Lignans, phenolic plant secondary metabolites, are derived from the phenylpropanoid biosynthetic pathway. Although, being investigated for their health benefits in terms of antioxidant, antitumor, anti-inflammatory and antiviral properties, the role of these molecules in plants remains incompletely elucidated; a potential role in stress response mechanisms has been, however, proposed. In this study, a non-targeted metabolomic analysis of the roots, stems, and leaves of wild-type and PLR1-RNAi transgenic flax, devoid of (+) secoisolariciresinol diglucoside ((+) SDG)—the main flaxseed lignan, was performed using ¹H-NMR and LC-MS, in order to obtain further insight into the involvement of lignan in the response of plant to osmotic stress. Results showed that wild-type and lignan-deficient flax plants have different metabolic responses after being exposed to osmotic stress conditions, but they both showed the capacity to induce an adaptive response to osmotic stress. These findings suggest the indirect involvement of lignans in osmotic stress response.

Erismadelphus exsul Mildbr bark is widely used in Gabonese folk medicine. However, little is known about the active compounds associated with its biological activities. In the present study, phytochemical profiling of the ethanolic extract of Erismadelphus exsul was performed using a de-replication strategy by coupling HPLC-ESI-Q/TOF with a molecular network approach. Eight families of natural compounds were putatively identified, including cyclopeptide alkaloids, esterified amino acids, isoflavonoid- and flavonoid-type polyphenols, glycerophospholipids, steroids and their derivatives, and quinoline alkaloids. All these compounds were identified for the first time in this plant. The use of molecular networking obtained a detailed phytochemical overview of this species. Furthermore, antioxidant (2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) and ferric reducing capacity (FRAP)) and in vitro antimicrobial activities were assessed. The crude extract, as well as fractions obtained from Erismadelphus exsul, showed a better reactivity to FRAP than DPPH. The fractions were two to four times more antioxidant than ascorbic acid while reacting to FRAP, and there was two to nine times less antioxidant than this reference while reacting to DPPH. In addition, several fractions and the crude extract exhibited a significant anti-oomycete activity towards the Solanaceae phytopathogen Phytophthora infestans in vitro, and, at a lower extent, the antifungal activity against the wheat pathogen Zymoseptoria tritici had growth inhibition rates ranging from 0 to 100%, depending on the tested concentration. This study provides new insights into the phytochemical characterization and the bioactivities of ethanolic extract from Erismadelphus exsul bark.

Throughout the past decades, annonaceous plants have been of particular interest to the natural product community because of their therapeutic value and their richness in isoquinoline alkaloids. Taking advantage from our laboratory historical collection of these compounds, a MS/MS database of 322 isoquinolines and other metabolites from Annonaceae was implemented and named IQAMDB. The present report describes the dereplication of known alkaloids from stem barks of Greenwayodendron suaveolens (Engl. & Diels) Verdc. leveraging IQAMDB-informed feature-based molecular networking further refined by in silico annotation and taxonomic weighting. This strategy annotated over 30 compounds and streamlined the isolation of three sesquiterpene indole alkaloids (SIA) (1-3). Structure elucidation and absolute configuration assignment by a combination of NMR, TDDFT-ECD or X-ray diffraction determined these compounds to be greenwaylactam D (1) and greenwaylactam E (2), previously undescribed Witkop-Winterfeldt oxidized diastereoisomers of the previously reported greenwaylactam A, and polyveodrine (3), that discloses an unprecedented relative configuration for a SIA. The isolated compounds were evaluated for their antibacterial and antifungal activities against Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Mycobacterium marinum as well as their antiviral activity against Zika virus. Polyveodrine exhibited moderate antimycobacterial activity against M. marinum, whereas greenwaylactam D (1) demonstrated moderate antiviral activity against Zika virus under non-cytotoxic concentrations.

