Ethnobotanical uses of celastraceae. Bioactive metabolites

Comprehensive mass spectrometric metabolomic profiling of a chemically diverse collection of plants of the Celastraceae family

Natural products exhibit interesting structural features and significant biological activities. The discovery of new bioactive molecules is a complex process that requires high-quality metabolite profiling data to properly target the isolation of compounds of interest and enable their complete structural characterization. The same metabolite profiling data can also be used to better understand chemotaxonomic links between species. This Data Descriptor details a dataset resulting from the untargeted liquid chromatography-mass spectrometry metabolite profiling of 76 natural extracts of the Celastraceae family. The spectral annotation results and related chemical and taxonomic metadata are shared, along with proposed examples of data reuse. This data can be further studied by researchers exploring the chemical diversity of natural products. This can serve as a reference sample set for deep metabolome investigation of this chemically rich plant family.

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.

Naturally occurring dimeric triterpenoids: Occurrence, chemistry and bioactivities

The triterpenes represent one of the most reported subclasses of specialized metabolites from the plant kingdom. They play a key role in the protection of plants and their metabolism in addition to displaying a high structural diversity and large scale of biological activities. The scaffold can undergo several reactions like oxidation or substitution at different positions of the skeleton leading to the formation of several types of compounds. More specifically, triterpene dimer is a small group of compounds found in nature (from plants precisely). Until 2021, the chemical and pharmacological works reported in the literature indicated the identification of 90 natural dimeric triterpenes and 11 synthetic derivatives from 19 plants species and very few of them have been biologically evaluated for their antibacterial, antioxidant, antiproliferative or molluscicide activities. This review aims to compile the literature on the occurrence, chemistry and biological activities of the triterpenoid dimers. To attend this goal, a literature survey has been done in a number of online libraries including Scifinder, PubMed, Web of Science and Google Scholar using keywords terpene, triterpene, dimer, celastroloid without language restriction. This paper provides the easiest access to the information on triterpene dimers for readers and researchers in view to enhancing the continuity of research works on this topic.

Pentacyclic Triterpenoids Isolated from Celastraceae: A Focus in the 13C-NMR Data

The Celastraceae family comprises about 96 genera and more than 1.350 species, occurring mainly in tropical and subtropical regions of the world. The species of this family stand out as important plant sources of triterpenes, both in terms of abundance and structural diversity. Triterpenoids found in Celastraceae species display mainly lupane, ursane, oleanane, and friedelane skeletons, exhibiting a wide range of biological activities such as antiviral, antimicrobial, analgesic, anti-inflammatory, and cytotoxic against various tumor cell lines. This review aimed to document all triterpenes isolated from different botanical parts of species of the Celastraceae family covering 2001 to 2021. Furthermore, a compilation of their ¹³C-NMR data was carried out to help characterize compounds in future investigations. A total of 504 pentacyclic triterpenes were compiled and distinguished as 29 aromatic, 50 dimers, 103 friedelanes, 89 lupanes, 102 oleananes, 22 quinonemethides, 88 ursanes and 21 classified as others.

Three new sesquiterpenoid alkaloids from the roots of Tripterygium wilfordii and its cytotoxicity

Three new sesquiterpenoid alkaloids, cangorin K (1), dimacroregelines C (2) and D (3), as well as two known sesquiterpenoids (4-5), were isolated from the roots of Tripterygium wilfordii Hook. f. The structures of new compounds were characterised by extensive 1D and 2D NMR spectroscopic analyses, as well as HRESIMS data, and the known compounds were established by 1 D NMR spectra referring to the literatures. Cytotoxicity evaluation of these compounds against two human tumour lines (SMMC7721, LN229) was investigated by CCK-8 assay and displayed that compounds 1-4 showed potent cytotoxicity against SMMC7721 cell with IC₅₀ value in the range of 0.26-9.67 μΜ and compounds 1-5 showed potent cytotoxicity against LN-229 cell with IC₅₀ values in the range of 0.50-7.38 μΜ.

