Integration of Wnt-inhibitory activity and structural novelty scoring results to uncover novel bioactive natural products: new Bicyclo[3.3.1]non-3-ene-2,9-diones from the leaves of Hymenocardia punctata

In natural products (NPs) research, methods for the efficient prioritization of natural extracts (NEs) are key for discovering novel bioactive NPs. In this study a biodiverse collection of 1,600 NEs, previously analyzed by UHPLC-HRMS2 metabolite profiling was screened for Wnt pathway regulation. The results of the biological screening drove the selection of a subset of 30 non-toxic NEs with an inhibitory IC50 ≤ 5 μg/mL. To increase the chance of finding structurally novel bioactive NPs, Inventa, a computational tool for automated scoring of NEs based on structural novelty was used to mine the HRMS2 analysis and dereplication results. After this, four out of the 30 bioactive NEs were shortlisted by this approach. The most promising sample was the ethyl acetate extract of the leaves of Hymenocardia punctata (Phyllanthaceae). Further phytochemical investigations of this species resulted in the isolation of three known prenylated flavones (3, 5, 7) and ten novel bicyclo[3.3.1]non-3-ene-2,9-diones (1, 2, 4, 6, 8-13), named Hymenotamayonins. Assessment of the Wnt inhibitory activity of these compounds revealed that two prenylated flavones and three novel bicyclic compounds showed interesting activity without apparent cytotoxicity. This study highlights the potential of combining Inventa's structural novelty scores with biological screening results to effectively discover novel bioactive NPs in large NE collections.

Antiprotozoal Activity of Plants Used in the Management of Sleeping Sickness in Angola and Bioactivity-Guided Fractionation of Brasenia schreberi J.F.Gmel and Nymphaea lotus L. Active against T. b. rhodesiense

Folk medicine is widely used in Angola, even for human African trypanosomiasis (sleeping sickness) in spite of the fact that the reference treatment is available for free. Aiming to validate herbal remedies in use, we selected nine medicinal plants and assessed their antitrypanosomal activity. A total of 122 extracts were prepared using different plant parts and solvents. A total of 15 extracts from seven different plants exhibited in vitro activity (>70% at 20 µg/mL) against Trypanosoma brucei rhodesiense bloodstream forms. The dichloromethane extract of Nymphaea lotus (leaves and leaflets) and the ethanolic extract of Brasenia schreberi (leaves) had IC50 values ≤ 10 µg/mL. These two aquatic plants are of particular interest. They are being co-applied in the form of a decoction of leaves because they are considered by local healers as male and female of the same species, the ethnotaxon "longa dia simbi". Bioassay-guided fractionation led to the identification of eight active molecules: gallic acid (IC50 0.5 µg/mL), methyl gallate (IC50 1.1 µg/mL), 2,3,4,6-tetragalloyl-glucopyranoside, ethyl gallate (IC50 0.5 µg/mL), 1,2,3,4,6-pentagalloyl-β-glucopyranoside (IC50 20 µg/mL), gossypetin-7-O-β-glucopyranoside (IC50 5.5 µg/mL), and hypolaetin-7-O-glucoside (IC50 5.7 µg/mL) in B. schreberi, and 5-[(8Z,11Z,14Z)-heptadeca-8,11,14-trienyl] resorcinol (IC50 5.3 µg/mL) not described to date in N. lotus. Five of these active constituents were detected in the traditional preparation. This work provides the first evidence for the ethnomedicinal use of these plants in the management of sleeping sickness in Angola.

A Sample-Centric and Knowledge-Driven Computational Framework for Natural Products Drug Discovery

The ENPKG framework organizes large heterogeneous metabolomics data sets as a knowledge graph, offering exciting opportunities for drug discovery and chemodiversity characterization.

Chloride, glutathiones, and insect-derived elicitors introduced into the xylem trigger electrical signaling

Ricca assays allow the direct introduction of compounds extracted from plants or the organisms that attack them into the leaf vasculature. Using chromatographic fractionation of Arabidopsis (Arabidopsis thaliana) leaf extracts, we found glutamate was the most active low mass elicitor of membrane depolarization. However, other known elicitors of membrane depolarization are generated in the wound response. These include unstable aglycones generated by glucosinolate (GSL) breakdown. None of the aglycone-derived GSL-breakdown products, including nitriles and isothiocyanates, that we tested using Ricca assays triggered electrical activity. Instead, we found that glutathione and the GSL-derived compound sulforaphane glutathione triggered membrane depolarizations. These findings identify a potential link between GSL breakdown and glutathione in the generation of membrane depolarizing signals. Noting that the chromatographic fractionation of plant extracts can dilute or exchange ions, we found that Cl- caused glutamate receptor-like3.3-dependent membrane depolarizations. In summary, we show that, in addition to glutamate, glutathione derivatives as well as chloride ions will need to be considered as potential elicitors of wound-response membrane potential change. Finally, by introducing aphid (Brevicoryne brassicae) extracts or the flagellin-derived peptide flg22 into the leaf vasculature we extend the use of Ricca assays for the exploration of insect/plant and bacteria/plant interactions.

Comparative metabolomic study of fungal foliar endophytes and their long-lived host Astrocaryum sciophilum: a model for exploring the chemodiversity of host-microbe interactions

Introduction

In contrast to the dynamics observed in plant/pathogen interactions, endophytic fungi have the capacity to establish enduring associations within their hosts, leading to the development of a mutually beneficial relationship that relies on specialized chemical interactions. Research indicates that the presence of endophytic fungi has the ability to significantly modify the chemical makeup of the host organism. Our hypothesis proposes the existence of a reciprocal exchange of chemical signals between plants and fungi, facilitated by specialized chemical processes that could potentially manifest within the tissues of the host. This research aimed to precisely quantify the portion of the cumulative fungal endophytic community's metabolome detectable within host leaves, and tentatively evaluate its relevance to the host-endophyte interplay. The understory palm Astrocaryum sciophilum (Miq.) Pulle was used as a interesting host plant because of its notable resilience and prolonged life cycle, in a tropical ecosystem.

Method

Using advanced metabolome characterization, including UHPLC-HRMS/MS and molecular networking, the study explored enriched metabolomes of both host leaves and 15 endophytic fungi. The intention was to capture a metabolomic "snapshot" of both host and endophytic community, to achieve a thorough and detailed analysis.

Results and discussion

This approach yielded an extended MS-based molecular network, integrating diverse metadata for identifying host- and endophyte-derived metabolites. The exploration of such data (>24000 features in positive ionization mode) enabled effective metabolome comparison, yielding insights into cultivable endophyte chemodiversity and occurrence of common metabolites between the holobiont and its fungal communities. Surprisingly, a minor subset of features overlapped between host leaf and fungal samples despite significant plant metabolome enrichment. This indicated that fungal metabolic signatures produced in vitro remain sparingly detectable in the leaf. Several classes of primary metabolites were possibly shared. Specific fungal metabolites and/or compounds of their chemical classes were only occasionally discernible in the leaf, highlighting endophytes partial contribution to the overall holobiont metabolome. To our knowledge, the metabolomic study of a plant host and its microbiome has rarely been performed in such a comprehensive manner. The general analytical strategy proposed in this paper seems well-adapted for any study in the field of microbial- or microbiome-related MS and can be applied to most host-microbe interactions.

Wound-response jasmonate dynamics in the primary vasculature

The links between wound-response electrical signalling and the activation of jasmonate synthesis are unknown. We investigated damage-response remodelling of jasmonate precursor pools in the Arabidopsis thaliana leaf vasculature. Galactolipids and jasmonate precursors in primary veins from undamaged and wounded plants were analysed using MS-based metabolomics and NMR. In parallel, DAD1-LIKE LIPASEs (DALLs), which control the levels of jasmonate precursors in veins, were identified. A novel galactolipid containing the jasmonate precursor 12-oxo-phytodienoic acid (OPDA) was identified in veins: sn-2-O-(cis-12-oxo-phytodienoyl)-sn-3-O-(β-galactopyranosyl) glyceride (sn-2-OPDA-MGMG). Lower levels of sn-1-OPDA-MGMG were also detected. Vascular OPDA-MGMGs, sn-2-18:3-MGMG and free OPDA pools were reduced rapidly in response to damage-activated electrical signals. Reduced function dall2 mutants failed to build resting vascular sn-2-OPDA-MGMG and OPDA pools and, upon wounding, dall2 produced less jasmonoyl-isoleucine (JA-Ile) than the wild-type. DALL3 acted to suppress excess JA-Ile production after wounding, whereas dall2 dall3 double mutants strongly reduce jasmonate signalling in leaves distal to wounds. LOX6 and DALL2 function to produce OPDA and the non-bilayer-forming lipid sn-2-OPDA-MGMG in the primary vasculature. Membrane depolarizations trigger rapid depletion of these molecules. We suggest that electrical signal-dependent lipid phase changes help to initiate vascular jasmonate synthesis in wounded leaves.

