Antiviral activities of flavonoids isolated from the bark of <Emphasis Type="Italic">Rhus verniciflua</Emphasis> stokes against fish pathogenic viruses <Emphasis Type="Italic">In Vitro</Emphasis>

An 80% methanolic extract of Rhus verniciflua Stokes bark showed significant anti-viral activity against fish pathogenic infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV) in a cell-based assay measuring virus-induced cytopathic effect (CPE). Activity-guided fractionation and isolation for the 80% methanolic extract of R. verniciflua yielded the most active ethyl acetate fraction, and methyl gallate (1) and four flavonoids: fustin (2), fisetin (3), butin (4) and sulfuretin (5). Among them, fisetin (3) exhibited high antiviral activities against both IHNV and VHSV showing EC₅₀ values of 27.1 and 33.3 μM with selective indices (SI = CC₅₀/EC₅₀) more than 15, respectively. Fustin (2) and sulfuretin (5) displayed significant antiviral activities showing EC50 values of 91.2–197.3 μM against IHNV and VHSV. In addition, the antiviral activity of fisetin against IHNV and VHSV occurred up to 5 hr post-infection and was not associated with direct virucidal effects in a timed addition study using a plaque reduction assay. These results suggested that the bark of R. verniciflua and isolated flavonoids have significant anti-viral activity against IHNV and VHSV, and also have potential to be used as anti-viral therapeutics against fish viral diseases.     

Improvement of Metabolic and Histological Changes of Adiposity in Rats by Synthetic Oleoyl Chalcones

We previously reported that synthetic oleoyl chalcones had a favorable effect to alleviate metabolic consequences of obesity in male SD rats. In this work, we prepared and characterized by spectroscopic tools, a set of six oleoyl chalcones ( 5a–c , 10 and 11a,b ). The comparative effects of the previously prepared oleoyl chalcones and their new synthetic analogs on metabolic and histological changes in obese male SD rats were studied. It was found that the oleoyl chalcones III_a and IV were the best in improving many metabolic parameters, e. g., FBG, FI, ISI, TG, and total cholesterol. They cured systemic inflammation, through inhibition of the TNF-α and induction of adiponectin production. Moreover, chalcones III_a and IV alleviated the oxidative stress accompanying obesity through the induction of the antioxidant enzymes GPX, SOD and CAT besides, GSH. Interestingly, chalcones III_a and IV exerted hepatoprotective potency and ameliorated the manifestations of NAFLD via inhibition of apoptosis and induction of autophagy of hepatic cells. In conclusion, the oleoyl chalcones III_a and IV were the most effective candidates among the series of synthetic chalcones in correcting body weight and the consequent metabolic and histological changes in adiposity.     

Chalcones isolated from Angelica keiskei inhibit cysteine proteases of SARS-CoV

Two viral proteases of severe acute respiratory syndrome coronavirus (SARS-CoV), a chymotrypsin-like protease (3CL^pro) and a papain-like protease (PL^pro) are attractive targets for the development of anti-SARS drugs. In this study, nine alkylated chalcones (1–9) and four coumarins (10–13) were isolated from Angelica keiskei, and the inhibitory activities of these constituents against SARS-CoV proteases (3CL^pro and PL^pro) were determined (cell-free/based). Of the isolated alkylated chalcones, chalcone 6, containing the perhydroxyl group, exhibited the most potent 3CL^pro and PL^pro inhibitory activity with IC₅₀ values of 11.4 and 1.2?µM. Our detailed protein-inhibitor mechanistic analysis of these species indicated that the chalcones exhibited competitive inhibition characteristics to the SARS-CoV 3CL^pro, whereas noncompetitive inhibition was observed with the SARS-CoV PL^pro.     

Novel cytotoxic chalcones from Litsea rubescens and Litsea pedunculata

Two novel flavonoids with chalcone skeleton, together with seven known flavonoids, were isolated from the stem barks of Litsea rubescens and Litsea pedunculata. The structures of the new compounds were elucidated on the basis of spectral methods including IR, UV, 1D and 2D NMR. The new chalcones were found to contain the rare epoxy or ethylidenedioxy group. This is the first report on the presence of chalcone in the plant genus Litsea. The cytotoxic potential of two new chalcones was evaluated in vitro against three human tumor cell lines. Both new chalcones displayed potent cytotoxic activities against myeloid leukaemia (HL-60) and epidermoid carcinoma (A431) cell lines and more active than cisplatin (DDP). Interestingly, compound 1 exhibited cytotoxic activity against HL-60 with IC₅₀ value 2.1-fold more sensitive to DDP.     