Antimicrobial Activity and Mode of Action of Celastrol, a Nortriterpen Quinone Isolated from Natural Sources

Species of the Celastraceae family are traditionally consumed in different world regions for their stimulating properties. Celastrol, a triterpene methylene quinone isolated from plants of celastraceas, specifically activates satiety centers in the brain that play an important role in controlling body weight. In this work, the antimicrobial activity and mechanism of action of celastrol and a natural derivative, pristimerin, were investigated in Bacillus subtilis. Celastrol showed a higher antimicrobial activity compared with pristimerin, being active against Gram-positive bacteria with minimum inhibitory concentrations (MICs) that ranged between 0.16 and 2.5 µg/mL. Killing curves displayed a bactericidal effect that was dependent on the inoculum size. Monitoring of macromolecular synthesis in bacterial populations treated with these compounds revealed inhibition in the incorporation of all radiolabeled precursors, but not simultaneously. Celastrol at 3 µg/mL and pristimerin at 10 µg/mL affected DNA and RNA synthesis first, followed by protein synthesis, although the inhibitory action on the uptake of radiolabeled precursors was more dramatic with celastrol. This compound also caused cytoplasmic membrane disruption observed by potassium leakage and formation of mesosome-like structures. The inhibition of oxygen consumption of whole and disrupted cells after treatments with both quinones indicates damage in the cellular structure, suggesting the cytoplasmic membrane as a potential target. These findings indicate that celastrol could be considered as an interesting alternative to control outbreaks caused by spore-forming bacteria.

Phenolic profile and antioxidant activity of Euonymus japonicus Thunb

The aim of this study was to characterise the phenolic profile and evaluate the antioxidant activity of aqueous and methanol leaf extracts from Euonymus japonicus Thunb., a species of flowering plant in the Celastraceae family. Liquid chromatography (HPLC) with diode array and electrospray-tandem mass spectrometry (DAD-ESI-MSⁿ) detection was used to characterise and quantify phenolic compounds. Thirty-two compounds were detected; among them, flavonoids (mainly quercetin and kaempferol glycosides) were the most abundant compounds in both extracts. The results obtained for DPPH and ABTS assays in the extracts were in agreement with the highest content of phenolics in the methanol extract.

Potential anti-neuroinflammatory compounds from Australian plants - A review

Neuroinflammation is a complex response to brain injury involving the activation of glia, release of inflammatory mediators, such as cytokines and chemokines, and generation of reactive oxygen and nitrogen species. Even though it is considered an event secondary to neuronal death or dysfunction, neuro-inflammation comprises a majority of the non-neuronal contributors to the cause and progression of neurodegenerative diseases like Alzheimer's Disease (AD), Parkinson's Disease (PD), Multiple Sclerosis (MS), Chronic Traumatic Encephalopathy (CTE) and others. As a result of the lack of effectiveness of current treatments for neurodegenerative diseases, neuroinflammation has become a legitimate therapeutic target for drug discovery, leading to the study of various in vivo and in vitro models of neuroinflammation. Several molecules sourced from plants have displayed anti-inflammatory properties in the study of neurodegenerative diseases. A group of these anti-inflammatory compounds has been classified as cytokine-suppressive anti-inflammatory drugs (CSAIDs), which target the pro-inflammatory AP1 and nuclear factor-κB signaling pathways and inhibit the expression of many pro-inflammatory cytokines, such as interleukin IL-1, IL-6, TNF-α, or nitric oxide. Australian plants, thriving amid the driest inhabited continent of the world, are an untapped source of chemical diversity in the form of secondary metabolites. These compounds are produced in response to biotic and abiotic stresses that the plants are exposed to in the highly biodiverse environment. This review is an attempt to highlight anti-inflammatory compounds isolated from Australian plants.

Structural Requirements for Antimicrobial Activity of Phenolic Nor-Triterpenes from Celastraceae Species

The emergence of pathogenic bacteria-resistant strains is a major public health issue. In this regard, natural product scaffolds offer a promising source of new antimicrobial drugs. In the present study, we report the antimicrobial activity against Gram-positive and Gram-negative bacteria and the yeast Candida albicans of five phenolic nor-triterpenes (1–5) isolated from Maytenus blepharodes and Maytenus canariensis in addition to four derivatives (6–9), three of them reported for the first time. Their stereostructures have been elucidated on the basis of spectroscopic analysis, including one-dimensional (1D) and two-dimensional (2D) NMR techniques, spectrometric methods, and comparison with data reported in the literature. To understand the structural basis for the antimicrobial activity of this type of compounds, we have performed an in-depth study of the structure–activity relationship (SAR) of a series of previously reported phenolic nor-triterpenes. The SAR analysis was based on the skeleton framework, oxidation degree, functional groups, and regiosubstitution patterns, revealing that these aspects modulate the antimicrobial activity.

