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Increasing evidence suggests the significant contribution of high levels of thioredoxin reductase (TrxR) in various stages of tumorigenesis and resistance to tumor chemotherapy. Thus, inhibition of TrxR with small molecules is an attractive strategy for cancer therapy. Eriocalyxin B (EriB), a naturally occurring diterpenoid extracted from Isodon eriocalyx, has reflected potential anticancer activities through numerous pathways. Here, we describe that EriB covalently modifies GSH and selectively inhibits TrxR activity by targeting the Sec residue of the enzyme. Pharmacological inhibition of TrxR by EriB results in elevated ROS levels, reduced total GSH and thiols content, which ultimately induced potent RKO cell apoptosis mediated by oxidative stress. Importantly, EriB indicates potent synthetic lethality with GSH inhibitors, BSO, in RKO cells. In summary, our results highlight that targeting TrxR by EriB explores a novel mechanism for the biological action of EriB. This opened up a new therapeutic indication for using EriB to combat cancers.

We identified two new diterpenoidal acrocalyenes A (1) and B (2) through chemical investigation on Acrocalymma sp., a plant-associated fungus from the tender stem isolates of Sinomenium acutum collected from the Qinling Mountains, along with seven already-recognized compounds (3-9). The HR-ESI-TOF-MS and 1D/2D NMR data were utilized for structural elucidation of these compounds, and the single-crystal X-ray diffraction was employed for absolute configuration clarification of the novel acrocalyenes 1 and 2. Bioassays revealed that the cytotoxicities of compounds 2, 4, 6, 7, and 8 against three human carcinoma cells (RKO, HeLa and HCC-1806) were moderate to strong, with IC

Elevated expression of thioredoxin reductase (TrxR) is associated with the tumorigenesis and resistance to cancer chemoradiotherapy, highlighting the potential of TrxR inhibitors as anticancer drugs. Deoxyelephantopin (DET) is the major active ingredient of Elephantopus scaber and reveals potent anticancer activity. However, the potential mechanism of action and the cellular target of DET are still unknown. Here, we found that DET primarily targets the Sec residue of TrxR and irreversibly prohibits enzyme activity. Suppression of TrxR by DET leads to accumulation of reactive oxygen species and dysregulation in intracellular redox balance, eventually inducing cancer cell apoptosis mediated by oxidative stress. Noticeably, down-regulation of TrxR1 by shRNA increases cell sensitivity to DET. Collectively, targeting of TrxR1 by DET uncovers a novel mechanism of action in DET and deepens the understanding of developing DET as a potential chemotherapeutic agent for treating cancers.

The first KI-catalyzed direct acyloxylation of indolin-3-ones with carboxylic acids has been developed using 30% aq. H2O2 as a green oxidant at room temperature. Through this strategy, various C2-acyloxy indolin-3-ones were obtained in up to 96% yield. Moreover, the C2-acyloxy indolin-3-ones can serve as versatile intermediates for the synthesis of nucleophilic 2-monoarylated indolin-3-ones and 3-ylidene indoles.

Pestalustaines A (1) and B (2), one unique sesquiterpene possessing an unusual 5/6/7-fused tricyclic ring system and one unprecedented coumarin derivative bearing 6/6/5/5-fused tetracyclic ring system, were isolated from the plant-derived Pestalotiopsis adusta. Their structures with absolute configurations were established by extensive NMR analysis, X-ray crystallography, and CD spectra associated with TD-DFT calculation. Hypothetical biosynthetic pathways for compounds 1 and 2 are proposed. Compounds 1 and 2 showed weak to moderate cytotoxic activities against three human tumor cell lines HeLa, HCT116, and A549, whose IC50 values were ranged from 21.01 to 55.43 μM.

Four new diphenyl ether derivatives, sinopestalotiollides A–D (1–4), one new natural α-pyrone product (11), as well as twelve known compounds (5–1 7), were obtained from the ethyl acetate extract of the endophytic fungus Pestalotiopsis palmarum isolated from the leaves of medicinal plant Sinomenium acutum (Thunb.) Rehd et Wils. The structures were elucidated by HR-ESI-MS and NMR spectrometry data. Bioassay experiments revealed that compounds 1–4 and 11 exhibited strong to weak cytotoxicities against three human tumor cell lines Hela, HCT116 and A549.

