Analysis Of 2D NMR Data Research Articles

Targeted isolation of dimeric sesquiterpene lactones and sesquiterpene derivatives from the roots of Inula helenium

LC-HRMS/MS-based molecular networking was applied to investigate the bioactive sesquiterpene lactones and their analogs contained in Inula helenium, enabling the isolation of four undescribed eudesmane-eudesmane sesquiterpene dimers (1–4), a sesquiterpene-amino acid adduct (5), and 17 known sesquiterpenes (6–22). The structures were determined based on 1D, 2D NMR, and HRESIMS data analysis, as well as DP4+ probability analyses and ECD calculations. The biosynthetic pathway of the sesquiterpene dimers is postulated to proceed via the Diels-Alder reaction as the key step. The inhibitory activity of all isolates on LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages was evaluated. Compounds 4, 17, and 20 exhibited significant inhibitory activity against NO production, with IC50 values of 8.4, 5.5, and 9.1 μM, respectively.

Labdane-type diterpenoids with cytotoxic and anti-inflammatory activities from the aerial parts of Hypoestes purpurea (L.) R. Br.

Two new ent-labdane diterpenoids, hypoestesins A-B (1–2) and five new labdane diterpenoids, hypopurolides H-L (3–7), were isolated from the aerial parts of Hypoestes purpurea. All of the structures were fully determined based on extensive analysis of 1H, 13C, 2D NMR, and HRESIMS data. The absolute configurations of 1–3 was established through comparing the experimental and calculated ECD curves and the structure of 5 was confirmed by single crystal X-ray diffraction experiment. Compounds 5–7 were unusual C23 labdane diterpenoids having a γ-acetonyl-α, β-unsaturated γ-lactone unit and each assigned as C-15 epimeric mixture. Furthermore, cytotoxic and anti-inflammatory activities of 3–7 were evaluated. The results showed that 3 had remarkable cytotoxic activity against HL-60, A549, SMMC-7721, MDA-MB-231, and SW480 cancer cell lines with IC50 values ranging from 2.35 to 17.06 μM. Compound 4 showed moderate cytotoxic activity against HL-60 and SMMC-7721 cancer cell lines with IC50 values of 15.12 ± 0.53 and 12.92 ± 0.60 μM, respectively. Furthermore, compound 4 was also found to exhibit inhibitory activity against NO production in RAW 264.7 macrophages with IC50 values of 23.56 ± 0.99 μM, compared to the positive control L-NMMA with an IC50 value of 41.11 ± 1.34 μM.

Solvent-Free Mechanosynthesis of Oligopeptides by Coupling Peptide Segments of Different Lengths - Elucidating the Role of Cesium Carbonate in Ball Mill Processes.

We report an idea for the synthesis of oligopeptides using a solvent-free ball milling approach. Our concept is inspired by block play, in which it is possible to construct different objects using segments (blocks) of different sizes and lengths. We prove that by having a library of short peptides and employing the ball mill mechanosynthesis (BMMS) method, peptides can be easily coupled to form different oligopeptides with the desired functional and biological properties. Optimizing the BMMS process we found that the best yields we obtained when TBTU and cesium carbonate were used as reagents. The role of Cs2CO3 in the coupling mechanism was followed on each stage of synthesis by 1H, 13C and 133Cs NMR employing Magic Angle Spinning (MAS) techniques. It was found that cesium carbonate acts not only as a base but is also responsible for the activation of substrates and intermediates. The unique information about the BMMS mechanism is based on the analysis of 2D NMR data. The power of BMMS is proved by the example of different peptide combinations, 2+2, 3+2, 4+2, 5+2 and 4+4. The tetra-, penta-, hexa-, hepta- and octapeptides obtained under this project were fully characterized by MS and NMR techniques.

