New quinolizidine and diaza-adamantane alkaloids from Acosmium dasycarpum (Vog.) Yakovlev—Fabaceae

The phytochemical investigation of the methanol crude extract obtained from Acosmium dasycarpum (Vog.) Yakovlev root bark led to the isolation of the quinolizidine alkaloids lupanine, acosmine, acosminine and lupanacosmine, as well as the diaza-adamantane alkaloids panacosmine and dasycarpumine. Lupanacosmine (4) and dasycarpumine (6) have been described for the first time herein.     

An LC–DAD Fingerprinting Method for Alkaloids,Flavonoids and Styrylpyrones from Cryptocarya mandioccana

An LC–DAD method has been developed in order to evaluate qualitatively and quantitatively quaternary aporphine alkaloids, flavonoid glycosides and styrylpyrones, which are the main secondary metabolites of leaves from C. mandioccana. The chromatographic method was validated considering both internal and external standard quantification methods and showed good performances in terms of selectivity, linearity, precision (repeatability and intermediate precision), limit of detection, limit of quantification, accuracy and stability.

     

2-methylindole analogs as cholinesterases and glutathione S-transferase inhibitors: Synthesis,biological evaluation,molecular docking,and pharmacokinetic studies

In this study, we aimed to (i) synthesize new 2-methylindole analogs containing various amino structures, pyrrolidine, piperidine, morpholine, and substituted phenyl groups through structural and molecular modifications, (ii) evaluate the pharmaceutical potential of 2-methylindole analogs via assessing enzyme inhibitory activity against glutathione S-transferase (GST), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE), (iii) predict ADMET and pharmacokinetic properties of the synthesized 2-methylindole analogs, (iv) reveal the possible interactions between the synthesized 2-methylindole analogs with GST, AChE, and BChE enzymes using several molecular docking software. In vitro enzyme inhibition assays showed that the synthesized indole analogs exhibited moderate to good inhibitory activities against GST, AChE, and BChE enzymes. Briefly, the inhibitory activities of the analogs 4b and 4i against AChE, 4a and 4b against BChE, and analogs 1 and 4i against GST were detected to be higher or close to the standard inhibitor compounds. The analog 4b was detected to have the best inhibitory activity against both AChE and BChE enzymes with the lowest IC₅₀ values as 0.648 µM for AChE and 0.745 µM for BChE. The analyses of enzyme inhibition relationship with the synthesized analogs could help to design new analogs for the inhibitors of cholinergic and glutathione pathways based on the indole derivatives.     

Heteroaromatic alkaloids,nakijinamines, from a sponge Suberites sp.

The structures of seven new secondary metabolites isolated from an Okinawan marine sponge Suberites sp., nakijinamines A (1), B (2), and F–I (3–6) and 6-bromoconicamin (7), have been elucidated on the basis of spectroscopic analysis, chemical conversion, and conformational analysis. These analyses disclosed that 1–6 were heteroaromatic alkaloids having the hybrid structures of an aaptamine-type alkaloid and an indole alkaloid, while 7 was a bromoindole alkaloid. Nakijinamine I (6) is the first example of an aaptamine-type alkaloid possessing a 1,4-dioxane ring. Antimicrobial activities of 1–7 were evaluated.     

Structural characterization of saturated pyrrolizidine alkaloids from Heliotropium transalpinum var. transalpinum Vell by NMR spectroscopy and theoretical calculations

The chemical investigation of Heliotropium transalpinum var. transalpinum Vell. (Boraginaceae) led to the isolation of transalpinecine (1), a novel pyrrolizidine alkaloid, in addition to known alkaloids subulacine (1β-2β-epoxy-1α-hydroxymethyl-8α-pyrrolizidine) (2), and 1α-2α-epoxy-1β-hydroxymethyl-8α-pyrrolizidine (3). The structures of the isolated compounds were elucidated based on spectroscopic data and theoretical calculations.     

First total synthesis of a new pyrrolizidine alkaloid, amphorogynine A

An efficient and stereodefined strategy is described for the first asymmetric synthesis of a new type of pyrrolizidine alkaloids, amphorogynine A and its 1-epi-isomer. The key 2,4-disubstituted pyrrolidine ring was constructed by elaboration of the chiral lactam derivative incorporating the d-malic acid-derived skeleton through asymmetric cis-allylation of the functionalized allysilane.     