Generation of potent antibacterial compounds through enzymatic and chemical modifications of the trans-δ-viniferin scaffold

Stilbene dimers are well-known for their diverse biological activities. In particular, previous studies have demonstrated the high antibacterial potential of a series of trans-δ-viniferin-related compounds against gram-positive bacteria such as Staphylococcus aureus. The trans-δ-viniferin scaffold has multiple chemical functions and can therefore be modified in various ways to generate derivatives. Here we report the synthesis of 40 derivatives obtained by light isomerization, O-methylation, halogenation and dimerization of other stilbene monomers. The antibacterial activities of all generated trans-δ-viniferin derivatives were evaluated against S. aureus and information on their structure-activity relationships (SAR) was obtained using a linear regression model. Our results show how several parameters, such as the O-methylation pattern and the presence of halogen atoms at specific positions, can determine the antibacterial activity. Taken together, these results can serve as a starting point for further SAR investigations.

One step bio-guided isolation of secondary metabolites from the endophytic fungus Penicillium crustosum using high-resolution semi-preparative HPLC

BACKGROUND

An endophytic fungal strain Penicillium crustosum was isolated from the seagrass Posidonia oceanica and investigated to identify its antimicrobial constituents and characterize its metabolome composition. The ethyl acetate extract of this fungus exhibited antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) as well as an anti-quorum sensing effect against Pseudomonas aeruginosa.

METHODS

The crude extract was profiled by UHPLC-HRMS/MS and the dereplication was assisted by feature-based molecular networking. As a result, more than twenty compounds were annotated in this fungus. To rapidly identify the active compounds, the enriched extract was fractionated by semi-preparative HPLC-UV applying a chromatographic gradient transfer and dry load sample introduction to maximise resolution. The collected fractions were profiled by 1H-NMR and UHPLC-HRMS.

RESULTS

The use of molecular networking-assisted UHPLC-HRMS/MS dereplication allowed preliminary identification of over 20 compounds present in the ethyl acetate extract of P. crustosum. The chromatographic approach significantly accelerated the isolation of the majority of compounds present in the active extract. The one-step fractionation allowed the isolation and identification of eight compounds (1-8).

CONCLUSION

This study led to the unambiguous identification of eight known secondary metabolites as well as the determination of their antibacterial properties.

Bioactivity-guided isolation of trypanocidal coumarins and dihydro-pyranochromones from selected Apiaceae plant species

Bioactivity-guided isolation of natural products from plant matrices is widely used in drug discovery. Here, this strategy was applied to identify trypanocidal coumarins effective against the parasite Trypanosoma cruzi, the etiologic agent of Chagas disease (American trypanosomiasis). Previously, phylogenetic relationships of trypanocidal activity revealed a coumarin-associated antichagasic hotspot in the Apiaceae. In continuation, a total of 35 ethyl acetate extracts of different Apiaceae species were profiled for selective cytotoxicity against T. cruzi epimastigotes over host CHO-K1 and RAW264.7 cells at 10 μg/mL. A flow cytometry-based T. cruzi trypomastigote cellular infection assay was employed to measure toxicity against the intracellular amastigote stage. Among the tested extracts, Seseli andronakii aerial parts, Portenschlagiella ramosissima and Angelica archangelica subsp. litoralis roots exhibited selective trypanocidal activity and were subjected to bioactivity-guided fractionation and isolation by countercurrent chromatography. The khellactone ester isosamidin isolated from the aerial parts of S. andronakii emerged as a selective trypanocidal molecule (selectivity index ∼9) and inhibited amastigote replication in CHO-K1 cells, though it was significantly less potent than benznidazole. The khellactone ester praeruptorin B and the linear dihydropyranochromones 3'-O-acetylhamaudol and ledebouriellol isolated from the roots of P. ramosissima were more potent and efficiently inhibited the intracellular amastigote replication at < 10 μM. The furanocoumarins imperatorin, isoimperatorin and phellopterin from A. archangelica inhibited T. cruzi replication in host cells only in combination, indicative of superadditive effects, while alloimperatorin was more active in fractions. Our study reports preliminary structure-activity relationships of trypanocidal coumarins and shows that pyranocoumarins and dihydropyranochromones are potential chemical scaffolds for antichagasic drug discovery.

Antiviral properties of trans-δ-viniferin derivatives against enveloped viruses

Over the last century, the number of epidemics caused by RNA viruses has increased and the current SARS-CoV-2 pandemic has taught us about the compelling need for ready-to-use broad-spectrum antivirals. In this scenario, natural products stand out as a major historical source of drugs. We analyzed the antiviral effect of 4 stilbene dimers [1 (trans-δ-viniferin); 2 (11',13'-di-O-methyl-trans-δ-viniferin), 3 (11,13-di-O-methyl-trans-δ-viniferin); and 4 (11,13,11',13'-tetra-O-methyl-trans-δ-viniferin)] obtained from plant substrates using chemoenzymatic synthesis against a panel of enveloped viruses. We report that compounds 2 and 3 display a broad-spectrum antiviral activity, being able to effectively inhibit several strains of Influenza Viruses (IV), SARS-CoV-2 Delta and, to some extent, Herpes Simplex Virus 2 (HSV-2). Interestingly, the mechanism of action differs for each virus. We observed both a direct virucidal and a cell-mediated effect against IV, with a high barrier to antiviral resistance; a restricted cell-mediated mechanism of action against SARS-CoV-2 Delta and a direct virustatic activity against HSV-2. Of note, while the effect was lost against IV in tissue culture models of human airway epithelia, the antiviral activity was confirmed in this relevant model for SARS-CoV-2 Delta. Our results suggest that stilbene dimer derivatives are good candidate models for the treatment of enveloped virus infections.

Shallow- and Deep-Water Ophiura Species Produce a Panel of Chlorin Compounds with Potent Photodynamic Anticancer Activities

A Pacific brittle star Ophiura sarsii has previously been shown to produce a chlorin (3S,4S)-14-Ethyl-9-(hydroxymethyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid (ETPA) (1) with potent phototoxic activities, making it applicable to photodynamic therapy. Using extensive LC-MS metabolite profiling, molecular network analysis, and targeted isolation with de novo NMR structure elucidation, we herein identify five additional chlorin compounds from O. sarsii and its deep-sea relative O. ooplax: 10S-Hydroxypheophorbide a (2), Pheophorbide a (3), Pyropheophorbide a (4), (3S,4S,21R)-14-Ethyl-9-(hydroxymethyl)-21-(methoxycarbonyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid (5), and (3S,4S,21R)-14-Ethyl-21-hydroxy-9-(hydroxymethyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid (6). Chlorins 5 and 6 have not been previously reported in natural sources. Interestingly, low amounts of chlorins 1-4 and 6 could also be identified in a distant species, the basket star Gorgonocephalus cf. eucnemis, demonstrating that chlorins are produced by a wide spectrum of marine invertebrates of the class Ophiuroidea. Following the purification of these major Ophiura chlorin metabolites, we discovered the significant singlet oxygen quantum yield upon their photoinduction and the resulting phototoxicity against triple-negative breast cancer BT-20 cells. These studies identify an arsenal of brittle star chlorins as natural photosensitizers with potential photodynamic therapy applications.

Evaluation of the Antiseizure Activity of Endemic Plant Halfordia kendack Guillaumin and Its Main Constituent, Halfordin, on a Zebrafish Pentylenetetrazole (PTZ)-Induced Seizure Model

Epilepsy is a neurological disease that burdens over 50 million people worldwide. Despite the considerable number of available antiseizure medications, it is estimated that around 30% of patients still do not respond to available treatment. Herbal medicines represent a promising source of new antiseizure drugs. This study aimed to identify new drug lead candidates with antiseizure activity from endemic plants of New Caledonia. The crude methanolic leaf extract of Halfordia kendack Guillaumin (Rutaceae) significantly decreased (75 μg/mL and 100 μg/mL) seizure-like behaviour compared to sodium valproate in a zebrafish pentylenetetrazole (PTZ)-induced acute seizure model. The main coumarin compound, halfordin, was subsequently isolated by liquid-liquid chromatography and subjected to locomotor, local field potential (LFP), and gene expression assays. Halfordin (20 μM) significantly decreased convulsive-like behaviour in the locomotor and LFP analysis (by 41.4% and 60%, respectively) and significantly modulated galn, and penka gene expression.

Inventa: A computational tool to discover structural novelty in natural extracts libraries

Collections of natural extracts hold potential for the discovery of novel natural products with original modes of action. The prioritization of extracts from collections remains challenging due to the lack of a workflow that combines multiple-source information to facilitate the data interpretation. Results from different analytical techniques and literature reports need to be organized, processed, and interpreted to enable optimal decision-making for extracts prioritization. Here, we introduce Inventa, a computational tool that highlights the structural novelty potential within extracts, considering untargeted mass spectrometry data, spectral annotation, and literature reports. Based on this information, Inventa calculates multiple scores that inform their structural potential. Thus, Inventa has the potential to accelerate new natural products discovery. Inventa was applied to a set of plants from the Celastraceae family as a proof of concept. The Pristimera indica (Willd.) A.C.Sm roots extract was highlighted as a promising source of potentially novel compounds. Its phytochemical investigation resulted in the isolation and de novo characterization of thirteen new dihydro-β-agarofuran sesquiterpenes, five of them presenting a new 9-oxodihydro-β-agarofuran base scaffold.

