Molecular basis of glycoalkaloid induced membrane disruption

Bioactive solanidane steroidal alkaloids from Solanum lyratum

Six previously unreported solanidane steroidal alkaloids, namely lyrasolanosides A-F, were isolated from Solanum lyratum. In addition, five known steroidal alkaloids were also identified. The structures of these compounds were determined through the use of NMR, HRESIMS,UV, IR and ECD analysis. To assess their bioactivities, the cytotoxic effects of the six previously unreported compounds were evaluated on A549 cells. The results revealed that lyrasolanoside B (2) exhibited the highest potency among them. Lyrasolanoside B (2) exhibited significant inhibition of cell migration, invasion, and adhesion dramatically. Mechanistically, it was found to suppress the activity of JAK2/STAT3 signaling pathway by downregulating the expression of phosphorylated JAK2/STAT3 in an exosome-dependent manner. In addition, lyrasolanoside B (2) was found to significantly upregulate the expression of E-cadherin and downregulate the expression of N-cadherin and vimentin. These findings indicate that lyrasolanoside B (2) inhibits the metastasis of A549 cells by suppressing exosome-mediated EMT. These findings suggest that lyrasolanoside B (2) may inhibit the metastasis of lung cancer by regulating A549-derived exosomes.

Structural Impact of Steroidal Glycoalkaloids: Barrier Integrity, Permeability, Metabolism, and Uptake in Intestinal Cells

SCOPE

Potato tubers represent an essential food component all over the world and an important supplier of carbohydrates, fiber, and valuable proteins. However, besides their health promoting effects, potatoes contain α-solanine and α-chaconine, which are toxic steroidal glycoalkaloids (SGAs). Other solanaceous plants like eggplants and tomatoes produce SGAs as well, different in their chemical structure. This study aims to investigate toxic effects (cholinesterase inhibition, membrane, and barrier disruption), permeability, metabolism, and structure-activity relationships of SGAs.

METHODS AND RESULTS

α-solanine, α-chaconine, α-solasonine, α-solamargine, α-tomatine, and their respective aglycones solanidine, solasodine, and tomatidine are analyzed using Ellman assay, cellular impedance spectroscopy, cell extraction, and Caco-2 intestinal model. Additionally, metabolism is analyzed by HPLC-MS techniques. The study observes dependencies of barrier disrupting potential and cellular uptake on the carbohydrate moiety of SGAs, while permeability and acetylcholinesterase (AChE) inhibition are dominated by the steroid backbone. SGAs show low permeabilities across Caco-2 monolayers in subtoxic concentrations. In contrast, their respective aglycones reveal higher permeabilities, but are extensively metabolized.

CONCLUSION

Besides structure-activity relationships, this study provides new information on the overall effects of steroidal alkaloids on intestinal cells and closes a gap of knowledge for the metabolic pathway from oral uptake to final excretion.

Green Hydrogels Loaded with Extracts from Solanaceae for the Controlled Disinfection of Agricultural Soils

The UN 2030 Agenda for Sustainable Development established the goal of cutting the use of pesticides in the EU by 50% by 2030. However, a ban on pesticides could seriously affect the productivity of agriculture, resulting in severe issues due to global hunger and food deficiency. Controlled release (CR) of bioactive chemicals could play a valid alternative in this context. To this aim, two biodegradable polymers, namely sodium alginate (AL) and sodium carboxymethylcellulose (CMC), were employed to obtain crosslinked hydrogel beads for the encapsulation and CR of glycoalkaloids extracted from tomato and potato leaves to be used as biocompatible disinfectants for agricultural soils. The physico-chemical characterization of the controlled-release systems was carried out by means of Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, Scanning Electron Microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC) (FWI > 80%) and drying kinetics. The plant extracts and the encapsulation efficiency (~84%) were, respectively, characterized and evaluated by High-performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). Finally, preliminary microbiological tests were conducted to test the efficacy of the most promising systems as biocidal formulations both in the lab and on a model soil, and interesting results were obtained in the reduction of bacterial and fungal load, which could lead to sustainable perspectives in the field.

Tetraose steroidal glycoalkaloids from potato provide resistance against Alternaria solani and Colorado potato beetle

Plants with innate disease and pest resistance can contribute to more sustainable agriculture. Natural defence compounds produced by plants have the potential to provide a general protective effect against pathogens and pests, but they are not a primary target in resistance breeding. Here, we identified a wild relative of potato, Solanum commersonii, that provides us with unique insight in the role of glycoalkaloids in plant immunity. We cloned two atypical resistance genes that provide resistance to Alternaria solani and Colorado potato beetle through the production of tetraose steroidal glycoalkaloids (SGA). Moreover, we provide in vitro evidence to show that these compounds have potential against a range of different (potato pathogenic) fungi. This research links structural variation in SGAs to resistance against potato diseases and pests. Further research on the biosynthesis of plant defence compounds in different tissues, their toxicity, and the mechanisms for detoxification, can aid the effective use of such compounds to improve sustainability of our food production.

Anti-fungal bioactive terpenoids in the bioenergy crop switchgrass (Panicum virgatum) may contribute to ecotype-specific microbiome composition

Plant derived bioactive small molecules have attracted attention of scientists across fundamental and applied scientific disciplines. We seek to understand the influence of these phytochemicals on rhizosphere and root-associated fungi. We hypothesize that - consistent with accumulating evidence that switchgrass genotype impacts microbiome assembly - differential terpenoid accumulation contributes to switchgrass ecotype-specific microbiome composition. An initial in vitro Petri plate-based disc diffusion screen of 18 switchgrass root derived fungal isolates revealed differential responses to upland- and lowland-isolated metabolites. To identify specific fungal growth-modulating metabolites, we tested fractions from root extracts on three ecologically important fungal isolates - Linnemania elongata, Trichoderma sp. and Fusarium sp. Saponins and diterpenoids were identified as the most prominent antifungal metabolites. Finally, analysis of liquid chromatography-purified terpenoids revealed fungal inhibition structure - activity relationships (SAR). Saponin antifungal activity was primarily determined by the number of sugar moieties - saponins glycosylated at a single core position were inhibitory whereas saponins glycosylated at two core positions were inactive. Saponin core hydroxylation and acetylation were also associated with reduced activity. Diterpenoid activity required the presence of an intact furan ring for strong fungal growth inhibition. These results inform future breeding and biotechnology strategies for crop protection with reduced pesticide application.

Assessment of drug permeability through an ex vivo porcine round window membrane model

Delivery of pharmaceutical therapeutics to the inner ear to treat and prevent hearing loss is challenging. Systemic delivery is not effective as only a small fraction of the therapeutic agent reaches the inner ear. Invasive surgeries to inject through the round window membrane (RWM) or cochleostomy may cause damage to the inner ear. An alternative approach is to administer drugs into the middle ear using an intratympanic injection, with the drugs primarily passing through the RWM to the inner ear. However, the RWM is a barrier, only permeable to a small number of molecules. To study and enhance the RWM permeability, we developed an ex vivo porcine RWM model, similar in structure and thickness to the human RWM. The model is viable for days, and drug passage can be measured at multiple time points. This model provides a straightforward approach to developing effective and non-invasive delivery methods to the inner ear.