Pyrroloquinoline derivatives from a Tongan specimen of the marine sponge Strongylodesma tongaensis

Pyrroloquinoline alkaloids are well known bioactive metabolites commonly found from latrunculiid sponges. Two new pyrroloquinoline alkaloids, 6-bromodamirone B (1) and makaluvamine W (2), were isolated from the Tongan sponge Strongylodesma tongaensis. Makaluvamine W (2) contains an oxazole moiety, which is rare in this large group of natural products, and is the first example of a pyrroloquinoline with nitrogen substitution at C-8. Both 1 and 2 lacked activity against a human promyelocytic leukemia cell line (HL-60), supporting the premise that an intact iminoquinone moiety plays a key role in the cytotoxicity of this compound class. The chemotaxonomic impact of these makaluvamine-type compounds is also discussed.     

Inunicosides A−K,rare polyacylated ent-kaurane diterpenoid glycosides from the flowers of Inula japonica

Inunicosides A?K (1–11), eleven unusual polyacylated ent-kaurane diterpenoid glycosides, were isolated from the flowers of a traditional Chinese herbal plant Inula japonica. Their structures with absolute configurations were determined on the basis of comprehensive spectroscopic analyses, chemical degradation, enzymatic hydrolysis and ECD experiments. Among these isolates, inunicoside K (11) showed mild antibacterial activity against Staphylococcus aureus ATCC 25923. Diterpene constituents have been rarely reported in the Inula species, and thus the discovery of this panel of compounds greatly enriches the chemical diversity of metabolites from the genus Inula.     

Mass‐spectrometry‐directed analysis and purification of pyrrolizidine alkaloid cis/trans isomers in Gynura japonica

Pyrrolizidine alkaloids are highly hepatotoxic natural chemicals that produce irreversible chronic and acute hepatotoxic effects on human beings. Purification of large amounts of pyrrolizidine alkaloids is necessary for toxicity studies. In this study, an efficient method for targeted analysis and purification of pyrrolizidine alkaloid cis/trans isomers from herbal materials was developed for the first time. Targeted analysis of the hepatotoxic pyrrolizidine alkaloids was performed by liquid chromatography with tandem mass spectrometry (precursor ion scan and daughter ion scan), and the purification of pyrrolizidine alkaloids was achieved with a mass‐directed auto purification system. The extraction and preparative liquid chromatography conditions were optimized. The developed method was applied to analysis of Gynura japonica (Thunb.) Juel., a herbal medicine traditionally used for detumescence and relieving pain but is potentially hepatotoxic as it contains pyrrolizidine alkaloids. Twelve pyrrolizidine alkaloids (six cis/trans isomer pairs) were identified with reference compounds or characterized by liquid chromatography with tandem mass spectrometry, and five individual pyrrolizidine alkaloids, including (E)‐seneciphylline, seneciphylline, integerrimine, senecionine, and seneciphyllinine, were prepared from G. japonica roots with high efficiency. The results of this work provide a new technique for the preparation of large amounts of pyrrolizidine alkaloid reference substances, which will also benefit toxicological studies of pyrrolizidine alkaloids and treatments for pyrrolizidine alkaloid‐induced toxicity.     

Cortistatins E, F, G, and H, four novel steroidal alkaloids from marine sponge Corticium simplex

Four novel steroidal alkaloids named cortistatins E (1), F (2), G (3), and H (4) have been isolated from the marine sponge Corticium simplex. The chemical structures of these four cortistatins, which are unique abeo-9(10-19)-stigmastane-type steroidal alkaloids having oxabicyclo[3.2.1]octene and N-methyl piperidine or 3-methylpyridine units in the side chain, were elucidated by the detailed 2D-NMR analysis. These four compounds showed only weak anti-proliferative activity against human umbilical vein endothelial cells (HUVECs) at 0.35-1.9 μM concentrations in contrast to cortistatin A (5), which was isolated as a highly selective inhibitor of proliferation of HUVECs from the same marine sponge.     

