemical, α-solanine, impairs biological parameters of greater wax moths Galleria mellonella. To test this idea, we reared wax moths on artificial diets with 0.015, 0.15, or 1.5 mg/100 g diet of α-solanine. Addition of α-solanine to the diet affected survival of seventh-instar larvae, pupae, and adults; and female fecundity and fertility. The diet containing the highest α-solanine concentration led to decreased survivorship, fecundity, and fertility. The diets supplemented with α-solanine led to increased malondialdehyde and protein carbonyl contents in midgut and fat body and the effect was dose-dependent. Dietary α-solanine led to increased midgut glutathione S-transferase activity and to decreased fat body glutathione S-transferase activitiy. We infer from these findings that α-solanine influences life history parameters and antioxidative enzyme activities in the midgut and fat body of G. mellonella.

Synergistic cytotoxicity induced by α-solanine and α-chaconine

α-Solanine and α-chaconine are well-known potato toxins, but the mechanism of the synergistic cytotoxic effect of these alkaloids has been little clarified. This study confirmed their synergistic cytotoxic effects on C6 rat glioma cells by three different cell viability tests, namely WST-1 (water-soluble tetrazolium) assay sensitive to intracellular NADH concentration, menadione-catalysed chemiluminescent assay depending on both NAD(P)H concentration and NAD(P)H:quinone reductase activity, and LDH (lactate dehydrogenase) assay sensitive to the release of LDH from damaged cells. The maximum cytotoxic effect was observed at a ratio of 1:1 between α-solanine and α-chaconine at micromolar concentrations. The cytotoxic effects of these alkaloids were observed immediately after incubation and were constant after 30min, suggesting that rapid damage of plasma membrane causes the lethal disorder of metabolism.

Bioactivities of glycoalkaloids and their aglycones from Solanum species

Potatoes, tomatoes, and aubergines are all species of the Solanum genus and contain a vast array of secondary metabolites including calystegine alkaloids, phenolic compounds, lectins, and glycoalkaloids. Glycoalkaloids have been the subject of many literature papers, occur widely in the human diet, and are known to induce toxicity. Therefore, from a food safety perspective further information is required regarding their analysis, toxicity, and bioavailability. This is especially important in crop cultivars derived from wild species to prevent glycoalkaloid-induced toxicity. A comprehensive review of the bioactivity of glycoalkaloids and their aglycones of the Solanum species, particularly focused on comparison of their bioactivities including their anticancer, anticholesterol, antimicrobial, anti-inflammatory, antinociceptive, and antipyretic effects, toxicity, and synergism of action of the principal Solanum glycoalkaloids, correlated to differences of their individual molecular structures is presented.

beta-Glucosidases as detonators of plant chemical defense

Some plant secondary metabolites are classified as phytoanticipins. When plant tissue in which they are present is disrupted, the phytoanticipins are bio-activated by the action of beta-glucosidases. These binary systems--two sets of components that when separated are relatively inert--provide plants with an immediate chemical defense against protruding herbivores and pathogens. This review provides an update on our knowledge of the beta-glucosidases involved in activation of the four major classes of phytoanticipins: cyanogenic glucosides, benzoxazinoid glucosides, avenacosides and glucosinolates. New aspects of the role of specific proteins that either control oligomerization of the beta-glucosidases or modulate their product specificity are discussed in an evolutionary perspective.

Potato glycoalkaloids and metabolites: roles in the plant and in the diet

Potatoes, members of the Solanaceae plant family, serve as major, inexpensive low-fat food sources providing energy (starch), high-quality protein, fiber, and vitamins. Potatoes also produce biologically active secondary metabolites, which may have both adverse and beneficial effects in the diet. These include glycoalkaloids, calystegine alkaloids, protease inhibitors, lectins, phenolic compounds, and chlorophyll. Because glycoalkaloids are reported to be involved in host-plant resistance and to have a variety of adverse as well as beneficial effects in cells, animals, and humans, a need exists to develop a clearer understanding of their roles both in the plant and in the diet. To contribute to this effort, this integrated review presents data on the (a) history of glycoalkaloids; (b) glycoalkaloid content in different parts of the potato plant, in processed potato products, and in wild, transgenic, and organic potatoes; (c) biosynthesis, inheritance, plant molecular biology, and glycoalkaloid-plant phytopathogen relationships; (d) dietary significance with special focus on the chemistry, analysis, and nutritional quality of low-glycoalkaloid potato protein; (e) pharmacology and toxicology of the potato glycoalkaloids comprising alpha-chaconine and alpha-solanine and their hydrolysis products (metabolites); (f) anticarcinogenic and other beneficial effects; and (g) possible dietary consequences of concurrent consumption of glycoalkaloids and other biologically active compounds present in fresh and processed potatoes. An enhanced understanding of the multiple and overlapping aspects of glycoalkaloids in the plant and in the diet will benefit producers and consumers of potatoes.

