Ai-Lin Liu

In vitro anti-influenza virus and anti-inflammatory activities of theaflavin derivatives.

The theaflavins fraction (TF80%, with a purity of 80%) and three theaflavin (TF) derivatives from black tea have been found to exhibit potent inhibitory effects against influenza virus in vitro. They were evaluated with a neuraminidase (NA) activity assay, a hemagglutination (HA) inhibition assay, a real-time quantitative PCR (qPCR) assay for gene expression of hemagglutinin (HA) and a cytopathic effect (CPE) reduction assay. The experimental results showed that they all exerted significant inhibitory effects on the NA of three different subtypes of influenza virus strains [A/PR/8/34(H1N1), A/Sydney/5/97(H3N2) and B/Jiangsu/10/2003] with 50% inhibitory concentration (IC(50)) values ranging from 9.27 to 36.55 μg/mL, and they also displayed an inhibitory effect on HA; these inhibitory effects might constitute two major mechanisms of their antiviral activity. Time-of-addition studies demonstrated that TF derivatives might have a direct effect on viral particle infectivity, which was consistent with the inhibitory effect on HA. Subsequently, the inhibitory effect of TF derivatives on the replication of the viral HA gene as assayed by qPCR and on the nuclear localization of the influenza virus vRNP further demonstrated that they may primarily act during the early stage of infection. Interestingly, besides the activity against functional viral proteins, TF derivatives also decreased the expression level of the inflammatory cytokine IL-6 during viral infection, expression of which may result in serious tissue injury and apoptosis. Our results indicated that TF derivatives are potential compounds with anti-influenza viral replication and anti-inflammatory properties. These findings will provide important information for new drug design and development for the treatment of influenza virus infection.

In vitro anti-influenza viral activities of constituents from Caesalpinia sappan.

Six constituents with neuraminidase (NA) inhibitory activity, namely brazilein, brazilin, protosappanin A, 3-deoxysappanchalcone, sappanchalcone and rhamnetin, were isolated from the hearthwood of Caesalpinia sappan (Leguminosae). Their in vitro anti-influenza virus activities were evaluated with the cytopathic effect (CPE) reduction method. The results showed that 3-deoxysappanchalcone and sappanchalcone exhibited the highest activity against influenza virus (H3N2) with IC50 values of 1.06 and 2.06 microg/mL, respectively, in comparison to the positive control oseltamivir acid and ribavirin with IC50 values of 0.065 and 9.17 microg/mL, respectively.

Predictions of BuChE Inhibitors Using Support Vector Machine and Naive Bayesian Classification Techniques in Drug Discovery

Butyrylcholinesterase (BuChE, EC 3.1.1.8) is an important pharmacological target for Alzheimers disease (AD) treatment. However, the currently available BuChE inhibitor screening assays are expensive, labor-intensive, and compound-dependent. It is necessary to develop robust in silico methods to predict the activities of BuChE inhibitors for the lead identification. In this investigation, support vector machine (SVM) models and naive Bayesian models were built to discriminate BuChE inhibitors (BuChEIs) from the noninhibitors. Each molecule was initially represented in 1870 structural descriptors (1235 from ADRIANA.Code, 334 from MOE, and 301 from Discovery studio). Correlation analysis and stepwise variable selection method were applied to figure out activity-related descriptors for prediction models. Additionally, structural fingerprint descriptors were added to improve the predictive ability of models, which were measured by cross-validation, a test set validation with 1001 compounds and an external test set validation with 317 diverse chemicals. The best two models gave Matthews correlation coefficient of 0.9551 and 0.9550 for the test set and 0.9132 and 0.9221 for the external test set. To demonstrate the practical applicability of the models in virtual screening, we screened an in-house data set with 3601 compounds, and 30 compounds were selected for further bioactivity assay. The assay results showed that 10 out of 30 compounds exerted significant BuChE inhibitory activities with IC50 values ranging from 0.32 to 22.22 μM, at which three new scaffolds as BuChE inhibitors were identified for the first time. To our best knowledge, this is the first report on BuChE inhibitors using machine learning approaches. The models generated from SVM and naive Bayesian approaches successfully predicted BuChE inhibitors. The study proved the feasibility of a new method for predicting bioactivities of ligands and discovering novel lead compounds.

Antioxidant, Anti-Inflammatory and Anti-Influenza Properties of Components from Chaenomeles speciosa

The fruit of Chaenomeles speciosa is a traditional Chinese medicine used for the treatment of dyspepsia and various inflammatory diseases. In the present study, we evaluated the potential radical scavenging capacity, and activity against nitrous oxide, inflammatory cytokines production and neuramindase (NA) of its isolates. The results showed that 3,4-dihydroxybenzoic acid (1) displayed higher inhibitory activities on DPPH and NA with IC50 values of 1.02 μg/mL and 1.27 μg/mL respectively, and quercetin (2) also showed significant inhibitory action on DPPH and NA, with IC50 values of 3.82 μg/mL and 1.90 μg/mL. Compounds 1, 2 and methyl 3-hydroxybutanedioic ester (3) could inhibit the production of TNF-α by 22.73%, 33.14% and 37.19% at 5 μg/mL (P < 0.05) compared with the control. In addition, compound 2 was found to be active on the release of IL-6 in RAW264.7 macrophage cells, with an inhibitory rate of 39.79% (P < 0.05). The anti-inflammatory effect of compound 3 is disclosed for the first time in this study. Avian influenza is usually accompanied by virus invasion followed by the occurrence of oxidative stress and serious inflammation, so the multiple effects of the isolates may play a cocktail-like role in the treatment of avian influenza, and C. speciosa components, especially quercetin, might be a potent source for anti-viral and anti-inflammatory agents.

