Sesquiterpene Pyridine Alkaloids Research Articles

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.

Proteome profiling reveals insights into secondary metabolism in Maytenus ilicifolia (Celastraceae) cell cultures producing quinonemethide triterpenes

Plants produce a wide variety of secondary metabolites (SMs) of pharmacological interest that, due to their high structural complexity, are difficult to obtain from chemical synthesis. Knowledge of the enzymatic process involved in the biosynthesis of these SMs may contribute to the development of new strategies for obtaining them from plant tissues. Maytenus ilicifolia contains three main classes of bioactive compounds: sesquiterpene pyridine alkaloids, flavonoids and, primarily, quinonemethide triterpenes, which are well known for their high and broad antitumor activity. Thus, to determine the enzymatic composition in the secondary metabolism of M. ilicifolia, we carried out proteomic profiling of M. ilicifolia cell cultures with and without increased concentrations of maytenin and 22β-hydroxy-maytenin by elicitation with methyl jasmonate for 48 h. For this purpose, the analysis of soluble proteins was performed via LCMS/MS experiments using a shotgun strategy and compared to specific databases, resulting in 1319 identifications in the two types of cells. Many enzymes involved in secondary metabolism were detected, including cytochrome P450-dependent monooxygenases, which potentially catalyze the final steps in the quinonemethide triterpene biosynthesis. In conclusion, we report for the first time a proteomic study of a cell culture system that is an effective elicitor of quinonemethide triterpene production.

Chemical constituents from the roots of Tripterygium wilfordii and their cytotoxic activity

In our ongoing search for bioactive constituents, a new sesquiterpene polyol ester, named triptersinine U (1), together with five known triterpenes (2–6) and seven sesquiterpene pyridine alkaloids (7–13), were isolated from the roots of Tripterygium wilfordii Hook. f. Their chemical structures were elucidated using extensive spectroscopic analyses, including 1D and 2D NMR, and HRESIMS, as well as comparison with previously reported data. Cytotoxic activities of all compounds 1–13 were evaluated against six human tumor cell lines (HepG2, Hep3B, Bcap37, U251, MCF-7 and A549) using the MTT in vitro assay. The results showed that triterpenes exhibited moderate cytotoxic activities toward the tested cell lines.

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.

Anti-inflammatory sesquiterpene pyridine alkaloids from Tripterygium wilfordii

During a screening procedure involving higher plants to find novel candidates for use as anti-inflammatory agents, Tripterygium wilfordii Hook. f. was shown to exhibit considerable inhibitory activity. Five new sesquiterpene pyridine alkaloids, tripterygiumines S–W (1–4,15), along with 14 known dihydroagarofuran derivatives, were isolated from the roots of the T. wilfordii Hook. f. Their structures were established by extensive use of spectroscopic techniques, including 1D and 2D NMR spectroscopy and high-resolution mass spectrometry. All compounds were evaluated for their anti-inflammatory activity by measuring the nitric oxide production by the LPS-induced murine macrophage cell line RAW264.7. It was found that 1, 5, and 19 possessed potent nitric oxide inhibitory activity with IC50 values ranging from 2.99 to 28.80μM, without any effect on the cell viability of RAW264.7 cells. Accordingly, compounds 1, 5, and 19, especially 5, were identified as promising candidates for further scientific investigation of their potential use as anti-inflammatory agents.

Rapid and simultaneous analysis of sesquiterpene pyridine alkaloids from Tripterygium wilfordii Hook. f. Using supercritical fluid chromatography-diode array detector-tandem mass spectrometry

