Activity-guided isolation of constituents of Renealmia nicolaioides with the potential to induce the phase II enzyme quinone reductase

Nicolaioidesin C: An Antiausterity Agent Shows Promising Antitumor Activity in a Pancreatic Cancer Xenograft Mouse Model

Human pancreatic tumors are hypovascular in nature, and their tumor microenvironment is often characterized by hypoxia and severe nutrient deprivation due to uncontrolled heterogeneous growth, a phenomenon known as "austerity". However, pancreatic tumor cells have the inherent ability to adapt and thrive even in such low nutrient and hypoxic microenvironments. Anticancer drugs such as gemcitabine and paclitaxel, which target rapidly proliferating cells, are often ineffective against nutrient-deprived pancreatic cancer cells. In order to overcome this limitation, the search for novel agents that can eliminate cancer cells' adaptations to nutrition starvation, also known as "antiausterity" agents, represents a promising strategy to make the cancer cells susceptible to treatment. The natural product (+)-nicolaioidesin C (Nic-C) was found to have potent antiausterity activity against the PANC-1 human pancreatic cancer cell line in a nutrient-deprived condition. However, its efficacy in vivo remained untested. To address this, we synthesized Nic-C in its racemic form and evaluated its antitumor potential in a human pancreatic cancer xenograft model. Nic-C inhibited pancreatic cancer cell migration and colony formation and significantly inhibited tumor growth in MIA PaCa-2 xenografts in a dose-dependent manner. Furthermore, Nic-C inhibited the Akt/mTOR and autophagy signaling pathways in both in vitro and in vivo studies. Metabolomic profiling of in vivo tumor samples suggests that Nic-C downregulates amino acid metabolism while upregulating sphingolipid metabolism.

Deciphering anti-infectious compounds from Peruvian medicinal Cordoncillos extract library through multiplexed assays and chemical profiling

High prevalence of parasitic or bacterial infectious diseases in some world areas is due to multiple reasons, including a lack of an appropriate health policy, challenging logistics and poverty. The support to research and development of new medicines to fight infectious diseases is one of the sustainable development goals promoted by World Health Organization (WHO). In this sense, the traditional medicinal knowledge substantiated by ethnopharmacology is a valuable starting point for drug discovery. This work aims at the scientific validation of the traditional use of Piper species ("Cordoncillos") as firsthand anti-infectious medicines. For this purpose, we adapted a computational statistical model to correlate the LCMS chemical profiles of 54 extracts from 19 Piper species to their corresponding anti-infectious assay results based on 37 microbial or parasites strains. We mainly identified two groups of bioactive compounds (called features as they are considered at the analytical level and are not formally isolated). Group 1 is composed of 11 features being highly correlated to an inhibiting activity on 21 bacteria (principally Gram-positive strains), one fungus (C. albicans), and one parasite (Trypanosoma brucei gambiense). The group 2 is composed of 9 features having a clear selectivity on Leishmania (all strains, both axenic and intramacrophagic). Bioactive features in group 1 were identified principally in the extracts of Piper strigosum and P. xanthostachyum. In group 2, bioactive features were distributed in the extracts of 14 Piper species. This multiplexed approach provided a broad picture of the metabolome as well as a map of compounds putatively associated to bioactivity. To our knowledge, the implementation of this type of metabolomics tools aimed at identifying bioactive compounds has not been used so far.

Alpinia hainanensis Rhizome Extract Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis: Active Ingredient Investigation and Evaluation

Alpinia hainanensis is an important food spice and ethnic medicine in Southwest China. In this study, we found that the EtOAc-soluble fraction (AHE) of the A. hainanensis rhizome ethanol extract could ameliorate dextran sulfate sodium-induced ulcerative colitis (UC). To explore active constituents, five pairs of previously unreported enantiomers (1-5), together with nine known ones (6-14), were obtained. Structural characterization was achieved by comprehensive spectroscopic methods. Compounds 1 and 2 were new curcumin-butyrovanillone hybrids featuring a rare structural fragment of 2,3-dihyrofuran. The anti-inflammatory activities of isolates were evaluated, and the results indicated that compounds (-)-1, (-)-3, 6, 9, 11, and 12 significantly inhibited the nuclear factor-κB signaling pathway. These findings indicate the major active fraction of the A. hainanensis rhizome ethanol extract enriched with diarylheptanoids, flavonoids, phenolics, and their hybrid mixtures, which could be developed as a nutritional and dietary supplement for treating UC.