Intestinal Metabolism of Selected Steroidal Glycoalkaloids in the Pig Cecum Model

Due to the presence of the steroidal glycoalkaloid solanine, the potato was chosen as Germany's poisonous plant of the year 2022. Steroidal glycoalkaloids are secondary plant metabolites which have been reported to induce toxic as well as beneficial health effects. Nevertheless, data regarding occurrence, toxicokinetics, and metabolism of steroidal glycoalkaloids is scarce, and substantially more research is required for a proper risk assessment. Therefore, the intestinal metabolism of solanine, chaconine, solasonine, solamargine, and tomatine was investigated using the ex vivo pig cecum model. All steroidal glycoalkaloids were degraded by the porcine intestinal microbiota, releasing the respective aglycon. Furthermore, the hydrolysis rate was strongly dependent on the linked carbohydrate side chain. Solanine and solasonine, which are linked to a solatriose, were metabolized significantly faster than the chaconine and solamargin, which are linked to a chacotriose. In addition, stepwise cleavage of the carbohydrate side chain and the formation of β- and γ-intermediates were detected by HPLC-HRMS. The results provide valuable insights into the intestinal metabolism of selected steroidal glycoalkaloids and help to reduce uncertainties and improve risk assessment.

Nightshade Vegetables: A Dietary Trigger for Worsening Inflammatory Bowel Disease and Irritable Bowel Syndrome?

The Solanaceae family of plants, commonly known as Nightshade vegetables or Nightshades, contains a diverse range of crops of over 2000 members with significant culinary, economic, and cultural importance. Familiar edible Nightshades include tomatoes, peppers, eggplants, and white potatoes. Many pharmacologically active compounds used in traditional medicine, including atropine and hyoscyamine, are derived from Nightshades. In addition to these beneficial pharmacologic agents, Nightshade-derived glycoalkaloid compounds, a key defense mechanism against predation, have been shown to disrupt intestinal epithelium and to potentially activate mast cells in the gut mucosa, leading to adverse symptoms in humans. There is a new appreciation that mast cell activation is an allergic inflammatory mechanism contributing both to pain in irritable bowel syndrome (IBS) and to gut inflammation in inflammatory bowel disease (IBD). Given their ubiquity in Western diets and their shared glycoalkaloid active compounds, edible Nightshades are attracting new interest as a potential trigger for worsening gut symptoms in functional and inflammatory gastrointestinal disorders. Here, we review the limited existing literature on the adverse effects of Nightshade consumption, including the effects of Nightshade-derived glycoalkaloids on IBD gut inflammation, and the under-recognized contribution of Nightshades to food allergies and allergic cross-reactivity. We then highlight new evidence on the contributions of mast cell activation to GI disorder pathogenesis, including potential linkages between Nightshade antigens, intestinal mast cells, and GI dysfunction in IBS and IBD.

Atomic force microscopy study of the complexation of sterols and the glycoalkaloid α-tomatine in Langmuir-Blodgett monolayers

Glycoalkaloids are secondary metabolites produced by plants that aid in their protection from pathogens and pests. They are known to form 1:1 complexes with 3β-hydroxysterols such as cholesterol causing membrane disruption. So far, the visual evidence showcasing the complexes formed between glycoalkaloids and sterols in monolayers has been mainly restricted to some earlier studies using Brewster angle microscopy which were of low resolution showing the formation of floating aggregates of these complexes. This study is aimed at using atomic force microscopy (AFM) for topographic and morphological analysis of the aggregates of these sterol-glycoalkaloid complexes. Langmuir-Blodgett (LB) transfer of mixed monolayers of the glycoalkaloid α-tomatine, sterols, and lipids in varying molar ratios onto mica followed by AFM examination was performed. The AFM method allowed visualization of the aggregation of sterol-glycoalkaloid complexes at nanometer resolution. While aggregation was observed in mixed monolayers of α-tomatine with cholesterol and in mixed monolayers with coprostanol, no sign of complexation was observed for the mixed monolayers of epicholesterol and α-tomatine, confirming their lack of interaction found in prior monolayer studies. Aggregates were observed in transferred monolayers of ternary mixtures of α-tomatine with cholesterol and the phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or egg sphingomyelin (egg SM). The formation of aggregates was found to be less prevalent for mixed monolayers of DMPC and cholesterol containing α-tomatine than it was for mixed monolayers containing egg SM and cholesterol with α-tomatine. The observed aggregates were generally elongated structures, of a width ranging from about 40-70 nm.

Specialized metabolites as versatile tools in shaping plant-microbe associations

Plants are rich repository of a large number of chemical compounds collectively referred to as specialized metabolites. These compounds are of importance for adaptive processes including responses against changing abiotic conditions and interactions with various co-existing organisms. One of the strikingly affirmed functions of these specialized metabolites is their involvement in plants' life-long interactions with complex multi-kingdom microbiomes including both beneficial and harmful microorganisms. Recent developments in genomic and molecular biology tools not only help to generate well-curated information about regulatory and structural components of biosynthetic pathways of plant specialized metabolites but also to create and screen mutant lines defective in their synthesis. In this review, we have comprehensively surveyed the function of these specialized metabolites and discussed recent research findings demonstrating the responses of various microbes on tested mutant lines having defective biosynthesis of particular metabolites. In addition, we attempt to provide key clues about the impact of these metabolites on the assembly of the plant microbiome by summarizing the major findings of recent comparative metagenomic analyses of available mutant lines under customized and natural microbial niches. Subsequently, we delineate benchmark initiatives that aim to engineer or manipulate the biosynthetic pathways to produce specialized metabolites in heterologous systems but also to diversify their immune function. While denoting the function of these metabolites, we also discuss the critical bottlenecks associated with understanding and exploiting their function in improving plant adaptation to the environment.

Solanaceae glycoalkaloids: α-solanine and α-chaconine modify the cardioinhibitory activity of verapamil

CONTEXT

Solanaceae glycoalkaloids (SGAs) possess cardiomodulatory activity.

OBJECTIVE

This study investigated the potential interaction between verapamil and glycoalkaloids.

MATERIAL AND METHODS

The cardioactivity of verapamil and glycoalkaloids (α-solanine and α-chaconine) was tested in adult beetle (Tenebrio molitor) myocardium in vitro using microdensitometric methods. The myocardium was treated with pure substances and mixtures of verapamil and glycoalkaloids for 9 min with saline as a control. Two experimental variants were used: simultaneous application of verapamil and glycoalkaloids or preincubation of the myocardium with one of the compounds followed by perfusion with a verapamil solution. We used 9 × 10^-6-5 × 10^-5 M and 10^-9-10^-5 M concentration for verapamil and glycoalkaloids, respectively.

RESULTS

Verapamil, α-solanine and α-chaconine showed cardioinhibitory activity with IC₅₀ values equal to 1.69 × 10^-5, 1.88 × 10^-7 and 7.48 × 10^-7 M, respectively. When the glycoalkaloids were applied simultaneously with verapamil, an antagonistic effect was observed with a decrease in the maximal inhibitory effect and prolongation of t₅₀ and the recovery time characteristic of verapamil. We also confirmed the expression of two transcript forms of the gene that encodes the α1 subunit of L-type calcium channels in the myocardium and brain with equal transcription levels of both forms in the myocardium and significant domination of the shorter form in the brain of the insect species tested.

DISCUSSION AND CONCLUSIONS

The results show that attention to the composition of the daily diet during therapy with various drugs is particularly important. In subsequent studies, the nature of interaction between verapamil and SGAs on the molecular level should be checked, and whether this interaction decreases the efficiency of cardiovascular therapy with verapamil in humans.

