Neolignan derivatives from Penthorum chinense with antitumor activity in human colorectal cancer cells by regulating Wnt/β-catenin signaling pathway

In vitro cytotoxicity-guided isolation based on a MTT assay was conducted for Penthorum chinense Pursh. (Penthoraceae). In the active components (EtOAc extract of P. chinense), eight undescribed neolignans, penthoneolignans A-H (1-8), and two known analogs (9 and 10) were obtained and identified. Their absolute configurations were determined by experimental and computational comparison of electronic circular dichroism spectra analysis. The MTT experiment results of the obtained neolignans on HT29 and LoVo cells indicated previously undescribed neolignans, penthoneolignans A (1) and F (6), showed better cytotoxicity than the positive drug 5-fluorouracil. Then, functional technologies such as the 5-ethyny1-2'-deoxyridine, wound healing, Transwell, and Western blot assays indicated that they could significantly inhibit the proliferation of HT29 and Lovo cells, promote apoptosis by up-regulating Bax, and down-regulating B-cell CLL/lymphoma 2 and poly ADP-ribose polymerase. Furthermore, a Western blot assay combining the Dsh homolog 2 agonist IWP-L6 and the β-catenin agonist MG132 suggested their mechanism of action was closely related to the inhibition of the Wnt/β-catenin signaling pathway. In conclusion, previously undescribed neolignans, penthoneolignans A (1) and F (6), may intervene in the development and progression of colorectal cancer by inhibiting the Wnt/β-catenin signaling pathway and have the potential to be drug candidates.

Enantioselective synthesis of α,α-diarylketones by sequential visible light photoactivation and phosphoric acid catalysis

Chiral ketones and their derivatives are useful synthetic intermediates for the synthesis of biologically active natural products and medicinally relevant molecules. Nevertheless, general and broadly applicable methods for enantioenriched acyclic α,α-disubstituted ketones, especially α,α-diarylketones, remain largely underdeveloped, owing to the easy racemization. Here, we report a visible light photoactivation and phosphoric acid-catalyzed alkyne-carbonyl metathesis/transfer hydrogenation one-pot reaction using arylalkyne, benzoquinone, and Hantzsch ester for the expeditious synthesis of α,α-diarylketones with excellent yields and enantioselectivities. In the reaction, three chemical bonds, including C═O, C─C, and C─H, are formed, providing a de novo synthesis reaction for chiral α,α-diarylketones. Moreover, this protocol provides a convenient and practical method to synthesize or modify complex bioactive molecules, including efficient routes to florylpicoxamid and BRL-15572 analogs. Computational mechanistic studies revealed that C-H/π interactions, π-π interaction, and the substituents of Hantzsch ester all play crucial roles in the stereocontrol of the reaction.

Identification of neolignans with PCSK9 downregulatory and LDLR upregulatory activities from Penthorum chinense and the potential in cholesterol uptake by transcriptional regulation of LDLR via SREBP2

ETHNOPHARMACOLOGICAL RELEVANCE

Penthorum chinense has been used in East Asia for the treatment of cholecystitis, infectious hepatitis, jaundice and to treat liver problems. Recent evidences provided the potential for the clinical use of P. chinense in the treatment of metabolic disease.

AIM OF THE STUDY

Based on the traditional use and recent evidences, we investigated the effects of constituents from P. chinense with modulation on proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein receptor (LDLR) expression, and the effect of the most active substance on cholesterol uptake, and genes relevant to lipid metabolism.

MATERIALS AND METHODS

The isolation of compounds from the BuOH-soluble extract of 80% methanol extract of P. chinense was conducted using chromatographic methods and the structures were established by interpreting spectroscopic data. Quantitative real time-PCR, and Western blot analysis were performed to monitor the regulatory activity on PCSK9 and LDLR expression. PCSK9-LDLR binding interaction was also tested. The cholesterol uptake in hepatocyte was measured using 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate (DiI)-labeled LDL cholesterol. Additionally, gene network analysis of LDLR and responses of its target proteins were carried out to discover genes germane to the effect of active compound on HepG2 cells. Moreover, we performed protein-protein interaction analysis via String and constructed the compound target network using Cytoscape.

RESULTS

Two new neolignans and 37 known compounds were characterized from P. chinense. Of the isolated compounds, (7'E,8S)-2',4,8-trihydroxy-3-methoxy-2,4'-epoxy-8,5'-neolign-7'-en-7-one (3), penthorin A (4) and methyl gallate (25) were found to suppress PCSK9 mRNA expression with IC₅₀ values of 5.13, 15.56 and 11.66 μM, respectively. However, all the isolated compounds were found to be inactive in PCSK9-LDLR interaction assay. Additionally, a dibenzoxepine-type lignan analog, (7'E,8S)-2',4,8-trihydroxy-3-methoxy-2,4'-epoxy-8,5'-neolign-7'-en-7-one (3) demonstrated to upregulate LDLR mRNA and protein expression via transcriptional factor sterol regulatory element-binding protein 2 (SREBP2). Furthermore, (7'E,8S)-2',4,8-trihydroxy-3-methoxy-2,4'-epoxy-8,5'-neolign-7'-en-7-one (3) increase the LDL-cholesterol uptake in DiI-LDL assay.

CONCLUSION

(7'E,8S)-2',4,8-trihydroxy-3-methoxy-2,4'-epoxy-8,5'-neolign-7'-en-7-one (3) seemed to increase potentially cholesterol uptake via the downregulation of PCSK9 and the activation of LDLR in hepatocytes. Moreover, SREBP2 was found to play an important role in regulation of PCSK9 and LDLR by (7'E,8S)-2',4,8-trihydroxy-3-methoxy-2,4'-epoxy-8,5'-neolign-7'-en-7-one.