Chiral Separation of Stilbene Dimers Generated by Biotransformation for Absolute Configuration Determination and Antibacterial Evaluation

A series of complex stilbene dimers have been generated through biotransformation of resveratrol, pterostilbene, and the mixture of both using the enzymatic secretome of Botrytis cinerea Pers. The process starts with achiral molecules and results in the generation of complex molecules with multiple chiral carbons. So far, we have been studying these compounds in the form of enantiomeric mixtures. In the present study, we isolated the enantiomers to determine their absolute configuration and assess if the stereochemistry could impact their biological properties. Eight compounds were selected for this study, corresponding to the main scaffolds generated (pallidol, leachianol, restrytisol and acyclic dimers) and the most active compounds (trans-δ-viniferin derivatives) against a methicillin-resistant strain of Staphylococcus aureus (MRSA). To isolate these enantiomers and determine their absolute configuration, a chiral HPLC-PDA analysis was performed. The analysis was achieved on a high-performance liquid chromatography system equipped with a chiral column. For each compound, the corresponding enantiomeric pair was obtained with high purity. The absolute configuration of each enantiomer was determined by comparison of experimental and calculated electronic circular dichroism (ECD). The antibacterial activities of the four trans-δ-viniferin derivatives against two S. aureus strains were evaluated.

Chemoenzymatic Synthesis of Original Stilbene Dimers Possessing Wnt Inhibition Activity in Triple-Negative Breast Cancer Cells Using the Enzymatic Secretome of Botrytis cinerea Pers

The Wnt signaling pathway controls multiple events during embryonic development of multicellular animals and is carcinogenic when aberrantly activated in adults. Breast cancer and triple-negative breast cancer (TNBC) in particular depend upon Wnt pathway overactivation. Despite this importance, no Wnt pathway-targeting drugs are currently available, which necessitates novel approaches to search for therapeutically relevant compounds targeting this oncogenic pathway. Stilbene analogs represent an under-explored field of therapeutic natural products research. In the present work, a library of complex stilbene derivatives was obtained through biotransformation of a mixture of resveratrol and pterostilbene using the enzymatic secretome of Botrytis cinerea. To improve the chemodiversity, the reactions were performed using i-PrOH, n-BuOH, i-BuOH, EtOH, or MeOH as cosolvents. Using this strategy, a series of 73 unusual derivatives was generated distributed among 6 scaffolds; 55 derivatives represent novel compounds. The structure of each compound isolated was determined by nuclear magnetic resonance and high-resolution mass spectrometry. The inhibitory activity of the isolated compounds against the oncogenic Wnt pathway was comprehensively quantified and correlated with their capacity to inhibit the growth of the cancer cells, leading to insights into structure-activity relationships of the derivatives. Finally, we have dissected mechanistic details of the stilbene derivatives activity within the pathway.

Chemoenzymatic Synthesis of Complex Phenylpropanoid Derivatives by the Botrytis cinerea Secretome and Evaluation of Their Wnt Inhibition Activity

In this study, a series of complex phenylpropanoid derivatives were obtained by chemoenzymatic biotransformation of ferulic acid, caffeic acid, and a mixture of both acids using the enzymatic secretome of Botrytis cinerea. These substrates were incubated with fungal enzymes, and the reactions were monitored using state-of-the-art analytical methods. Under such conditions, a series of dimers, trimers, and tetramers were generated. The reactions were optimized and scaled up. The resulting mixtures were purified by high-resolution semi-preparative HPLC combined with dry load introduction. This approach generated a series of 23 phenylpropanoid derivatives, 11 of which are described here for the first time. These compounds are divided into 12 dimers, 9 trimers (including a completely new structural scaffold), and 2 tetramers. Elucidation of their structures was performed with classical spectroscopic methods such as NMR and HRESIMS analyses. The resulting compound series were analyzed for anti-Wnt activity in TNBC cells, with several derivatives demonstrating specific inhibition.

Combination of Pseudo-LC-NMR and HRMS/MS-Based Molecular Networking for the Rapid Identification of Antimicrobial Metabolites From Fusarium petroliphilum

An endophytic fungal strain isolated from a seagrass endemic to the Mediterranean Sea (Posidonia oceanica) was studied in order to identify its antimicrobial constituents and further characterize the composition of its metabolome. It was identified as Fusarium petroliphilum by in-depth phylogenetic analyses. The ethyl acetate extract of that strain exhibited antimicrobial activities and an ability to inhibit quorum sensing of Staphylococcus aureus. To perform this study with a few tens of mg of extract, an innovative one-step generic strategy was devised. On one side, the extract was analyzed by UHPLC-HRMS/MS molecular networking for dereplication. On the other side, semi-preparative HPLC using a similar gradient profile was used for a single-step high-resolution fractionation. All fractions were systematically profiled by ¹H-NMR. The data were assembled into a 2D contour map, which we call “pseudo-LC-NMR,” and combined with those of UHPLC-HRMS/MS. This further highlighted the connection within structurally related compounds, facilitated data interpretation, and provided an unbiased quantitative profiling of the main extract constituents. This innovative strategy led to an unambiguous characterization of all major specialized metabolites of that extract and to the localization of its bioactive compounds. Altogether, this approach identified 22 compounds, 13 of them being new natural products and six being inhibitors of the quorum sensing mechanism of S. aureus and Pseudomonas aeruginosa. Minor analogues were also identified by annotation propagation through the corresponding HRMS/MS molecular network, which enabled a consistent annotation of 27 additional metabolites. This approach was designed to be generic and applicable to natural extracts of the same polarity range.

Kaempferol-3-O-α-(3,4-di-E-p-coumaroyl)-rhamnopyranoside from Nectandra oppositifolia releases Ca2+ from intracellular pools of Trypanosoma cruzi affecting the bioenergetics system

Phytochemical analysis of EtOH extract from leaves of Nectandra oppositifolia afforded three flavonoids: kaempferol (1), kaempferol-3-O-α-rhamnopyranoside (2) and kaempferol-3-O-α-(3,4-di-E-p-coumaroyl)-rhamnopyranoside (3), which were characterized by NMR and ESI-HRMS. When tested against the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease, flavonoids 1 and 3 were effective to kill the trypomastigotes with IC₅₀ values of 32.0 and 6.7 μM, respectively, while flavonoid 2 was inactive. Isolated flavonoids 1-3 were also tested in mammalian fibroblasts and showed CC₅₀ values of 24.8, 48.7 and 153.1 μM, respectively. Chemically, these results suggested that the free aglycone plays an important role in the bioactivity while the presence of p-coumaroyl unities linked in the rhamnoside unity is important to enhance the antitrypanosomal activity and reduce the mammalian cytotoxicity. The mechanism of cellular death was investigated for the most potent flavonoid 3 in the trypomastigotes using fluorescent and luminescent-based assays. It indicated that this compound induced neither permeabilization of the plasma membrane nor depolarization of the membrane electric potential. However, early time incubation (20 min) with flavonoid 3 resulted in a constant elevation of the Ca²⁺ levels inside the parasite. This effect was followed by a mitochondrial imbalance, leading to a hyperpolarization and depolarization of the mitochondrial membrane potential, with reduction of the ATP levels. During this time, the levels of reactive oxygen species levels (ROS) were unaltered. The leakage of Ca²⁺ from the intracellular pools can affect the bioenergetics system of T. cruzi, leading to the parasite death. Therefore, flavonoid 3 can be a useful tool for future studies against T. cruzi parasites.

Hypoglycemic active principles from the leaves of Bauhinia holophylla: Comprehensive phytochemical characterization and in vivo activity profile

Bauhinia holophylla leaves, also known as "pata-de-vaca", are traditionally used in Brazil to treat diabetes. Although the hypoglycemic activity of this medicinal plant has already been described, the active compounds responsible for the hypoglycemic activity have not yet been identified. To rapidly obtain two fractions in large amounts compatible with further in vivo assay, the hydroalcoholic extract of B. holophylla leaves was fractionated by Vacuum Liquid Chromatography and then purified by medium pressure liquid chromatography combined with an in vivo Glucose Tolerance Test in diabetic mice. This approach resulted in the identification of eleven compounds (1-11), including an original non-cyanogenic cyanoglucoside derivative. The structures of the isolated compounds were elucidated by nuclear magnetic resonance and high-resolution mass spectrometry. One of the major compounds of the leaves, lithospermoside (3), exhibited strong hypoglycemic activity in diabetic mice at the doses of 10 and 20 mg/kg b.w. and prevents body weight loss. The proton nuclear magnetic resonance (1H NMR) quantification revealed that the hydroalcoholic leaves extract contained 1.7% of lithospermoside (3) and 3.1% of flavonoids. The NMR analysis also revealed the presence of a high amount of pinitol (4) (9.5%), a known compound possessing in vivo hypoglycemic activity. The hypoglycemic properties of the hydroalcoholic leaves extract and the traditional water infusion extracts of the leaves of B. holophylla seem thus to be the result of the activity of three unrelated classes of compounds. Such results support to some extent the traditional use of Bauhinia holophylla to treat diabetes.