Cytostatic effects of structurally different ginsenosides on yeast cells with altered sterol biosynthesis and transport

Triterpene glycosides are a diverse group of plant secondary metabolites, consisting of a sterol-like aglycon and one or several sugar groups. A number of triterpene glycosides show membranolytic activity, and, therefore, are considered to be promising antimicrobial drugs. However, the interrelation between their structure, biological activities, and target membrane lipid composition remains elusive. Here we studied the antifungal effects of four Panax triterpene glycosides (ginsenosides) with sugar moieties at the C-3 (ginsenosides Rg3, Rh2), C-20 (compound K), and both (ginsenoside F2) positions in Saccharomyces cerevisiae mutants with altered sterol plasma membrane composition. We observed reduced cytostatic activity of the Rg3 and compound K in the UPC2-1 strain with high membrane sterol content. Moreover, LAM gene deletion reduced yeast resistance to Rg3 and digitonin, another saponin with glycosylated aglycon in the C-3 position. LAM genes encode plasma membrane-anchored StARkin superfamily-member sterol transporters. We also showed that the deletion of the ERG6 gene that inhibits ergosterol biosynthesis at the stage of zymosterol increased the cytostatic effects of Rg3 and Rh2, but not the other two tested ginsenosides. At the same time, in silico simulation revealed that the substitution of ergosterol with zymosterol in the membrane changes the spatial orientation of Rg3 and Rh2 in the membranes. These results imply that the plasma membrane sterol composition defines its interaction with triterpene glycoside depending on their glycoside group position. Our results also suggest that the biological role of membrane-anchored StARkin family protein is to protect eukaryotic cells from triterpenes glycosylated at the C-3 position.

Quantitation of Toxic Steroidal Glycoalkaloids and Newly Identified Saponins in Post-Harvest Light-Stressed Potato (Solanum tuberosum L.) Varieties

Although domesticated potatoes contain a large variety of steroidal glycoalkaloids (SGAs) and saponins, in the past, many research projects mainly focused on the two major SGAs, α-solanine and α-chaconine. This study investigates the quantitative changes, induced by post-harvest LED light exposure, of six SGAs and four saponins in 12 potato cultivars at three different time points (1, 7, and 16 days), by using ultra-performance liquid chromatography tandem mass spectrometry. Altogether, SGA contents of 3.0-17.1 mg/100 g fresh weight (FW) could be observed in the analyzed tubers with potato varieties highly exceeding the newly discussed safety limit of 10 mg/100 g. The overall contents of 0.1-5.4 mg/100 g FW of the so far barely studied saponins, like protoneodioscin or barogenin-solatrioside, highly differed between the assayed potato cultivars. Furthermore, cultivar-specific regulations of SGAs and saponins could be observed due to light exposure.

Impact of the Hydrolysis and Methanolysis of Bidesmosidic Chenopodium quinoa Saponins on Their Hemolytic Activity

Saponins are specific metabolites abundantly present in plants and several marine animals. Their high cytotoxicity is associated with their membranolytic properties, i.e., their propensity to disrupt cell membranes upon incorporation. As such, saponins are highly attractive for numerous applications, provided the relation between their molecular structures and their biological activities is understood at the molecular level. In the present investigation, we focused on the bidesmosidic saponins extracted from the quinoa husk, whose saccharidic chains are appended on the aglycone via two different linkages, a glycosidic bond, and an ester function. The later position is sensitive to chemical modifications, such as hydrolysis and methanolysis. We prepared and characterized three sets of saponins using mass spectrometry: (i) bidesmosidic saponins directly extracted from the ground husk, (ii) monodesmosidic saponins with a carboxylic acid group, and (iii) monodesmosidic saponins with a methyl ester function. The impact of the structural modifications on the membranolytic activity of the saponins was assayed based on the determination of their hemolytic activity. The natural bidesmosidic saponins do not present any hemolytic activity even at the highest tested concentration (500 µg·mL⁻¹). Hydrolyzed saponins already degrade erythrocytes at 20 µg·mL⁻¹, whereas 100 µg·mL⁻¹ of transesterified saponins is needed to induce detectable activity. The observation that monodesmosidic saponins, hydrolyzed or transesterified, are much more active against erythrocytes than the bidesmosidic ones confirms that bidesmosidic saponins are likely to be the dormant form of saponins in plants. Additionally, the observation that negatively charged saponins, i.e., the hydrolyzed ones, are more hemolytic than the neutral ones could be related to the red blood cell membrane structure.

Specialized metabolites: Physiological and biochemical role in stress resistance, strategies to improve their accumulation, and new applications in crop breeding and management

Specialized plant metabolites (SPMs), traditionally referred to as 'secondary metabolites', are chemical compounds involved in a broad range of biological functions, including plant responses to abiotic and biotic stresses. Moreover, some of them have a role in end-product quality with potential health benefits in humans. For this reason, they became an important target of studies focusing on their mechanisms of action and use in crop breeding and management. In this review we summarize the specific role of SPMs in physiological processes and in plant resistance to abiotic and biotic stresses, and the different strategies to enhance their production/accumulation in plant tissues under stress, including genetic approaches (marker-assisted selection and biotechnological tools) and agronomic management (fertilizer applications, cultivation method and beneficial microorganisms). New crop management strategies based on the direct application of the most promising compounds in form of plant residuals or liquid formulations are also described.

Microwave-Assisted Desulfation of the Hemolytic Saponins Extracted from Holothuria scabra Viscera

Saponins are plant and marine animal specific metabolites that are commonly considered as molecular vectors for chemical defenses against unicellular and pluricellular organisms. Their toxicity is attributed to their membranolytic properties. Modifying the molecular structures of saponins by quantitative and selective chemical reactions is increasingly considered to tune the biological properties of these molecules (i) to prepare congeners with specific activities for biomedical applications and (ii) to afford experimental data related to their structure-activity relationship. In the present study, we focused on the sulfated saponins contained in the viscera of Holothuria scabra, a sea cucumber present in the Indian Ocean and abundantly consumed on the Asian food market. Using mass spectrometry, we first qualitatively and quantitatively assessed the saponin content within the viscera of H. scabra. We detected 26 sulfated saponins presenting 5 different elemental compositions. Microwave activation under alkaline conditions in aqueous solutions was developed and optimized to quantitatively and specifically induce the desulfation of the natural saponins, by a specific loss of H₂SO₄. By comparing the hemolytic activities of the natural and desulfated extracts, we clearly identified the sulfate function as highly responsible for the saponin toxicity.