Toward the use ofBoesenbergia rotundaextracts and the chalcone panduratin A to treat periodontitis

Novel affordable medications are needed to treat chronic periodontitis, which is one of the most common dental pathologies worldwide. Extracts prepared from the rhizome of the medicinal plant Boesenbergia rotunda (L.) Mansf., commonly known as fingerroot, are used to treat a variety of human pathologies. These extracts contain potent anti-inflammatory compounds, including the chalcone derivative panduratin A (Pa-A), which is the lead compound of a series of analogues, designated panduratins A to Y. The anti-inflammatory properties of the extracts of B. rotunda and the most abundant bioactive products found in these extracts (including Pa-A, 4-hydroxyoanduratin, isopanduratin, and others) have been reviewed. A standardized extract of the plant has promising utility in the treatment of gingival inflammation. The effects are characterized by three actions: (i) a direct antimicrobial effect against fungi and oral pathogens such as Porphyromonas gingivalis, (ii) a marked anti-inflammatory effect via a reduced production of mediators, like prostaglandin E2 and different interleukins, and (iii) a dual bone-preserving effect, with a reduction in bone resorption and an increase in bone formation. Acting as a protease inhibitor, Pa-A is one of the main active ingredients of the extract, implicated in these actions. A Pa-A-standardized extract of B. rotunda has been used in humans for treating dyspepsia. The product is safe and well-tolerated. The development of panduratin-containing dental products, for the prevention and treatment of periodontitis, has been proposed. The structural analogues, Pa-A to-Y, should also be investigated for the treatment of dental inflammation.

Total Synthesis of Palodesangrens A and C

Palodesangrens A and C along with the common tetracyclic core are prepared from simple benzaldehyde and acetophenone derivatives in a 10-step longest linear sequence which featured the Diels-Alder reaction forming the cyclohexene moiety, LiAlH₄ isomerization, stereoselective acid-catalyzed cyclization forming the chroman moiety, regioselective iodination/vinyl Suzuki cross-coupling reaction, and ring-closing metathesis (RCM) forming the 2H-pyran-2-one. Overall, the desired palodesangrens A and C are obtained in 6.1% and 6.4% yields, respectively.

Naturally occurring prenylated chalcones from plants: structural diversity, distribution, activities and biosynthesis

Covering: up to July 2020Naturally occurring chalcones carrying up to three modified or unmodified C5-, C10-, and C15-prenyl moieties on both rings A and B as well as at the α- and β-carbons are widely distributed in plants of the families of Fabaceae, Moraceae, Zingiberaceae and Cannabaceae. Xanthohumol and isobavachalcone being the most investigated representatives, exhibit diverse and remarkable biological and pharmacological activities. The present review deals with their structural characters, biological activities and occurrence in the plant kingdom. Biosynthesis of prenylated chalcones and metabolism of xanthohumol are also discussed.

Bioactive Compounds from Medicinal Plants in Myanmar

Myanmar is a country with rich natural resources and of these, medicinal plants play a vital role in the primary health care of its population. The people of Myanmar have used their own system of traditional medicine inclusive of the use of medicinal plants for 2000 years. However, systematic and scientific studies have only recently begun to be reported. Researchers from Japan, Germany, and Korea have collaborated with researchers in Myanmar on medicinal plants since 2000. During the past two decades, over 50 publications have been published in peer-reviewed journals. Altogether, 433 phytoconstituents, including 147 new and 286 known compounds from 26 plant species consisting of 29 samples native to Myanmar, have been collated. In this contribution, phytochemical and biological investigations of these plants, including information on traditional knowledge are compiled and discussed.

