Extensive 2D NMR Research Articles

Novel Flavonol Alkaloids in Green Tea: Synthesis, Detection, and Anti-Alzheimer's Disease Effect in a Transgenic Caenorhabditis elegans CL4176 Model.

Novel N-ethy-2-pyrrolidinone-substituted flavonols, myricetin alkaloids A-C (1-3), quercetin alkaloids A-C (4a, 4b, and 5), and kaempferol alkaloids A and B (6 and 7), were prepared from thermal reaction products of myricetin, quercetin, kaempferol─l-theanine, respectively. We used HPLC-ESI-HRMS/MS to detect 1-7 in 14 cultivars of green tea and found that they were all present in "Shuchazao," "Longjing 43", "Fudingdabai", and "Zhongcha 108" green teas. The structures of 1-4 and 6 were determined by extensive 1D and 2D NMR spectroscopies. These flavonol alkaloids along with their skeletal flavonols were assessed for anti-Alzheimer's disease effect based on molecular docking, acetylcholinesterase inhibition, and the transgenic Caenorhabditis elegans CL4176 model. Compound 7 strongly binds to the protein amyloid β (Aβ1-42) through hydrogen bonds (BE: -9.5 kcal/mol, Ki: 114.3 nM). Compound 3 (100 μM) is the strongest one in significantly extending the mean lifespan (13.4 ± 0.5 d, 43.0% promotion), delaying the Aβ1-42-induced paralysis (PT50: 40.7 ± 1.9 h, 17.1% promotion), enhancing the locomotion (140.0% promotion at 48 h), and alleviating glutamic acid (Glu)-induced neurotoxicity (153.5% promotion at 48 h) of CL4176 worms (p < 0.0001).

Monoterpenoid indole alkaloids from Melodinus axillaris W.T.Wang exhibit anti-inflammatory activities by inhibiting the NF-κB signaling pathways

Ethnopharmacological relevanceMelodinus axillaris W.T.Wang has been widely used as an important medicine in China. In the folk of China, its whole plant has been used for fractures, rheumatic heart disease, testitis, hernia, abdominal pain, and dyspepsia, etc. Despite its extensive use, there is a shortage of literature investigating the specific bioactive compounds and underlying mechanisms responsible for their anti-inflammatory effects. This knowledge gap serves as the primary impetus for conducting this study, which aims to shed light on the previously unexplored therapeutic potential of M. axillaris. Aim of the studyThis study aims to investigate the material basis and potential mechanism of anti-inflammatory activity of M. axillaris. Materials and methodsCompounds were isolated from the 95% ethanol extract of M. axillaris using a systematic phytochemical method. The structures were established by extensive spectroscopic analysis, including 1D and 2D NMR, HR-ESI-MS, ECD calculation, and DP4+ analysis. The anti-inflammatory activities of ethanol extract and compounds from M. axillaris were tested by an inflammation model of LPS-stimulated RAW264.7 cells in vitro. Western blot analysis was employed to evaluate the expressions of COX-2, iNOS, and NF-κB signaling pathways, aiming to elucidate the underlying mechanisms. ResultsEleven undescribed monoterpenoid indole alkaloids (MIAs), axillines A−K (1–11), along with thirteen known analogs were isolated from M. axillaris. Compound 1 was the first representative of vincadine alkaloid with unprecedented 6/5/9/6/6 skeletons. Compounds 1–11 and ethanol extract showed significant anti-inflammatory effects in vitro. Among them, compound 2 had the best activity of inhibiting NO release (IC50 = 3.7 ± 0.9 μM). Additionally, subsequent Western blot analysis revealed that 2 could significantly inhibit the up-regulation of NF-κB signaling pathways, iNOS, and COX-2 in LPS-stimulated RAW264.7 cells, thereby demonstrating its anti-inflammatory activity. ConclusionThis study provides support for the traditional use of M. axillaris in terms of its anti-inflammatory properties and highlights the potential of MIAs as promising candidates for further development as anti-inflammatory drugs.