The steroidal alkaloids α-tomatine and tomatidine: Panorama of their mode of action and pharmacological properties

The steroidal glycoalkaloid α-tomatine (αTM) and its aglycone tomatidine (TD) are abundant in the skin of unripe green tomato and present in tomato leaves and flowers. They mainly serve as defensive agents to protect the plant against infections by insects, bacteria, parasites, viruses, and fungi. In addition, the two products display a range of pharmacological properties potentially useful to treat various human diseases. We have analyzed all known pharmacological activities of αTM and TD, and the corresponding molecular targets and pathways impacted by these two steroidal alkaloids. In experimental models, αTM displays anticancer effects, particularly strong against androgen-independent prostate cancer, as well as robust antifungal effects. αTM is a potent cholesterol binder, useful as a vaccine adjuvant to improve delivery of protein antigens or therapeutic oligonucleotides. TD is a much less cytotoxic compound, able to restrict the spread of certain viruses (such as dengue, chikungunya and porcine epidemic diarrhea viruses) and to provide cardio and neuro-protective effects toward human cells. Both αTM and TD exhibit marked anti-inflammatory activities. They proceed through multiple signaling pathways and protein targets, including the sterol C24 methyltransferase Erg6 and vitamin D receptor, both directly targeted by TD. αTM is a powerful regulator of the NFkB/ERK signaling pathway implicated in various diseases. Collectively, the analysis shed light on the multitargeted action of αTM/TD and their usefulness as chemo-preventive or chemotherapeutic agents. A novel medicinal application for αTM is proposed.

Marine natural products targeting the eukaryotic cell membrane

The cell membrane, with high fluidity and alternative curvatures, maintains the robust integrity to distinguish inner and outer space of cells or organelles. Lipids are the main components of the cell membrane, but their functions are largely unknown. Even the visualization of lipids is not straightforward since modification of lipids often hampers its correct physical properties. Many natural products target cell membranes, some of which are used as pharmaceuticals and/or research tools. They show specific recognition on lipids, and thus exhibit desired pharmacological effects and unique biological phenotypes. This review is a catalog of marine natural products that target eukaryotic cell membranes. Chemical structures, biological activities, and molecular mechanisms are summarized. I hope that this review will be helpful for readers to notice the potential of marine natural products in the exploration of the function of lipids and the druggability of eukaryotic cell membranes.

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.

Solanum nigrum Extract and Solasonine Affected Hemolymph Metabolites and Ultrastructure of the Fat Body and the Midgut in Galleria mellonella

Glycoalkaloids, secondary metabolites abundant in plants belonging to the Solanaceae family, may affect the physiology of insect pests. This paper presents original results dealing with the influence of a crude extract obtained from Solanum nigrum unripe berries and its main constituent, solasonine, on the physiology of Galleria mellonella (Lepidoptera) that can be used as an alternative bioinsecticide. G. mellonella IV instar larvae were treated with S. nigrum extract and solasonine at different concentrations. The effects of extract and solasonine were evaluated analyzing changes in carbohydrate and amino acid composition in hemolymph by RP-HPLC and in the ultrastructure of the fat body cells by TEM. Both extract and solasonine changed the level of hemolymph metabolites and the ultrastructure of the fat body and the midgut cells. In particular, the extract increased the erythritol level in the hemolymph compared to control, enlarged the intracellular space in fat body cells, and decreased cytoplasm and lipid droplets electron density. The solasonine, tested with three concentrations, caused the decrease of cytoplasm electron density in both fat body and midgut cells. Obtained results highlighted the disturbance of the midgut and the fat body due to glycoalkaloids and the potential role of hemolymph ingredients in its detoxification. These findings suggest a possible application of glycoalkaloids as a natural insecticide in the pest control of G. mellonella larvae.

A review of emerging and non-US FDA-approved topical agents for the treatment of basal cell carcinoma

Although surgical therapy continues to be the gold standard for the treatment of basal cell carcinoma given high cure rates and the ability to histologically confirm tumor clearance, there are a number of nonsurgical treatment options that may be considered based on individual tumor characteristics, functional and cosmetic considerations, patient comorbidities and patient preference. Topical 5-fluorouracil 5% cream and imiquimod 5% cream have been US FDA-approved for the treatment of superficial basal cell carcinoma. Additionally, a number of new and emerging topical agents and techniques have been described for the treatment of basal cell carcinoma and will be reviewed herein.

Sustainable Use of Bioactive Compounds from Solanum Tuberosum and Brassicaceae Wastes and by-Products for Crop Protection-A Review

Defatted seed meals of oleaginous Brassicaceae, such as Eruca sativa, and potato peel are excellent plant matrices to recover potentially useful biomolecules from industrial processes in a circular strategy perspective aiming at crop protection. These biomolecules, mainly glycoalkaloids and phenols for potato and glucosinolates for Brassicaceae, have been proven to be effective against microbes, fungi, nematodes, insects, and even parasitic plants. Their role in plant protection is overviewed, together with the molecular basis of their synthesis in plant, and the description of their mechanisms of action. Possible genetic and biotechnological strategies are presented to increase their content in plants. Genetic mapping and identification of closely linked molecular markers are useful to identify the loci/genes responsible for their accumulation and transfer them to elite cultivars in breeding programs. Biotechnological approaches can be used to modify their allelic sequence and enhance the accumulation of the bioactive compounds. How the global challenges, such as reducing agri-food waste and increasing sustainability and food safety, could be addressed through bioprotector applications are discussed here.

Bitter and sweet make tomato hard to (b)eat

The glycoalkaloid saponin α-tomatine is a tomato-specific secondary metabolite that accumulates to millimolar levels in vegetative tissues and has antimicrobial and antinutritional activity that kills microbial pathogens and deters herbivorous insects. We describe recent insights into the biosynthetic pathway of α-tomatine synthesis and its regulation. We discuss the mode of action of α-tomatine by physically interacting with sterols, thereby disrupting membranes, and how tomato protects itself from its toxic action. Tomato pathogenic microbes can enzymatically hydrolyze, and thereby inactivate, α-tomatine using either of three distinct types of glycosyl hydrolases. We also describe findings that extend well beyond the simple concept of plants producing toxins and pathogens inactivating them. There are reports that toxicity of α-tomatine is modulated by external pH, that α-tomatine can trigger programmed cell death in fungi, that cellular localization matters for the impact of α-tomatine on invading microbes, and that α-tomatine breakdown products generated by microbial hydrolytic enzymes can modulate plant immune responses. Finally, we address a number of outstanding questions that deserve attention in the future.

Is the Membrane Lipid Matrix a Key Target for Action of Pharmacologically Active Plant Saponins?

This study was focused on the molecular mechanisms of action of saponins and related compounds (sapogenins and alkaloids) on model lipid membranes. Steroids and triterpenes were tested. A systematic analysis of the effects of these chemicals on the physicochemical properties of the lipid bilayers and on the formation and functionality of the reconstituted ion channels induced by antimicrobial agents was performed. It was found that digitonin, tribulosin, and dioscin substantially reduced the boundary potential of the phosphatidylcholine membranes. We concluded that saponins might affect the membrane boundary potential by restructuring the membrane hydration layer. Moreover, an increase in the conductance and lifetime of gramicidin A channels in the presence of tribulosin was due to an alteration in the membrane dipole potential. Differential scanning microcalorimetry data indicated the key role of the sapogenin core structure (steroid or triterpenic) in affecting lipid melting and disordering. We showed that an alteration in pore forming activity of syringomycin E by dioscin might be due to amendments in the lipid packing. We also found that the ability of saponins to disengage the fluorescent marker calcein from lipid vesicles might be also determined by their ability to induce a positive curvature stress.

