Comparaison de différentes méthodes d'extraction d'acides dicaféoylquiniques à partir d'une plante halophile

AbstractThe aim of this study is the evaluation of different extraction methods for dicaffeoylquinic acids (diCQA), previously identified by a LC-DAD-ESI-QTOF dereplication strategy from a halophyte plant rich in polyphenols. Three different eco-friendly extraction methods are tested: microwave-assisted extraction (MAE), pressurized fluid extraction (PFE), supercritical fluid extraction (SFE). Various specific parameters are optimized for each of them. Global extraction yields are calculated for all extracts. Moreover, the extracts are analyzed by HPLC–DAD–ELSD, and the obtained profiles are compared to estimate qualitatively and semi-quantitatively their composition. The practicality of each technique is also discussed. The results show that the various parameters tested for PFE and MAE do not drastically affect the extraction of our interest compounds. However, the parameters tested on SFE are more decisive, such as the addition of a modifier in CO2, which allows the extraction of diCQA

Methyl Jasmonate Elicited Helichrysum stoechas (L.) Moench Cell Suspensions, A Promising Source of Extracts with Allelopathic Activity?

International audienceHelichrysum stoechas (L.) Moench cell suspensions were analyzed by LC-ESI-QTOF, which highlighted the predominance of 3,5-O-dicaffeoylquinic acid (3,5-diCQA). Elicitation of H. stoechas cells with methyl jasmonate (200 mM) led to a massive rise in 3,5-diCQA, up to 5-fold-increase compared with control, reaching the concentration of 10.2 mg. g-1dry weight after 14 days of culture. Previous data showed that diCQA isomers are potent allelopathic compounds, thus the methanolic extracts of control and MeJa-elicited H. stoechas cells were tested for their phytotoxicity. With this in mind, activity on the seed germination and seedling growth of the model plant Lepidium sativum were tested. Phytotoxicity of both extracts occurred in a dose-dependent manner, with a greater activity of elicited cells extract. Indeed, in the concentration range from 0.31 to 0.83 mg. mL-1, the latter showed a significantly higher inhibition rate of L. sativum seedlings root growth, when compared to control cells extract. The data presented may contribute to explore new strategies towards the conception of bioherbicides from plant origin. To our knowledge, this study is the first report of the use of elicited plant cells grown in vitro as a raw material for the production of allelopathic metabolites

Orchids and their mycorrhizal fungi: an insufficiently explored relationship

International audienceOrchids are associated with diverse fungal taxa, including nonmycorrhizal endophytic fungi as well as mycorrhizal fungi. The orchid mycorrhizal (OM) symbiosis is an excellent model for investigating the biological interactions between plants and fungi due to their high dependency on these symbionts for growth and survival. To capture the complexity of OM interactions, significant genomic, numerous transcriptomic, and proteomic studies have been performed, unraveling partly the role of each partner. On the other hand, several papers studied the bioactive metabolites from each partner but rarely interpreted their significance in this symbiotic relationship. In this review, we focus from a biochemical viewpoint on the OM dynamics and its molecular interactions. The ecological functions of OM in plant development and stress resistance are described first, summarizing recent literature. Secondly, because only few studies have specifically looked on OM molecular interactions, the signaling pathways and compounds allowing the establishment/maintenance of mycorrhizal association involved in arbuscular mycorrhiza (AM) are discussed in parallel with OM. Based on mechanistic similarities between OM and AM, and recent findings on orchids’ endophytes, a putative model representing the different molecular strategies that OM fungi might employ to establish this association is proposed. It is hypothesized here that (i) orchids would excrete plant molecule signals such as strigolactones and flavonoids but also other secondary metabolites; (ii) in response, OM fungi would secrete mycorrhizal factors (Myc factors) or similar compounds to activate the common symbiosis genes (CSGs); (iii) overcome the defense mechanism by evasion of the pathogen-associated molecular patterns (PAMPs)-triggered immunity and by secretion of effectors such as small inhibitor proteins; and (iv) finally, secrete phytohormones to help the colonization or disrupt the crosstalk of plant defense phytohormones. To challenge this putative model, targeted and untargeted metabolomics studies with special attention to each partner’s contribution are finally encouraged and some technical approaches are proposed

Orchids and their mycorrhizal fungi

Orchids are associated with diverse fungal taxa, including non-mycorrhizal endophytic fungi and mycorrhizas. Orchid mycorrhiza (OM) symbiosis is an excellent model for investigating the biological interactions between plants and fungi due to their high dependency on these symbionts for growth and survival. To capture the complexity of OM interactions, significant genomic, numerous transcriptomic, and proteomics studies have been performed, unravelling partly the role of each partner. In this review, the orchid and mycorrhizal fungus relationship will be described summarizing the recent published literature on OM with special attention to the nutrient exchange model, the correlation on fitness and distribution of orchid populations, and finally the chemical communication and defense mechanisms. Based on the recent finding on orchids endophytes, OM relationship, arbuscular mycorrhiza (AM) and OM similarities [1], [2], a putative model representing the different strategies that OM fungi might employ to establish this symbiosis is proposed. It is hypothesized here that (i) orchids would excrete signaling molecules such as strigolactones and flavonoids to facilitate the establishment of the symbiosis. In response, (ii) OM fungi would secrete mycorrhizal (Myc) factors to activate the common symbiosis genes, (iii) evade the pathogen associated molecular patterns triggered immunity and secrete effectors to overcome the defense mechanism (iv) and finally secrete phytohormones to help the colonization or disrupt the crosstalk of plant defense phytohormones. To challenge this supposed model, metabolomics studies with special attention to each partner contribution are encouraged and some technical approaches are proposed

Plant-microbe features of Dendrobium fimbriatum (Orchidaceae) fungal community

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Extensive Phytochemical Assessment of Dendrobium fimbriatum Hook (Orchidaceae)

International audienceDendrobium fimbriatum Hook is an important medicinal and ornamental orchid that may lead to important drugs and cosmetics. In this study, 2 analytical strategies were combined to describe the detailed composition of a hydroethanolic extract of the whole plant. The CARAMEL approach, based on centrifugal partition chromatography and nuclear magnetic resonance data interpretation, allowed the rapid dereplication of 21 major constituents, mainly including polyols, nucleosides, zwitterionic compounds, phenolic compounds, and organic acids. Further semipreparative high-performance liquid chromatography and spectroscopic analyses led to the isolation of 6 additional compounds; 4 phenanthrenes (plicatol B, hircinol, plicatol A, and plicatol C), 1 bibenzyl (3′,4-dihydroxy-3,5′-dimethoxybibenzyl), and 1 furostanol saponin (protodioscin), as well as a new phenanthrene derivative, plicatol D. A total of 28 metabolites were structurally elucidated, among which 23 are described for this species for the first time