Distinct sesquiterpene pyridine alkaloids from in Salvadoran and Peruvian Celastraceae species

As part of a bioprospecting program aimed at the discovery of undescribed natural products from Salvadoran and Peruvian flora, the phytochemical investigations of four Celastraceae species, Celastrus vulcanicola, Maytenus segoviarum, Maytenus jeslkii, and Maytenus cuzcoina, were performed. The current study reports the isolation and structural characterization of five previously undescribed macrolide sesquiterpene pyridine alkaloids, named vulcanicoline-A, cuzcoinine, vulcanicoline-B, jelskiine, and vulcanicoline-C, along with sixteen known alkaloids. The structures of the alkaloids were established by spectrometric and extensive 1D and 2D NMR spectroscopic analysis, including COSY, HSQC, HMBC, and ROESY experiments. The absolute configurations of alkaloids were proposed based on optical rotation sign, and biogenetic considerations. This study represents the first phytochemical analysis of Maytenus segoviarum.

Aedes aegypti Larvicidal Sesquiterpene Alkaloids from Maytenus oblongata

Four new sesquiterpene alkaloids (1-4) with a β-dihydroagrofuran skeleton and a new triterpenoid (5) were isolated from an ethyl acetate extract of Maytenus oblongata stems. Their structures were elucidated using 1D and 2D NMR spectroscopy as well as MS and ECD experiments. The M. oblongata stem EtOAc extract and the pure compounds isolated were tested for larvicidal activity against Aedes aegypti under laboratory conditions, and compounds 2 and 3 were found to be active.

Dimacrolide Sesquiterpene Pyridine Alkaloids from the Stems of Tripterygium regelii

Two new dimacrolide sesquiterpene pyridine alkaloids (DMSPAs), dimacroregelines A (1) and B (2), were isolated from the stems of Tripterygium regelii. The structures of both compounds were characterized by extensive 1D and 2D NMR spectroscopic analyses, as well as HRESIMS data. Compounds 1 and 2 are two rare DMSPAs possessing unique 2-(3′-carboxybutyl)-3-furanoic acid units forming the second macrocyclic ring, representing the first example of DMSPAs bearing an extra furan ring in their second macrocyclic ring system. Compound 2 showed inhibitory effects on the proliferation of human rheumatoid arthritis synovial fibroblast cell (MH7A) at a concentration of 20 μM.

Bioactive Dihydro-β-agarofuran Sesquiterpenoids from the Australian Rainforest Plant Maytenus bilocularis

Chemical investigations of the CH2Cl2 extract obtained from the leaves of the Australian rainforest tree Maytenus bilocularis afforded three new dihydro-β-agarofurans, bilocularins A-C (1-3), and six known congeners, namely, celastrine A (4), 1α,6β,8α-triacetoxy-9α-benzoyloxydihydro-β-agarofuran (5), 1α,6β-diacetoxy-9α-benzoyloxy-8α-hydroxydihydro-β-agarofuran (6), Ejap-10 (11), 1α,6β-diacetoxy-9β-benzoyloxydihydro-β-agarofuran (12), and Ejap-2 (13). The major compound 1 was used in semisynthetic studies to afford four ester derivatives (7-10). The chemical structures of 1-3 were elucidated following analysis of 1D/2D NMR and MS data. The absolute configurations of bilocularins A (1) and B (2) were determined by single-crystal X-ray diffraction analysis. All compounds were evaluated for cytotoxic activity against the human prostate cancer cell line LNCaP; none of the compounds were active. However, several compounds showed similar potency to the drug efflux pump inhibitor verapamil in reversing the drug resistance of the human leukemia CEM/VCR R cell line. In addition, similar to verapamil, compound 5 was found to inhibit leucine uptake in LNCaP cells (IC50 = 15.5 μM), which was more potent than the leucine analogue 2-aminobicyclo[2.2.1]heptane-2-carbocyclic acid. This is the first report of secondary metabolites from Maytenus bilocularis.

Antimicrobial activity and cytotoxicity of triterpenes isolated from leaves of Maytenus undata (Celastraceae)

Background

Plants of the genus Maytenus belong to the family Celastraceae and are widely used in folk medicine as anti-tumour, anti-asthmatic, analgesic, anti-inflammatory, antimicrobial and anti-ulcer agents, and as a treatment for stomach problems. The aim of this study was to isolate and identify active compounds with antifungal activity from Maytenus undata after a preliminary study highlighted promising activity in crude extracts.