Chiral Hydroxytetraphenylene-Boron Complex Catalyzed Asymmetric Diels-Alder Cycloaddition of 2'-Hydroxychalcones

(S)-2,15-Cl₂-DHTP-boron complex catalyst for the asymmetric Diels-Alder cycloaddition of 2'-hydroxychalcones and dienes was developed and tested. The resulting cyclohexenes with three chiral centers were obtained in high yields (up to 98%) with excellent stereoselectivities (up to >20:1 endo/exo, >99% ee). This catalytic system features high efficiency, broad substrate scopes, and mild reaction conditions. In addition, a DFT study was performed to explain the stereochemical course of the asymmetric induction.

Total Synthesis of Palodesangren B Trimethyl Ether and D Dimethyl Ether via a Late-Stage Formation of 2H-Pyran-2-one of the Tetrahydrobenzo[c]pyranochromenone Core

In four steps from the tricyclic core, palodesangren B trimethyl ether and palodesangren D dimethyl ether could be synthesized in 29 and 18% overall yields, respectively. A reaction sequence comprising the regioselective MgCl₂-mediated Casnati-Skattebøl ortho-formylation of phenol, Wittig methylenation, acryloylation, and Ru(II)-catalyzed ring-closing metathesis (RCM) led to the formation of the final 2H-pyran-2-one ring of the desired tetracyclic core.

Phenolic compounds from the rhizome of Renealmia nicolaioides Loes.: a new diarylheptanoid

This study aims to identify phenolic compounds in dichloromethane and methanolic extracts of the rhizome of Renealmia nicolaioides collected in the North Region of Brazil. Two known diarylheptanoids, 1,7-bis(4-hydroxyphenyl)-(1E)-1-hepten-3-one (1), and 5R-1,7-bis(4-hydroxyphenyl)-1E-hepten-5-ol (2), and a new one (1R,2S,5S)-2-hydroxy-1,7(p-hydroxyphenyl)-centrolobine (3), as well as one flavonoid, 3-metoxi-quercetin (4) were isolated by chromatographic procedure and identified by spectroscopic techniques (1H and13C NMR, HRMS and CD). The acetyl derivative of 2 was used to confirm its structure. All four compounds are reported for the first time for this genus, and this is the first occurrence of compound 1 as a natural metabolite. The results reported here are unprecedented for the genus Renealmia.

(+)- and (-)-Ecarlottones, Uncommon Chalconoids from Fissistigma latifolium with Pro-Apoptotic Activity

Four new compounds, (+)- and (-)-ecarlottone (1), (±)-fislatifolione (5), (±)-isofislatifolione (6), and (±)-fislatifolic acid (7), and the known desmethoxyyangonin (2), didymocarpin-A (3), and dehydrodidymocarpin-A (4) were isolated from the stem bark of Fissistigma latifolium, by means of bioassay-guided purification using an in vitro affinity displacement assay based on the modulation of Bcl-xL/Bak and Mcl-1/Bid interactions. The structures of the new compounds were elucidated by NMR spectroscopic data analysis, and the absolute configurations of compounds (+)-1 and (-)-1 were assigned by comparison of experimental and computed ECD spectra. (-)-Ecarlottone 1 exhibited a potent antagonistic activity on both protein-protein associations with K_i values of 4.8 μM for Bcl-xL/Bak and 2.4 μM for Mcl-1/Bid.

Constituents of the Rhizomes of Boesenbergia pandurata and Their Antiausterity Activities against the PANC-1 Human Pancreatic Cancer Line

Human pancreatic cancer cell lines have a remarkable tolerance to nutrition starvation, which enables them to survive under a tumor microenvironment. The search for agents that preferentially inhibit the survival of cancer cells under low nutrient conditions represents a novel antiausterity strategy in anticancer drug discovery. In this investigation, a methanol extract of the rhizomes of Boesenbergia pandurata showed potent preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrient-deprived conditions, with a PC₅₀ value of 6.6 μg/mL. Phytochemical investigation of this extract led to the isolation of 15 compounds, including eight new cyclohexene chalcones (1-8). The structures of the new compounds were elucidated by NMR spectroscopic data analysis. Among the isolated compounds obtained, isopanduratin A1 (14) and nicolaioidesin C (15) exhibited potent preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrition-deprived conditions, with PC₅₀ values of 1.0 and 0.84 μM, respectively.