Selection, characterization and application of new RNA HIV gp 120 aptamers for facile delivery of Dicer substrate siRNAs into HIV infected cells

The envelope glycoprotein of human immunodeficiency virus (HIV) consists of an exterior glycoprotein (gp120) and a trans-membrane domain (gp41) and has an important role in viral entry into cells. HIV-1 entry has been validated as a clinically relevant anti-viral strategy for drug discovery. In the present work, several 2′-F substituted RNA aptamers that bind to the HIV-1_BaL gp120 protein with nanomole affinity were isolated from a RNA library by the SELEX (Systematic Evolution of Ligands by EXponential enrichment) procedure. From two of these aptamers we created a series of new dual inhibitory function anti-gp120 aptamer–siRNA chimeras. The aptamers and aptamer–siRNA chimeras specifically bind to and are internalized into cells expressing HIV gp160. The Dicer-substrate siRNA delivered by the aptamers is functionally processed by Dicer, resulting in specific inhibition of HIV-1 replication and infectivity in cultured CEM T-cells and primary blood mononuclear cells (PBMCs). Moreover, we have introduced a ‘sticky’ sequence onto a chemically synthesized aptamer which facilitates attachment of the Dicer substrate siRNAs for potential multiplexing. Our results provide a set of novel inhibitory agents for blocking HIV replication and further validate the use of aptamers for delivery of Dicer substrate siRNAs.     

Natural mimetic 4-benzyloxychalcones as potent pancreatic lipase inhibitors: Virtual screening,synthesis and biological evaluation

Pancreatic lipase is a well-known target for obesity drug development. The inhibition of this enzyme mitigates the digestion and absorption of dietary fat. Despite some inconvenient side effects, orlistat is currently the only medication with FDA approval that works by inhibition of pancreatic lipase. Several natural flavonoids, including chalcones, have been reported to possess promising lipase inhibitory activity. In this paper, we describe the evaluation of the lipase inhibitory activity of our in-house natural mimetic chalcone library via virtual screening, followed by the synthesis and biological evaluation of the hits. Compound C82 showed low-micromolar activity against pancreatic lipase in vitro (IC₅₀ = 1.01 ± 0.86 µM). The interaction of C82 and lipase was additionally confirmed by a fluorescence quenching study.     

Inhibition of prostaglandin E2 production by synthetic minor prenylated chalcones and flavonoids: Synthesis,biological activity,crystal structure,and in silico evaluation

The discovery of potent inhibitors of prostaglandin E₂ (PGE₂) synthesis in recent years has been proven to be an important game changer in pharmaceutical industry. It is known that excessive production of PGE₂ triggers a vast array of biological signals and physiological events that contributes to inflammatory diseases such as rheumatoid arthritis, atherosclerosis, cancer, and pain. In this Letter, we report the synthesis of a series of minor prenylated chalcones and flavonoids which was found to be significantly active in suppressing the PGE₂ production secreted by lipopolysaccharide-induced mouse macrophage cells (RAW 264.7). Among the compounds tested, 14b showed a dose-response inhibition of PGE₂ production with an IC₅₀ value of 2.1 μM. The suppression upon PGE₂ secretion was not due to cell death since 14b did not reduce the cell viability in close proximity to the PGE₂ inhibition concentration. The obtained atomic coordinates for the single-crystal XRD of 14b was then applied in the docking simulation to determine the potential important binding interactions with murine COX-2 and mPGES-1 putative binding sites.     

