Structurally Diverse Sesquiterpenoid Glycoside Esters from Pittosporum qinlingense with Anti-neuroinflammatory Activity

Chemical constituents with their alpha-glucosidase inhibitory activity from the whole plant of Ceratophyllum demersum

From Ceratophyllum demersum growing in Vietnam, twelve compounds were isolated and structurally elucidated, including six previously undescribed compounds, demersones A-D (1-4), acetylvelutins A and B (8 and 9), together with six known compounds, (+)-cyclocolorenone (5), 1-hydroxycyclocolorenone (6), 10-hydroxycyclocolorenone (7), retusin (10), betulinic acid (11), and lupeol (12). The chemical structures and stereochemistry of 1-12 were identified through analysis of spectroscopic data (1D and 2D NMR and HRESIMS), ECD data, and DFT calculation. Notably, this is the first time that humulene-type (1 and 2), guaiane-type (3), and aromadendrane-type (4-7) sesquiterpenoids have been reported in this genus. Compounds 8 and 9 are the first examples of 8-acetoxyflavones found in nature. Upon evaluation of the alpha-glucosidase of 1-3 and 5-12, it was found that 12 exhibited the highest potential with an IC50 value of 15.4 ± 1.1 μM. The molecular docking of 3 and 8 was further studied.

Bioactive secondary metabolites isolated from the branches and leaves of Pittosporum pulchrum Gagnep

Five new compounds, including two sesquiterpenoid glycosides (1 and 2), two monoterpenoid glycosides (3 and 4), and a quinovose ester (5), together with four known compounds (6-9) were isolated from branches and leaves of Pittosporum pulchrum Gagnep. Their structures were established by 1D and 2D NMR, HR-ESI-MS, IR and UV spectral analyses. This is the first time to investigate the chemical constituents of P. pulchrum. Subsequently, the anti-inflammatory and antioxidant activities of different solvent fractions of ethanol extract and isolated compounds were evaluated. Dichloromethane and ethyl acetate fractions dramatically inhibited the production of NO in a concentration-dependent manner in LPS-induced RAW264.7 cells. Ethyl acetate and n-butanol fractions showed excellent DPPH radical scavenging activities with IC50 values of 24.31 μg/mL and 27.81 μg/mL, respectively. Compounds 7 and 8 might be potential natural antioxidants with IC50 values of 16.13 μM and 24.81 μM, respectively.

Structure, anti-inflammatory and anti-bacterial activities of novel pentacyclic triterpenoids and other constituents from the leaves of Pittosporum elevaticostatum

The investigation of the leaves of Pittosporum elevaticostatum Chang et Yan led to the isolation of fifteen pentacyclic triterpenoids (1-15), including five previously undescribed ones (1-5), and nine others (16-24). The structures of compounds 1-5 were elucidated based on comprehensive spectroscopic techniques, including one dimension (1D) and 2D nuclear magnetic resonance (NMR), high resolution electrospray ionization mass spectroscopy (HR-ESI-MS), and other methods. Compounds 2 and 13 demonstrated significant inhibitory activity against Listeria monocytogenes (L. monocytogenes) with minimum inhibitory concentration (MIC) values of 32 μM. Scanning electron microscopy (SEM) observations revealed insights into the antibacterial mechanism, indicating that compounds 2 and 13 either prevent biofilm formation of dispersed the preformed cell membranes. Additionally, compounds 1, 5, 7, and 12 exhibited anti-inflammatory activity on lipopolysaccharide (LPS)-stimulated BV-2 microglial cells with IC50 values ranging from 11.27 to 17.80 μM.

Discovery of 23,24-diols containing ergosterols with anti-neuroinflammatory activity from Penicillium citrinum TJ507

Citristerones A-E (1-5), five new 23,24-diols containing ergosterols, along with three known analogues, were isolated from the endophytic fungus Penicillium citrinum TJ507 obtained from Hypericum wilsonii N. Robson. Their structures and absolute configurations were determined by NMR, HRESIMS, Snatzke's method, X-ray diffraction analyses and ECD calculation. Subsequently, the anti-neuroinflammatory effects of these isolates were screened using lipopolysaccharide (LPS)-induced BV-2 microglial cells, and citristerone B (2) showed outstanding anti-neuroinflammatory activity, with IC50 value of 0.60 ± 0.04 μM. Moreover, immunofluorescence and western blot analysis suggested that citristerone B not only reduced the release of nitric oxide (NO) and proinflammatory cytokines in LPS-induced BV-2 microglial cells, but also significantly inhibited the expression of TNF-α, iNOS and NF-κB, along with the production of cellular ROS.