Alpha-glucosidase inhibitory compounds from Vietnamese lichen Usnea baileyi: in vitro and in silico aspects.

Using a bio-guided isolation on the Vietnamese lichen Usnea baileyi based on alpha-glucosidase inhibition, eleven compounds were isolated and structurally elucidated, namely, protocetraric acid (1), 8'-methylstictic acid (2), stictic acid (3), 4,6-diformyl-8-hydroxy-3-methoxy-1,9-dimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepine-7-carboxylic acid (4), vicanicin (5), norstictic acid (6), diffractaic acid (7), barbatic acid (8), atranol (9), 5-chlorohaematommic acid (10), and eumitrin A1 (11). Their chemical structures were identified by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy and compared with those reported in literature. Protocetraric acid (1) and norstictic acid (6) were selected for further modification to derive new compounds, namely, 1a-1e and 6a. Both isolated and synthesized compounds were assessed for their alpha-glucosidase inhibitory activity. Compounds 1-6, 1a-1e, 6a, and 11 showed significant alpha-glucosidase inhibition with IC50 values ranging from 10.4 to 130 μM. Molecular docking was applied to the most active compounds 1-3, 6, 1a-1e, and 6a to clarify the inhibitory mechanism. Compound 1e was determined to be a mixed inhibitor through a kinetic study.

Laxilignans A-C from the leaves of Terminalia laxiflora Engl. and their α-glucosidase inhibitory activity

Three previously undescribed dibenzylbutane lignans, laxilignans A−C, together with fifteen known compounds were isolated and characterized from the leaves of Terminalia laxiflora Engl. The structures of laxilignans A−C were elucidated by extensive 1D and 2D NMR analyses, together with mass spectrometry. The inhibitory activity of the isolated compounds against α-glucosidase enzyme, obtained from Saccharomyces cerevisiae, was evaluated in comparison to acarbose (IC50 = 16.42 ± 0.14 µM). The results revealed that corilagin, chebulagic acid, laxilignan A, termilignan B, termitomenin C, arjunglucoside II, and laxilignan B possess α-glucosidase inhibitory potential, with IC50 values in the range of 1.61 ± 0.05 – 403.5 ± 29.5 μM, respectively. The results of the molecular docking revealed that the two laxilignans A and B showed comparable binding affinities to those of acarbose with the binding sites of the human α-glucosidase enzyme. These findings suggest that dibenzylbutane lignans may act as promising lead compounds for the development of α-glucosidase inhibitors.

Suppression of lipopolysaccharide-induced COX-2 expression via p38MAPK, JNK, and C/EBPβ phosphorylation inhibition by furomagydarin A, a benzofuran glycoside from Magydaris pastinacea

The phytochemical investigation of the methanol extract of the seeds of Magydaris pastinacea afforded two undescribed benzofuran glycosides, furomagydarins A-B (1, 2), together with three known coumarins. The structures of the new isolates were elucidated after extensive 1D and 2D NMR experiments as well as HR MS. Compound 1 was able to inhibit the COX-2 expression in RAW264.7 macrophages exposed to lipopolysaccharide, a pro-inflammatory stimulus. RT-qPCR and luciferase reporter assays suggested that compound 1 reduces COX-2 expression at the transcriptional level. Further studies highlighted the capability of compound 1 to suppress the LPS-induced p38MAPK, JNK, and C/EBPβ phosphorylation, leading to COX-2 down-regulation in RAW264.7 macrophages.

Cistadesertosides B-E, Four New Diastereomeric Lignan Glycosides from the Stems of Cultural Cistanche deserticola in Tarim Desert.