A novel nor-megastigmane from the leaves of Rhaphiostylis beninensis

A novel nor-megastigmane, normegastigmane-5α,9-epoxy-3β,8-diol (1), together with 10 known compounds of diverse classes including megastigmanes, sesquiterpenoids, and triterpenoids were isolated from the leaves of Rhaphiostylis beninensis. The structure of 1 was established by 1D and 2D NMR and HRESIMS data analysis. The known compounds were identified as 5,11-epoxy-3,9-megastigmanediol (2), 7-megastigmene-3,6,9-triol (3), 1,3-dihydroxypropan-2-yl stearate (4), (1E,5E)-1,5-dimethyl-8-(propan-2-ylidene)cyclodeca-1,5-diene germacrene (5) 3,5-dihyroxy-6,7-megastigmadien-9-one (6), squalene (7), β-amyrin (8), β-amyrone (9), β-amyrin eicosanoate (10), and β-sitosterol (11). Compounds 2, 3, and 6 displayed inhibitory effects on acetylcholinesterase enzyme. This is the first report of these compounds from the plant and their anticholinesterase activity.

Isolation and identification of three new phenylpropanoids from the culms of phyllostachys nigra var. henonis (mitford) Rendle

Three new phenylpropanoids, namely (7′R,8′R) guaiacylglycerol 4′-O-β-D-[6″-O-(4-O-β-D-glucopyranosyl)-p-hydroxyl­benzoyl]-glucopyranoside (1), (7 R,8R) guaiacylglycerol 8-O-1′-(2′,6′-dimethoxy-4′-O-β-D-glucopyranosyl)-benzene (2), (7′R,8′R) guaiacylglycerol 4′-O-β-D-[6″-O-3,5-dimethoxy-4-hydroxylbenzoyl]-gluco­pyranoside (3), along with one known phenylpropanoid (4) were isolated from the ethanol extract of Phyllostachys nigra var. henonis fresh culm. The structures of all compounds were determined by analysis of UV, 1D NMR, 2D NMR, HR-ESI-MS and CD data. All compounds were evaluated for their DPPH radical scavenging activity. Compound 2 (IC50 54.9 μM) and 3 (IC50 77.2 μM) exhibited moderate antioxidant activity compared with two positive control compounds L-ascorbic acid (IC50 15.5 μM) and 2,6-ditertbutyl-4-methyl phenol (IC50 19.1 μM).

New 19(10 → 9)abeo-euphane-type triterpenoids from Trichilia dregeana leaves and NO production inhibitory activities

Phytochemical investigation of the EtOAc soluble fraction from leaves of Trichilia dregeana Sond. (Meliaceae) afforded naturally rare four new pentacyclic triterpenoids (1–4), together with five known pentacyclic analogs (5–8, and 11) and two steroids (9 and 10). Their structures were elucidated by extensive spectroscopic techniques such as 1D and 2D NMR and HRESIMS data analyses. The absolute configuration of 1 was determined by using the single-crystal X-ray diffraction analysis. The nitric oxide (NO) production inhibitory assay indicated that the EtOAc fraction as well as 4 and 7 inhibited the NO production in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells with the IC50 values of 83.53 μg/mL and 81.31 and 85.71 μM, respectively. Compounds 1–4 are rare 19(10 → 9)abeo-euphane-type triterpenoids bearing a 3,10-ether bridge. To the best of our knowledge, this study is the first isolation of triterpenoids with the 3,10-ether bridge in their skeleton from the genus Trichilia, providing new insights into the chemodiversity of the terpenoids in T. dregeana.