Eudesmane-type sesquiterpenoids: Structural diversity and biological activity

Sesquiterpenoids are integral constituents of terpenoid-bearing plants, comprising a diverse and abundant class of natural compounds, among which eudesmane-type sesquiterpenoids have bicyclic structures that feature the fusion of two six-membered carbon rings, thereby attracting considerable attention. They are widespread in nature, with multifaceted biological activities such as anti-inflammatory, anticancer, antimicrobial, antimalarial, and insecticidal activities, thus gaining focus in life science research. The discovery and identification of these active compounds have laid a foundation for unraveling their potential medicinal value. In this review, we comprehensively explore the natural eudesmane-type sesquiterpenoids isolated (totaling 391 compounds) between 2016 and 2022, elucidating their chemical structures, plant distribution patterns, and pertinent biological properties. Accordingly, the study serves not only as a framework for researchers to thoroughly comprehend these compounds but also as a robust reference for future endeavors aimed at exploring the pharmaceutical potential and prospective applications of these molecules.

Chemical composition and biological activities of Pittosporum eriocarpum Royle: an unexplored medicinal plant of Indian himalayan region

In this study, different parts (leaf, bark, and fruit) of Pittosporum eriocarpum were investigated to explore its chemical composition and biological activities. The GC-MS analysis confirmed the presence of fifty-seven, eighty-one, and forty-six compounds in leaf, fruit, and bark extract, respectively. The important identified bioactive compounds include 1,3,4,5-tetrahydroxy-cyclohexanecarboxylic acid (quinic acid), falcarinol, tetradecanoic acid, and isopropyl myristate. Further, four polyphenolic compounds namely p-coumaric, chlorogenic, ferulic acid, and catechin were also identified and quantified in different parts through HPLC-PDA analysis. Of the studied parts of P. eriocapum, leaf extract contains the highest total phenolic, flavonoid, and tannin content, and exhibited potent antioxidant activity in ABTS assay. P. eriocarpum extracts also exhibited strong antimicrobial activity against gram-negative bacteria and showed considerable high protection against free radical-mediated DNA damage. To the best of our knowledge, this is the first detailed study of the chemical composition and biological activities of P. eriocarpum.

Aromatic glycosides and lignans glycosides with their acetylcholinesterase inhibitory activities from the leaves of Picrasma quassioides

In this study, eight new natural products were isolated from the leaves of Picrasma quassioides. Spectroscopic techniques were used for the elucidation of their planar structures. Their absolute configurations were elucidated on the basis of electron circular dichroism (ECD) techniques combined with the P/M helicity rule for the 2,3-dihydrobenzofuran chromophore, and saccharide hydrolysis. Cholinesterase inhibitors are often used as Alzheimer's disease inhibitors.Thus, acetylcholinesterase and butyrylcholinesterase inhibitory activity of these eight compounds were tested, and results showed that only compound 6 showed weakly acetylcholinesterase inhibitory activity. In particular, molecular docking was used to illustrate the bindings between compound 6 and the active sites of AChE.

Eudesmane sesquiterpenoid glycosides from the leaves of Pittosporum lenticellatum with anti-neuroinflammatory activity

Chemical investigation of the EtOAc extract of the leaves of Pittosporum lenticellatum led to the isolation of twenty-five previously undescribed eudesmane sesquiterpenoid glycosides, pitlencosides A－Y (1-25); their structures were elucidated by extensive spectroscopic analysis, including 1D and 2D NMR, HR-ESI-MS, ECD spectra, and X-ray crystallographic analysis. Among them, compounds 4, 5, 7, 8, 15 and 16 exhibited significant inhibitory effects on the production of nitric oxide in lipopolysaccharide-induced BV-2 microglial cells by suppressing the expression of inducible nitric oxide synthase and cyclooxygenase-2, with IC50 values ranging from 7.95 to 25.88 μM, which showed stereo-chemical and substituent dependents. Western blot analysis and molecular docking simulation confirmed the anti-inflammatory activity of compounds 4, 5, 7, 8, 15 and 16.

Pitsubcosides A-L, highly esterified eudesmane sesquiterpenoid glycosides with antibacterial activity from Pittosporum subulisepalum and their mechanism

BACKGROUND

Plants from the genus Pittosporum are traditionally used as antibacterial, antifungal and antiviral agents. A bioassay evaluation of the extract of Pittosporum subulisepalum revealed antibacterial activity. This study focused on the discovery of the antibacterial metabolism in P. subulisepalum, as well as the modes of action of its active components.

