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Article ; Online: Horse Chestnut Saponins–Escins, Isoescins, Transescins, and Desacylescins

Philippe Savarino / Emmanuel Colson / Julien André / Pascal Gerbaux

Molecules, Vol 28, Iss 2087, p

2023 Volume 2087

Abstract: Escins constitute an abundant family of saponins (saponosides) and are the most active components in Aesculum hippocastanum (horse chestnut—HC) seeds. They are of great pharmaceutical interest as a short-term treatment for venous insufficiency. Numerous ... ...

Abstract	Escins constitute an abundant family of saponins (saponosides) and are the most active components in Aesculum hippocastanum (horse chestnut—HC) seeds. They are of great pharmaceutical interest as a short-term treatment for venous insufficiency. Numerous escin congeners (slightly different compositions), as well as numerous regio-and stereo-isomers, are extractable from HC seeds, making quality control trials mandatory, especially since the structure–activity relationship (SAR) of the escin molecules remains poorly described. In the present study, mass spectrometry, microwave activation, and hemolytic activity assays were used to characterize escin extracts (including a complete quantitative description of the escin congeners and isomers), modify the natural saponins (hydrolysis and transesterification) and measure their cytotoxicity (natural vs. modified escins). The aglycone ester groups characterizing the escin isomers were targeted. A complete quantitative analysis, isomer per isomer, of the weight content in the saponin extracts as well as in the seed dry powder is reported for the first time. An impressive 13% in weight of escins in the dry seeds was measured, confirming that the HC escins must be absolutely considered for high-added value applications, provided that their SAR is established. One of the objectives of this study was to contribute to this development by demonstrating that the aglycone ester functions are mandatory for the toxicity of the escin derivative, and that the cytotoxicity also depends on the relative position of the ester functions on the aglycone.
Keywords	mass spectrometry ; structure–activity relationship ; microwave activation ; liquid chromatography ; hemolytic activity ; Organic chemistry ; QD241-441
Language	English
Publishing date	2023-02-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Microwave-Assisted Desulfation of the Hemolytic Saponins Extracted from Holothuria scabra Viscera

Philippe Savarino / Emmanuel Colson / Guillaume Caulier / Igor Eeckhaut / Patrick Flammang / Pascal Gerbaux

Molecules, Vol 27, Iss 537, p

2022 Volume 537

Abstract: 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 ... ...

Abstract	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 H 2 SO 4 . By comparing the hemolytic activities of the natural and desulfated extracts, we clearly identified the sulfate function as highly responsible for the saponin toxicity.
Keywords	saponins ; triterpene glycosides ; sea cucumbers ; mass spectrometry ; microwave activation ; desulfation ; Organic chemistry ; QD241-441
Subject code	290
Language	English
Publishing date	2022-01-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
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Article ; Online: Impact of the Hydrolysis and Methanolysis of Bidesmosidic Chenopodium quinoa Saponins on Their Hemolytic Activity

Philippe Savarino / Carolina Contino / Emmanuel Colson / Gustavo Cabrera-Barjas / Julien De Winter / Pascal Gerbaux

Molecules, Vol 27, Iss 3211, p

2022 Volume 3211

Abstract: 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 ... ...

Abstract	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.
Keywords	saponins ; mass spectrometry ; structure-activity relationship ; chemical modification ; hemolytic activity ; Organic chemistry ; QD241-441
Subject code	333
Language	English
Publishing date	2022-05-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
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Article ; Online: Poison or Potion

Antoine Gekière / Irène Semay / Maxence Gérard / Denis Michez / Pascal Gerbaux / Maryse Vanderplanck

Biology, Vol 11, Iss 545, p

Effects of Sunflower Phenolamides on Bumble Bees and Their Gut Parasite

2022 Volume 545

Abstract: Specific floral resources may help bees to face environmental challenges such as parasite infection, as recently shown for sunflower pollen. Whereas this pollen diet is known to be unsuitable for the larval development of bumble bees, it has been shown ... ...