Four previously undescribed diastereomeric lignan glycosides, namely cistadesertosides B-E (1-4) were isolated from the stems of cultural Cistanche deserticola in Tarim desert. The structures of these compounds were elucidated on the basis of extensive spectroscopic analyses, including IR, HR-ESI-MS, 1D and 2D NMR, circular dichroism (CD) data and chemical degradation. The in vitro anti-inflammatory activity of the isolates was also investigated. It showed that compounds 3 and 4 exhibited potential effects with IC50 values of 21.17 μM and 26.97 μM, respectively (positive control quercetin, IC50 , 10.01 μM).

Phenopyrrolizins A and B, Two Novel Pyrrolizine Alkaloids from Marine-Derived Actinomycetes Micromonospora sp. HU138.

Two previously undescribed pyrrolizine alkaloids, named phenopyrrolizins A and B (1 and 2), were obtained from the fermentation broth of marine-derived Micromonospora sp. HU138. Their structures were established by extensive spectroscopic analysis, including 1D and 2D NMR spectra as well as HRESIMS data. The structure of 1 was confirmed by single-crystal diffraction analysis and its racemization mechanism was proposed. The antifungal activity assay showed that 2 could inhibit the mycelial growth of Botrytis cinerea with the inhibitory rates of 18.9% and 35.9% at 20 μg/disc and 40 μg/disc, respectively.

New Meroterpenoid Derivatives from the Pomegranate-Derived Endophytic Fungus Talaromyces purpureogenus.

In this study, we report the isolation of two new meroterpenoids, miniolutelide D (1) and miniolutelide E (13-epi-miniolutelide C) (2), along with two meroterpenoidal analogues (3 and 4) and two phenolic compounds (5 and 6) from the endophytic fungus Talaromyces purpureogenus derived from Punica granatum fruits. Their structures were elucidated using extensive MS, 1D, and 2D NMR spectroscopic analyses as well as by comparing with data in the literature. The absolute configurations of 1 and 2 were determined using TDDFT-ECD calculations. Antimicrobial activity was evaluated. Compound 5 displayed significant activity against methicillin-resistant Staphylococcus aureus strain ATCC 700699 and moderate activity against S. aureus strain ATCC 29213.

Five new biflavonoids with acetylcholinesterase inhibitory activity from Diphylleia sinensis

Five new biflavonoids, diphybiflavonoids A − E (1–5), were isolated from the roots and rhizomes of Diphylleia sinensis. Their structures were elucidated by extensive spectroscopic data, including UV, IR, HR-ESI-MS and 2D NMR. Their absolute configurations were determined by ECD spectra. All isolated compounds were evaluated for acetylcholinesterase (AChE) inhibitory activity. Compounds 1–4 exhibited the potent AChE inhibitory activities with IC50 values of 1.62, 2.10, 2.08, and 5.15 μM, respectively. The preliminary structure-activity relationship study indicated that the connection mode (C2-O-C4′′′/C3-O-C3′′′ or C2-O-C3′′′/C3-O-C4′′′) of biflavonoid subunits, and 3-hydroxy group of flavonol subunit were important structural factors for AChE inhibitory activity. Biflavonoids, containing a C2-O-C4′′′/C3-O-C3′′′ or C2-O-C3′′′/C3-O-C4′′′ linkage, can be a potentially useful platform for development of cholinesterase inhibitors.

Marihysin B, a new cyclic lipopeptide from culture broth of Staphylococcus sp. - antimicrobial and glucoamylase inhibitory activities

A new cyclic lipopeptide, marihysin B (1) and the well-known marihysin A (2) were isolated from Staphylococcus sp. culture broth obtained from Corallina officinalis L. Extensive 1D (1H and 13C) and 2D (1H–1H COSY, HSQC, HMBC, and NOESY) NMR spectral investigations were used to determine the structures of isolated compounds. With inhibition zone widths of 11 to 25 mm and MICs of 25 µg/mL, compounds 1 and 2 showed marked antifungal activity against Aspergillus niger, Penicillum crustosum, Trichophyton concentricum, and Schizophyllum commune compared to nystatin (inhibition zone diameters 23–31 mm). Additionally, computational study was done to determine the possible mechanism underlying the antifungal activity of the two cyclic lipopeptides against Schizophyllum commune glucoamylase. These substances showed similar binding affinities to the target's reference compound.