Antioxidant properties of di-tert-butylhydroxylated flavonoids

Epidemiological evidence suggests an inverse relationship between dietary intake of flavonoids and cardiovascular risk. The biological activities of flavonoids are related to their antioxidative effects, but they also can be mutagenic, due to the prooxidant activity of the catechol pattern. To prevent these problems, we synthesized new flavonoids where one or two di-tert-butylhydroxyphenyl (DBHP) groups replaced catechol moiety at position 2 of the benzopyrane heterocycle. Two DBHP moieties can also be arranged in an arylidene structure or one DBHP fixed on a chalcone structure. Position 7 on the flavone and arylidene or position 4 on the chalcone was substituted by H, OCH(3), or OH. New structures were compared with quercetin and BHT in an LDL oxidation system induced by Cu(II) ions. Arylidenes and chalcones had the best activities (ED(50) = 0.86 and 0.21) compared with vitamin E, BHT, and quercetin (ED(50) = 10.0, 7. 4, and 2.3 microM). Activity towards stable free radical 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) was measured by log Z and ECR(50) parameters. Synthesized flavones proved to be poor DPPH radical scavengers, the activity increasing with the number of DBHP units. In contrast, arylidenes and chalcones were stronger DPPH radical scavengers (log Z > 3, 0.3 < ECR(50) < 2.12) than BHT (log Z = 0.75, ECR(50) = 12.56) or quercetin (log Z = 2.76, ECR(50) = 0.43). Unlike quercetin, synthesized compounds neither chelated nor reduced copper, proving that these new flavonoids had no prooxidant activity in vitro.     

Antiproliferative activity of long chain acylated esters of quercetin-3-O-glucoside in hepatocellular carcinoma HepG2 cells

Despite their strong role in human health, poor bioavailability of flavonoids limits their biological effects in vivo. Enzymatically catalyzed acylation of fatty acids to flavonoids is one of the approaches of increasing cellular permeability and hence, biological activities. In this study, six long chain fatty acid esters of quercetin-3-O-glucoside (Q3G) acylated enzymatically and were used for determining their antiproliferative action in hepatocellular carcinoma cells (HepG2) in comparison to precursor compounds and two chemotherapy drugs (Sorafenib and Cisplatin). Fatty acid esters of Q3G showed significant inhibition of HepG2 cell proliferation by 85 to 90% after 6 h and 24 h of treatment, respectively. The cell death due to these novel compounds was associated with cell-cycle arrest in S-phase and apoptosis observed by DNA fragmentation, fluorescent microscopy and elevated caspase-3 activity and strong DNA topoisomerase II inhibition. Interestingly, Q3G esters showed significantly low toxicity to normal liver cells than Sorafenib (P < 0.05), a chemotherapy drug for hepatocellular carcinoma. Among all, oleic acid ester of Q3G displayed the greatest antiproliferation action and a high potential as an anti-cancer therapeutic. Overall, the results of the study suggest strong antiproliferative action of these novel food-derived compounds in treatment of cancer.     

Anti-influenza (H1N1) potential of leaf and stem bark extracts of selected medicinal plants of South India

Variations in antioxidant and anti-viral activities (against Influenza AP/R/8 (H1N1) virus) between the leaves and stem bark of selected medicinal plants were studied. Malin Darby canine kidney (MDCK) cells were used for the viral infection and the antiviral activity of the extracts was studied using sulphorhodamine B (SRB) assay. The stem bark of the plants including Strychnos minor, Diotacanthus albiflorus, Strychnos nux-vomica and Chloroxylon swietenia showed higher flavonoid contents as well as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity when compared with their leaves. In case of 1,1-diphenyl-2-picrylhydrazyl (DPPH) activity, the stem bark of S. nux-vomica and leaf extract of C. swietenia showed the highest activity. Based on the IC₅₀ values, the stem bark extracts of Cayratia pedata (20.5 μg/mL) and S. minor (22.4 μg/mL) showed high antiviral activity. In the mean-time S. nux-vomica, C. swietenia and C. swietenia bark extracts showed cytotoxicity to the MDCK cells. When comparing the stem bark and leaves the content of gallic acid, ferulic acid, o-coumaric acid, total flavonoids (TFC) and total phenols (TPC) was higher in stem bark and hence their anti-viral activity was high. Further study based on the metabolites against H1N1 can reveal the potential of therapeutic compounds against the viral disease.     