Dammarane-type triterpenoids from Gynostemma longipes and their protective activities on hypoxia-induced injury in PC12 cells

Sixteen new dammarane-type triterpenoid saponins (1–16) featuring diverse structural variations in the side chain at C-17, along with twenty-one known analogues (17–37), have been isolated from the rhizomes of Gynostemma longipes C. Y. Wu, a plant renowned for its medicinal and edible properties. The structural elucidation of these compounds was accomplished through comprehensive analyses of 1D and 2D NMR and HRMS spectroscopic data, supplemented by comparison with previously reported data. Subsequent assays on the isolates for their protective effects against hypoxia-induced damage in pheochromocytoma cells (PC12 cells) revealed that nine saponins exhibited significant anti-hypoxic activities. Further investigation into the anti-hypoxia mechanisms of the representative saponins demonstrated that compounds 22 and 36 markedly reduced the levels of hypoxia-induced apoptosis. Additionally, these compounds were found to decrease the release of lactate dehydrogenase (LDH) and malondialdehyde (MDA), while increasing the activity of superoxide dismutase (SOD), thereby indicating that the saponins could mitigate hypoxia-induced injuries by ameliorating apoptosis and oxidative stress. These findings offer substantial evidence for the future utilization and development of G. longipes, identifying dammarane-type triterpenoid saponins as its active anti-hypoxic constituents.

Triterpenoid saponins from Bupleurum marginatum and their anti-liver fibrotic activities

A new triterpenoid saponin (1), along with five known compounds (2–6), was isolated from Bupleurum marginatum Wall. ex DC, of which compounds 2–4 were obtained for the first time from this plant. The structures were confirmed by the analysis of 1D, 2D NMR, and HR-ESIMS data, and comparison with previous spectral data. Anti-liver fibrotic activities of the isolates were determined as proliferation inhibition of LPS-induced activation of HSC-T6 in vitro.

Chemical constituents of açai berry pulp (Euterpe oleracea Mart.) by LC-UV-BPSU/NMR and LC-UV-SPE/NMR

The techniques LC-UV-BPSU and LC-UV-SPE/NMR were applied for the first time in the analysis of açai berry (Euterpe oleracea Mart.) pulp extracts. Those techniques allowed the identification of twenty-three metabolites: Valine (1), citric acid (2), tachioside (3), isotachioside (4), α-guaiacylglycerol (5), syringylglycerol (6), uridine (7), adenosine (8), dimethoxy-1,4-benzoquinone (9), koaburaside (10), protocatechuic acid (11), eurycorymboside B (12), 7′,8′-dihydroxy-dihydrodehydroconiferyl alcohol-9-O-β-D-glucopyranoside (13), orientin (14), homoorientin (15), dihydrokaempferol-3-glucoside (16), isolariciresinol-9′-O-β-D-glucopyranoside (17), 5′-methoxyisolariciresinol-9′-O-β-D-glucopyranoside (18), cyanidin-3-O-glucoside (19), cyandin-3-O-rutenoside (20), 9,12-octadecadienoic acid (Z,Z)-2-hydroxy-1-(hydroxymethyl) ethyl ester (21), linolenic acid (22), and 1,2-di-O-α-linolenoyl-3-O-β-D-galactopyranosyl-sn-glycerol (23). In this plant, compounds 3, 4, 5, 6, 8, 10, 12, 17, 18, 21, and 23 are reported for the first time. All the structures were determined through extensive analyses of 1D and 2D NMR data, mass spectrometry, and comparison with published data. This methodology has proven to be an efficient alternative to the analysis of complex extracts containing a large variety of compounds.

Discovery of structurally important cycloartane-type triterpenes from Dysoxylum binectariferum leaves and their anti-inflammatory activity