A New 3-Benzylphthalide from the Moss Erythrodontium julaceum.

From the moss Erythrodontium julaceum Paris growing in Vietnam, julacelide (1), a new 3-benzylphthalide, along with methyl orsellinate (2), ethyl orsellinate (3), 4-O-methylhaematommic acid (4), and zeorin (5), were isolated and structurally elucidated. Their chemical structures were elucidated through extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy as well as through comparisons to the existing literature. Compound 4-O-methylhaematommic acid was a new natural product. The absolute configuration of julacelide was defined using time-dependent density functional theory (TDDFT) calculations. Julacelide was evaluated for α-glucosidase inhibition.

Sulfur-containing spiroketals from Breynia disticha and evaluations of their anti-inflammatory effect.

Breynia spp. are a key source of sulfur-containing spiroketal glycosides with potential anti-inflammatory activity. In this study, three new sulfur-containing spiroketals - breynin J (1), epibreynin J (2), and probreynogenin (3) - along with four known compounds - probreynin I (4), phyllaemblic acid (5), breynin B (6), and epibreynin B (7) - were isolated from the roots of Breynia disticha. The structures of compounds 1-7 were elucidated by extensive 1D and 2D NMR spectroscopic analyses, including 1D total correlation spectroscopy (TOCSY), HSQC, HMBC, double quantum-filtered (DQF)-COSY, heteronuclear two-bond correlation (H2BC), and HSQC-TOCSY experiments, as well as high-resolution electrospray ionization HRESIMS analysis, and quantum chemical electronic CD calculations. Furthermore, the absolute configurations of sugar residues were determined by derivatization of the hydrolysates with ʟ-cysteine methyl ester and o-tolyl isothiocyanate followed by HPLC analysis. The anti-inflammatory effects of the isolated compounds were evaluated based on the mRNA levels of proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophage cells. Compounds 1, 2, 6, and 7 inhibited the increase in interleukin (IL)-1β and IL-6 mRNA levels stimulated by LPS. Moreover, the most potent compound 7 was found to significantly inhibit the production of IL-1β and IL-6 proteins, as revealed by the analysis of culture supernatants.

Megastigmane glycoside and phenol glycosides from the bark of Mallotus barbatus

A new megastigmane glycoside, barbatcoside A (1), and two new phenol glycosides, barbatcosides B (2) and C (3), together with eight known compounds (4-11) were isolated from the bark of Mallotus barbatus Müll. Arg. Their structures were elucidated using extensive 1D and 2D NMR as well as HRESIMS spectroscopic data. The stereochemistry of compounds 1 and 2 were established based on the experimental CD curves. The anti-inflammatory activities of compounds 1-11 from M. barbatus were evaluated using LPS-stimulated RAW 264.7 cell models. Compounds 2 and 3 substantially inhibited the release of NO with IC50 values of 34.78 μM and 20.73 μM, respectively.

Steroid and triterpenoid saponins from the rhizomes of Paris polyphylla var. stenophylla.

Five new saponins, including three steroid saponins, paristenoids A-C (1-3), and two triterpenoid saponins, paristenoids D-E (4-5), along with four known ones (6-9) were isolated from the rhizomes of Paris polyphylla var. stenophylla. The structures of the isolated compounds were identified mainly by detailed spectroscopic analysis, including extensive 1D and 2D NMR, MS, as well as chemical methods. Compound 3 is a new cyclocholestanol-type steroidal saponin with a rare 6/6/6/5/5 fused-rings cholestanol skeleton, and this skeleton has been first found from the genus Paris. The cytotoxicities of the isolated compounds against three human three glioma cell lines (U87MG, U251MG and SHG44) were evaluated, and compound 7 displayed certain inhibitory effect with IC50 values of 15.22 ± 1.73, 18.87 ± 1.81 and 17.64 ± 1.69 μmol·L-1, respectively.