Abstract	Specific floral resources may help bees to face environmental challenges such as parasite infection, as recently shown for sunflower pollen. Whereas this pollen diet is known to be unsuitable for the larval development of bumble bees, it has been shown to reduce the load of a trypanosomatid parasite ( Crithidia bombi ) in the bumble bee gut. Recent studies suggested it could be due to phenolamides, a group of compounds commonly found in flowering plants. We, therefore, decided to assess separately the impacts of sunflower pollen and its phenolamides on a bumble bee and its gut parasite. We fed Crithidia -infected and -uninfected microcolonies of Bombus terrestris either with a diet of willow pollen (control), a diet of sunflower pollen (natural diet) or a diet of willow pollen supplemented with sunflower phenolamides (supplemented diet). We measured several parameters at both microcolony (i.e., food collection, parasite load, brood development and stress responses) and individual (i.e., fat body content and phenotypic variation) levels. As expected, the natural diet had detrimental effects on bumble bees but surprisingly, we did not observe any reduction in parasite load, probably because of bee species-specific outcomes. The supplemented diet also induced detrimental effects but by contrast to our a priori hypothesis, it led to an increase in parasite load in infected microcolonies. We hypothesised that it could be due to physiological distress or gut microbiota alteration induced by phenolamide bioactivities. We further challenged the definition of medicinal effects and questioned the way to assess them in controlled conditions, underlining the necessity to clearly define the experimental framework in this research field.
Keywords	Crithidia bombi ; Bombus terrestris ; Helianthus annuus ; specialised metabolites ; microcolony performance ; phenotypic variation ; Biology (General) ; QH301-705.5
Subject code	580
Language	English
Publishing date	2022-04-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
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Article ; Online: A Distinct Saponin Profile Drives an Olfactory-Mediated Aggregation in the Aquacultivated Sea Cucumber Holothuria scabra

Emily J. S. Claereboudt / Michel R. Claereboudt / Philippe Savarino / Guillaume Caulier / Loic Gaumez / Magali Deleu / Pascal Gerbaux / Igor Eeckhaut

Marine Drugs, Vol 21, Iss 184, p

2023 Volume 184

Abstract: Intraspecific chemical communication between echinoderms has often been limited to prespawning aggregation. However, sea cucumber farmers have long observed year-round adult aggregation as a potential source of disease propagation and the suboptimal use ... ...

Abstract	Intraspecific chemical communication between echinoderms has often been limited to prespawning aggregation. However, sea cucumber farmers have long observed year-round adult aggregation as a potential source of disease propagation and the suboptimal use of available sea pen acreage and food resources. In this study, through spatial distribution statistics, we demonstrated the significant aggregation of the aquacultivated sea cucumber Holothuria scabra both as adults in large sea-based pens and as juveniles in laboratory-based aquaria, proving that aggregation in these animals is not only observed during spawning. The role of chemical communication in aggregation was investigated using olfactory experimental assays. Our study established that the sediment that H. scabra feeds on as well as the water preconditioned by conspecifics induced positive chemotaxis in juvenile individuals. More specifically, through comparative mass spectrometry, a distinct triterpenoid saponin profile/mixture was identified to be a pheromone allowing sea cucumber intraspecific recognition and aggregation. This “attractive” profile was characterized as containing disaccharide saponins. This “attractive” aggregation-inducing saponin profile was, however, not conserved in starved individuals that were no longer attractive to other conspecifics. In summary, this study sheds new light on the pheromones in echinoderms. It highlights the complexity of the chemical signals detected by sea cucumbers and suggests a role of saponins well beyond that of a simple toxin.
Keywords	saponins ; Holothuria scabra ; aggregation ; behavior ; pheromone ; Biology (General) ; QH301-705.5
Language	English
Publishing date	2023-03-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Asteraceae Paradox

Maryse Vanderplanck / Hélène Gilles / Denis Nonclercq / Pierre Duez / Pascal Gerbaux

Insects, Vol 11, Iss 304, p

Chemical and Mechanical Protection of Taraxacum Pollen

2020 Volume 304

Abstract: Excessive pollen harvesting by bees can compromise the reproductive success of plants. Plants have therefore evolved different morphological structures and floral cues to narrow the spectrum of pollen feeding visitors. Among “filtering” mechanisms, the ... ...

Abstract	Excessive pollen harvesting by bees can compromise the reproductive success of plants. Plants have therefore evolved different morphological structures and floral cues to narrow the spectrum of pollen feeding visitors. Among “filtering” mechanisms, the chemical and mechanical protection of pollen might shape bee-flower interactions and restrict pollen exploitation to a specific suite of visitors such as observed in Asteraceae. Asteraceae pollen is indeed only occasionally exploited by generalist bee species but plentifully foraged by specialist ones (i.e., Asteraceae paradox). During our bioassays, we observed that micro-colonies of generalist bumblebee ( Bombus terrestris L.) feeding on Taraxacum pollen (Asteraceae) reduced their pollen collection and offspring production. Bees also experienced physiological effects of possible defenses in the form of digestive damage. Overall, our results suggest the existence of an effective chemical defense in Asteraceae pollen, while the hypothesis of a mechanical defense appeared more unlikely. Pre- and post-ingestive effects of such chemical defenses (i.e., nutrient deficit or presence of toxic compounds), as well as their role in the shaping of bee-flower interactions, are discussed. Our results strongly suggest that pollen chemical traits may act as drivers of plant selection by bees and partly explain why Asteraceae pollen is rare in generalist bee diets.
Keywords	Asteraceae ; pollen defenses ; generalist floral visitors ; Bombus terrestris ; chemical protection ; mechanical protection ; Science ; Q
Subject code	580 ; 333
Language	English
Publishing date	2020-05-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Specialized Metabolites in Floral Resources