Identification of Novel Iso-Esculeoside B from Tomato Fruits and LC-MS/MS-Based Food Screening for Major Dietary Steroidal Alkaloids Focused on Esculeosides

Plants from the Solanaceae family are known to be sources of several nutritionally relevant steroidal glycoalkaloids (SGAs). With the aim of quantitatively investigating the occurrence of the main SGA from tomatoes, eggplants, and potatoes in various food samples and evaluating their relevance in the human diet, a rapid single-step extraction liquid chromatography-tandem mass spectrometry method was developed. Over the course of isolating several commercially unavailable SGAs from tomato products to use them as reference standards, a previously unknown derivative was detected, structurally characterized, and identified as a novel isomer of esculeoside B-1 and B-2. After validation of the method, 36 food items exclusively derived from Solanaceae plants were analyzed for their SGA contents and a specific occurrence of each alkaloid in tomato, eggplant, or potato products was revealed. This is the first study reporting quantitative data on the occurrence of esculeoside A, B-1, B-2, and iso-esculeoside B in tomato products obtained by using appropriate reference compounds rather than applying a semi-quantitative approach based on α-tomatine as a reference. Some of the analyzed tomato products contained the esculeosides in concentrations of >500 mg/kg, clearly indicating their relevance in the human diet and the need of investigating their potential bioactivities in the future.

Exploring the possible use of saponin adjuvants in COVID-19 vaccine

There is an urgent need for a safe, efficacious, and cost-effective vaccine for the coronavirus disease 2019 (COVID-19) pandemic caused by novel coronavirus strain, severe acute respiratory syndrome-2 (SARS-CoV-2). The protective immunity of certain types of vaccines can be enhanced by the addition of adjuvants. Many diverse classes of compounds have been identified as adjuvants, including mineral salts, microbial products, emulsions, saponins, cytokines, polymers, microparticles, and liposomes. Several saponins have been shown to stimulate both the Th1-type immune response and the production of cytotoxic T lymphocytes against endogenous antigens, making them very useful for subunit vaccines, especially those for intracellular pathogens. In this review, we discuss the structural characteristics, mechanisms of action, structure-activity relationship of saponins, biological activities, and use of saponins in various viral vaccines and their applicability to a SARS-CoV-2 vaccine.

The Role of Cholesterol on Triterpenoid Saponin-Induced Endolysosomal Escape of a Saporin-Based Immunotoxin

Cholesterol seems to play a central role in the augmentation of saporin-based immunotoxin (IT) cytotoxicity by triterpenoid saponins. Endolysosomal escape has been proposed as one mechanism for the saponin-mediated enhancement of targeted toxins. We investigated the effects of lipid depletion followed by repletion on Saponinum album (SA)-induced endolysosomal escape of Alexa Fluor labelled saporin and the saporin-based immunotoxin OKT10-SAP, directed against CD38, in Daudi lymphoma cells. Lipid deprived cells showed reduced SA-induced endolysosomal escape at two concentrations of SA, as determined by a flow cytometric method. The repletion of membrane cholesterol by low density lipoprotein (LDL) restored SA-induced endolysosomal escape at a concentration of 5 µg/mL SA but not at 1 µg/mL SA. When LDL was used to restore the cholesterol levels in lipid deprived cells, the SA augmentation of OKT10-SAP cytotoxicity was partially restored at 1 µg/mL SA and fully restored at 5 µg/mL SA. These results suggest that different mechanisms of action might be involved for the two different concentrations of SA and that endosomal escape may not be the main mechanism for the augmentation of saporin IT cytotoxicity by SA at the sub-lytic concentration of 1 µg/mL SA.

Lipid Membranes as Key Targets for the Pharmacological Actions of Ginsenosides

In this review, we will focus on the activity of ginsenosides on membranes and their related effects, from physicochemical, biophysical, and pharmacological viewpoints. Ginsenosides are a class of saponins with a large structural diversity and a wide range of pharmacological effects. These effects can at least partly be related to their activity on membranes which results from their amphiphilic character. Some ginsenosides are able to interact with membrane lipids and associate into nanostructures, making them possible adjuvants for vaccines. They are able to modulate membrane biophysical properties such as membrane fluidity, permeability or the formation of lateral domains with some degree of specificity towards certain cell types such as bacteria, fungi, or cancer cells. In addition, they have shown antioxidant properties which protect membranes from lipid oxidation. They further displayed some activity on membrane proteins either through direct or indirect interaction. We investigate the structure activity relationship of ginsenosides on membranes and discuss the implications and potential use as anticancer, antibacterial, and antifungal agents.

Risk assessment of glycoalkaloids in feed and food, in particular in potatoes and potato-derived products

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of glycoalkaloids (GAs) in feed and food. This risk assessment covers edible parts of potato plants and other food plants containing GAs, in particular, tomato and aubergine. In humans, acute toxic effects of potato GAs (α-solanine and α-chaconine) include gastrointestinal symptoms such as nausea, vomiting and diarrhoea. For these effects, the CONTAM Panel identified a lowest-observed-adverse-effect level of 1 mg total potato GAs/kg body weight (bw) per day as a reference point for the risk characterisation following acute exposure. In humans, no evidence of health problems associated with repeated or long-term intake of GAs via potatoes has been identified. No reference point for chronic exposure could be identified from the experimental animal studies. Occurrence data were available only for α-solanine and α-chaconine, mostly for potatoes. The acute dietary exposure to potato GAs was estimated using a probabilistic approach and applying processing factors for food. Due to the limited data available, a margin of exposure (MOE) approach was applied. The MOEs for the younger age groups indicate a health concern for the food consumption surveys with the highest mean exposure, as well as for the P95 exposure in all surveys. For adult age groups, the MOEs indicate a health concern only for the food consumption surveys with the highest P95 exposures. For tomato and aubergine GAs, the risk to human health could not be characterised due to the lack of occurrence data and the limited toxicity data. For horses, farm and companion animals, no risk characterisation for potato GAs could be performed due to insufficient data on occurrence in feed and on potential adverse effects of GAs in these species.

Enhancing the Membranolytic Activity of Chenopodium quinoa Saponins by Fast Microwave Hydrolysis

Saponins are plant secondary metabolites. There are associated with defensive roles due to their cytotoxicity and are active against microorganisms. Saponins are frequently targeted to develop efficient drugs. Plant biomass containing saponins deserves sustained interest to develop high-added value applications. A key issue when considering the use of saponins for human healthcare is their toxicity that must be modulated before envisaging any biomedical application. This can only go through understanding the saponin-membrane interactions. Quinoa is abundantly consumed worldwide, but the quinoa husk is discarded due to its astringent taste associated with its saponin content. Here, we focus on the saponins of the quinoa husk extract (QE). We qualitatively and quantitively characterized the QE saponins using mass spectrometry. They are bidesmosidic molecules, with two oligosaccharidic chains appended on the aglycone with two different linkages; a glycosidic bond and an ester function. The latter can be hydrolyzed to prepare monodesmosidic molecules. The microwave-assisted hydrolysis reaction was optimized to produce monodesmosidic saponins. The membranolytic activity of the saponins was assayed based on their hemolytic activity that was shown to be drastically increased upon hydrolysis. In silico investigations confirmed that the monodesmosidic saponins interact preferentially with a model phospholipid bilayer, explaining the measured increased hemolytic activity.