Methods

Sequential extracts of M. undata leaves prepared using hexane, dichloromethane (DCM), acetone and methanol (MeOH) were tested for activity against Cryptococcus neoformans, a fungal organism implicated in opportunistic infections. Bioassay-guided fractionation of the hexane extract using C. neoformans as test organism was carried out to isolate antifungal compounds. The cytotoxicity of compounds isolated in sufficient quantities was evaluated using a tetrazolium-based colorimetric cellular assay (MTT) and a haemagglutination assay (HA).

Results

The hexane extract was most active with an MIC of 20 μg/ml against C. neoformans. The triterpene compounds friedelin (1), epifriedelanol (2), taraxerol (3), 3-oxo-11α-methoxyolean-12-ene-30-oic acid (4), 3-oxo-11α-hydroxyolean-12-ene-30-oic acid (5) and 3,11-dihydroxyolean-12-ene-30-oic acid (6) were isolated. Compound 6 was isolated for the first time from a plant species. The antimicrobial activity of compounds 1, 3, 5 and 6 was determined against a range of bacteria and fungi implicated in opportunistic and nosocomial infections. Compounds 5 and 6 were the most active against all the tested microorganisms with MIC values ranging between 24 and 63 μg/ml, except against Staphylococcus aureus which was relatively resistant. Compounds 1 and 3 had a low toxicity with an LC₅₀ > 200 μg/ml towards Vero cells in the MTT assay. Compounds 5 and 6 were toxic with LC₅₀ values of 6.03±0.02 and 2.98±0.01 μg/ml, respectively. Compounds 1 and 3 similarly were not toxic to the red blood cells (RBCs) but compounds 5 and 6 were toxic, showing HA titer values of 1.33 and 0.67 respectively.

Conclusions

Compounds 5 and 6 were the most active but were also relatively cytotoxic to monkey kidney cells and red blood cells, while the other isolated compounds were less active and less cytotoxic.

Antiprotozoal sesquiterpene pyridine alkaloids from Maytenus ilicifolia

As part of a bioprospecting program aimed at the discovery of antiprotozoal agents from the Brazilian flora, two new sesquiterpene pyridine alkaloids, ilicifoliunines A (1) and B (2), along with the known alkaloids aquifoliunine E-I (3) and mayteine (4), were isolated from the root bark of Maytenus ilicifolia. The structures of 1 and 2 were established on the basis of spectroscopic data interpretation. Alkaloid 3 displayed potent in vitro antiprotozoal activity against Leishmania chagasi and Trypanosoma cruzi, with IC(50) values of 1.4 and 41.9 μM, respectively, as well as low cytotoxicity against murine peritoneal macrophages (IC(50) of 1.8 mM).

Sesquiterpenes from Maytenus jelskii as potential cancer chemopreventive agents

Seven new (1-4 and 7-9) sesquiterpenes with a dihydro-beta-agarofuran skeleton, along with four known compounds (5, 6, 10, and 11), have been isolated from the leaves of Maytenus jelskii. The structures of the new compounds were elucidated by means of spectroscopic data analysis, including 1D and 2D NMR techniques, and their absolute configurations were determined by circular dichroism and chemical correlations. The compounds have been tested for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Compound 10 was found to be an effective antitumor-promoting agent and also showed a potent chemopreventive effect in an in vivo two-stage carcinogenesis model.

Activity and mechanism of the action of zeylasterone against Bacillus subtilis

AIMS

To investigate the antimicrobial properties of 6-oxophenolic triterpenoids isolated from Maytenus blepharodes against different micro-organisms and the mode of action on Bacillus subtilis.

METHODS AND RESULTS

The activity of zeylasterone and demethylzeylasterone was evaluated by microdilution method. Zeylasterone showed a higher activity, being active against Gram-positive bacteria (minimum inhibitory concentration 3-20 microg ml(-1)) and Candida albicans (10 microg ml(-1)). Killing curves revealed a bacteriostatic effect on B. subtilis that was dependent on the growth phase and inoculum size. Zeylasterone caused cell membrane alterations in B. subtilis, as shown by potassium leakage and formation of mesosome-like structures. However, membrane disruption was not revealed by either LIVE/DEAD Baclight assay or measurement of intracellular constituent efflux. Zeylasterone showed an early effect on N-acetyl-glucosamine and uridine incorporation and later on that of thymidine and leucine.

CONCLUSIONS

Diverse micro-organisms exhibit sensitivities towards compounds studied. The permeability changes in the cytoplasmic membrane and nonsimultaneous ceasing of macromolecular synthesis suggest that zeylasterone could act on multiple targets on B. subtilis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The activity showed against B. subtilis as a model of spore-forming bacteria would provide valuable information for further studies in the development of 6-oxophenolic triterpenoids as antiseptic and disinfectant properties.