Isolation and Identification of Isocoumarin Derivatives With Specific Inhibitory Activity Against Wnt Pathway and Metabolome Characterization of Lasiodiplodia venezuelensis

The Wnt signaling pathway controls multiple events during embryonic development of multicellular animals and is carcinogenic when aberrantly activated in adults. Breast cancers are dependent on Wnt pathway overactivation mostly through dysregulation of pathway component protein expression, which necessitates the search for therapeutically relevant compounds targeting them. Highly diverse microorganisms as endophytes represent an underexplored field in the therapeutic natural products research. In the present work, the objective was to explore the chemical diversity and presence of selective Wnt inhibitors within a unique collection of fungi isolated as foliar endophytes from the long-lived tropical palm Astrocaryum sciophilum. The fungi were cultured, extracted with ethyl acetate, and screened for their effects on the Wnt pathway and cell proliferation. The endophytic strain Lasiodiplodia venezuelensis was prioritized for scaled-up fractionation based on its selective activity. Application of geometric transfer from analytical HPLC conditions to semi-preparative scale and use of dry load sample introduction enabled the isolation of 15 pure compounds in a single step. Among the molecules identified, five are original natural products described for the first time, and six are new to this species. An active fraction obtained by semi-preparative HPLC was re-purified by UHPLC-PDA using a 1.7 µm phenyl column. 75 injections of 8 µg were necessary to obtain sufficient amounts of each compound for structure elucidation and bioassays. Using this original approach, in addition to the two major compounds, a third minor compound identified as (R)-(-)-5-hydroxymellein (18) was obtained, which was found to be responsible for the significant Wnt inhibition activity recorded. Further studies of this compound and its structural analogs showed that only 18 acts in a highly specific manner, with no acute cytotoxicity. This compound is notably selective for upstream components of the Wnt pathway and is able to inhibit the proliferation of three triple negative breast cancer cell lines. In addition to the discovery of Wnt inhibitors of interest, this study contributes to better characterize the biosynthetic potential of L. venezuelensis.

Characterization of Pseudomonas aeruginosa Quorum Sensing Inhibitors from the Endophyte Lasiodiplodia venezuelensis and Evaluation of Their Antivirulence Effects by Metabolomics

The opportunistic pathogen Pseudomonas aeruginosa is one of the "critical priority pathogens" due to its multidrug resistance to a wide range of antibiotics. Its ability to invade and damage host tissues is due to the use of quorum sensing (QS) to collectively produce a plethora of virulence factors. Inhibition of QS is an attractive strategy for new antimicrobial agents because it disrupts the initial events of infection without killing the pathogen. Highly diverse microorganisms as endophytes represent an under-explored source of bioactive natural products, offering opportunities for the discovery of novel QS inhibitors (QSI). In the present work, the objective was to explore selective QSIs within a unique collection of fungal endophytes isolated from the tropical palm Astrocaryum sciophilum. The fungi were cultured, extracted, and screened for their antibacterial and specific anti-QS activities against P. aeruginosa. The endophytic strain Lasiodiplodia venezuelensis was prioritized for scaled-up fractionation for its selective activity, leading to the isolation of eight compounds in a single step. Among them, two pyran-derivatives were found to be responsible for the QSI activity, with an effect on some QS-regulated virulence factors. Additional non-targeted metabolomic studies on P. aeruginosa documented their effects on the production of various virulence-related metabolites.

METABOLOMICS REVEALS BIOMARKERS IN HUMAN URINE AND PLASMA TO PREDICT CYP2D6 ACTIVITY

Background and Purpose

Individualized assessment of cytochrome P450 2D6 (CYP2D6) activity is usually performed through phenotyping following administration of a probe drug to measure the enzyme's activity. To avoid any iatrogenic harm (allergic drug reaction, dosing error) related to the probe drug, the development of non‐burdensome tools for real‐time phenotyping of CYP2D6 could significantly contribute to precision medicine. This study focuses on the identification of markers of the CYP2D6 enzyme in human biofluids using an LC‐high‐resolution mass spectrometry‐based metabolomic approach.

Experimental Approach

Plasma and urine samples from healthy volunteers were analysed before and after intake of a daily dose of paroxetine 20 mg over 7 days. CYP2D6 genotyping and phenotyping, using single oral dose of dextromethorphan 5 mg, were also performed in all participants.

Key Results

We report four metabolites of solanidine and two unknown compounds as possible novel CYP2D6 markers. Mean relative intensities of these features were significantly reduced during the inhibition session compared with the control session (n = 37). Semi‐quantitative analysis showed that the largest decrease (−85%) was observed for the ion m/z 432.3108 normalized to solanidine (m/z 398.3417). Mean relative intensities of these ions were significantly higher in the CYP2D6 normal–ultrarapid metabolizer group (n = 37) compared with the poor metabolizer group (n = 6). Solanidine intensity was more than 15 times higher in CYP2D6‐deficient individuals compared with other volunteers.

Conclusion and Implications

The applied untargeted metabolomic strategy identified potential novel markers capable of semi‐quantitatively predicting CYP2D6 activity, a promising discovery for personalized medicine.

Identification of Potential Antiseizure Agents in Boswellia sacra using In Vivo Zebrafish and Mouse Epilepsy Models

The resin of the tree Boswellia sacra Flueck. (synonym: B. carterii; Burseraceae), also known as "frankincense", is a traditional remedy used for central nervous system disorders in East Africa. Here we report the evaluation of its antiseizure activity in zebrafish and mouse epilepsy models to identify novel antiseizure compounds. The resin was extracted by solvents of increasing polarity. The hexane extract demonstrated the strongest antiseizure activity and was therefore subjected to bioactivity-guided isolation, which leaded to the isolation of eight terpene derivatives. A new prenylbicyclogermacrene derivative (2) was isolated along with seven other compounds (1, 3-8). Among them, the triterpene β-boswellic acid (5) showed the strongest activity and reduced 90% of pentylenetetrazole (PTZ)-induced seizures at 100 μg/mL. In parallel to B. sacra, a commercial extract of Boswellia serrata was also evaluated and showed moderate bioactivity (45% reduction at 30 μg/mL). The extract of B. serrata was subjected to targeted isolation of other boswellic acid derivatives (9-13), which were evaluated for antiseizure activity in comparison with 5. In the whole series, β-boswellic acid (5) was the most active (60% reduction at 200 μM), and its potency was also confirmed with its purchased standard (S5). Pure nanoparticles of S5 and a commercially formulated extract of B. serrata were tested in a PTZ-kindling mouse seizure model. This notably revealed that the S5 administration reduced seizures by 50% in this mouse model, which was consistent with its detection and quantification in plasma and brain samples. This study and the preclinical evaluation performed indicate that β-boswellic acid, common to various species of Boswellia, has some potential as an antiseizure agent.

Hibiscus sabdariffa, a Treatment for Uncontrolled Hypertension. Pilot Comparative Intervention

In Iraq, in 2019, there were about 1.4 million Internally Displaced Persons (IDP); medical treatments were often interrupted. The feasibility of using Hibiscus sabdariffa (HS) decoction to curb hypertension was evaluated. A multicentric comparative pilot intervention for 121 participants with high blood pressure (BP) (≥140/90 mmHg) was conducted. Participants of the intervention group (with or without conventional medication) received HS decoction on a dose regimen starting from 10 grams per day. BP was measured five times over six weeks. The major active substances were chemically quantified. Results: After 6 weeks, 61.8% of participants from the intervention group (n = 76) reached the target BP < 140/90 mmHg, compared to 6.7% in the control group (n = 45). In the intervention group, a mean (±SD) reduction of 23.1 (±11.8) mmHg and 12.0 (±11.2) for systolic and diastolic BP, respectively, was observed, while in the control group the reduction was 4.4 (±10.2)/3.6 (±8.7). The chemical analysis of the starting dose indicated a content of 36 mg of total anthocyanins and 2.13 g of hibiscus acid. The study shows the feasibility of using HS decoction in IDP’s problematic framework, as hibiscus is a safe, local, affordable, and culturally accepted food product.

Saponins from Saffron Corms Inhibit the Gene Expression and Secretion of Pro-Inflammatory Cytokines

Corms are obtained as a byproduct during the cultivation of saffron (Crocus sativus). In a project aimed at the valorization of this waste product, we observed that a 70% EtOH extract of the corms and a sugar-depleted MeOH fraction of the extract inhibited the TNF-α/IFN-γ-induced secretion and gene expression of the chemokines IL-8, MCP-1, and RANTES in human HaCaT cells. The effects were in part stronger than those of the positive control hydrocortisone. For preparative isolation, the 70% EtOH extract was partitioned between n-BuOH and water. Separation of the n-BuOH-soluble fraction by centrifugal partition chromatography, followed by preparative and semipreparative HPLC, afforded a series of bidesmosidic glycosides of echinocystic acid bearing a 3,16-dihydroxy-10-oxo-hexadecanoic acid residue attached to the glycosidic moiety at C-28. They include azafrines 1 and 2, previously reported in saffron, and eight new congeners named azafrines 3-10. Saffron saponins significantly inhibited TNF-α/IFN-γ-induced secretion of RANTES in human HaCaT cells at 1 μM (p < 0.001). Some of them further lowered TNF-α/IFN-γ-induced gene expression.