RESULTS

A chemical investigation of an ethyl acetate (EtOAc) extract of the aerial parts of P. subulisepalum led to the isolation of 12 previously undescribed eudesmane sesquiterpenoid glycoside esters (ESGEs), pitsubcosides A-L (1-12). Their structures were elucidated by extensive spectroscopic analysis, including one- and two-dimensional NMR, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism spectra and single-crystal X-ray crystallography analysis or by comparing with authentic samples. The new ESGEs were characterized by their highly esterified glycoside moieties. Among them, compounds 1-3, 5 and 8 showed a moderate inhibitory effect against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Bacillus cereus, Bacillus subtilis, Pseudomonas syringae pv. actinidiae (Psa) and Erwinia carotovora with minimum inhibitory concentrations (MICs) ranging from 3.13 to 100 μm. Among them, compounds 3 and 5 showed remarkable antibacterial activity against S. aureus and Psa with MIC values of 6.25 and 3.13 μm, respectively. Live bacterial mass and the biofilms of S. aureus and Psa were quantified using methyl tetrazolium and crystal violet assays. Fluorescence microscopy and scanning electron microscopy experiments revealed an antibacterial mechanism of cell membrane architectural disruption.

CONCLUSION

The results suggest that ESGEs possess great potential for the development of antibacterial agents to control plant pathogens. © 2023 Society of Chemical Industry.

A new anti-inflammatory thujane monoterpenoid glycoside ester from Pittosporum heterophyllum Franch

Phytochemical investigation of EtOH extract of Pittosporum heterophyllum led to one new esterified thujane monoterpenoid glycoside, pitheteroside A (1), together with one eudesmane sesquiterpenoid (2) and twelve lignans (3－14). Their structures were elucidated by extensive spectroscopic analysis, including 1D and 2D NMR, ECD calculation and HRESIMS spectra. Pitheteroside A is an unreported and highly esterified monoterpenoid glycoside. All isolates were evaluated for their nitric oxide production inhibition against LPS-induced BV-2 microglial cells. Among them, compounds 1, 6 and 8 showed significant activities with IC50 values less than 10 μM. The results indicated the metabolisms from P. heterophyllum possess potential anti-inflammatory effects.

Iridoids from Patrinia heterophylla and their anti-inflammatory activity

A phytochemical investigation led to the isolation of five undescribed compounds (1-5) from the methanol extract of the rhizomes and roots of Patrinia heterophylla. The structures and configurations of these compounds were characterized by HRESIMS, ECD, and NMR data analyses. These compounds were assayed for their anti-inflammatory potential using LPS-stimulated BV-2 cells, of which compound 4 showed strong nitric oxide (NO) inhibitory effects with an IC₅₀ of 6.48 μM. The potential anti-inflammatory mechanism was examined utilizing Western blotting and molecular docking. Further in vivo anti-inflammatory experiments revealed that compound 4 inhibited the production of NO and reactive oxygen species in the zebrafish model.

Phytoecdysteroids from Dianthus superbus L.: Structures and anti-neuroinflammatory evaluation

Six undescribed C₂₇-phytoecdysteroid derivatives, named superecdysones A-F, and ten known analogs were extracted from the whole plant of Dianthus superbus L. Their structures were identified by extensive spectroscopy, mass spectrometric methods, chemical transformations, chiral HPLC analysis, and the single-crystal X-ray diffraction analysis. Superecdysone A and B possess a tetrahydrofuran ring in the side chain and superecdysone C-E are rare phytoecdysones containing a (R)-lactic acid moiety, whereas superecdysone F is an uncommon B-ring-modified ecdysone. Notably, based on the variable temperature (from 333 K to 253 K) NMR experiments of superecdysone C, the missing carbon signals were visible at 253 K and assigned. The neuroinflammatory bioassay of all compounds were evaluated, and 22-acetyl-2-deoxyecdysone, 2-deoxy-20-hydroxyecdysone, 20-hydroxyecdysone, ecdysterone-22-O-benzoate, 20-hydroxyecdysone-20,22-O-R-ethylidene, and acetonide derivative 20-hydroxyecdysterone-20, 22-acetonide significantly suppressed the LPS-induced nitric oxide generation in microglia cells (BV-2), with IC₅₀ values ranging from 6.9 to 23.0 μM. Structure-activity relationships were also discussed. Molecular docking simulations of the active compounds confirmed the possible mechanism of action against neuroinflammations. Furthermore, none compounds showed cytotoxicity against HepG2 and MCF-7. It is the first report about the occurrence and anti-neuroinflammatory activity of the phytoecdysteroids in the genus Dianthus. Our findings demonstrated that ecdysteroids may be used as potential anti-inflammatory drugs.