Interactions of OSW-1 with Lipid Bilayers in Comparison with Digitonin and Soyasaponin

OSW-1, a unique steroidal saponin isolated from the bulbs of Ornithogalum saundersiae, has potent cell-growth inhibition activity. In this study, we conducted fluorescence measurements and microscopic observations using palmitoyloleoylphosphatidylcholine (POPC)-cholesterol (Chol) bilayers to evaluate the membrane-binding affinity of OSW-1 in comparison with another steroidal saponin, digitonin, and the triterpenoid saponin, soyasaponin Bb(I). The membrane activities of these saponins were evaluated using calcein leakage assays and fitted to the binding isotherm by changing the ratios of saponin-lipids. Digitonin showed the highest binding affinity for the POPC-Chol membrane (K_app = 0.38 μM^-1) and the strongest membrane disruptivity in the bound saponin-lipid ratio at the point of 50% calcein leakage (r₅₀ = 0.47) occurrence. OSW-1 showed slightly lower activity (K_app = 0.31 μM^-1; r₅₀ = 0.78), and the soyasaponin was the lowest in the membrane affinity and the calcein leakage activity (K_app = 0.017 μM^-1; r₅₀ = 1.66). The effect of OSW-1 was further assessed using confocal microscopy in an experiment utilizing DiI and rhodamine 6G as the fluorescence probes. The addition of 30 μM OSW-1 induced inward membrane curvature in some giant unilamellar vesicles (GUVs). At the higher OSW-1 concentration (58 μM, r₅₀ = 0.78) where the 50% calcein leakage was observed, the morphology of some GUVs became elongated. With digitonin at the corresponding concentration (35 μM, r₅₀ = 0.47), membrane disruption and formation of large aggregates in aqueous solution were observed, probably due to a detergent-type mechanism. These saponins, including OSW-1, required Chol to exhibit their potent membrane activity although their mechanisms are thought to be different. At the effective concentration, OSW-1 preferably binds to the bilayers without prominent disruption of vesicles and exerts its activity through the formation of saponin-Chol complexes, probably resulting in membrane permeabilization.

Liposomal membrane permeability assessment by fluorescence techniques: Main permeabilizing agents, applications and challenges

Liposomes are lipid vesicles made of one or multiple lipid bilayers surrounding an internal aqueous core. They are broadly employed as models to study membrane structure and properties. Among these properties, liposome membrane permeability is crucial and widely assessed by fluorescence techniques. The first part of this review is devoted to describe the various techniques used for membrane permeability assessment. Attention is paid to fluorescence techniques based on vesicle leakage of self-quenching probes, dye/quencher pair or cation/ligand pair. Secondly, the membrane-active agents inducing membrane permeabilization is presented and details on their mechanisms of action are given. Emphasis is also laid on the intrinsic and extrinsic factors that can modulate the membrane permeability. Hence, a suitable liposomal membrane should be formulated according to the aim of the study and its application.

Major challenges and perspectives in the diagnostics and treatment of dermatophyte infections

Dermatophytes are the aetiological factors of a majority of superficial fungal infections. What distinguishes them from other pathogenic filamentous fungi is their unique ability to degrade keratin. The remarkable ability of this group of fungi to survive in different ecosystems results from their morphological and ecological diversity as well as high adaptability to changing environmental conditions. Paradoxically, despite the progress in medicine, the prevalence of dermatophyte infections is increasing from year to year. At the beginning of the third millennium, practical diagnostic and therapeutic options are still very limited. This review focuses on understanding the major problems in this aspect of dermatophyte infections and indicates future strategies and perspectives for novel approaches to identification and drugs for elimination of dermatophytes. Particular importance is placed on development of a strategy for a diagnostic pathway and implementation of rapid and reliable diagnostics methods designed by international teams. Furthermore, among compounds that currently arouse great interest, representatives of terpenoids, alkaloids, saponins, flavonoids and essential oils deserve attention. Many of these compounds are undergoing clinical trials as potential antifungal agents, and future research should focus on attempts at determination of the applicability of tested substances. Finally, the advantages and disadvantages in implementation of new diagnostic paths and medicinal substances for routine use are indicated.

Chemical diversity and mode of action of natural products targeting lipids in the eukaryotic cell membrane

Covering: up to 2019Nature furnishes bioactive compounds (natural products) with complex chemical structures, yet with simple, sophisticated molecular mechanisms. When natural products exhibit their activities in cells or bodies, they first have to bind or react with a target molecule in/on the cell. The cell membrane is a major target for bioactive compounds. Recently, our understanding of the molecular mechanism of interactions between natural products and membrane lipids progressed with the aid of newly-developed analytical methods. New technology reconnects old compounds with membrane lipids, while new membrane-targeting molecules are being discovered through the screening for antimicrobial potential of natural products. This review article focuses on natural products that bind to eukaryotic membrane lipids, and includes clinically important molecules and key research tools. The chemical diversity of membrane-targeting natural products and the molecular basis of lipid recognition are described. The history of how their mechanism was unveiled, and how these natural products are used in research are also mentioned.

Steroidal glycoalkaloids from Solanum lyratum inhibit the pro-angiogenic activity of A549-derived exosomes

In this study, seven previously undescribed steroidal glycoalkaloids, compounds 1-7, were isolated from Solanum lyratum, along with two known ones (8 and 9). Comprehensive spectroscopy techniques were used to determine their structures. Although 1-8 only showed a weak inhibitory effect on the proliferation of the tumor-derived vascular endothelial cells, however, in a former study we found both total steroidal glycoalkaloids from Solanum lyratum (TSGS) and 9 significantly inhibited tumor angiogenesis and its mechanism was linked to its ability to interfere with cell membrane lipid rafts. Lipid rafts are closely related to the functions of tumor-derived exosomes, a vital factor in cancer progression. Thus, we investigated the impacts of TSGS and 9 on the functions of A549-derived exosomes. Our results indicated that A549-derived exosomes can significantly enhance the angiogenesis abilities of human umbilical vein endothelial cells, whereas the intervention of TSGS or 9 significantly inhibited this activity of A549-derived exosomes. These findings suggest that TSGS and 9 exert anti-tumor angiogenesis by inhibiting the pro-angiogenic activity of A549-derived exosomes.

Evolution of Structural Diversity of Triterpenoids

Plants have evolved to produce a blend of specialized metabolites that serve functional roles in plant adaptation. Among them, triterpenoids are one of the largest subclasses of such specialized metabolites, with more than 14,000 known structures. They play a role in plant defense and development and have potential applications within food and pharma. Triterpenoids are cyclized from oxidized squalene precursors by oxidosqualene cyclases, creating more than 100 different cyclical triterpene scaffolds. This limited number of scaffolds is the first step towards creating the vast structural diversity of triterpenoids followed by extensive diversification, in particular, by oxygenation and glycosylation. Gene duplication, divergence, and selection are major forces that drive triterpenoid structural diversification. The triterpenoid biosynthetic genes can be organized in non-homologous gene clusters, such as in Avena spp., Cucurbitaceae and Solanum spp., or scattered along plant chromosomes as in Barbarea vulgaris. Paralogous genes organized as tandem repeats reflect the extended gene duplication activities in the evolutionary history of the triterpenoid saponin pathways, as seen in B. vulgaris. We review and discuss examples of convergent and divergent evolution in triterpenoid biosynthesis, and the apparent mechanisms occurring in plants that drive their increasing structural diversity within and across species. Using B. vulgaris' saponins as examples, we discuss the impact a single structural modification can have on the structure of a triterpenoid and how this affect its biological properties. These examples provide insight into how plants continuously evolve their specialized metabolome, opening the way to study uncharacterized triterpenoid biosynthetic pathways.