A theoretical study of an electronically mismatched Diels–Alder cycloaddition

The stepwise mechanism of the Diels–Alder cycloaddition between two electon-rich components.

Natural Products as Cathepsin Inhibitors

Cathepsins are proteases found in all animals as well as other organisms. There are approximately a dozen members of this family, which are distinguished by their structure, their catalytic mechanism, and which proteins they cleave. Most of the members become activated at the low pH found in lysosomes. Cathepsins have been identified as therapeutic targets in the search for new drugs against a number of human pathologies, including cancer, Alzheimer's, and osteoporosis.

A number of natural products have been reported as selective inhibitors of some cathepsins. Chemical structure of natural products as inhibitors of cathepsins can be very diverse. Some peptidic natural products are inhibitors of the cysteine protease cathepsins such as E-64 isolated from Aspergillus, which is a cathepsin B inhibitor, or more recently the marine cyanobacterial metabolite gallinamide A which is a selective inhibitor of human cathepsin L. Also amino acid derivatives have been reported as inhibitors of cathepsin A.

Other natural products include chalcone natural products possessing cytotoxic activities against prostate cancer cells and inhibiting cysteine cathepsins in vitro, antipain and its analogues isolated from Streptomyces as inhibitors of cathepsin K, and natural biflavones as novel inhibitors of cathepsins B and K.

In this review we will report the most representative examples of natural products as inhibitors of cathepsins, especially the ones reported during the last decade.

A review on biological sources, chemistry and pharmacological activities of pinostrobin

Pinostrobin, a dietary bioflavonoid discovered more than 6 decades ago in the heart-wood of pine (Pinus strobus), has depicted many pharmacological activities including anti-viral, anti-oxidant, anti-leukaemic, anti-inflammatory and anti-aromatase activities. It is an inhibitor of sodium channel and Ca(2+) signalling pathways and also inhibits intestinal smooth muscle contractions. In spite of the fact that pinostrobin has an application as functional foods, till-to-date no comprehensive review on pinostrobin has been carried out. Hence, the present review deals with the biological sources, chemistry and pharmacological activities of pinostrobin.

Leishmanicidal compounds and potent PPARγ activators from Renealmia thyrsoidea (Ruiz & Pav.) Poepp. & Endl

ETHNOPHARMACOLOGICAL RELEVANCE

Leaves and rhizomes of Renealmia thyrsoidea (Ruiz & Pav.) Poepp. & Endl. traditionally used in the Yanesha pharmacopoeia to treat skin infections such as leishmaniasis ulcers, or to reduce fever were chemically investigated to identify leishmanicidal compounds, as well as PPARγ activators.

METHODS

Compounds were isolated through a bioassay-guided fractionation and their structures were determined via detailed spectral analysis. The viability of Leishmania amazonensis axenic amastigotes was assessed by the reduction of tetrazolium salt (MTT), the cytotoxicity on macrophage was evaluated using trypan blue dye exclusion method, while the percentage of infected macrophages was determined microscopically in the intracellular macrophage-infected assay. The CD36, mannose receptor (MR) and dectin-1 mRNA expression on human monocytes-derived macrophages was evaluated by quantitative real-time PCR.

RESULTS

Six sesquiterpenes (1-6), one dihydrobenzofuranone (7) and four flavonoids (8-11) were isolated from the leaves. Alongside, two flavonoids (12-13) and five diarylheptanoids (14-18) were identified in the rhizomes. Leishmanicidal activity against Leishmania amazonensis axenic amastigotes was evaluated for all compounds. Compounds 6, 7, and 11, isolated from the leaves, showed to be the most active derivatives. Diarylheptanoids 14-18 were also screened for their ability to activate PPARγ nuclear receptor in macrophages. Compounds 17 and 18 bearing a Michael acceptor moiety strongly increased the expression of PPARγ target genes such as CD36, Dectin-1 and mannose receptor (MR), thus revealing interesting immunomodulatory properties.