Ombeline Sculfort / Maxence Gérard / Antoine Gekière / Denis Nonclercq / Pascal Gerbaux / Pierre Duez / Maryse Vanderplanck

Frontiers in Ecology and Evolution, Vol

Effects and Detection in Buff-Tailed Bumblebees

2021 Volume 9

Abstract: The selection of appropriate food resources by bees is a critical aspect for the maintenance of their populations, especially in the current context of global change and pollinator decline. Wild bees have a sophisticated ability to forage selectively on ... ...

Abstract	The selection of appropriate food resources by bees is a critical aspect for the maintenance of their populations, especially in the current context of global change and pollinator decline. Wild bees have a sophisticated ability to forage selectively on specific resources, and can assess the quality of pollen using contact chemosensory perception (taste). While numerous studies have investigated the detection of pollen macronutrients in bees and their impact on bee health and reproductive success, only a few studies have described the gustatory responses of bees toward specialized metabolites. In addition, these studies mostly focused on the response to nectar and neglected pollen, which is the main food resource for both bee imagines and larvae. Whether bees have the ability to detect specialized toxic metabolites in pollen and then rapidly adapt their foraging behavior to avoid them is very little studied. In this study, we tested whether pollen specialized metabolites affect bumblebees at both the micro-colony and individual levels (i.e., bioassays using supplemented pollen), and whether foragers detect these specialized metabolites and potentially display an avoidance behavior (i.e., preference tests using supplemented syrup). Bumblebees were fed with either amygdalin-, scopolamine- or sinigrin-supplemented pollen diets in ratios that mimic 50%, 100%, and 200% of naturally occurring concentrations. We found no effect of these specialized metabolites on resource collection, reproductive success and stress response at the micro-colony level. At the individual level, bumblebees fed on 50%-amygdalin or 50%-scopolamine diets displayed the highest scores for damage to their digestive systems. Interestingly, during the preference tests, the solution with 50%-scopolamine displayed a phagostimulatory activity, whereas solution with 50%-amygdalin had a deterrent effect and could trigger an active avoidance behavior in bumblebees, with a faster proboscis retraction. Our results suggest that regulation of toxin intake ...
Keywords	plant–pollinator interactions ; amygdalin ; sinigrin ; scopolamine ; detection ; behavior ; Evolution ; QH359-425 ; Ecology ; QH540-549.5
Subject code	333
Language	English
Publishing date	2021-09-01T00:00:00Z
Publisher	Frontiers Media S.A.
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Article ; Online: Species-specific metabolites mediate host selection and larval recruitment of the symbiotic seastar shrimp

Alexia Lourtie / Igor Eeckhaut / Jérôme Mallefet / Philippe Savarino / Mathilde Isorez / Lisa Mussoi / Hugo Bischoff / Jérôme Delroisse / Laetitia Hédouin / Pascal Gerbaux / Guillaume Caulier

Scientific Reports, Vol 13, Iss 1, Pp 1-

2023 Volume 15

Abstract: Abstract In marine environments, host selection, defining how symbiotic organisms recognize and interact with their hosts, is often mediated by olfactory communication. Although adult symbionts may select their hosts detecting chemosensory cues, no ... ...

Abstract	Abstract In marine environments, host selection, defining how symbiotic organisms recognize and interact with their hosts, is often mediated by olfactory communication. Although adult symbionts may select their hosts detecting chemosensory cues, no information is available concerning the recruitment of symbiotic larvae which is a crucial step to sustain symbioses over generations. This study investigates the olfactory recognition of seastar hosts by adult Zenopontonia soror shrimps and the recruitment of their larvae. We examine the semiochemicals that influence host selection using chemical extractions, behavioural experiments in olfactometers, and mass spectrometry analyses. After describing the symbiotic population and the embryonic development of shrimps, our results demonstrate that asterosaponins, which are traditionally considered as chemical defences in seastars, are species-specific and play a role in attracting the symbiotic shrimps. Adult shrimps were found to be attracted only by their original host species Culcita novaeguineae, while larvae were attracted by different species of seastars. This study provides the first chemical identification of an olfactory cue used by larvae of symbiotic organisms to locate their host for recruitment. These findings highlight the importance of chemical communication in the mediation of symbiotic associations, which has broader significant implications for understanding the ecological dynamics of marine ecosystems.
Keywords	Medicine ; R ; Science ; Q
Subject code	590
Language	English
Publishing date	2023-08-01T00:00:00Z
Publisher	Nature Portfolio
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Article ; Online: Echinometra mathaei and its ectocommensal shrimps

Lola Brasseur / Guillaume Caulier / Gilles Lepoint / Pascal Gerbaux / Igor Eeckhaut

Scientific Reports, Vol 8, Iss 1, Pp 1-

the role of sea urchin spinochrome pigments in the symbiotic association

2018 Volume 10

Abstract: Abstract Tuleariocaris holthuisi and Arete indicus are two ectocommensal shrimps closely associated with the tropical sea urchin Echinometra mathaei. This study provides a comparison of these two E. mathaei symbiotic crustaceans and particularly focuses ... ...