Sesquiterpene pyridine alkaloids are considered to be the active components of Tripterygium wilfordii Hook. f. A rapid method was developed for comprehensive profiling of sesquiterpene pyridine alkaloids from an extract of root bark of T. wilfordii using supercritical fluid chromatography-diode array detector-tandem mass spectrometry (SFC-DAD-MS/MS). Alkaloids were separated on a BEH 2EP column within 10min, eluted by CO2-methanol as mobile phase with a back pressure of 13.8Mpa and a column temperature of 45°C. MS/MS analysis of [M+H]+ ion of each alkaloid standard showed that all the pyridine alkaloids produced very similar fragmentation patterns. The product-ions at m/z 206 and 204 were identified as the diagnostic fragments while mass region of 200–500Da was assigned as the characteristic region. As a result, 71 components in the extract were identified as sesquiterpene pyridine alkaloids, including 40 wilfordate/evoninate type alkaloids, 13 iso-wilfordate/evoninate type alkaloids and 19 hydroxyl-wilfordate/evoninate type alkaloids. The results proved the feasibility of SFC-DAD-MS/MS method for the rapid and high-throughput analysis of sesquiterpene pyridine alkaloids in complex samples.

Untargeted analysis of sesquiterpene pyridine alkaloids from the dried roots of Tripterygium wilfordii using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry.

Sesquiterpene pyridine alkaloids are a large group of highly oxygenated sesquiterpenoids that have attracted attention in the fields of medicine because of their significant biological activities. Reference compounds including 14 sesquiterpene pyridine alkaloids and one dihydroagarofuran ester were analyzed by collision-induced dissociation tandem mass spectrometry (CID-MS/MS). A high-performance liquid chromatography/electrospray ionization (HPLC/ESI)-MS/MS method at two collision energies was adopted to investigate the botanical extracts of Tripterygium wilfordii. For 15 reference compounds, in the high mass range, the product ions were formed by the loss of side chains or H2 O. In the low mass range, the high-abundance product ions at m/z 206, 204, or 194 were the characteristic ions of the pyridine moiety. The characteristic product ion at m/z 310 was formed through an ion-neutral complex intermediate. Fifty-four sesquiterpenoid derivatives, including 50 sesquiterpene pyridine alkaloids, were identified or tentatively characterized in botanical extracts of T. wilfordii based on their elemental constituents, characteristic fragmentation patterns, and the major product ion profiles of the reference compounds ascertained with HPLC/ESI-MS/MS at two collision energies. It seems that isocratic energy was appropriate for the untargeted analysis of compounds with molecular weights exceeding 800 Da, whereas a linear gradient energy vs molecular weight was suitable for those compounds with molecular weights below 800 Da. The HPLC/ESI-MS/MS method, combining characteristic fragmentation patterns and the profiles of the product ions generated at different collision energies, is an effective technique for characterizing untargeted compounds.

Analysis of sesquiterpene pyridine alkaloids using ESI–MS/MS: The product ion at m/z 310 formed by an ion–dipole intermediate

Sesquiterpene pyridine alkaloids are a large group of highly oxygenated sesquiterpenoids, attracting attention in the fields of medicine because of their significant biological activities. Three representative sesquiterpene pyridine alkaloids were analyzed by electrospray ionization collision-induced dissociation–tandem mass spectrometry (ESI–CID–MS/MS/MS). In the high mass range, the product ions were formed by the loss of side chains or H2O. In the low mass range, the high-abundance product ions at m/z 206 and 178 were the characteristic ions of the pyridine moiety. Interestingly, the characteristic product ion at m/z 310 was formed through an ion–dipole (ion–neutral) complex. Addition of oxo(phenyl)methylium formed by the loss of the side chain linked to C1 and pyridine moiety produces m/z 310. The product ions at m/z 188 and 105 from m/z 310 support the proposed processes. The product ions were supported by d-labeling experiment. It was found that the formation of the product ion at m/z 310 was related to the position of substituted groups.

Identification of Genes Involved in the Biosynthesis of Tripterygium wilfordii Hook.f. Secondary Metabolites by Suppression Subtractive Hybridization