A Cytotoxic Porphyrin from North Pacific Brittle Star Ophiura sarsii

Triple-negative breast cancer (TNBC) represents the deadliest form of gynecological tumors currently lacking targeted therapies. The ethanol extract of the North Pacific brittle star Ophiura sarsii presented promising anti-TNBC activities. After elimination of the inert material, the active extract was submitted to a bioguided isolation approach using high-resolution semipreparative HPLC-UV, resulting in one-step isolation of an unusual porphyrin derivative possessing strong cytotoxic activity. HRMS and 2D NMR resulted in the structure elucidation of the compound as (3S,4S)-14-Ethyl-9-(hydroxymethyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid. Never identified before in Ophiuroidea, porphyrins have found broad applications as photosensitizers in the anticancer photodynamic therapy. The simple isolation of a cytotoxic porphyrin from an abundant brittle star species we describe here may pave the way for novel natural-based developments of targeted anti-cancer therapies.

A Mass Spectrometry Based Metabolite Profiling Workflow for Selecting Abundant Specific Markers and Their Structurally Related Multi-Component Signatures in Traditional Chinese Medicine Multi-Herb Formulae

In Traditional Chinese Medicine (TCM), herbal preparations often consist of a mixture of herbs. Their quality control is challenging because every single herb contains hundreds of components (secondary metabolites). A typical 10 herb TCM formula was selected to develop an innovative strategy for its comprehensive chemical characterization and to study the specific contribution of each herb to the formula in an exploratory manner. Metabolite profiling of the TCM formula and the extract of each single herb were acquired with liquid chromatography coupled to high-resolution mass spectrometry for qualitative analyses, and to evaporative light scattering detection (ELSD) for semi-quantitative evaluation. The acquired data were organized as a feature-based molecular network (FBMN) which provided a comprehensive view of all types of secondary metabolites and their occurrence in the formula and all single herbs. These features were annotated by combining MS/MS-based in silico spectral match, manual evaluation of the structural consistency in the FBMN clusters, and taxonomy information. ELSD detection was used as a filter to select the most abundant features. At least one marker per herb was highlighted based on its specificity and abundance. A single large-scale fractionation from the enriched formula enabled the isolation and formal identification of most of them. The obtained markers allowed an improved annotation of associated features by manually propagating this information through the FBMN. These data were incorporated in the high-resolution metabolite profiling of the formula, which highlighted specific series of related components to each individual herb markers. These series of components, named multi-component signatures, may serve to improve the traceability of each herb in the formula. Altogether, the strategy provided highly informative compositional data of the TCM formula and detailed visualizations of the contribution of each herb by FBMN, filtered feature maps, and reconstituted chromatogram traces of all components linked to each specific marker. This comprehensive MS-based analytical workflow allowed a generic and unbiased selection of specific and abundant markers and the identification of multiple related sub-markers. This exploratory approach could serve as a starting point to develop more simple and targeted quality control methods with adapted marker specificity selection criteria to given TCM formula.

Symphytum officinale L.: Liquid-liquid chromatography isolation of caffeic acid oligomers and evaluation of their influence on pro-inflammatory cytokine release in LPS-stimulated neutrophils

ETHNOPHARMACOLOGICAL RELEVANCE

Symphytum officinale L. (comfrey, Boraginaceae) has been traditionally used for millennia in joint distortions, myalgia, bone fractures and hematomas. However, key activity-determining constituents and molecular mechanisms underlying its use have not been completely elucidated.

AIM OF THE STUDY

The objective of this study was to isolate and identify the major compounds from a hydroethanolic root extract of S. officinale and evaluate their antioxidant potential, alongside their effect on the cytokine production of ex vivo stimulated neutrophils, thus providing scientific support for the traditional use of comfrey root.

MATERIAL AND METHODS

Four caffeic acid oligomers were isolated from comfrey roots by liquid-liquid chromatography, their structures being established by MS and NMR analyses. In vitro antioxidant evaluation was performed by DPPH and ABTS assays. The cytotoxicity of isolated compounds was established by flow cytometry. The effect on cytokine release, such as interleukin (IL)-1β, IL-8 and tumor necrosis factor alpha (TNF-α), in lipopolysaccharide (LPS)-stimulated neutrophils was determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The main constituents found in comfrey root were represented by four caffeic acid oligomers, namely globoidnan B (1), rabdosiin (2), rosmarinic acid (3) and globoidnan A (4). Rabdosiin, globoidnans A and B were isolated for the first time from S. officinale. In the in vitro antioxidant tests, compound 2 was the most active, with EC₅₀ values in DPPH and ABTS assays of 29.14 ± 0.43 and 11.13 ± 0.39, respectively. Neutrophils' viability over the tested concentration domain of 12.5-50 μM was not altered. At 50 μM, all compounds significantly inhibited IL-1β release, with compound 3 (45.60% release vs. LPS stimulated neutrophils) being the most active, followed by compounds 1 (53.85%), 2 (69.89%) and 4 (60.68%).

CONCLUSIONS

The four caffeic acid oligomers reported in S. officinale root may contribute to the overall anti-inflammatory activity for which comfrey preparations are used in traditional medicine.

Phytochemical and Biological Investigation of Helianthemum nummularium, a High-Altitude Growing Alpine Plant Overrepresented in Ungulates Diets

Helianthemum nummularium is a European shrub growing at high altitude where it copes with a high level of stress. It was found to be overexpressed in ungulates diets compared to more abundant surrounding plants. These elements combined with the fact that H. nummularium from the Alps has never been investigated prompted us to study the phytochemical composition of its aerial parts. The analysis of the polar extract allowed for the isolation of eight compounds: p-hydroxybenzoic acid, tiliroside, kaempferol, astragalin, quercetin, plantainoside B, quercetin-3-O-glucoside, and quercetin-3-O-glucuronide. We investigated the effect of the polar extract and isolated compounds on nuclear factor erythroid 2-related factor 2 transcription factor, which regulates the expression of a wide variety of cytoprotective genes. We found that the ethanolic extract activates the expression of nuclear factor erythroid 2-related factor 2 in a dose-dependent manner, whereas the pure compounds were much less active. The activation of the nuclear factor erythroid 2-related factor 2 pathway by the plant extract could pave the way for studies to promote healthy aging through protection of cells against oxidative stress. Moreover, the isolated compounds could be investigated alone or in combination in the perspective of making the link between the ungulate's preference for this plant and possible use of it for self-medication.

Phosphatidylcholines from Pieris brassicae eggs activate an immune response in Arabidopsis

Recognition of conserved microbial molecules activates immune responses in plants, a process termed pattern-triggered immunity (PTI). Similarly, insect eggs trigger defenses that impede egg development or attract predators, but information on the nature of egg-associated elicitors is scarce. We performed an unbiased bioactivity-guided fractionation of eggs of the butterfly Pieris brassicae. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry of active fractions led to the identification of phosphatidylcholines (PCs). PCs are released from insect eggs, and they induce salicylic acid and H₂O₂ accumulation, defense gene expression and cell death in Arabidopsis, all of which constitute a hallmark of PTI. Active PCs contain primarily C16 to C18-fatty acyl chains with various levels of desaturation, suggesting a relatively broad ligand specificity of cell-surface receptor(s). The finding of PCs as egg-associated molecular patterns (EAMPs) illustrates the acute ability of plants to detect conserved immunogenic patterns from their enemies, even from seemingly passive structures such as eggs.

Production of Highly Active Antiparasitic Compounds from the Controlled Halogenation of the Arrabidaea brachypoda Crude Plant Extract

Direct halogenation of phenolic compounds present in the CH₂Cl₂ extract of the roots of Arrabidaea brachypoda was investigated to enhance chemodiversity. The approach is based on eco-friendly reactions using NaBr, NaI, and NaCl in aqueous media to generate multiple "unnatural" halogenated natural products from crude extracts. The halogenation reactions, monitored by UHPLC-PDA-ELSD-MS, were optimized to generate mono-, di-, or trihalogenated derivatives. To isolate these compounds, the reactions were scaled up and the halogenated analogues were isolated by semipreparative HPLC-UV and fully characterized by NMR and HR-MS data. All of the original 16 halogenated derivatives were evaluated for their antiparasitic activities against the parasites Leishmania amazonensis and Trypanosoma cruzi. Compounds presenting selective antiparasitic activities against one or both parasites with IC₅₀ values comparable to the reference were identified.

Antiseizure potential of the ancient Greek medicinal plant Helleborus odorus subsp. cyclophyllus and identification of its main active principles

ETHNOPHARMACOLOGICAL RELEVANCE

Ethnopharmacological data and ancient texts support the use of black hellebore (Helleborus odorus subsp. cyclophyllus, Ranunculaceae) for the management and treatment of epilepsy in ancient Greece.

AIM OF THE STUDY

A pharmacological investigation of the root methanolic extract (RME) was conducted using the zebrafish epilepsy model to isolate and identify the compounds responsible for a potential antiseizure activity and to provide evidence of its historical use. In addition, a comprehensive metabolite profiling of this studied species was proposed.

MATERIALS AND METHODS

The roots were extracted by solvents of increasing polarity and root decoction (RDE) was also prepared. The extracts were evaluated for antiseizure activity using a larval zebrafish epilepsy model with pentylenetetrazole (PTZ)-induced seizures. The RME exhibited the highest antiseizure activity and was therefore selected for bioactivity-guided fractionation. Isolated compounds were fully characterized by NMR and high-resolution tandem mass spectrometry (HRMS/MS). The UHPLC-HRMS/MS analyses of the RME and RDE were used for dereplication and metabolite profiling.