Metabolites from Lactococcus lactis subsp. lactis: Isolation, Structure Elucidation, and Antimicrobial Activity.

Herein, we disclose the identification of novel metabolites from a potential probiotic strain, Lactococcus lactis subsp. lactis, obtained from traditional dairy milk samples collected in Maharashtra, India (in January 2021). Isolated metabolites include pyrazin-2-carboxamide [1, pyrazinamide, a potential antitubercular drug], 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (2, DDMP), 2,4-di-tert-butylphenol (3), and hexadecanoic acid (4, palmitic acid). The chemical structures of these metabolites were elucidated through extensive 1D NMR (1H and 13C) and 2D NMR (HSQC, HMBC, and NOESY) analyses, high-resolution mass spectrometry, high-performance liquid chromatography, and single-crystal X-ray crystallography. Furthermore, these novel metabolites exhibited potent inhibitory activities against various bacteria, fungi, and yeast strains with minimum inhibitory concentrations ranging between 1.56 and 25 μg/mL, and compounds 1 and 3 were found to be most active against a wide range of microbial strains tested.

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.

Euchronin A-F isolated from the Arnebia euchroma (Royle) Johnst. and their anti-proliferative activities in vitro.

Six new naphthoquinones, euchronin A-F (1-6) and nine known naphthoquinones (7-15), were isolated from the roots of Arnebia euchroma (Royle) Johnst. The structures of the new compounds were confirmed by extensive spectroscopic analyses, including UV, IR, HR-ESI-MS, 1D and 2D NMR. In the present study, we estimated the anti-proliferative activities of these compounds with HaCaT cells. The results indicated that compounds 2 and 4 showed strong anti-proliferative activities at 25μM, with relative viability at 38.83% and 68.44%, respectively.

Three new isoquinoline alkaloids from the fermentation of Aspergillus sp. 0338 and their anti-MRSA activities

There is growing evidence that bioactive substances produced by microbial endophytes have applicability in medicine, agriculture and industry. To enrich the bioactive substances, in our search for new bioactive metabolites from fungi Aspergillus, the phytochemical reinvestigation on the Aspergillus sp. 0338 was carried out, and this led to the isolation of three new (1-3) and five known alkaloids (4-8). Their structures were elucidated by spectroscopic analysis, including extensive 1D and 2D NMR techniques, as well as comparison with literature values. Additionally, compounds 1-3 were evaluated for their anti-MRSA activities. The results revealed that compounds 1-3 exhibited good inhibitions with IZD of 15.2 ± 1.8, 14.6 ± 2.0, and 13.4 ± 2.2 mm, respectively.

Cytotoxic and anti-bacterial evaluation of two new aromatic A-ring steroids isolated from the Red Sea soft coral Dendronephthya spp.

A successful column chromatography of a CHCl3/MeOH crude extract of Dendronephthya spp. soft coral led to the isolation of two new aromatic A-ring steroids (1–2), together with three known compounds (3–5). Both 1 and 2 are 19-norsteroids. The chemical structures were elucidated based on extensive 1D, 2D NMR, and EIMS analyses. In cytotoxic bioassays, compounds 1–5 were tested against three cancer cell lines: MCF-7, NCI-1299, and HepG2, with IC50 in the ranges of 22.1–85.4, 26.9–88.7, and 25.9–93.7 μM, respectively. Compounds 1, 2, and 5 showed moderate degrees of inhibition against Escherichia coli and Pseudomonas sp. at 100 and 150 µg/mL, while exhibiting weak inhibition against Bacillus cereus and Staphylococcus aureus at 150 µg/mL.

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.