Tripterygium wilfordii Hook.f. (Celastraceae) produces a vast array of natural products, mainly terpenes and sesquiterpene pyridine alkaloids, which have strong biological activities. The limited gene information on the biosynthesis pathways restricts the metabolic engineering of this valuable natural resource. In this study, a suppression subtractive hybridization library of methyl jasmonate (MeJA)-elicited T. wilfordii Hook.f. adventitious root was successfully constructed. To clone the genes involved in the downstream of biosynthetic pathways, a long elicitation time of 12 days was applied. After evaluating the subtraction efficiency through polymerase chain reaction and reverse northern hybridization, 818 clones were randomly sequenced. Basic Local Alignment Search Tool (BLAST) analysis showed that 568 of the 735 successfully expressed sequence tags were annotated. Overrepresentation of gene ontology analysis indicated that the suppression subtractive hybridization library enriched genes that are related to biotic and abiotic stimuli. After BLAST and phylogenetic analyses, 11 genes were found to be putatively involved in the biosynthesis of terpene and sesquiterpene pyridine alkaloid, and nine transcription factors were putatively involved in modulation. The expression modulations of these promising genes were further examined after short MeJA treatment. This study provides valuable information for further research on the production improvement of terpene and sesquiterpene pyridine alkaloids through biotechnology methods.

β-Agarofurans and Sesquiterpene Pyridine Alkaloids from Maytenus spinosa.

Nine new β-dihydroagarofurans (1-9) and four new sesquiterpene pyridine alkaloids (10-13) were isolated from the leaves of Maytenus spinosa. Their structures were determined mainly by 1D- and 2D-NMR spectroscopic studies. The absolute configuration of compound 6 was established using CD spectroscopy. Several derivatives (14-20) were prepared from the sesquiterpene 13. Most of the sesquiterpenoids were tested for anti-HIV activity, but only compound 1 was found to be active.

Bioactive sesquiterpene polyol esters from the leaves of Tripterygium wilfordii

Tripterygium wilfordii, a member of Celastraceae family, has been used as a traditional plant insecticide and a medicinal plant. Phytochemical investigation of the leaves of T. wilfordii has resulted in the isolation of eight sesquiterpene polyol esters triptersinines M–T (1–8) and one sesquiterpene pyridine alkaloid (9). The structures of the compounds were elucidated on the basis of spectroscopic data analyses, including UV, IR, MS, and NMR experiments. The inhibitory effects on nitric oxide production in LPS-induced macrophages of 1–9 were also evaluated.

Abietane Diterpenoids and a Sesquiterpene Pyridine Alkaloid from Euonymus lutchuensis

Four new abietane diterpenoids (1-4), a new 9(10→20)-abeo-abietane diterpenoid (5), and a new sesquiterpene pyridine alkaloid (6) were isolated from the roots of Euonymus lutchuensis along with 19 known compounds. The structures of the new compounds were elucidated by interpretation of the spectroscopic data.

Chemical constituents of the stems of Celastrus rugosus

Two new sesquiterpene pyridine alkaloids rugosusines A and B (1 and 2), and thirty-one known compounds were isolated from the stems of Celastrus rugosus. The structures of new compounds were elucidated by detailed spectroscopic analysis, including HR-ESI-MS and 2D NMR spectroscopic data. All the compounds were isolated from this plant for the first time. The cytotoxicities of these compounds were tested against SKOV3 and MGC-803 cell lines by CCK-8 method.

Anti-inflammatory Sesquiterpene Derivatives from the Leaves of Tripterygium wilfordii

Twelve new dihydroagarofuran sesquiterpene polyol esters, triptersinines A-L (1-12), and eight known sesquiterpene pyridine alkaloids were isolated from the leaves of Tripterygium wilfordii. Their structures were elucidated on the basis of spectroscopic analyses, including UV, IR, and NMR experiments ((1)H-(1)H COSY, NOESY, HSQC, and HMBC). Furthermore, in an in vitro bioassay, compounds 1, 9, 11, 13, 14, and 18 showed moderate inhibitory effects on nitric oxide production in LPS-induced macrophages at 5 μM; all compounds were inactive when tested against five human cancer cell lines (IC(50) values >1 μM).

Dihydro-β-agarofuran sesquiterpene pyridine alkaloids from the seeds of Euonymus hamiltonianus

Plants of the Celastraceae family produce various dihydro-β-agarofuran sesquiterpene pyridine alkaloids. Two dihydro-β-agarofuran sesquitepene pyridine alkaloids (1,2) apart from four known compounds euojaponin C (3), wilforine (4), austronine (5) and O9-benzoyl-O9-deacetylevonine (6), were isolated from the ripe seeds of Euonymus hamiltonianus. Their chemical structures were elucidated mainly by analysis of NMR and MS spectral data. All compounds were evaluated for insecticidal activity.