Structural characterization and identification of major constituents in jitai tablets by high-performance liquid chromatography/diode-array detection coupled with electrospray ionization tandem mass spectrometry

In the present study a universally applicable HPLC-DAD/ESI-MS/MS method was developed for carrying out the comprehensive characterization of Jitai tablets (JTT). Based on the ESI-MSⁿ fragmentation patterns of the reference standards, a total of 101 components were identified or tentatively characterized by comparing their retention times, UV and MS spectra with those of reference standards or through the matching of empirical information with those of published components in the in-house library. The characteristic fragmentation pattern of alkaloids, phenolic acids, tanshinones, flavonoid glycosides, cyanogenic glycosides, ginsenosides, 2-(2-phenylethyl) chromones, phthalides and gingerol-related compounds were tentatively elucidated using structurally-relevant product ions. It was observed that neutral losses of C₉H₁₀O₃ and C₉H₈O₂ were the characteristic product ions of scopola alkaloids. Neutral fragment mandelonitrile was the characteristic ion of cyanogenic glycosides. To our knowledge, tropylium ion and C₄H₂O unit were the characteristic ions of 2-(2-phenylethyl) chromone, which resulted from the Retro-Diels-Alder (RDA) cleavage of the C ring. The results indicated that the developed analysis method could be employed as a rapid, effective technique for structural characterization of chemical constituents in TCM. This work is expected to provide comprehensive information for the quality evaluation and pharmacokinetic studies of JTT.     

Angustifolinoid A,a macrocyclic flavonoid glycoside from Elaeagnus angustifolia flowers

A novel macrocyclic flavonoid glycoside, angustifolinoid A (1), featuring an unprecedented 13-membered heterocyclic ring moiety, along with a known flavonoid glycoside, tiliroside (2), were isolated from Elaeagnus angustifolia flowers. Their structures were determined by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Biosynthesis analysis indicated that compound 1 might be derived from compound 2 via a key enzymatic intramolecular oxidative coupling. Compounds 1 and 2 showed inhibitory activities against cyclooxygenases, COX-1 and COX-2.     

Biosynthesis of naphthylisoquinoline alkaloids: synthesis and incorporation of an advanced C2-labeled isoquinoline precursor

Biosynthetic studies on naphthylisoquinoline alkaloids involving a specifically [1,1′-¹³C₂]-labeled dihydroisoquinoline 7 are described. The synthesized precursor 7 was fed to callus cultures of Triphyophyllum peltatum and the isolated secondary metabolites were characterized by spectroscopic methods (¹H, ¹³C NMR, and INADEQUATE experiments). The unambiguous incorporation of the precursor into dioncophylline A and two minor naphthylisoquinolines, together with the formation of the labeled corresponding trans-configured tetrahydroisoquinoline, proves the implication of such advanced intermediates in the proposed biosynthetic pathway of naphthylisoquinoline alkaloids.     

LC-MS/MS Screening,Total Phenolic,Flavonoid and Antioxidant Contents of Crude Extracts from Three Asclepiadaceae Species Growing in Jordan

This study aimed to evaluate the antioxidant activity and total phenolic content (TPC) and total flavonoid content (TFC) of crude extracts obtained from three Asclepiadaceae species, namely, Calotropis procera L., Peruglaria tomentosa L., and Pentatropis spiralis (Forsk.) Decne. Both butanol and aq. methanol extracts of the three species showed the highest amount of phenol and flavonoid contents, which exhibited the greatest antioxidant activity in the scavenging of 2,2-diphenyl-2-picrylhydrazyl free radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS), ferrous chelating effect (FIC), and hydroxyl radical (HDR) assays. Phytochemical screening of the extracts revealed the presence of alkaloids, tannins, sponins, flavonoids, terpenoids, and glycosides. LC-MS analysis was carried out to identify the major compounds from each crude extract. A total of 12 phenolic compounds in the extracts of the 3 species were identified and quantified, including 9 flavonoids, 2 hydroxybenzoic acids, and 3 hydroxycinnamic acids. The current study also revealed a good correlation between total phenolic contents and the observed antioxidant activity of the crude extracts.     

Marinocyanins,cytotoxic bromo-phenazinone meroterpenoids from a marine bacterium from the streptomycete clade MAR4

Six cytotoxic and antimicrobial metabolites of a new bromo-phenazinone class, the marinocyanins A-F (1–6), were isolated together with the known bacterial metabolites 2-bromo-1-hydroxyphenazine (7), lavanducyanin (8, WS-9659A) and its chlorinated analog WS-9659B (9). These metabolites were purified by bioassay-guided fractionation of the extracts of our MAR4 marine actinomycete strains CNS-284 and CNY-960. The structures of the new compounds were determined by detailed spectroscopic methods and marinocyanin A (1) was confirmed by crystallographic methods. The marinocyanins represent the first bromo-phenazinones with an N-isoprenoid substituent in the skeleton. Marinocyanins A-F show strong to weak cytotoxicity against HCT-116 human colon carcinoma and possess modest antimicrobial activities against Staphylococcus aureus and amphotericin-resistant Candida albicans.     