One new flavone hydrate named lobatflavate (1), one new chromone named lobatchrosin (2), and one new isoflavone named 3S,4R-tuberosin (3), along with four known isoflavone analogues (4-7), were isolated from the traditional Chinese medicinal plant of Pueraria lobata (Willd.) ohwi. Their structures were elucidated by extensive spectroscopic methods of IR, UV, HR-ESI-MS, 1D and 2D NMR. The absolute configuration of 3 was determined by CD spectrum associated with TD-DFT calculation analysis. All compounds except for 2 were assayed the inhibitory activity against α-glucosidase. Every tested compound was proved to be more active than positive control of acarbose. Of which 1 and 4 showed significant activity with IC50 value of 1.79μM and 23.01μM (IC50 of acarbose was 1998.79μM). Enzyme kinetic experiments revealed that 1 was irreversible whereas 4 was reversible and non-competitive α-glucosidase inhibitors. Moreover, structure-activity relationship was discussed and the docking studies of 1, 3 and 4 were also carried out.

A palladium-catalyzed conia-ene reaction of 1-alkynylindolin-3-ones has been developed. Three examples of pyrrolo[1,2-a]indoline derivatives were readily obtained with yields up to 82% utilizing this strategy. Importantly, this palladium-catalyzed intramolecular cyclization process represents an important contribution to the application of indole-3-one derivatives.

A pair of new

Four new highly oxidized caryophyllene-type sesquiterpenes (1–4), one new caryophyllene-type natural product (5), and two new drimane-type sesquiterpenes (6, 7), along with eight known compounds have been isolated from an endophytic fungus Pestalotiopsis adusta. Their structures were elucidated on the basis of HRESIMS, 1D and 2D NMR spectroscopic data analyses. The absolute configurations for 1 and 5 were determined by single-crystal X-ray crystallographic analysis using Cu Kα radiation. The absolute configuration of 6 was determined by CD spectrum associated with TD-DFT calculation of its benzoylated derivative 6a. The in vitro bioassay revealed that 8 and 9 presented cytotoxicity against cancer cell lines A549, HeLa, and SMMC-7721, in which 8 showed comparable activity (IC50 = 28.3 μM) to the positive control etoposide (IC50 = 23.2 μM) against SMMC-7721.

A pair of new neo-clerodane diterpenoid epimers, 3S-methoxyl-teucvin (1) and 3R-methoxyl-teucvin (2), were isolated from the Roots of Croton crassifolius. Their structures were completely established on the basis of spectroscopic methods, and the absolute configurations were determined by analysis of electronic circular dichroism (ECD) spectroscopy and X-ray diffraction analysis. Compounds 1 and 2 exhibited anti-inflammatory activities with IC50 values of 0.82 and 0.54 μM, respectively, while the IC50 value of dexamethasone as a positive control was found to be 0.14 μM.

A one-pot approach to substituted 1,2,4-triazolo[4,3-a]pyridines has been developed that is based on a KI-catalyzed oxidative cyclization of α-keto acids and 2-hydrazinopyridines. This transition-metal-free procedure was highly efficient and shows good economical and environmental advantages.

Background Osmanthus fragrans has been used as folk medicine for thousands of years. The extracts of Osmanthus fragrans flowers were reported to have various bioactivities including free radical scavenging, anti-inflammation, neuroprotection and antitumor effects. However, there is still lack of knowledge about its essential oil. Methods In this work, we analyzed the chemical composition of the essential oil from Osmanthus fragrans var. thunbergii by GC-MS. A complex network approach was applied to investigate the interrelationships between the ingredients, target proteins, and related pathways for the essential oil. Statistical characteristics of the networks were further studied to explore the main active ingredients and potential bioactivities of O. fragrans var. thunbergii essential oil. Results A total of 44 ingredients were selected from the chemical composition of O. fragrans var. thunbergii essential oil, and that 191 potential target proteins together with 70 pathways were collected for these compounds. An ingredient-target-pathway network was constructed based on these data and showed scale-free property as well as power-law degree distribution. Eugenol and geraniol were screened as main active ingredients with much higher degree values. Potential neuroprotective and anti-tumor effect of the essential oil were also found. A core subnetwork was extracted from the ingredient-target-pathway network, and indicated that eugenol and geraniol contributed most to the neuroprotection of this essential oil. Furthermore, a pathway-based protein association network was built and exhibited small-world property. MAPK1 and MAPK3 were considered as key proteins with highest scores of centrality indices, which might play an important role in the anti-tumor effect of the essential oil. Conclusions This work predicted the main active ingredients and bioactivities of O. fragrans var. thunbergii essential oil, which would benefit the development and utilization of Osmanthus fragrans flowers. The application of complex network theory was proved to be effective in bioactivities studies of essential oil. Moreover, it provides a novel strategy for exploring the molecular mechanisms of traditional medicines. Electronic supplementary material The online version of this article (10.1186/s12918-017-0523-0) contains supplementary material, which is available to authorized users.