Two sesquiterpene pyridine alkaloids and a triterpenoid saponin from the root barks of Tripterygium hypoglaucum

Two new sesquiterpene pyridine alkaloids hypoglaunines E (1) and F (2) and a new triterpenoid saponin hypoglaside A (3), together with a known diterpenoid glucoside 11-O-β-d-glucopyranosyl neotriptophenolide (4) and two known triterpenoids 23-nor-oxopristimerol (5) and 2,3-dihydroxy-6-oxo-D:A-froedo-24 nor-1,3,5(10),7-oleanatetraen-29-oic acid (6), have been isolated from the root barks of Tripterygium hypoglaucum. Their structures were elucidated by NMR spectroscopy and MS analysis. Compounds 1–3 were screened for their cytotoxic activities against five cancer cell lines, but all of them were inactive.

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).

Determination of four pyridine alkaloids from Tripterygium wilfordii Hook. f. in human plasma by high-performance liquid chromatography coupled with mass spectrometry

A novel liquid chromatography–atmospheric-pressure chemical ionization–mass spectrometry (LC–APCI/MS) method was developed and validated for the simultaneous determination of four sesquiterpene pyridine alkaloids (wilfortrine, wilfordine, wilforgine and wilforine) in human plasma. The chromatographic separation was performed on a Shim-pack XR-ODS column using an ammonium acetate buffer solution–acetonitrile in a gradient program. The detection was achieved by an ion trap mass spectrometry in the positive selected ion monitoring (SIM) mode. The method utilized acetonitrile as protein precipitation solvent and followed by solid-phase extraction (SPE). Calibration curves were linear for the four alkaloids over the range of 0.5–100.0 μg/L with the limits of quantification of 0.5 μg/L, while the method exhibited the recovery of 86.5–98.6%, intra- and inter-day RSDs of less than 8.2% and 12.8%, respectively. Methodology was validated in line with the EU requirements (Commission Decision 2002/657/EC). Results of incurred samples demonstrated excellent reproducibility. To our knowledge, this is the first analytical method for simultaneous determination of the four sesquiterpene pyridine alkaloids in plasma. The method was applicable to clinical pharmaceutical research of alkaloids in rheumatoid arthritis volunteer patients after oral administrations.

Three New Sesquiterpene Pyridine Alkaloids from Euonymus fortunei

AbstractThree new macrocyclic β‐dihydroagarofuran‐type sesquiterpene pyridine alkaloids, fortuneines A (1), B (2), and C (3), together with the four known alkaloids wilfornine E (4), aquifoliunine E‐I (5), euoverrine B (6), and euojaponine I (7), were isolated from the aerial parts of Euonymus fortunei. Their structures were elucidated by spectroscopic methods, including HR‐ESI‐MS, 1H‐ and 13C‐NMR, DEPT, 1H,1H‐COSY, HSQC, HMBC, and ROESY. This is the first isolation of the above sesquiterpene pyridine alkaloids from this plant, except for compound 6.

Facile synthesis of hydroxy wilfordic acid, a esterifying unit of anti-HIV sesquiterpene pyridine alkaloids

Sesquiterpene pyridine alkaloids were isolated mainly from plants of the genus Tripterygium (Celastraceae) which have been used traditionally in Chinese medicine. These compounds have polyhydroxy dihydro-beta-agarofuran core and esterifying substituent with dilactone bridges, and recently demonstrated promising anti-HIV activity. We have achieved the synthesis of hydroxy wilfordic acid and its ester via asymmetric cyanosilylation. With a NMR study of (S)- and (R)-PGME (phenylglycine methyl ester) amide, the tertiary alcohol stereochemistry of synthetic hydroxyl wilfordic acids was determined. Our synthetic approach will provide a contribution to the synthesis of sesquiterpene pyridine alkaloids and the development of their analogs for anti-HIV activity.