Glycoalkaloids: Structure, Properties, and Interactions with Model Membrane Systems

The glycoalkaloids which are secondary metabolites from plants have proven to be of significant interest for their biological properties both in terms of their roles in plant biology and the effects they exhibit when ingested by humans. The main feature of the action of glycoalkaloids is their strong binding to 3β-hydroxysterols, such as cholesterol, to form complexes with the consequence that membrane structure is significantly perturbed, and leakage or release of contents inside cells or liposomes becomes possible. The glycoalkaloids have been studied for their ability to inhibit the growth of cancer cells and in other roles such as vaccine adjuvants and as synergistic agents when combined with other therapeutics. The glycoalkaloids have rich and complex physical behavior when interacting with model membranes for which many aspects are yet to be understood. This review introduces the general properties of glycoalkaloids and aspects of their behavior, and then summarizes their effects against model membrane systems. While there are many glycoalkaloids that have been identified, most physical or biological studies have focused on the readily available ones from tomatoes (α-tomatine), potatoes (α-chaconine and α-solanine), and eggplant (α-solamargine and α-solasonine).

The Structure and Function of Major Plant Metabolite Modifications

Plants produce a myriad of structurally and functionally diverse metabolites that play many different roles in plant growth and development and in plant response to continually changing environmental conditions as well as abiotic and biotic stresses. This metabolic diversity is, to a large extent, due to chemical modification of the basic skeletons of metabolites. Here, we review the major known plant metabolite modifications and summarize the progress that has been achieved and the challenges we are facing in the field. We focus on discussing both technical and functional aspects in studying the influences that various modifications have on biosynthesis, degradation, transport, and storage of metabolites, as well as their bioactivity and toxicity. Finally, we discuss some emerging insights into the evolution of metabolic pathways and metabolite functionality.

Phenotypic and genetic characterization of tomato mutants provides new insights into leaf development and its relationship to agronomic traits

BACKGROUND

Tomato mutants altered in leaf morphology are usually identified in the greenhouse, which demands considerable time and space and can only be performed in adequate periods. For a faster but equally reliable scrutiny method we addressed the screening in vitro of 971 T-DNA lines. Leaf development was evaluated in vitro in seedlings and shoot-derived axenic plants. New mutants were characterized in the greenhouse to establish the relationship between in vitro and in vivo leaf morphology, and to shed light on possible links between leaf development and agronomic traits, a promising field in which much remains to be discovered.

RESULTS

Following the screening in vitro of tomato T-DNA lines, putative mutants altered in leaf morphology were evaluated in the greenhouse. The comparison of results in both conditions indicated a general phenotypic correspondence, showing that in vitro culture is a reliable system for finding mutants altered in leaf development. Apart from providing homogeneous conditions, the main advantage of screening in vitro lies in the enormous time and space saving. Studies on the association between phenotype and nptII gene expression showed co-segregation in two lines (P > 99%). The use of an enhancer trap also allowed identifying gain-of-function mutants through reporter expression analysis. These studies suggested that genes altered in three other mutants were T-DNA tagged. New mutants putatively altered in brassinosteroid synthesis or perception, mutations determining multiple pleiotropic effects, lines affected in organ curvature, and the first tomato mutant with helical growth were discovered. Results also revealed new possible links between leaf development and agronomic traits, such as axillary branching, flower abscission, fruit development and fruit cracking. Furthermore, we found that the gene tagged in mutant 2635-MM encodes a Sterol 3-beta-glucosyltransferase. Expression analysis suggested that abnormal leaf development might be due to the lack-off-function of this gene.

CONCLUSION

In vitro culture is a quick, efficient and reliable tool for identifying tomato mutants altered in leaf morphology. The characterization of new mutants in vivo revealed new links between leaf development and some agronomic traits. Moreover, the possible implication of a gene encoding a Sterol 3-beta-glucosyltransferase in tomato leaf development is reported.

Steroidal Glycoalkaloids: Isolation, Structure, Analysis, and Biosynthesis

In recent years, the steroidal glycoalkaloids have emerged as an important class of bioactive compounds. Their occurrence in a number of foods and their diverse biological activities has encouraged the development of more efficient procedures for their isolation, purification and analysis, and more sensitive methods of detection and structure determination. This review is mainly concerned with new approaches for the characterization of these metabolites. The formation of artifacts of isolation and purification is discussed. The limited information on their biosynthesis is summarized.

Antifungal Activity of Eclipta alba Metabolites against Sorghum Pathogens

Unscientific use of synthetic fungicides in plant disease management has environmental ramifications, such as disease resurgence and serious health problems due to their carcinogenicity. This has prompted the identification and development of eco-friendly greener alternatives. Eclipta alba extract was evaluated for its antifungal activity in in vitro and in vivo against sorghum fungal pathogens Fusarium thapsinum, Alternaria alternata, Epicoccum sorghinum, and Curvularia lunata. The column purified methanolic extract of E. alba exhibited good antifungal activity against the target pathogens. The MIC was observed at 80 mg/mL for all tested pathogenic fungi, whereas MFC was 80 mg/mL for E. sorghinum, 100 mg/mL for F. thapsinum, A. alternata, and C. lunata. In vitro germination percentage was significantly high in seeds treated with E. alba extract (98%) over untreated control (91%). Significant disease protection of 95% was observed in greenhouse and 66% disease protection was noticed in field experiments. The efficacy of E. alba extract in field conditions was improved with the use of E. alba extract formulation. The profile of phytochemicals in E. alba methanol fractions was obtained by ultra-performance liquid chromatography (UPLC) mass spectroscopy. The [M-H]⁻ at m/z 313.3, m/z 797.9, and m/z 269.0 revealed the presence of wedelolactone, eclalbasaponin II, and apigenin, respectively. The H-nuclear magnetic resonance spectroscopy (¹H-NMR) chemical shift value supported the findings of the mass spectrometry. The results highlighted the possible use of E. alba methanolic extract as alternative to chemical fungicide in sorghum disease management.

Synthesis and insecticidal activities of novel solanidine derivatives

BACKGROUND

Potato (Solanum tuberosum) is the fourth culture in the world and is widely used in the agri-food industries. They generate by-products in which α-chaconine and α-solanine, the two major solanidine-based glycoalkaloids of potato, are present. As secondary metabolites, they play an important role in the protection system of potato and are involved in plant protection against insects. To add value to these by-products, we described here new glycoalkaloids that could have phytosanitary properties.

RESULTS

Solanidine, as a renewable source, was modified with an azido linker and coupled by copper-catalyzed alkyne azide cycloaddition to alkynyl derivatives of the monosaccharides found in the natural potato glycoalkakoids: D-glucose, D-galactose and L-rhamnose. The efficacy of our compounds was evaluated on the potato aphid Macrosiphum euphorbiae. The synthetic compounds have stronger aphicidal properties against nymphs than unmodified solanidine. They also showed strong aphicidal activities on adults and a negative impact on fecundity.

CONCLUSION

Our synthetic neoglycoalkaloids affected Macrosiphum euphorbiae survival at the nymphal stage as well as at the adult stage. Furthermore, they induced a decrease in fecundity. Our results show that chemical modifications of by-products may afford new sustainable compounds for crop and plant protection. © 2018 Society of Chemical Industry.