CONCLUSIONS

Phytochemical investigation of Renealmia thyrsoidea has led to the isolation of leishmanicidal compounds from the leaves and potent PPARγ activators from the rhizomes. These results are in agreement with the traditional uses of the different parts of Renealmia thyrsoidea.

Synthetic cyclohexenyl chalcone natural products possess cytotoxic activities against prostate cancer cells and inhibit cysteine cathepsins in vitro

A number of cyclohexenyl chalcone Diels-Alder natural products possess promising biological properties including strong cytotoxicity in various human cancer cells. Herein, we show that natural products in this class including panduratin A and nicolaioidesin C inhibit cysteine cathepsins as indicated by protease profiling assays and cell-free cathepsin L enzyme assays. Owing to the critical roles of cathepsins in the biology of human tumor progression, invasion, and metastasis, these findings should pave the way for development of novel antitumor agents for use in clinical settings.

The cytoprotective role of the Keap1-Nrf2 pathway

An elaborate network of highly inducible proteins protects aerobic cells against the cumulative damaging effects of reactive oxygen intermediates and toxic electrophiles, which are the major causes of neoplastic and chronic degenerative diseases. These cytoprotective proteins share common transcriptional regulation, through the Keap1-Nrf2 pathway, which can be activated by various exogenous and endogenous small molecules (inducers). Inducers chemically react with critical cysteine residues of the sensor protein Keap1, leading to stabilisation and nuclear translocation of transcription factor Nrf2, and ultimately to coordinate enhanced expression of genes coding for cytoprotective proteins. In addition, inducers inhibit pro-inflammatory responses, and there is a linear correlation spanning more than six orders of magnitude of concentrations between inducer and anti-inflammatory activity. Genetic deletion of transcription factor Nrf2 renders cells and animals much more sensitive to the damaging effects of electrophiles, oxidants and inflammatory agents in comparison with their wild-type counterparts. Conversely, activation of the Keap1-Nrf2 pathway allows survival and adaptation under various conditions of stress and has protective effects in many animal models. Cross-talks with other signalling pathways broadens the role of the Keap1-Nrf2 pathway in determining the fate of the cell, impacting fundamental biological processes such as proliferation, apoptosis, angiogenesis and metastasis.

Efficient microwave-assisted prenylation of pinostrobin and biological evaluation of its derivatives as antitumor agents

Pinostrobin (5-hydroxy-7-methoxyflavanone) obtained in relatively large amounts from fingerroot (Boesenbergia pandurata) was converted to its C-6 and C-8 prenylated derivatives. The Mitsunobu reaction, europium(III)-catalyzed Claisen-Cope rearrangement, and Claisen reaction coupled with cross-metathesis were used as the key steps. Using a sealed-vessel microwave reactor, the Mitsunobu and Claisen/Cope reactions occurred smoothly with short reaction times and in satisfactory yields. The target compounds and five new intermediary substances showed cytotoxic activity toward SK-BR-3, MCF-7, PC-3, and Colo-320DM human tumor cell lines, and all of them had significantly lower IC(50) (microM) values than pinostrobin.

Electron transfer-initiated Diels-Alder cycloadditions of 2'-hydroxychalcones

An efficient approach to cyclohexenyl chalcones employing highly electron rich 2'-hydroxychalcone dienophiles via electron transfer-initiated Diels-Alder cycloaddition is described. Using the methodology, the total synthesis of nicolaiodesin C has been accomplished.