Membrane disruption and enzyme inhibition by naturally-occurring and modified chacotriose-containing Solanum steroidal glycoalkaloids

Naturally-occurring 3beta-O-chacotriosides of solasodine (solamargine), of its 22S, 25S isomer tomatidenol (beta-solamarine), and of solanidine (chaconine), as well as ring E- and F-modified derivatives of solamargine were prepared and assayed in order to assess the relevance of aglycone structural features to membrane-disruption and enzyme-inhibitory activities of the related glycoalkaloids. A ring E-opened dihydro-derivative of solasodine (the chacotrioside of dihydrosolasodine A) did not bind to cholesterol, stigmasterol or ergosterol in vitro, disrupt PC/cholesterol liposomes or mammalian erythrocytes. or inhibit acetylcholinesterase in vitro. It did not synergise with the solatrioside of dihydrosolasodine A or solasonine (nor did solamargine with dihydrosolasodine A solatrioside) in haemolysis tests. The ring F modified derivative, N-nitrososolamargine, did not inhibit acetylcholinesterase in vitro, but lysed liposomes at > or = 150 microM and pH 7. Increasing the pH to 8 (but not 9) further enhanced disruption. The combination of N-nitrososolamargine and solasonine did not cause any disruption of liposomes. Beta-solamarine showed no anti-acetylcholinesterase activity in vitro at up to 100 microM, but disrupted liposomes at 75 and 150 microM, although not to the extent caused by solamargine or chaconine. In combination with both the (inactive) solatriosides, solasonine and solanine, 75 microM beta-solamarine produced synergistic effects, with liposome disruption greater than 150 microM beta-solamarine alone. Beta-solamarine, solamargine and chaconine showed similar haemolytic activity. Beta-solamarine synergised with the solatriosides solasonine and solanine in disrupting erythrocytes. Preliminary structure-activity relationships were evaluated for the active chacotriosides in an attempt to define the scope and limitations of this model study.

Anticancer activity evaluation of the solanum glycoalkaloid solamargine. Triggering apoptosis in human hepatoma cells

Solamargine, an herbal and molluscicidal medicine derived from Solanum incanum, is a steroidal alkaloid glycoside. To characterize the anticancer mechanism of solamargine on human hepatoma cells (Hep3B), changes of cell morphology, DNA content, and gene expression of cells after solamargine treatment were studied. The appearance in solamargine-treated cells of chromatin condensation, DNA fragmentation, and a sub-G(1) peak in a DNA histogram suggests that solamargine induces cell death by apoptosis. The maximum number of dead Hep3B cells was detected within 2 hr of incubation with constant concentrations of solamargine, and no further cell death was observed after an extended incubation with solamargine, indicating that the action of solamargine was irreversible. To determine the susceptibility of cell phases to solamargine-mediated apoptosis, Hep3B cells were synchronized at defined cell cycles by cyclosporin A, colchicine, and genistein, followed by solamargine treatment. The IC(50) values of solamargine for control, G(0)/G(1)-, M-, and G(2)/M-synchronized Hep3B cells were 5.0, > 10, 3.7, and 3.1 microg/mL, implying that cells in the G(2)/M phases are relatively susceptible to solamargine-mediated apoptosis. In addition, a parallel up-regulation of tumor necrosis factor receptor (TNFR)-I and -II on Hep3B cells was detected after solamargine treatment, and the solamargine-mediated cytotoxicity could be neutralized with either TNFR-I or -II specific antibody. Therefore, these results reveal that the actions of TNFR-I and -II on Hep3B cells may be independent, and both are involved in the mechanism of solamargine-mediated apoptosis.

Stagonospora avenae secretes multiple enzymes that hydrolyze oat leaf saponins

The phytopathogenic fungus Stagonospora avenae is able to infect oat leaves despite the presence of avenacoside saponins in the leaf tissue. In response to pathogen attack, avenacosides are converted into 26-desglucoavenacosides (26-DGAs), which possess antifungal activity. These molecules are comprised of a steroidal backbone linked to a branched sugar chain consisting of one alpha-L-rhamnose and two (avenacoside A) or three (avenacoside B) beta-D-glucose residues. Isolates of the fungus that are pathogenic to oats are capable of sequential hydrolysis of the sugar residues from the 26-DGAs. Degradation is initiated by removal of the L-rhamnose, which abolishes antifungal activity. The D-glucose residues are then hydrolyzed by beta-glucosidase activity. A comprehensive analysis of saponin-hydrolyzing activities was undertaken, and it was established that S. avenae isolate WAC1293 secretes three enzymes, one alpha-rhamnosidase and two beta-glucosidases, that carry out this hydrolysis. The major beta-glucosidase was purified and the gene encoding the enzyme cloned. The protein is similar to saponin-hydrolyzing enzymes produced by three other phytopathogenic fungi, Gaeumannomyces graminis, Septoria lycopersici, and Botrytis cinerea, and is a family 3 beta-glucosidase. The gene encoding the beta-glucosidase is expressed during infection of oat leaves but is not essential for pathogenicity.