Seven undescribed cycloartane-type triterpenes (4–10) were isolated from the leaves of Dysoxylum binectariferum. The chemical structures and relative stereochemistry of all cycloartane triterpenes were determined by analysis of 1D and 2D NMR and ESI-HRMS spectroscopic data. Compound 4 was found to be a diastereoisomer of the previously discovered compound 2 (beddomeilactol). The compound 5 was identified as the methyl ester of compound 1 (beddomeilactone). The compounds 6 and 7 were found to be diastereoisomers with only a stereochemical change at C-4 and their absolute stereochemistry established by X-ray analysis. Compounds 6–8 and 10 were identified as 3,4-seco-cycloartane type triterpenes, while compound 9 was elucidated as nor-3,4-seco-cycloartane triterpene. Nitric oxide (NO) inhibition was used to assess the anti-inflammatory effects of all newly isolated natural products in LPS-induced RAW 264.7 cell line. It was found that compounds 1, 2, 6 and 8 showed good IC50 values of 14.98 ± 4.06, 38.50 ± 2.88, 36.95 ± 3.24, and 35.37 ± 4.51 µM respectively for NO production inhibition and were non-toxic to RAW 264.7 macrophages.

Constituents of Chimaphila japonica and Their Diuretic Activity.

Three new phenols (1-3), one new cyclohexanol (4), two known phenols (5-6), and six known flavonoids (7-12) were isolated from the n-butanol of the 75% ethanol extract of all plants of Chimaphila japonica Miq. Among them, compound 5 was named and described in its entirety for the first time, and compounds 9 and 10 were reported in C. japonica for the first time. The structures of all compounds were confirmed using a comprehensive analysis of 1D and 2D NMR and HRESIMS data. Biological results show that compounds 4, 7, and 11 exhibited potent diuretic activity. The modes of interaction between the selected compounds and the target diuretic-related WNK1 kinase were investigated in a preliminary molecular docking study. These results provided insight into the chemodiversity and potential diuretic activities of metabolites in C. japonica.

New clerodane diterpenoids from Callicarpa pseudorubella and their antitumor proliferative activity

Six previously undescribed clerodane diterpenes, cardorubellas A-F (1-6), along with seven known ones (7-13), were isolated from the aerial parts of Callicarpa pseudorubella. Their chemical structures were established by analysis of 1D and 2D NMR, HR-ESI-MS, X-ray diffraction, and electronic circular dichroism (ECD) data. Notably, cardorubella B (2) represented the first examples of naturally occurring succinic anhydride-containing clerodane diterpenes derivatives. The anti-proliferative activities of these compounds were assessed. Remarkably, compound 2 exhibited comparable inhibitory activity against HEL cell lines, surpassing the positive control with an IC50 value of 14.01 ± 0.77 μM, compared to 17.02 ± 4.70 μM for 5-fluorouracil.

Novel anti-inflammatory diketopiperazine alkaloids from the marine-derived fungus Penicillium brasilianum

Diketopiperazine alkaloids have proven the most abundant heterocyclic alkaloids up to now, which usually process diverse scaffolds and rich biological activities. In our search for bioactive diketopiperazine alkaloids from marine-derived fungi, two novel diketopiperazine alkaloids, penipiperazine A (1) and its biogenetically related new metabolite (2), together with a known analogue neofipiperzine C (3), were obtained from the strain Penicillium brasilianum. Their planar structures and absolute configurations were elucidated by extensive spectroscopic analyses, 13C NMR calculation, Marfey’s, ECD, and ORD methods. Compound 1 featured a unique 6/5/6/6/5 indole-pyrazino-pyrazino-pyrrolo system, and its plausible biogenetic pathway was also proposed. Additionally, compounds 1–3 have been tested for their inflammatory activities. 1 and 2 significantly inhibited the release of NO and the expression of related pro-inflammatory cytokines on LPS-stimulated RAW264.7 cells, suggesting they could be attracting candidate for further development as anti-inflammatory agent.Key points• A novel diketopiperazine alkaloid featuring a unique 6/5/6/6/5 indole-pyrazino-pyrazino-pyrrolo system was isolated from the marine fungus Penicillium brasilianum.• The structure of 1 was elucidated by detailed analysis of 2D NMR data, 13C NMR calculation, Marfey’s, ECD, and ORD methods.• Compounds 1 and 2 significantly inhibited the release of NO and the expression of related pro-inflammatory cytokines on LPS-stimulated RAW264.7 cells.Graphical