Medicinal plants are traditionally used in Gabon to treat several types of illnesses. The studys purpose was to determine the toxic, antibacterial, and anti-inflammatory effects of Antrocaryon klaineanum Pierre extracts and to characterize their phytochemical compounds. Toxicity was evaluated on frog tadpoles (Phrynobatrachus africanus Hallowell). The microorganism susceptibility test was performed by the diffusion method, while minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated using the microdilution technique. Anti-inflammatory activity was tested through protein denaturation and membrane stabilization methods. Chromatography and molecular network techniques were used to characterize chemical compounds. The lethality test showed that the lethal concentration (LC₅₀) increased from 110.03±1.25 to 15.86±2.21μg/mL after 24 and 96hours of exposure. In tadpoles exposed to 7.81μg/mL extract, the first mortalities (12.5) were observed on the fifth day of exposure. A relative decrease in mature erythrocytes exposed to plant extracts was observed. The antibacterial activity shows that the Ak F₂, Ak F₃, and Ak F₄ fractions (from the water-ethanol crude extract) gave the greatest antibacterial activities compared to the other extracts. The water, water-acetone, and water-ethanol extracts showed good inhibition of denaturation. The haemolysis test shows that the extracts exhibited good anti-inflammatory activities. Phytochemical characterisation revealed four major compounds, including monogallate epicatechin and hydroxy-ergostadian. The molecular network revealed five main clusters. Our study shows that A. klaineanum Pierre could be a promising natural product for the isolation of molecules with potential biological activities.

Mass spectrometry-based natural products targeted discovery often relies on a complicated decision-making process involving tedious comparison of exact masses data and tandem mass spectra-based annotation tools output against various spectral reference libraries. To address this bottleneck, we present tandem mass spectrum to decision (MS2DECIDE) which leverages Decision Theory and expert knowledge to aggregate the outputs of three widely used annotation tools (GNPS, Sirius, and ISDB-LOTUS) and compute a recommendation for targeting natural products with regard to their potential novelty. We demonstrate, through two case studies, that MS2DECIDE reliably captures the novelty of natural products from their tandem mass spectra. MS2DECIDE is freely accessible on GitHub.

Plants used in traditional medicine represent an important source of new compounds. Hallea ledermannii (H. ledermannii) (Krause) Verdc. (Rubiaceae), Gossypium barbadense (G. barbadense) (Malvaceae), Pycnanthus angolensis (P. angolensis) (Myristicaceae), Drypetes gossweileri (D. gossweileri) S. Moore (Euphorbiaceae) and Scyphocephalium ochocoa (S. ochocoa) Warb (Myristicaceae) are five plants widely used in traditional Gabonese medicine as antimicrobials. However, little is known about the active compounds associated with their biological activities. Based on botanical studies and the claims of traditional healers regarding the antimicrobial effects of these plants, a study to evaluate the antimicrobial activity and phyto-chemical profile of aqueous extracts of three plants (bark of H. ledermannii, G. barbadense root bark and P. angolensis bark) and methanolic extracts of two plants (S. ochocoa stem bark and D. gossweileri root bark). Under the guidance of LC-MS detection, identified twenty seven (27) potentially active compounds. Eight (8) of these belong to the quinovic acid-type triterpenoid sap-onins identified in the aqueous extract of H. ledermannii, eleven (11) are dibenzofurans, chroman and stigmasterol detected in the methanolic extract of S. ochocoa and eight (8) compounds in the methanolic extract of D. gossweileri are friedelin, drypemolundein B and gossweilone, to name but a few. In parallel, the five extracts were tested on reference bacterial strains: Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 278533, Salmonella thyphi ATCC 13311, Klebsiella pneumoniae ATCC 700603, Shigella flexneri ATCC 24570. Three of these extracts (aqueous extract of H. ledermannii and two methanolic extracts of S. ochocoa stem bark and D. gossweileri root bark) showed moderate activity against Staphylococcus aureus ATCC 25923, with inhibition zones of 12.3 ± 0.5 mm, 10.1 ± 0.5 mm and 7,6 ± 0 mm respectively. In addition, we assessed the toxicity of the three extracts that showed antimicrobial activity using an invertebrate model, Galleria mellonella (GM). We found that the LD varied according to the concentration of the plant material. The aqueous extract of H. ledermannii and the methanolic extracts of S. ochocoa and D. gossweileri were not toxic to G. mellonella. The LD_50s (mg/mL) obtained were 93.2 mg/mL [717.2 g/kg body weight (bw)] and 100 mg/mL (762.3 g/kg bw), 95.4 mg/mL [721.1 g/kg body weight (bw)].