New dammarane triterpenes from Maytenus macrocarpa

Two new dammarane triterpenes have been isolated from the stem bark exudates of Maytenus macrocarpa. Their structures were determined by extensive 1D and 2D NMR spectroscopic studies as 24(Z)-3-oxodammara-20(21),24-dien-27-oic acid (1) and octa-nor-13-hydroxydammara-1-en-3,17-dione (2). These compounds were tested for antitumoral activity.

Conjugate addition of 2- and 4-pyridylcuprates: an expeditious asymmetric synthesis of natural (-)-evoninic acid

[reaction: see text] The scope and limitations of the conjugate addition of 2- and the first 4-pyridyl Gilman homocuprates to various alpha,beta-unsaturated Michael acceptors are delineated. The conjugate addition of the cuprate of 2-bromo-3-methylpyridine to (E)-methyl crotonate then diastereoselective enolate alkylation and lipase-mediated enantioselective ester hydrolysis have enabled an efficient four-step first asymmetric synthesis of the Celastraceae sesquiterpenoid esterifying ligand (-)-(1'S,2'S)-evoninic acid.

Lupane triterpenoids from Maytenus species

Five new lupane triterpenes (1-5), in addition to 24 known ones, were isolated from Maytenus cuzcoina and M. chiapensis. Their structures were elucidated on the basis of spectroscopic analysis, including homonuclear and heteronuclear correlation NMR (COSY, ROESY, HSQC, and HMBC) experiments. The compounds were assayed for antimicrobial and cytotoxic activities, with 3-epi-betulinic acid and 28,30-dihydroxy-3-oxolup-20(29)-ene showing moderate cytotoxicity.

Insecticidal sesquiterpene pyridine alkaloids from Maytenus chiapensis

The new sesquiterpene pyridine alkaloids chiapenines ES-I (1), ES-II (2), ES-III (3), and ES-IV (4), in addition to the known alkaloids wilfordine (5), alatamine (6), wilforidine (7), alatusinine (8), euonine (9), euonymine (10), ebenifoline E-I (11), forrestine (12), mayteine (13), and 4-hydroxy-7-epi-chuchuhuanine E-V (14), were isolated from the leaves of Maytenus chiapensis. Their structures were elucidated by 1D and 2D NMR spectroscopy, including homonuclear and heteronuclear correlation (COSY, ROESY, HSQC, and HMBC) experiments. Wilfordine, alatusinine, and euonine exhibited strong antifeedant activity against Spodoptera littoralis.

Absolute configuration of sesquiterpenes from Crossopetalum tonduzii and their inhibitory effects on Epstein-Barr virus early antigen activation in Raji cells

Two new sesquiterpenoids (1 and 2) with a dihydro-beta-agarofuran skeleton were isolated from Crossopetalum tonduzii. Their structures were elucidated on the basis of spectral analysis, including homonuclear and heteronuclear correlation NMR experiments (COSY, ROESY, HSQC, and HMBC). Their absolute configurations were determined by CD studies on 3, the benzoylated derivative of 1. Chemical correlations have allowed the absolute configurations of 4 and 5, two previously known dihydro-beta-agarofuran analogues, to be reported for the first time. Compounds 1, 2, and 5 showed strong antitumor-promoting effects on Epstein-Barr virus early antigen (EBV-EA) activation.

Absolute configuration and complete assignment of 13C NMR data for new sesquiterpenes from Maytenus chiapensis

Five new dihydro-beta-agarofuran sesquiterpenes (1-5) were isolated from the leaves of Maytenus chiapensis. The structures of 1-5 were determined by means of 1D and 2D NMR techniques. A semiselective HMBC technique was applied in order to obtain complete (13)C NMR assignments. Absolute configurations were determined by CD studies and chemical correlations and on biogenetic grounds. Compound 4 showed weak activity against a multidrug-resistant Leishmania tropica line.

New sesquiterpenes from Euonymus europaeus (Celastraceae)

A new sesquiterpene evoninate alkaloid (1), and two sesquiterpenes (2, 3) with a dihydro-beta-agarofuran skeleton, along with three known sesquiterpenes (4-6), were isolated from the seeds of Euonymus europaeus. Their structures were elucidated by high resolution mass analysis, and one- and two-dimensional (1D and 2D) NMR spectroscopy, including homonuclear and heteronuclear correlation [correlation spectroscopy (COSY), rotating frame Overhauser enhancement spectroscopy (ROESY), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlation (HMBC)] experiments.