Abstract	Abstract Tuleariocaris holthuisi and Arete indicus are two ectocommensal shrimps closely associated with the tropical sea urchin Echinometra mathaei. This study provides a comparison of these two E. mathaei symbiotic crustaceans and particularly focuses on the relationship between T. holthuisi and its host’s pigments (i.e. spinochromes), and its dependency on its host. While all the analyses underline a close association between A. indicus and E. mathaei, they reveal a particularly close interaction between T. holthuisi and its host. Chemical analyses reveal that these shrimps present the same spinochrome composition as E. mathaei, and have similar colouration, allowing camouflage. Isotopic composition and pigment loss after host separation suggest that these pigments are certainly assimilated upon feeding on the urchin. Moreover, symbiont isolation experiments demonstrate the high dependency of T. holthuisi on its host and the importance of the host’s pigments on their survival capacity. Finally, some host recognition mechanisms are investigated for T. holthuisi and show the probable implication of spinochromes in host selection, through chemical recognition. Hence, all the results suggest the essential roles of spinochromes for T. holthuisi, which, in turn, suggests the potential implication of these pigments in the shrimps’ metabolism.
Keywords	Medicine ; R ; Science ; Q
Language	English
Publishing date	2018-12-01T00:00:00Z
Publisher	Nature Publishing Group
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Article ; Online: Epidemiology of a SKin Ulceration Disease (SKUD) in the sea cucumber Holothuria scabra with a review on the SKUDs in Holothuroidea (Echinodermata)

Jérôme Delroisse / Kévin Van Wayneberghe / Patrick Flammang / David Gillan / Pascal Gerbaux / Noel Opina / Gildas Georges Boleslas Todinanahary / Igor Eeckhaut

Scientific Reports, Vol 10, Iss 1, Pp 1-

2020 Volume 19

Abstract: Abstract Aquacultivated sea cucumbers often suffer from SKin Ulceration Diseases (SKUDs). SKUDs have been observed in six holothuroid species from nine countries. All SKUDs present a similar symptom—the skin ulceration—and can be induced by bacteria, ... ...

Abstract	Abstract Aquacultivated sea cucumbers often suffer from SKin Ulceration Diseases (SKUDs). SKUDs have been observed in six holothuroid species from nine countries. All SKUDs present a similar symptom—the skin ulceration—and can be induced by bacteria, viruses, or abiotic factors. We here provide an update on SKUDs in holothuroids and analyse the case of the SKUD observed in Holothuria scabra in Madagascar. Field observations revealed a seasonality of the disease (i.e. wintertime maximum peak). Morphological analyses of integument ulcers showed that sea cucumbers react by forming a collagen fibre plug. Metagenomic analyses revealed a higher proportion of Vibrionaceae (Gammaproteobacteria) in ulcers in comparison to the healthy integument of the same individuals. Experimental infection assays were performed with ulcer crude extracts and bacteria isolated from these extracts (e.g. Vibrio parahaemolyticus) but did not significantly induce skin ulceration. Our results suggest that the disease is not induced by a pathogen or, at the very least, that the pathogen is not found within the ulcers as the disease is not transmissible by contact. An initial cause of the SKUD in Madagascar might be the repeated and prolonged exposures to cold temperatures. Opportunistic bacteria could settle in the dermis of ulcerated individuals and promote the ulcer extension. We propose a general nomenclature for SKUDs based on the acronym of the disease, the affected sea cucumber species (e.g. Hs for Holothuria scabra), the concerned region using an ISO code 3166-2 (e.g. MG for Madagascar), the description date (e.g. 20 for the year 2020), and, when known, the inducing agent (first letter of the general taxon, b for bacteria, v for virus in currently known cases; a a if it is an abiotic inducing parameter; nothing if the inducing cause has not been precisely identified). The disease described in this work will be designated under the name SKUD Hs-MG-20.
Keywords	Medicine ; R ; Science ; Q
Subject code	630
Language	English
Publishing date	2020-12-01T00:00:00Z
Publisher	Nature Portfolio
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