RESULTS

The RME showed 80% inhibition of PTZ-induced locomotor activity (300 μg/ml). This extract was fractionated and resulted in the isolation of a new glucopyranosyl-deoxyribonolactone (1) and a new furostanol saponin derivative (2), as well as of 20-hydroxyecdysone (3), hellebrin (4), a spirostanol glycoside derivative (5) and deglucohellebrin (6). The antiseizure activity of RME was found to be mainly due to the new furostanol saponin (2) and hellebrin (4), which reduced 45% and 60% of PTZ-induced seizures (135 μM, respectively). Besides, the aglycone of hellebrin, hellebrigenin (S34), was also active (45% at 7 μM). To further characterize the chemical composition of both RME and RDE, 30 compounds (A7-33, A35-37) were annotated based on UHPLC-HRMS/MS metabolite profiling. This revealed the presence of additional bufadienolides, furostanols, and evidenced alkaloids.

CONCLUSIONS

This study is the first to identify the molecular basis of the ethnopharmacological use of black hellebore for the treatment of epilepsy. This was achieved using a microscale zebrafish epilepsy model to rapidly quantify in vivo antiseizure activity. The UHPLC-HRMS/MS profiling revealed the chemical diversity of the extracts and the presence of numerous bufadienolides, furostanols and ecdysteroids, also present in the decoction.

Generation of Stilbene Antimicrobials against Multiresistant Strains of Staphylococcus aureus through Biotransformation by the Enzymatic Secretome of Botrytis cinerea

The biotransformation of a mixture of resveratrol and pterostilbene was performed by the protein secretome of Botrytis cinerea. Several reaction conditions were tested to overcome solubility issues and to improve enzymatic activity. Using MeOH as cosolvent, a series of unusual methoxylated compounds was generated. The reaction was scaled-up, and the resulting mixture purified by semipreparative HPLC-PDA-ELSD-MS. Using this approach, 15 analogues were isolated in one step. Upon full characterization by NMR and HRMS analyses, eight of the compounds were new. The antibacterial activities of the isolated compounds were evaluated in vitro against the opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus. The selectivity index was calculated based on cytotoxic assays performed against human liver carcinoma cells (HepG2) and the human breast epithelial cell line (MCF10A). Some compounds revealed remarkable antibacterial activity against multidrug-resistant strains of S. aureus with moderate human cell line cytotoxicity.

Metabolite Profiling of Javanese Ginger Zingiber purpureum and Identification of Antiseizure Metabolites via a Low-Cost Open-Source Zebrafish Bioassay-Guided Isolation

The rhizomes of Zingiber purpureum, "Bangle", were investigated for its antiseizure properties using a streamlined and cost-effective zebrafish screening strategy and a mouse epilepsy assay. Its hexane extract demonstrated strong antiseizure activity in zebrafish epilepsy assay and was, therefore, selected for bioactivity-guided fractionation. Twelve compounds (1-12) were isolated, and two bioactive phenylbutenoids, trans- (11) and cis-banglene (12), reduced up to 70% of pentylenetetrazole (PTZ)-induced seizures. These compounds showed moderate activity against PTZ-induced seizures in a mouse epilepsy assay. To understand the specificity of Z. purpureum active compounds, its chemical profile was compared to that of Z. officinale. Their composition was assessed by differential metabolite profiling visualized by a molecular network, which revealed only vanillin derivatives and terpenoids as common metabolites and gave a comprehensive view of Z. purpureum composition. This study demonstrates the efficacy of a streamlined zebrafish epilepsy assay, which is therefore suitable for routine screening in phytochemistry laboratories.

Metabolomics of Myrcia bella Populations in Brazilian Savanna Reveals Strong Influence of Environmental Factors on Its Specialized Metabolism

Environmental conditions influence specialized plant metabolism. However, many studies aiming to understand these modulations have been conducted with model plants and/or under controlled conditions, thus not reflecting the complex interaction between plants and environment. To fully grasp these interactions, we investigated the specialized metabolism and genetic diversity of a native plant in its natural environment. We chose Myrcia bella due to its medicinal interest and occurrence in Brazilian savanna regions with diverse climate and soil conditions. An LC-HRMS-based metabolomics approach was applied to analyze 271 samples harvested across seven regions during the dry and rainy season. Genetic diversity was assessed in a subset of 40 samples using amplified fragment length polymorphism. Meteorological factors including rainfall, temperature, radiation, humidity, and soil nutrient and mineral composition were recorded in each region and correlated with chemical variation through multivariate analysis (MVDA). Marker compounds were selected using a statistically informed molecular network and annotated by dereplication against an in silico database of natural products. The integrated results evidenced different chemotypes, with variation in flavonoid and tannin content mainly linked to soil conditions. Different levels of genetic diversity and distance of populations were found to be correlated with the identified chemotypes. These observations and the proposed analytical workflow contribute to the global understanding of the impact of abiotic factors and genotype on the accumulation of given metabolites and, therefore, could be valuable to guide further medicinal exploration of native species.

Zebrafish bioassay-guided isolation of antiseizure compounds from the Cameroonian medicinal plant Cyperus articulatus L

BACKGROUND

Epilepsy is a chronic neurological disorder affecting more than 50 million people worldwide, of whom 80% live in low- and middle-income countries. Due to the limited availability of antiseizure drugs (ASDs) in these countries, medicinal plants are the first-line treatment for most epilepsy patients. In Cameroon, a decoction of Cyperus articulatus L. rhizomes is traditionally used to treat epilepsy.

PURPOSE

The aim of this study was to identify and isolate the active compounds responsible for the antiseizure activity of C. articulatus in order to confirm both its traditional medicinal usage and previous in vivo studies on extracts of this plant in mouse epilepsy models.

METHODS

The dried rhizomes of C. articulatus were extracted with solvents of increasing polaritie (hexane, dichloromethane, methanol and water). A traditional decoction and an essential oil were also prepared. These extracts were evaluated for antiseizure activity using a larval zebrafish seizure model with seizures induced by the GABAA antagonist pentylenetetrazole (PTZ). The hexane extract demonstrated the highest antiseizure activity and was therefore selected for bioassay-guided fractionation. The isolated bioactive compounds were characterized by classical spectroscopic methods. Since they were found to be volatile, they were quantified by GC-FID. In addition, the absorption of the active compounds through the gastrointestinal tract and the blood-brain barrier was evaluated using a hexadecane and a blood-brain barrier parallel artificial membrane permeability assays (HDM-PAMPA and PAMPA-BBB).

RESULTS

The hexane extract of C. articulatus exhibited the highest antiseizure activity with a reduction of 93% of PTZ-induced seizures, and was therefore subjected to bioassay-guided fractionation in order to isolate the active principles. Four sesquiterpenoids were identified as cyperotundone (1), mustakone (2), 1,2-dehydro-α-cyperone (3) and sesquichamaenol (4) and exhibited significant antiseizure activity. These volatile compounds were quantified by GC in the hexane extract, the essential oil and the simulated traditional decoction. In addition, the constituents of the hexane extract including compounds 1 and 2 were found to cross the gastrointestinal barrier and the major compound 2 crossed the blood-brain barrier as well.

CONCLUSION

These results highlight the antiseizure activity of various sesquiterpene compounds from a hexane extract of C. articulatus dried rhizomes and support its use as a traditional treatment for epilepsy.

Puerariae lobatae root extracts and the regulation of brown fat activity

BACKGROUND

Obesity is one of the major health problems worldwide. The induction of brown adipocyte formation and activity represents a promising therapeutic option by increasing energy expenditure. Asian herbs have the potential to treat obesity, however, pharmacological effects should be well documented at the molecular level first.

HYPOTHESIS

A novel hypothesis-driven screening approach identified the root of Pueraria montana var. lobata (Willd.) Sanjappa & Pradeep (PLR) to have potential effects on obesity by stimulating brown adipocytes.

STUDY DESIGN

This study explored the metabolic effects of PLR water extract (PLRE) in a high-fat diet-induced obesity mouse model and characterized its secondary metabolite composition.

METHODS

Animals were orally treated daily for two weeks and the bioactivity of PLRE evaluated by measuring various parameters including body weight, circulating metabolites, energy expenditure and insulin sensitivity. The chemical composition of the mains components was obtained by HPLC-MS-ELSD-PDA. Based on the dereplication results and semi-quantitative estimation, pure molecules were selected for tests on adipocytes in vitro.

RESULTS

PLRE induces brown adipocyte activity and triggers the formation of brown-like cells in inguinal fat tissue, weight loss, and improved glucose metabolism. These effects are primarily caused by cell-autonomous activation of brown adipocytes and not by autonomic nervous system regulation. Even though the analysis of PLRE revealed puerarin as the most abundant secondary metabolite, it showed no effect on brown adipocyte formation and function. Brown adipocyte activity was induced dose-dependently by two other isoflavones, daidzein, and genistein. Daidzein is present in a very small amount in PLRE, but various glycosidic isoflavones, including puerarin, may release daidzein after metabolism.