Homoerythrina-type alkaloids with neuroprotective activity from the branches of Cephalotaxus hainanensis Li

Lucidinine β-N-oxide (1), one previously unreported homoerythrina N-oxide type alkaloid, and three known homoerythrina-type alkaloids (2−4) were isolated and elucidated from Cephalotaxus hainanensis Li. The structure of 1 were elucidated by extensive analysis of HRESIMS, 1D and 2D NMR data. The structures of three known alkaloids were elucidated by comparison with known compounds. The absolute configuration of 1 was established on the basis of experimental and computed ECD. All compounds was evaluated for neuroprotective activity against H2O2-induced apoptosis in human neuroblastoma SH-SY5Y cells. Lucidinine β-N-oxide (1) significantly improved cell vitality of SH-SY5Y cells to 82.90 ± 2.14% at concentration of 80 μM.

Additional Sarasinosides from the Marine Sponge Melophlus sarasinorum Collected from the Bismarck Sea.

In our continuing efforts to describe the biological and chemical diversity of sponges from Kimbe Bay, Papua New Guinea, the known 30-norlanostane saponin sarasinoside C1 (1) was identified along with six new analogues named sarasinosides C4, C5, C6, C7, C8, and C9 (2-7) from the sponge Melophlus sarasinorum. The structures of the new compounds were elucidated by analysis of 1D and 2D NMR and HRMS data, as well as comparison with literature data. All new compounds are characterized by the same tetraose moiety, β-d-Xylp-(1→6)-β-d-GlcNAcp-(1→2)-[β-d-GalNAcp-(1→4)]-β-d-Xylp, as described previously for sarasinoside C1, but differed in their aglycone moieties. When comparing NMR data of sarasinoside C8 with those of known analogues, a misassignment was identified in the configuration of the C-8/C-9 diol for the previously described sarasinoside R (8), and it has been corrected here using a combination of ROESY analysis and molecular modeling.

Iridoid constituents from the branches of Viburnum chinshanense and their inhibitory effects on α-amylase and α-glucosidase

Ten previously undescribed iridoid constituents, viburnshosins A−E (1−5) and viburnshosides A−E (6−10), together with one known analogue (11), were isolated from the branches of Viburnum chinshanense. Their structures were unambiguously elucidated by a comprehensive analysis of 1D and 2D NMR data, together with HRESIMS spectroscopic data. The absolute configurations of compounds 1−10 were assigned by means of the calculated ECD spectra. Interestingly, compounds 2 and 3 are the first iridoids with an unusual C-3−C-7 oxo bridge. Compounds 4, 5, and 10 displayed remarkable inhibitory effects against α-amylase (IC50: 38.42, 37.65, and 21.64 μM, respectively) and α-glucosidase (IC50: 12.97, 19.34, and 25.71 μM, respectively), comparable to those of the positive control acarbose (IC50: 39.75 and 23.66 μM, respectively). The interaction modes of compounds 4 and 10 with two enzymes were analyzed by molecular modeling.

Two Pairs of New Bisabolane-Type Sesquiterpenoids from Aspergillus sydowii.

Two pairs of new bisabolane-type sesquiterpenoids, (+)-aspersydowin A (7S) [(+)-1], (-)-aspersydowin A (7R) [(-)-1], (+)-aspersydowin B (7S,11S) [(+)-2], (-)-aspersydowin B (7R,11R) [(-)-2], along with six known compounds (1-8) were isolated from the fungus Aspergillus sydowii. Compounds 1 and 2 are enantiomers resolved by the Chiralpak IC, using a hexane- propan-2-ol mobile phase. The structure of 1 and 2 with absolute configuration were assigned tentatively by 1D (1 H, 13 C, and DEPT) & 2D (HSQC, 1 H-1 H COSY, HMBC, and NOESY) NMR data analyses and ECD calculations. Compounds 1-8 were screened for the biological activities in vitro. The results showed that compounds 3, 4 and 8 exhibited immunosuppressive activities with IC50 values of 10.9, 17.6 and 13.4 μM, respectively.