A review of Penthorum chinense Pursh for hepatoprotection: Traditional use, phytochemistry, pharmacology, toxicology and clinical trials

ETHNOPHARMACOLOGICAL RELEVANCE

In China, Penthorum chinense Pursh (P. chinense) has been used for hundreds of years traditionally for alleviating symptoms by excessive intake of alcohol as well as in the treatment of traumatic injury, edema and liver diseases. Recently, P. chinense and its extract have been developed into tea, drinks or medicines for treatment of liver diseases, including hepatic virus infections, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD) and liver fibrosis.

AIM OF THE STUDY

The main purpose of this review is to provide a critical appraisal of the existing knowledge on the phytochemical data, quality control aspect, pharmacological, as well as toxicological and clinical studies performed on P. chinense, including the identification of scientific gaps.

MATERIALS AND METHODS

A detailed literature search was conducted using various online search engines, such as Pubmed, Scopus, Google Scholar, Mendeley, Web of Science as well as China National Knowledge Infrastructure (CNKI) database.

RESULTS

In the pharmacological studies, there clearly are links between local/traditional uses and the biomedical investigations. Most pharmacological studies indicated potential liver protective effects in experimental models of chemicals-induced liver injury, acute and chronic alcoholic liver injury, NAFLD, liver fibrosis and viral infection, potentially through antioxidant effects, balancing key liver enzyme levels, inhibition of hepatic virus DNA replication, inhibition of hepatic stellate cells activation and inflammation either in vitro or in vivo. In some models, the effects of P. chinense is comparable with the one of silymarin. Clinical studies have suggested that P. chinense is safe and effective in treating several liver diseases, although most of them are not double-blinded and placebo-controlled studies. Toxicology studies show that P. chinense has no obvious toxicity or side effects in animals or human. Flavonoids, lignans, coumarins, polyphenols and organic acids have been identified. However, only a few studies have investigated the active compounds (mainly flavonoids and lignans) and molecular mechanisms of P. chinense.

CONCLUSION

P. chinense seems to be safe and shows relevant liver protecting effects. Therefore, it might be a promising candidate for developing as new hepatoprotective agents. However, a lack of understanding of the active compounds and mechanisms of action needs further attention.

Characterization of chemical composition and prebiotic effect of a dietary medicinal plant Penthorum chinense Pursh

Penthorum chinense Pursh is a dietary medicinal plant widely distributed in Asia-Pacific countries. The present study aims to profile the chemical constituents of P. chinense and investigate its prebiotic role in modulating gut microbiota. Fifty polyphenolic compounds were rapidly identified using UPLC-HR-MS. Total flavonoid and phenolic contents of P. chinense were 46.6% and 61.3% (w/w), respectively. Thirteen individual polyphenols were quantified, which accounted for 33.1% (w/w). P. chinense induced structural arrangement of microbial community in mice, showing increased microbiota diversity, elevated Bacteroidetes/Firmicutes ratio and enriched gut health-promoting bacteria. After a one-week drug-free wash, most of these changes were recovered, but the abundance of some beneficial bacteria was further increased. The altered composition of gut microbiota enriched several metabolic pathways. Moreover, P. chinense increased antioxidant capacity in vivo. The results suggest that polyphenol-enriched P. chinense modulates gut microbiota and enhances antioxidant capacity in mice toward a beneficial environment for host health.

Relative Strength of Common Directing Groups in Palladium-Catalyzed Aromatic C-H Activation

Efficient functionalization of C-H bonds can be achieved using transition metal catalysts, such as Pd(OAc)2. To better control the regioselectivity in these reactions, some functional groups on the substrate may be used as directing groups, guiding the reactivity to an ortho position. Herein, we describe a methodology to score the relative strength of such directing groups in palladium-catalyzed aromatic C-H activation. The results have been collected into a scale that serves to predict the regioselectivity on molecules with multiple competing directing groups. We demonstrate that this scale yields accurate predictions on over a hundred examples, taken from the literature. In addition to the regioselectivity prediction on complex molecules, the knowledge of the relative strengths of directing groups can also be used to work with new combinations of functionalities, exploring uncharted chemical space.

Synthesis of Bisheteroarylalkanes by Heteroarylboration: Development and Application of a Pyridylidene-Copper Complex

The development of pyridylidene-Cu-complexes and their application in Cu/Pd-catalyzed heteroarylboration of alkenylheteroarenes is reported. The significance of 1,1'-heteroarylalkanes as building blocks for drug discovery, as well as the straightforward and modular sequence to prepare the pyridylidene-Cu-complexes, makes this catalyst and it applications attractive for chemical synthesis. Furthermore, chiral variants of the pyridylidene-Cu-complexes have been prepared and utilized in the enantioselective arylboration of E-alkenes, further demonstrating the value and potential of this class of catalysts.

Catalytic Alkyne Arylation Using Traceless Directing Groups

By using Pd0 /Mandyphos, we achieved a three-component aminoarylation of alkynes to generate enamines, which are then hydrolyzed to either α-arylphenones or α,α-diarylketones. This Pd-catalyzed method overcomes established known pathways to enable the use of amines as traceless directing groups for C-C bond formation.

Natural Products Research in China From 2015 to 2016

This review covers the literature published by chemists from China during the 2015-2016 on natural products (NPs), with 1,985 citations referring to 6,944 new compounds isolated from marine or terrestrial microorganisms, plants, and animals. The emphasis is on 730 new compounds with a novel skeleton or/and significant bioactivity, together with their source organism and country of origin.