Regulation of Escherichia coli phosphofructokinase in situ

The activity of E. coli phosphofructokinase in situ has been studied in cells permeabilized to its substrates, products and effectors by a toluene-freezing treatment. The in situ enzyme exhibits moderate cooperativity in respect to F6P (n_H up to 2.0), rather low affinity for ATP (with Km up to 1 mM when saturated with F6P), activation by ADP, and inhibition, within the physiological range of concentrations, by high ATP and phosphoenolpyruvate. This behaviour of the enzyme in situ at concentrations of the effector metabolites as those reported in intact cells in glycolytic and gluconeogenic conditions could account for the changes of phosphofructokinase activity needed for metabolic regulation in vivo.     

Promising anti-inflammatory effects of chalcones via inhibition of cyclooxygenase,prostaglandin E2, inducible NO synthase and nuclear factor κb activities

Chalcones (1, 3-Diphenyl-2-propen-1-one) consist of a three carbon α, β-unsaturated carbonyl system and act as precursors for the biosynthesis of flavonoids in plants. However, laboratory synthesis of various chalcones has also been reported. Both natural and synthetic chalcones are known to exhibit a variety of pharmacological activities such as anti-inflammatory, antitumor, antibacterial, antifungal, antimalarial and antituberculosis. These promising activities, ease of synthesis and simple chemical structure have awarded chalcones considerable attraction. This review focuses on the anti-inflammatory effects of chalcones, caused by their inhibitory action primarily against the activities and expressions of four key inflammatory mediators viz., cyclooxygenase, prostaglandin E₂, inducible NO synthase, and nuclear factor κB. Various methodologies for the synthesis of chalcones have been discussed. The potency of recently synthesized chalcones is given in terms of their IC₅₀ values. Structure-Activity Relationships (SARs) of a variety of chalcone derivatives have been discussed. Computational methods were applied to calculate the ideal orientation of a typical chalcone scaffold against three enzymes, namely, cyclooxygenase-1, cyclooxygenase-2 and inducible NO synthase for the formation of stable complexes. The global market of anti-inflammatory drugs and its expected growth (from 2018 to 2026) have been discussed. SAR analysis, docking studies, and future prospects all together provide useful clues for the synthesis of novel chalcones of improved anti-inflammatory activities.     

黑姜的化学成分、药理作用及毒理学研究进展

黑姜（Kaempferia parviflora）是东南亚地区广泛栽培的民间药用植物,被用于制造食品、化妆品和医药品。黑姜在我国西双版纳傣族自治州亦有较长的民间药用栽培历史。根茎是黑姜重要的药用部位,主要含有黄酮类物质。许多药理作用研究表明黑姜具有抗肿瘤、增强男性性能力、抗炎、抗氧化、抗真菌、抗病毒、神经保护、血管舒张和心脏保护活性、经皮促渗等作用。对黑姜的化学成分、药理作用及毒理学研究进行综述,以期为进一步深入研究和开发利用黑姜资源提供帮助。     

Phenols displaying tyrosinase inhibition from Humulus lupulus

Tyrosinase is the rate-limiting enzyme for the production of melanin and other pigments via the oxidation of l-tyrosine. The methanol extract from Humulus lupulus showed potent inhibition against mushroom tyrosinase. The bioactivity-guided fractionation of this methanol extract resulted in the isolation of seven flavonoids (1–7), identified as xanthohumol (1), 4′-O-methylxanthohumol (2), xanthohumol C (3), flavokawain C (4), xanthoumol B (5), 6-prenylnaringenin (6) and isoxanthohumol (7). All isolated flavonoids (1–7) effectively inhibited the monophenolase (IC₅₀s?=?15.4–58.4?µM) and diphenolase (IC₅₀s?=?27.1–117.4?µM) activities of tyrosinase. Kinetic studies using Lineweaver–Burk and Dixon-plots revealed that chalcones (1–5) were competitive inhibitors, whereas flavanones (6 and 7) exhibited both mixed and non-competitive inhibitory characteristics. In conclusion, this study is the first to demonstrate that the phenolic phytochemicals of H. lupulus display potent inhibitory activities against tyrosinase.     