Saponins from the Leaves of Eclipta prostrata

Eclipta prostrata (L.) is a traditional herbal medicine belonging to the Eclipta genus in the Asteraceae family. This plant is widely distributed in tropical and subtropical regions such as South America and Asia. According to the traditional medicine of some Asian countries (China, India, Thailand), E. prostrata is used to treat hepatic and renal diseases, diabetes, skin diseases, respiratory disorders, cool blood, and stanch bleeding. Besides, it also shows antioxidant, anti-inflammatory, antibacterial, and antimicrobial activities. In Vietnam, the plant grows naturally in moist soil and is distributed from mountainous areas to plains. It is used to treat coughs and burns, respiratory infections, and boils. In this research, four saponins including eclalbasaponin I-II and eclalbasaponin IV-V were isolated from the methanol extract of Eclipta prostrata using various modern chromatography methods such as TLC, CC, and HPLC. Their chemical structures were identified by analysis of 1D, 2D-NMR, and ESI-MS spectra data and by comparison of the spectral data in the literature. Eclalbasaponin IV and V were first reported from Eclipta prostrata cultivated in Vietnam.

Five undescribed abietane-type diterpenes of Callicarpa macrophylla

A phytochemical investigation of the medicinal plant Callicarpa macrophylla resulted in the characterization of two rare rearrangement abietane-type diterpenoids, macrophypene F-G (1–2), and three abietane diterpenoids, named macrophypene H-J (3–5). Additionally, five known diterpenoids (6–10) were identified. The structures of the newly discovered compounds were fully established through extensive analysis of HRESIMS, 1D and 2D NMR data. The absolute configurations of the isolated compounds were determined using CD comparison, chemical methods, and X-ray crystal diffraction experiments. Subsequently, all isolated diterpenoids were evaluated for their inhibitory effects on extracellular PCSK9 protein levels by PCSK9 AlphaLISA screening. Jiadfenoic acid B (6, 56.80% inhibition at 20 μM) and holophyllin F (10, 43.18% inhibition at 20 μM) significantly decreased PCSK9 protein levels in medium of HepG2 cells.

Investigation of the Dietary Preferences of Two Dorid Nudibranchs by Feeding-Choice Experiments and Chemical Analysis

Feeding-choice experiments were conducted under laboratory conditions with two dorid spongivorous nudibranchs, Goniobranchus aureomarginatus and Ceratosoma amoenum, collected from a sponge meadow off Tauranga, New Zealand with two sponge prey (Dysidea teawanui sp.nov. and an undescribed species from the Dictyodendrillidae family, possibly Dictyodendrilla tenella (Lendenfeld 1888). The first choice of prey, the total number of prey choices made, and the time spent on each prey target was recorded, results indicating that each nudibranch had strong preferences for specific prey species. Preferences were significant when the time spent grazing on prey was taken into consideration. Goniobranchus aureomarginatus had a strong preference for the undescribed Dictyodendrillid sponge, while Ceratosoma ameonum preferred Dysidea teawanui. The results of the feeding-choice experiments matched observations in the wild. Chemical analysis of the undescribed Dictyodendrillid sponge led to the isolation and characterisation of six known bioactive metabolites, dictyodendrin C (1), D (2) and F (3), as well as denigrin E (4), dactylpyrrole A (5) and lamellarin O1 (6). Two of the known compounds, dictyodendrins C (1) and F (3) were also isolated from G. aureomarginatus individuals. Chemical analysis of D. teawanui afforded ergosterol peroxide, 5α,8α-epidioxy-24-methylcholesta-6,22-dien-3β-ol (7). The structures of the isolated natural products were elucidated based on extensive analysis of 1D and 2D NMR data.