Bioactive secondary metabolites from Boesenbergia pandurata of Myanmar and their preferential cytotoxicity against human pancreatic cancer PANC-1 cell line in nutrient-deprived medium

The chloroform extract of rhizomes of Boesenbergia pandurata demonstrated marked preferential cytotoxicity against human pancreatic PANC-1 cancer cells in nutrient-deprived medium. Bioactivity-directed investigation of this extract yielded four new secondary metabolites, geranyl-2,4-dihydroxy-6-phenethylbenzoate ( 1), 2',4'-dihydroxy-3'-(1''-geranyl)-6'-methoxychalcone ( 2), (1' R,2' S,6' R)-2-hydroxyisopanduratin A ( 3), and (2 R)-8-geranylpinostrobin ( 4), and twenty known compounds ( 5- 24). Among the known compounds, (2 S)-6-geranylpinostrobin ( 5), (+/-)-6-methoxypanduratin A ( 6), and (2 S)-7,8-dihydro-5-hydroxy-2-methyl-2-(4''-methyl-3''-pentenyl)-8-phenyl-2 H,6 H-benzo[1,2- b:5,4- b']dipyran-6-one ( 7) were isolated for the first time from a natural source. The structures of these compounds were elucidated using extensive spectroscopic techniques including CD measurements. All the isolated compounds showed varying degrees of in vitro preferential cytotoxicity against PANC-1 cells. Nicolaioidesin B ( 11) and panduratin A ( 17) were most potent, each showing a PC 100 at 2.5 microM.

Enzymatic catalysis of the Diels–Alder reaction in the biosynthesis of natural products

Recent studies on enzymes catalyzing the Diels- Alder reaction. often named "Diels-Alderases", clearlydemonstrated the involvement of this synthetically useful reaction in the biosynthesis of natural products.This review covers natural Diels-Alder type cycloadducts. synthetic efforts on the chemical feasibility ofthe biosynthctic Diels - Alder reaction and a brief history of studies on Diels-Alderases. In addition,reaction mechanisms of artificial and natural Diels--Alderases are discussed.

Compounds obtained from sida acuta with the potential to induce quinone reductase and to inhibit 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions in a mouse mammary organ culture model

Activity-guided fractionation of the EtOAc-soluble extract of the whole plants of Sida acuta using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells, led to the isolation of ten active compounds of previously known structure, quindolinone (1), cryptolepinone (2), 11-methoxyquindoline (3), N-trans-feruloyltyramine (4), vomifoliol (5), loliolide (6), 4-ketopinoresinol (7), scopoletin (8), evofolin-A (9), and evofolin-B (10), along with five inactive compounds of known structure, ferulic acid, sinapic acid, syringic acid, (+/-)-syringaresinol, and vanillic acid. These isolates were identified by physical and spectral data measurement. A new derivative of quindolinone, 5,10-dimethylquindolin-11-one (1a) was synthesized and characterized spectroscopically. Of the active substances, compounds 1-3 and 1a exhibited the most potent QR activity, with observed CD (concentration required to double induction) values ranging from 0.01 to 0.12 microg/mL. Six compounds were then evaluated in a mouse mammary organ culture assay, with cryptolepinone (2), N-trans-feruloyltyramine (4), and 5,10-dimethylquindolin-11-one (1a) found to exhibit 83.3, 75.0, and 66.7% inhibition of 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions, respectively, at a dose of 10 microg/mL.

Activity-guided isolation of the chemical constituents of Muntingia calabura using a quinone reductase induction assay

Activity-guided fractionation of an EtOAc-soluble extract of the leaves of Muntingia calabura collected in Peru, using an in vitro quinone reductase induction assay with cultured Hepa 1c1c7 (mouse hepatoma) cells, resulted in the isolation of a flavanone with an unsubstituted B-ring, (2R,3R)-7-methoxy-3,5,8-trihydroxyflavanone (5), as well as 24 known compounds, which were mainly flavanones and flavones. The structure including absolute stereochemistry of compound 5 was determined by spectroscopic (HRMS, 1D and 2D NMR, and CD spectra) methods. Of the isolates obtained, in addition to 5, (2S)-5-hydroxy-7-methoxyflavanone, 2',4'-dihydroxychalcone, 4,2',4'-trihydroxychalcone, 7-hydroxyisoflavone and 7,3',4'-trimethoxyisoflavone were found to induce quinone reductase activity.