Structurally diverse new eudesmane sesquiterpenoids with anti-inflammatory activity from the fruits of Alpinia oxyphylla

The phytochemical investigation of the fruits of Alpinia oxyphylla led to the isolation and identification of 40 structurally diverse sesquiterpenoids, including 17 new eudesmane sesquiterpenoids (1-17) and 23 known analogues (18-40). Among the isolates, 14 and 17 were unusual rearranged eudesmane sesquiterpenoids, featuring rare 5/6-fused and 6/8-fused bicyclic carbon skeleton, respectively; 15 and 16 were the novel 6,7-seco-eudesmane sesquiterpenoids isolated from plant-origin for the first time, 1 and 3-6 were rare nor-eudesmane sesquiterpenoids. Their structures were elucidated by comprehensive spectroscopic data analysis (NMR, HRESIMS, IR, UV), single crystal X-ray diffraction, and quantum chemistry calculations (ECD and ¹³C NMR). Moreover, all isolates were evaluated by measuring their inhibitory effect on nitric oxide (NO) in LPS-stimulated BV-2 cells. As a result, compounds 11, 20, 24 and 40 showed moderate to strong inhibition on NO productions, with IC₅₀ values ranging from 21.63 to 60.70 μM. Meanwhile, these compounds also partially decreased the secretion of TNF-α and IL-6 in LPS-stimulated BV-2 cells. Furthermore, 20 could down-regulate protein expressions (COX-2 and iNOS) and observably inhibit the mRNA expressions of TNF-α, IL-6, COX-2 and iNOS. In this study, the discovery of structurally diverse anti-inflammatory sesquiterpenoids from the fruits of A. oxyphylla could benefit the further development and utilization of this plant.

Syntheses of Bufospirostenin A and Ophiopogonol A by a Conformation-Controlled Transannular Prins Cyclization

Controlling the conformation of medium-sized rings is challenging because of their flexibility and ring strain effects. Herein, we report non-Curtin-Hammett conditions for the precise control of the conformation of cyclodecenones to effect the first cis-selective transannular Prins cyclization, which enabled concise syntheses of the 5(10→1)abeo-steroids bufospirostenin A and ophiopogonol A in only seven steps from inexpensive starting materials. Computational results indicated that the key cyclization was kinetically controlled and proceeded via either a Prins pathway or a carbonyl-ene pathway, depending on the reaction conditions. Moreover, conformational isomerization played a critical role in determining the stereochemistry of the products.

Further sesquiterpenoids from Pittosporum qinlingense and their anti-inflammatory activity

Four new sesquiterpenoid glycoside esters, Pitqinlingoside N-Q (1-4), together with eleven known metabolites (5-15), were isolated from 95% EtOH extract of the twigs, fruits and leaves of P. qinlingense. The structures of new compounds were elucidated on the basis of extensive spectroscopic analyses, including IR, UV, HRMS, NMR and electronic circular dichroism spectra. Unusal glycoside esters are characterized by the presence of polyacylated β-D-fucopyranosyl and β-d-glucopyranosyl units. Pitqinlingoside N (1), O (2), P (3), boscialin (5) and arvoside C (6) showed significant nitric oxide production inhibition in lipopolysaccharide (LPS)-induced BV-2 microglial cells with IC₅₀ values ranging from 1.58 to 28.74 μM. Structure-activity relationships of the isolated compounds are discussed.

Tigliane and rhamnofolane glycosides from Euphorbia wallichii prevent oxidative stress-induced neuronal death in PC-12 cells

Tigliane and rhamnofolane diterpenoids bearing glycosyl substituents are rarely found in nature. In the current study, seven new tigliane glycosides, euphorwallsides A - G (1-7), and five new rhamnofolane glycosides, euphorwallsides H - L (8-12), were isolated from the whole plants of Euphorbia wallichii. Their structures were elucidated by a combination of spectroscopic, computational, and chemical means. The aglycones of 1-5 represent a rare class of 13-deoxygenated tiglianes, while those of 8-12 represent the first examples of 4-deoxygenated rhamnofolanes. 2, 3, 5, 7, 8, and 12 showed significant neuroprotective effects on sodium nitroprusside (SNP)-induced neuronal death in pheochromocytoma cell line PC-12 at 10 μM, being more active than the clinical drug, edaravone. Mechanistic study revealed that the most active compound, 3, could inhibit reactive oxygen species (ROS) accumulation and restore the mitochondrial membrane potential via modulating the Nrf2 signaling pathway in PC-12 cells.