Augmentation of Saporin-Based Immunotoxins for Human Leukaemia and Lymphoma Cells by Triterpenoid Saponins: The Modifying Effects of Small Molecule Pharmacological Agents

Triterpenoid saponins from Saponinum album (SA) significantly augment the cytotoxicity of saporin-based immunotoxins but the mechanism of augmentation is not fully understood. We investigated the effects of six small molecule pharmacological agents, which interfere with endocytic and other processes, on SA-mediated augmentation of saporin and saporin-based immunotoxins (ITs) directed against CD7, CD19, CD22 and CD38 on human lymphoma and leukaemia cell lines. Inhibition of clathrin-mediated endocytosis or endosomal acidification abolished the SA augmentation of saporin and of all four immunotoxins tested but the cytotoxicity of each IT or saporin alone was largely unaffected. The data support the hypothesis that endocytic processes are involved in the augmentative action of SA for saporin ITs targeted against a range of antigens expressed by leukaemia and lymphoma cells. In addition, the reactive oxygen species (ROS) scavenger tiron reduced the cytotoxicity of BU12-SAP and OKT10-SAP but had no effect on 4KB128-SAP or saporin cytotoxicity. Tiron also had no effect on SA-mediated augmentation of the saporin-based ITs or unconjugated saporin. These results suggest that ROS are not involved in the augmentation of saporin ITs and that ROS induction is target antigen-dependent and not directly due to the cytotoxic action of the toxin moiety.

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.

Identification of novel compounds, oleanane- and ursane-type triterpene glycosides, from Trevesia palmata: their biocontrol activity against phytopathogenic fungi

Plants contain a number of bioactive compounds that exhibit antimicrobial activity, which can be recognized as an important source of agrochemicals for plant disease control. As part of our search for new antimicrobial agents from natural sources, we found that a crude methanol extract of Trevesia palmata exhibited a promising antifungal activity against phytopathogenic fungi, such as Magnaporthe oryzae and Botrytis cinerea. Furthermore, based on activity-guided fractionation, we isolated five antifungal compounds from the methanol extract of T. palmata: two new triterpene glycosides (TPGs), TPG1 (hederagenin-3-O-β-_D-glucopyranosyl-(1  → 3)-α-_L-rhamnopyranosyl-(1 → 2)-α-_L-rhamnopyranosyl-(1 → 2)-α-_L-arabinopyranoside) and TPG5 (3-O-α-_L-rhamnopyranosyl asiatic acid), along with three known TPGs (TPG2 [macranthoside A], TPG3 [α-hederin], and TPG4 [ilekudinoside D]). The chemical structures of the TPGs were determined by spectroscopic analyses and by comparison with literature data. An in vitro antifungal bioassay revealed that except for TPG4 (ilekudinoside D; IC₅₀ >256 μg/ml), the other TPGs exhibited strong antifungal activities against the rice blast pathogen M. oryzae with IC₅₀ values ranging from 2–5 μg/ml. In particular, when the plants were treated with compound TPG1 (500 μg/ml), disease control values against rice blast, tomato grey mold, tomato late blight, and wheat leaf rust were 84, 82, 88, and 70%, respectively, compared to the non-treatment control. Considering the in vitro and in vivo antifungal activities of the TPGs and the T. palmata methanol extracts, our results suggest that T. palmata can be a useful source to develop new natural fungicides.

Dermatophyte Resistance to Antifungal Drugs: Mechanisms and Prospectus

Dermatophytes comprise pathogenic fungi that have a high affinity for the keratinized structures present in nails, skin, and hair, causing superficial infections known as dermatophytosis. A reasonable number of antifungal drugs currently exist on the pharmaceutical market to control mycoses; however, their cellular targets are restricted, and fungi may exhibit tolerance or resistance to these agents. For example, the stress caused by antifungal and cytotoxic drugs in sub-inhibitory concentrations promotes compensatory stress responses, with the over-expression of genes involved in cellular detoxification, drug efflux, and signaling pathways being among the various mechanisms that may contribute to drug tolerance. In addition, the ATP-binding cassette transporters in dermatophytes that are responsible for cellular efflux can act synergistically, allowing one to compensate for the absence of the other, revealing the complexity of drug tolerance phenomena. Moreover, mutations in genes coding for target enzymes could lead to substitutions in amino acids involved in the binding of antifungal agents, hindering their performance and leading to treatment failure. The relevance of each one of these mechanisms of resistance to fungal survival is hard to define, mainly because they can act simultaneously in the cell. However, an understanding of the molecular mechanisms involved in the resistance/tolerance processes, the identification of new antifungal targets, as well as the prospective of new antifungal compounds among natural or synthetic products, are expected to bring advances and new insights that facilitate the improvement or development of novel strategies for antifungal therapy.

α-Chaconine and α-Solanine Inhibit RL95-2 Endometrium Cancer Cell Proliferation by Reducing Expression of Akt (Ser473) and ERα (Ser167)

The aim of this study is to investigate the potential inhibitory effect of α-chaconine and α-solanine on RL95-2 estrogen receptor (ER) positive human endometrial cancer cell line and to identify the effect of these glycoalkaloids on the Akt signaling and ERα. The cell proliferation profiles and the cytotoxicity studies were performed by Real-Time Cell Analyzer (xCELLigence) and compared with Sulphorhodamine B (SRB) assay. The effects of α-chaconine (2.5, 5, 10 µM), α-solanine (20, 30, 50 µM), API-1 (25 µM) and MPP (20 µM) effects on Akt (Ser473) and ERα (Ser167) expressions evaluated by Western blot and qPCR method. Their IC₅₀ values were as α-chaconine (4.72 µM) < MPP (20.01 µM) < α-solanine (26.27 µM) < API-1 (56.67 µM). 10 μM α-chaconine and 20, 30 and 50 μM α-solanine were effective in decreasing p-Akt(Ser473)/Akt ratio compared to positive control API-1. When the p-ERα/ERα ratios were evaluated, it was observed that α-chaconine (2.5, 5, 10 μM) and α-solanine (50 μM) were as effective as the specific ERα inhibitor MPP in reducing the ratio of p-ERα/ERα compared to the control group. In conclusion, it has been shown that the proliferation of α-chaconine and α-solanine in human endometrial carcinoma cells reduces the expression and activity of the Akt and ERα signaling pathway.

A Reliable and Reproducible Model for Assessing the Effect of Different Concentrations of α-Solanine on Rat Bone Marrow Mesenchymal Stem Cells

Αlpha-solanine (α-solanine) is a glycoalkaloid present in potato (Solanum tuberosum). It has been of particular interest because of its toxicity and potential teratogenic effects that include abnormalities of the central nervous system, such as exencephaly, encephalocele, and anophthalmia. Various types of cell culture have been used as experimental models to determine the effect of α-solanine on cell physiology. The morphological changes in the mesenchymal stem cell upon exposure to α-solanine have not been established. This study aimed to describe a reliable and reproducible model for assessing the structural changes induced by exposure of mouse bone marrow mesenchymal stem cells (MSCs) to different concentrations of α-solanine for 24 h. The results demonstrate that nonlethal concentrations of α-solanine (2-6 μM) changed the morphology of the cells, including an increase in the number of nucleoli, suggesting elevated protein synthesis, and the formation of spicules. In addition, treatment with α-solanine reduced the number of adherent cells and the formation of colonies in culture. Immunophenotypic characterization and staining of MSCs are proposed as a reproducible method that allows description of cells exposed to the glycoalkaloid, α-solanine.