CONCLUSION

This approach demonstrated the positive effects of PLRE on a diet-induced obesity mouse model and provided clues on the mode of action of PLRE at the molecular level.

Antimycobacterial activity in a single-cell infection assay of ellagitannins from Combretum aculeatum and their bioavailable metabolites

ETHNOPHARMACOLOGICAL RELEVANCE

The water decoction of Combretum aculeatum aerial parts is traditionally used in Senegal to treat tuberculosis (TB). The extract shows significant antimycobacterial activity in a validated single-cell infection assay.

AIM OF THE STUDY

The main aim of this study was to identify the antimycobacterial compounds in the water decoction of Combretum aculeatum. Since the traditional preparations are used orally, a bioactivity assessment of the possible bioavailable human metabolites was also performed.

MATERIALS AND METHODS

The Combretum aculeatum water decoction extract was first fractionated by flash chromatography. The fractions were submitted to an antibiotic assay against Mycobacterium marinum and to a single-cell infection assay involving Acanthamoeba castellanii as a host. Using these approaches, it was possible to correlate the antimycobacterial activity with two zones of the chromatogram. In parallel with this liquid chromatography (LC)-based activity profiling, high-resolution mass spectrometry (UHPLC-HRMS/MS) revealed the presence of ellagitannin (Et) derivatives in the active zones of the chromatogram. Isolation of the active compounds was performed by preparative chromatography. The structures of the isolated compounds were elucidated by nuclear magnetic resonance (NMR). Additionally, the main human metabolites of commercially available Ets were biologically evaluated in a similar manner.

RESULTS

The in vitro bioassay-guided isolation of the Combretum aculeatum water extract led to the identification of three Ets (1-3) and ellagic acid (4). The major compounds 2 and 3 (α- and β-punicalagin, respectively), exhibited anti-infective activity with an IC₅₀ of 51.48 μM. In view of the documented intestinal metabolism of these compounds, some metabolites, namely, urolithin A (5), urolithin B (6) and urolithin D (7), were investigated for their antimycobacterial activity in the two assays. Urolithin D (7) exhibited the strongest anti-infective activity, with an IC₅₀ of 345.50 μM, but this was moderate compared to the positive control rifampin (IC₅₀ of 6.99 μM). The compounds assayed had no observable cytotoxicity towards the amoeba host cells at concentrations lower than 200 μg/mL.

CONCLUSION

The observed antimycobacterial properties of the traditional water decoction of Combretum aculeatum might be related to the activity of Ets derivatives (1-3) and their metabolites, such as ellagic acid (4) and urolithin D (7). Despite the relatively weak activity of these metabolites, the high consumption of tannins achieved by taking the usual traditional decoction doses should lead to an important increase in the plasmatic concentrations of these active and bioavailable metabolites. These results support to some extent the traditional use of Combretum aculeatum to treat tuberculosis.

Chemo-Diversification of Plant Extracts Using a Generic Bromination Reaction and Monitoring by Metabolite Profiling

A generic procedure for direct bromination of polyphenol in crude plant extracts was developed to generate multiple "unnatural" halogenated natural products for further bioassay evaluation. To better control the halogenation procedure, the bromination was optimized with a flavonoid standard, and the reactions were monitored by high-performance liquid chromatography photometric diode array coupled to the evaporative light scattering detection (ELSD). ELSD detection was successfully used for a relative yield estimation of the compounds obtained. From the halogenation of hesperitin (11), five brominated compounds were obtained. After optimization, the reaction was successfully applied to the methanolic extract of Citrus sinensis peels, a typical waste biomass and also to the methanolic extract of the medicinal plant Curcuma longa. In both cases, the methanolic extracts were profiled by NMR for a rapid estimation of the polyphenol versus primary metabolite content. An enriched secondary metabolites extract was obtained using vacuum liquid chromatography and submitted to bromination. Metabolite profiling performed by ultrahigh purity liquid chromatography time-of-flight high-resolution mass spectrometry revealed the presence of various halogenated products. To isolate these compounds, the reactions were scaled up, and six halogenated analogues were isolated and fully characterized by NMR and high-resolution electrospray ionization mass spectrometry analyses. The antibacterial properties of these compounds were evaluated using in vitro bioassays against multiresistant strains of Staphylococcus aureus and Pseudomonas aeruginosa. Some of the halogenated derivatives obtained presented moderate antibacterial properties.

Anti-inflammatory and Quinone Reductase-Inducing Compounds from Beilschmiedia mannii

Previous studies on the therapeutic potential of plant species found in the diet of chimpanzees living in Taï National Park have shown that they could be potential candidates for the search of new molecules useful for humans. Based on the screening of some of these plants, the fruits of Beilschmiedia mannii, whose dichloromethane extract showed cancer chemopreventive properties, were selected. Bioactivity-guided fractionation of the extract resulted in the isolation and identification of two γ-pyrones, including desmethoxydihydromethysticin (1: ), found in a natural source for the first time, and a new congener, beilschmiediapyrone (2: ), as well as five known alkamides (3:  - 7: ). Their structures were established by using nuclear magnetic resonance spectroscopy and mass spectrometry methods. The isolated compounds were evaluated for their cancer chemopreventive potential by using quinone reductase induction and nuclear factor-kappa B inhibition tests in Hepa 1c1c7 and HEK-293/NF-κB-Luc cells, respectively. Among them, compounds 1: and 2: were the most active. The concentrations to double the quinone reductase activity were 7.5 µM for compound 1: and 6.1 µM for compound 2: . Compounds 1: and 2: inhibited nuclear factor-kappa B with IC₅₀ values of 2.1 and 3.4 µM, respectively. These results are promising with regard to cancer chemoprevention, especially because this plant is also used for cooking by the local population around the Taï forest.

High-performance counter-current chromatography isolation and initial neuroactivity characterization of furanocoumarin derivatives from Peucedanum alsaticum L (Apiaceae)

BACKGROUND

Medicinal plants are a proven source of drug-like small molecules with activity towards targets relevant for diseases of the central nervous system (CNS). Plant species of the Apiaceae family have to date yielded a number of neuroactive metabolites, such as coumarin derivatives with acetylcholinesterase inhibitory activity or anti-seizure activity.

PURPOSE

To accelerate the discovery of neuroactive phytochemicals with potential as CNS drug leads, we sought to rapidly isolate furanocoumarins, primary constituents of the dichloromethane (DCM) extract of the fruits of Peucedanum alsaticum L. (Apiaceae), using high-performance counter-current chromatography (HPCCC) and to evaluate their neuroactivity using both in vitro and in vivo microscale bioassays based on cholinesterase ELISAs and zebrafish epilepsy models.

RESEARCH METHODS AND PROCEDURE

In this study the DCM extract was subjected to HPCCC for the efficient separation (60 min) and isolation of furanocoumarins. Isolated compounds were identified with TOF-ESI-MS and NMR techniques and examined as inhibitors of AChE and BChE using ELISA microtiter assays. Anti-seizure properties of the extract and of the isolated compounds were evaluated using a zebrafish epilepsy model based on the GABA_A antagonist pentylenetetrazol (PTZ), which induces increased locomotor activity and seizure-like behavior.

RESULTS

The solvent system, composed of n-heptane, ethyl acetate, methanol and water (3:1:3:1, v/v/v/v), enabled the isolation of 2.63 mg lucidafuranocoumarin A (purity 98%) and 8.82 mg bergamottin (purity 96%) from 1.6 g crude DCM extract. The crude extract, at a concentration of 100 µg/ml, exhibited a weak inhibitory activity against acetylcholinesterase (AChE) (9.63 ± 1.59%) and a moderate inhibitory activity against butyrylcholinestrase (BChE) (49.41 ± 2.19%). Lucidafuranocoumarin A (100 µg/ml) was inactive against AChE but showed moderate inhibition towards BChE (40.66 ± 1.25%). The DCM extract of P. alsaticum fruits (0.62-1.75 µg/ml) and bergamottin (2-10 µm) exhibited weak anti-seizure activity, while lucidafuranocoumarin A (10-16 µm) was found to significantly inhibit PTZ-induced seizures. The percentage of seizure inhibition for the isolated compounds, at their most bioactive concentration, was 26% for bergamottin and 69% for lucidafuranocoumarin A.

CONCLUSION

Our findings underscore the utility of HPCCC for the rapid isolation of rare coumarin derivatives, and the potential of microscale in vivo bioassays based on zebrafish disease models for the rapid assessment of neuroactivity of these drug-like natural products.