Investigation of antibacterial and cytotoxic potential of phenolics derived from Cistus incanus L. by means of thin-layer chromatography-direct bioautography and cytotoxicity assay

Cistus incanus L. (hairy rockrose) is a medicinal plant which belongs to the Cistaceae family and the Cistus genus, with a well established position in traditional medicine of the Mediterranean basin and the Middle East. It was the aim of this study to compare antibacterial activity of the phenolics derived from fourteen C. incanus samples of different origin (Turkey, Albania, Greece, and an unknown geographical location) obtained as herbal teas from a local market of diet supplements. This activity was assessed with the use of thin-layer chromatography–direct bioautography (TLC-DB) applied to crude extracts against the Gram negative naturally luminescent marine bacterium Aliivibrio fischeri and the Gram positive soil bacterium Bacillus subtilis as the test microorganisms. It was established that in spite of different origin of the investigated herbal samples, in qualitative terms their antibacterial activity was closely comparable and more strongly pronounced against the Gram positive than the Gram negative bacterium. Crude extract originating from one herbal specimen labelled A3 (sample no. 3 from Albania) underwent selective multi-step extraction of the phenolics, dividing them into six fractions (I to VI) that expectedly contain flavonoid aglycons, free phenolic acids, non-polar flavonoid glycosides, polar flavonoid glycosides, and phenolic acids obtained through the acidic and basic hydrolysis from the respective glycosides. Antibacterial activity of each A3 fraction was then assessed with the use of the same TLC-DB approach and it was established that the strongest effect was exerted by fractions I and II (flavonoid aglycons and free phenolic acids). Moreover, cytotoxic assay was performed for the crude C. incanus extracts against the human colon adenocarcinoma cells and a moderate yet well measurable cytotoxic effect was observed with all investigated C. incanus samples. In analogy to antibacterial activity, also in this case cytotoxic potential of all investigated crude C. incanus extracts was similar.     

Efficient strategies for preparative separation of iridoid glycosides and flavonoid glycosides from Hedyotis diffusa

Efficient strategies for the preparative separation of iridoid glycosides and flavonoid glycosides from Hedyotis diffusa using preparative high-performance liquid chromatography combined with appropriate pretreatment technologies were developed. Four fractions (Fr.1-1, Fr.1-2, Fr.1-3, and Fr.2-1) were firstly isolated from the crude extract of Hedyotis diffusa by column chromatography with C18, resin, and silica gel materials, respectively. Then, corresponding separation strategies were developed according to the polarity and chemical constituents. High-polar compounds of Fr.1-1 were purified by hydrophilic reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography mode. The combination of C18 and phenyl columns realized the complementary separation of iridoid glycosides in Fr.1-2. Meanwhile, the improved selectivity caused by the change of organic solvent in the mobile phase was utilized to realize the purification of flavonoid glycosides in Fr.1-3 and Fr. 2-1. Finally, 27 compounds (purity > 95%) mainly involving nine iridoid glycosides and five flavonoid glycosides were obtained. A complete strategy was established for the separation of a complex sample with a wide polarity range, to jointly solve the problems of enrichment of target components and separation of structural analogs.     

Rapid discovery and identification of the prototypes and their metabolites of Da‐Huang‐Xiao‐Shi decoction in rat plasma by an integrative strategy based on liquid chromatography coupled with mass spectrometry

Da‐Huang‐Xiao‐Shi decoction has been used to treat damp‐heat jaundice for centuries in China. However, the absorbed components of the decoction and their related metabolites are little known until now. In this work, an integrative strategy based on liquid chromatography coupled with mass spectrometry (time‐of‐flight/triple‐quadruple tandem) was adopted to effectively identify the prototypes and their metabolites and to speculate the possible transformation pathways among these compounds. Using pattern recognition approaches, the exogenous compounds in rat plasma were screened out from endogenous compounds and then distinguished into prototypes and metabolites according to the characteristic information from the self‐building database of Da‐Huang‐Xiao‐Shi decoction. On this basis, the metabolic profiles of main prototypes (such as iridoid glycosides, alkaloids, and anthraquinones) were proposed. As a result, a total of 62 related prototypes and their metabolites were detected and tentatively identified in rat plasma after administration, and among them, three prototypes were found for the first time. Glucuronidation and sulfation were deduced to be the main metabolic pathways of alkaloids, iridoid glycosides, and anthraquinones. The integrative strategy used in this study was an effective approach to rapidly discover and characterize the prototypes and their metabolites from a complex bio‐sample without the use of standard substances.