Pingbeimunone A (1), a new compound, together with the known ussuriedine (2), benzo[7,8]fluoreno[2,1-b]quinolizine cevane-3,6,16,20-tetrol (3), ebeiedinone (4), pingbeimine C (5) and verticine (6) were isolated from Fritillaria ussuriensis. The structure was elucidated on the basis of spectral analysis (IR, NMR and MS spectroscopy). In addition, their AChE inhibitory activities were also tested.

A new bufadienolide named dyscinobufotalin (1), along with twenty known bufadienolides (2–21) were isolated from the venom of Bufo bufo gargarizans. Their structures were elucidated by spectroscopic analysis. The absolute configuration of the new natural product 2 was determined by X-ray single crystal diffraction and the complete NMR data for 3 was delivered for the first time. Both compounds 4 and 8 showed comparable α-glucosidase inhibitory activity (IC50 values of 0.25 and 0.26 μM, respectively) to the positive control acarbose (IC50 value of 0.42 μM), and 5 displayed potent inhibitory activity on acetylcholinesterase with an IC50 value of 0.12 μM. Moreover, 5, 8 and 13 presented moderate toxicity against brine shrimp.

A new diphenyl ether derivative, named pestalotilide A (1), along with four known compounds (2-5) have been isolated from the organic extracts of an endophytic fungus Pestalotiposis guepinii. Their structures were elucidated on the basis of HR-ESI-MS, 1D and 2D NMR spectroscopic data analyses. These isolates were evaluated for cytotoxicity against three cancer cell lines: Hela, HCT116 and A549; pestalotilide A exhibited weak in vitro anti-proliferative activities against the tested cell lines, with IC50 values of 23.8, 18.4 and 35.2 μM, respectively.

The present work describes modifications to an existing TLC bioautographic method for detecting acetylcholinesterase inhibitors from plant extracts. The basic principle of the method is that the enzyme converts 1-naphthyl acetate into naphthol which reacts with Fast Blue B salt to make a purple-colored background on the TLC plates. Inhibitors of acetylcholinesterases produced white spots on the background. Our modifications involve changes in the concentration of the enzyme, the reagents, and the time of the reaction. With these changes, the consumption of the enzyme was reduced by 85% and the detection limits were decreased remarkably.

Aims Inhibition of acetylcholinesterase (AChE) is still considered as a strategy for the treatment of neurological disorders such as Alzheimer's disease (AD). Many plant derived alkaloids (such as huperzine A, galanthamine and rivastigmine) are known for their AChE inhibitory activity. The aim of the present work was to isolate and identify new AChE inhibitors from Holarrhen antidysenterica . Main methods These compounds were tested for AChE inhibiting activity by the Ellman's method in 96-well microplates. In addition, molecular modeling was performed to explore the binding mode of inhibitors 1 – 5 at the active site of AChE, and the preliminary structure–activity relationships (SARs) were discussed. Key findings In the course of searching for AChE inhibitors from herb medicines, the total alkaloidal extract from the seeds of H. antidysenterica was found having potent AChE inhibitory activity with an IC 50 value of 6.1 μg/mL. Further bioactivity-guided chromatographic fractionation afforded five steroidal alkaloids, conessine 1 , isoconessimine 2 , conessimin 3 , conarrhimin 4 and conimin 5 . All the isolated compounds, except for 2 , showed strong AChE inhibiting activity with IC 50 values ranging from 4 to 28 μM. The most active inhibitor is compound 3 with an IC 50 value of 4 μM. The mode of AChE inhibition by 3 was reversible and non-competitive. Significance The results suggest that these alkaloids could be potential candidates for further development of new drugs against AD.

Geissoschizine methyl ether (1), a newly discovered strong acetylcholinesterase (AChE) inhibitor, along with six weakly active alkaloids, vallesiachotamine (2), hisuteine (3), hirsutine (4), isorhynchophylline (5), cisocorynoxeine (6) and corynoxeine (7) have been isolated from Uncaria rhynchophylla. Geissoschizine methyl ether (1) inhibited 50% of AChE activity at concentrations of 3.7 ± 0.3 µg mL(-1) while the IC(50) value of physostigmine as a standard was 0.013 ± 0.002 µg mL(-1). The mode of AChE inhibition by 1 was reversible and non-competitive. In addition, molecular modelling was performed to explore the binding mode of inhibitor 1 at the active site of AChE.