Chalcones and bis-chalcones: As potential α-amylase inhibitors; synthesis,in vitro screening,and molecular modelling studies

Despite of a diverse range of biological activities associated with chalcones and bis-chalcones, they are still neglected by the medicinal chemist for their possible α-amylase inhibitory activity. So, the current study is based on the evaluation of this class for the identification of new leads as α-amylase inhibitors. For that purpose, a library of substituted chalcones 1–13 and bis-chalcones 14–18 were synthesized and characterized by spectroscopic techniques EI-MS and ¹H NMR. CHN analysis was carried out and found in agreement with the calculated values. All compounds were evaluated for in vitro α-amylase inhibitory activity and demonstrated good activities in the range of IC₅₀ = 1.25 ± 1.05–2.40 ± 0.09 µM as compared to the standard acarbose (IC₅₀ = 1.04 ± 0.3 µM). Limited structure–activity relationship (SAR) was established by considering the effect of different groups attached to aryl rings on varying inhibitory activity. SMe group in chalcones and OMe group in bis-chalcones were found more influential on the activity than other groups. However, in order to predict the involvement of different groups in the binding interactions with the active site of α-amylase enzyme, in silico studies were also conducted.     

Cytotoxicity and modes of action of 4′-hydroxy-2′,6′-dimethoxychalcone and other flavonoids toward drug-sensitive and multidrug-resistant cancer cell lines

IntroductionResistance of cancer to chemotherapy is a main cause in treatment failure. Naturally occurring chalcones possess a wide range of biological activities including anti-cancer effects. In this work, we evaluated the antiproliferative activity of three chalcones [4′-hydroxy-2′,6′-dimethoxychalcone (1), cardamomin (2), 2′,4′-dihydroxy-3′,6′-dimethoxychalcone (3)], and four flavanones [(S)-(–)-pinostrobin (4), (S)-(–)-onysilin (5) and alpinetin (6)] toward nine cancer cell lines amongst which were multidrug resistant (MDR) types.MethodsThe resazurin reduction assay was used to detect the antiproliferative activity of the studied samples whilst flow cytometry for the mechanistic studies of the most active molecule (1).ResultsIC₅₀ values in a range of 2.54 μM against CEM/ADR5000 leukemia cells to 58.63 μM toward hepatocarcinoma HepG2 cells were obtained with 1. The lowest IC₅₀ values of 8.59 μM for 2 and 10.67 μM for 3 were found against CCRF-CEM cells leukemia cells, whilst the corresponding values were above 80 μM for 4 and 6. P-glycoprotein-expressing and multidrug-resistant CEM/ADR5000 cells were much more sensitive toward compound 1 than toward doxorubicin and low cross-resistance or even collateral sensitivity was observed in other drug-resistent cell lines to this compound. Normal liver AML12 cells were more resistant to the studied compounds than HepG2 liver cancer cells, indicating tumor specificity at least to some extent. Compound 1 arrested the cell cycle between Go/G1 phase, strongly induced apoptosis via disrupted mitochondrial membrane potential (MMP) and increased production of reactive oxygen species (ROS) in the studied leukemia cell line.ConclusionsChalcone 1 was the best tested cytotoxic molecule and further studies will be performed in order to envisage its possible use in the fight against multifactorial resistant cancer cells.     

Santin and cirsimaritin from Betula pubescens and Betula pendula buds induce apoptosis in human digestive system cancer cells

Flavonoids are bioactive secondary metabolites of plants, which exert anti-cancer effects. However, metabolism in enterocytes and the liver can influence the biological activity of flavonoids contained in the diet. Therefore, results from in vitro studies on cancer cells from the digestive tract and liver may reflect the real effects in the human body. Previously, we have found that the extract from birch buds exerts antiproliferative activity in a panel of cancer cells. In the present study, the anti-cancer activity of ten flavonoids isolated from the buds of Betula pubescens and Betula pendula was characterized. Among them, santin and cirsimaritin significantly reduced viability, proliferation and clonogenicity of gastric (AGS), colon (DLD-1) and liver (HepG2) cancer cells. Both flavonoids induced apoptosis, accompanied by activation of caspase-3, caspase-7, caspase-8 and caspase-9. Moreover, upregulation of p53 was detected only in wild-type p53 harbouring cells. Together, our results suggest that santin and cirsimaritin exhibit promising anti-cancer activity in cultures of digestive system cancer cells.