High-performance countercurrent chromatographic isolation of acylated iridoid diglycosides from Verbascum ovalifolium Donn ex Sims and evaluation of their inhibitory potential on IL-8 and TNF-α production

In traditional folk medicine, Verbascum species have been used since ancient times to treat respiratory disorders, hemorrhoids, diarrhea, wounds, eczema and other types of inflammatory skin conditions. Despite the fact that more than 200 bioactive constituents (phenylethanoids, flavonoids, neolignan glycosides, phenolic acids, iridoids, saponins and polysaccharides) have been previously isolated from various Verbascum species, to date preparative high-performance countercurrent chromatography (HPCCC) has never been employed for this purpose. Therefore, in this study, simple HPCCC methods were successfully developed with the aim to primarily isolate acylated iridoid diglycosides from Verbascum ovalifolium Donn ex Sims (oval-leaved mullein). By the use of several biphasic solvent systems containing n-hexane, ethyl acetate, n-butanol/methanol and water, premnacorymboside B (3, 4 mg, 95.4% purity), saccatoside (4, 6 mg, 95.7% purity), premnacorymboside A (7, 6 mg, 98.3%), scorodioside (8, 11 mg, 96.0%) and 6-O-(3'',4''-di-O-trans-cinnamoyl)-α-L-rhamnopyranosylcatalpol (9, 8 mg, 95.3%) were afforded; compounds 7, 8 and 9 have not been previously reported in Verbascum genus. Additionally, two phenolic acids (1, 2), two flavonoids (6, 10) and verbascoside (5) were secondarily isolated. Evaluation of interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α) inhibitory properties of the acylated iridoid diglycosides proved that these compounds down-regulated TNF-α release more efficiently than IL-8 secretion. The activity might be dependent on the degree of esterification, as diacyl derivatives showed more potent effects than monoesters. The HPCCC methods herein developed could serve to large scale isolation of constituents from Verbascum genus for extensive biological investigations.

Antileishmanial Activity of Dimeric Flavonoids Isolated from Arrabidaea brachypoda

Leishmaniasis are diseases caused by parasites belonging to Leishmania genus. The treatment with pentavalent antimonials present high toxicity. Secondary line drugs, such as amphotericin B and miltefosine also have a narrow therapeutic index. Therefore, there is an urgent need to develop new drugs to treat leishmaniasis. Here, we present the in vitro anti-leishmanial activity of unusual dimeric flavonoids purified from Arrabidaea brachypoda. Three compounds were tested against Leishmana sp. Compound 2 was the most active against promastigotes. Quantifying the in vitro infected macrophages revealed that compound 2 was also the most active against intracellular amastigotes of L. amazonensis, without displaying host cell toxicity. Drug combinations presented an additive effect, suggesting the absence of interaction between amphotericin B and compound 2. Amastigotes treated with compound 2 demonstrated alterations in the Golgi and accumulation of vesicles inside the flagellar pocket. Compound 2-treated amastigotes presented a high accumulation of cytoplasmic vesicles and a myelin-like structure. When administered in L. amazonensis-infected mice, neither the oral nor the topical treatments were effective against the parasite. Based on the high in vitro activity, dimeric flavonoids can be used as a lead structure for the development of new molecules that could be useful for structure-active studies against Leishmania.

Anti-inflammatory and antiproliferative diterpenoids from Plectranthus scutellarioides

Chemical investigation of the dichloromethane extract of the aerial parts of Plectranthus scutellarioides led to the isolation and characterization of 10 diterpenoids with an abietane skeleton and one cembrane-type diterpenoid. Among them, six have not yet been described in the literature. Their structures were established by 1D and 2D NMR, UV and IR spectroscopy, and HRESIMS. The relative configuration was determined by Gauge-Independent Atomic Orbital NMR chemical shift calculations supported by the advanced statistical method DP4 plus and further confirmed by electronic circular dichroism. The isolated constituents were evaluated for their in vitro NF-κB inhibitory activity, as well as for their cytotoxic effects in human multiple myeloma cancer stem cells and RPMI 8226 tumor cell line. Coleon O, coleon G, lanugone K and 6-acetylfredericone B showed the highest inhibitory effect against NF-κB, displaying IC₅₀ of 11.2, 11.0, 4.5 and 9.7 μM, respectively. Coleon O exhibited also a significant activity towards human multiple myeloma cancer stem cells and RPMI 8226 cells with IC₅₀ of 9.2 and 8.4 μM, respectively.

The plant pathogen Pseudomonas aeruginosa triggers a DELLA-dependent seed germination arrest in Arabidopsis

To anticipate potential seedling damage, plants block seed germination under unfavorable conditions. Previous studies investigated how seed germination is controlled in response to abiotic stresses through gibberellic and abscisic acid signaling. However, little is known about whether seeds respond to rhizosphere bacterial pathogens. We found that Arabidopsis seed germination is blocked in the vicinity of the plant pathogen Pseudomonas aeruginosa. We identified L-2-amino-4-methoxy-trans-3-butenoic acid (AMB), released by P. aeruginosa, as a biotic compound triggering germination arrest. We provide genetic evidence that in AMB-treated seeds DELLA factors promote the accumulation of the germination repressor ABI5 in a GA-independent manner. AMB production is controlled by the quorum sensing system IQS. In vitro experiments show that the AMB-dependent germination arrest protects seedlings from damage induced by AMB. We discuss the possibility that this could serve as a protective response to avoid severe seedling damage induced by AMB and exposure to a pathogen.

The plant embryo within a seed is well protected. While it cannot stay within the seed forever, the embryo can often wait for the right conditions before it develops into a seedling and continues its life cycle. Indeed, plants have evolved several ways to time this process – which is known as germination – to maximize the chances that their seedlings will survive. For example, if the environment is too hot or too dark, the seed will make a hormone that stops it from germinating.

In addition to environmental factors like light and temperature, a seed in the real word is continuously confronted with soil microbes that may harm or benefit the plant. However, few researchers have asked whether seeds control their germination in response to other living organisms.

The bacterium Pseudomonas aeruginosa lives in a wide spectrum of environments, including the soil, and can cause diseases in both and plants and animals. Chahtane et al. now report that seeds of the model plant Arabidopsis thaliana do indeed repress their germination when this microbe is present. Specifically, the seeds respond to a molecule released from the bacteria called L-2-amino-4-methoxy-trans-3-butenoic acid, or AMB for short. Like the bacteria, AMB is harmful to young seedlings, but Chahtane et al. showed that the embryo within the seed is protected from its toxic effects.

Further experiments revealed that the seed's response to the bacterial molecule requires many of the same signaling components that repress germination when environmental conditions are unfavorable. However, Chahtane et al. note that AMB activates these components in an unusual way that they still do not understand.

The genes that control the production of AMB are known to also control how bacterial populations behave as they accumulate to high densities. It is therefore likely that Pseudomonas aeruginosa would make AMB if it reached a high density in the soil. This raises the possibility that plants have specifically evolved to stop germination if there are enough microbes nearby to pose a risk of disease. This hypothesis, however, is only one of several possible explanations and remains speculative at this stage; further work is now needed to evaluate it. Nevertheless, identifying how AMB interferes with the signaling components that control germination and plant growth may guide the design of new herbicides that could, for example, control weeds in the farming industry.

NF-κB and Angiogenesis Inhibitors from the Aerial Parts of Chresta martii

The ethyl acetate extract of the aerial parts of Chresta martii showed significant in vitro NF-κB inhibition. Bioactivity-guided isolation was undertaken using HPLC microfractionation to localize the active compounds. Different zones of the HPLC chromatogram were linked to NF-κB inhibition. In parallel to this HPLC-based activity profiling, HPLC-PDA-ESI-MS and UHPLC-TOF-HRMS were used for the early identification of some of the compounds present in the extract and to get a complete phytochemical overview. The isolation of the compounds was performed by high-speed counter-current chromatography and further semipreparative HPLC. Using this approach, 14 compounds were isolated, two of them being new sesquiterpene lactones. The structures of the isolated compounds were elucidated by spectroscopic methods including UV, ECD, NMR, and HRMS. All isolated compounds were evaluated for their inhibitory activity of NF-κB and angiogenesis, and compound 2 showed promising NF-κB inhibition activity with an IC₅₀ of 0.7 μM. The isolated compounds 1, 2, 5, 7, and 8 caused a significant reduction in angiogenesis when evaluated by an original 3D in vitro angiogenesis assay.

Isolation and Antimicrobial Activity of Coumarin Derivatives from Fruits of Peucedanum luxurians Tamamsch

As a continuation of searching for phytoconstituents that act as promising agents for antimicrobial therapy, rare coumarins were isolated from fruits of Peucedanum luxurians and tested. In a first step, the content of major compounds in the aerial parts and fruits of P. luxurians were compared. The results clearly showed that the fruits with dichloromethane as a solvent yielded, in most cases, higher concentrations of almost all the analyzed coumarins than the aerial parts, with peucedanin detected as the most abundant compound with a concentration of 4563.94 ± 3.35 mg/100 g. Under this perspective, the dichloromethane extract from the fruits of P. luxurians was further submitted to high performance countercurrent chromatography with a mixture of n-hexane, ethyl acetate, methanol, and water 6:5:6:5 (v/v). Combination of HPCCC and prep-HPLC yielded 6',7'-dihydroxybergamottin (1), officinalin (2), stenocarpin isobutyrate (3), officinalin isobutyrate (4), 8-methoxypeucedanin (5), and peucedanin (6). Isolated compounds were tested against several Gram-positive and Gram-negative bacteria strains. 6',7'-Dihydroxybergamottin, peucedanin, and officinalin isobutyrate appeared to be the most active against all tested bacteria strains with minimum inhibitory concentration (MIC) values between 1.20 and 4.80 mg/mL. To the best of our knowledge, this is the first report about countercurrent isolation of mentioned coumarins, as well as the first information about their antimicrobial activity.