Discovery of multitarget-directed ligands against Alzheimer's disease through systematic prediction of chemical-protein interactions.

To determine chemical-protein interactions (CPI) is costly, time-consuming, and labor-intensive. In silico prediction of CPI can facilitate the target identification and drug discovery. Although many in silico target prediction tools have been developed, few of them could predict active molecules against multitarget for a single disease. In this investigation, naive Bayesian (NB) and recursive partitioning (RP) algorithms were applied to construct classifiers for predicting the active molecules against 25 key targets toward Alzheimers disease (AD) using the multitarget-quantitative structure-activity relationships (mt-QSAR) method. Each molecule was initially represented with two kinds of fingerprint descriptors (ECFP6 and MACCS). One hundred classifiers were constructed, and their performance was evaluated and verified with internally 5-fold cross-validation and external test set validation. The range of the area under the receiver operating characteristic curve (ROC) for the test sets was from 0.741 to 1.0, with an average of 0.965. In addition, the important fragments for multitarget against AD given by NB classifiers were also analyzed. Finally, the validated models were employed to systematically predict the potential targets for six approved anti-AD drugs and 19 known active compounds related to AD. The prediction results were confirmed by reported bioactivity data and our in vitro experimental validation, resulting in several multitarget-directed ligands (MTDLs) against AD, including seven acetylcholinesterase (AChE) inhibitors ranging from 0.442 to 72.26 μM and four histamine receptor 3 (H3R) antagonists ranging from 0.308 to 58.6 μM. To be exciting, the best MTDL DL0410 was identified as an dual cholinesterase inhibitor with IC50 values of 0.442 μM (AChE) and 3.57 μM (BuChE) as well as a H3R antagonist with an IC50 of 0.308 μM. This investigation is the first report using mt-QASR approach to predict chemical-protein interaction for a single disease and discovering highly potent MTDLs. This protocol may be useful for in silico multitarget prediction of other diseases.

Design, synthesis, inhibitory activity, and SAR studies of hydrophobic p-aminosalicylic acid derivatives as neuraminidase inhibitors

A series of hydrophobic p-aminosalicylic acid derivatives containing a lipophilic side chain at C-2 and an amino or guanidine at C-5 were synthesized and evaluated for their ability to inhibit neuraminidase (NA) of influenza A virus (H3N2). All compounds were synthesized in good yields starting from commercially available p-aminosalicylic acid (PAS) using a suitable synthetic strategy. These compounds showed potent inhibitory activity against influenza A NA. Within this series, six compounds, 11, 12, 13e, 16e, 17c, and 18e, have the good potency (IC(50)=0.032-0.049 microM), which are compared to Oseltamivir (IC(50)=0.021 microM) and could be used as lead compounds in the future.

Inhibition of acetylcholinesterase by two genistein derivatives: kinetic analysis, molecular docking and molecular dynamics simulation.

In this study two genistein derivatives (G1 and G2) are reported as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and differences in the inhibition of AChE are described. Although they differ in structure by a single methyl group, the inhibitory effect of G1 (IC50=264 nmol/L) on AChE was 80 times stronger than that of G2 (IC50=21,210 nmol/L). Enzyme-kinetic analysis, molecular docking and molecular dynamics (MD) simulations were conducted to better understand the molecular basis for this difference. The results obtained by kinetic analysis demonstrated that G1 can interact with both the catalytic active site and peripheral anionic site of AChE. The predicted binding free energies of two complexes calculated by the molecular mechanics/generalized born surface area (MM/GBSA) method were consistent with the experimental data. The analysis of the individual energy terms suggested that a difference between the net electrostatic contributions (ΔEele+ΔGGB) was responsible for the binding affinities of these two inhibitors. Additionally, analysis of the molecular mechanics and MM/GBSA free energy decomposition revealed that the difference between G1 and G2 originated from interactions with Tyr124, Glu292, Val294 and Phe338 of AChE. In conclusion, the results reveal significant differences at the molecular level in the mechanism of inhibition of AChE by these structurally related compounds.

In vitro anti-influenza viral activities of stilbenoids from the lianas of Gnetum pendulum.

The anti-influenza viral activities of six stilbenoids from the lianas of Gnetum pendulum C. Y. Cheng were evaluated with two different assays, neuraminidase (NA) activity assay and cytopathic effect (CPE) reduction assay. The NA assay results showed that all six stilbenoids exerted an NA inhibitory effect, while the CPE assay indicated that among them, isorhapontigenin (2), gnetupendin B (3), shegansu B (4), and gnetin D 6) exhibit significant in vitro anti-influenza viral activity in MDCK cells, with IC(50) values from 0.67 to 11.99 µg/mL in comparison to the positive controls oseltamivir acid and ribavirin whose IC(50) values were 0.040 and 5.54 µg/mL, respectively.

Isocryptotanshinone, a STAT3 inhibitor, induces apoptosis and pro-death autophagy in A549 lung cancer cells

Abstract Signal transducer and activator of transcription 3 (STAT3) is a potential drug target for chemotherapy. Cryptotanshinone (CTS) was identified as a potent STAT3 inhibitor, while the effect of other tanshinones remains unknown. In this study, the influence of eight tanshinones on STAT3 activity was initially screened and isocryptotanshinone (ICTS) significantly inhibited STAT3 activity in a dual luciferase assay. ICTS inhibited the constitutive and inducible phosphorylation of STAT3 at Y705 without affecting the phosphorylation of STAT3 at S727 in A549 lung cancer cells. Furthermore, ICTS inhibited the nuclear translocation of STAT3. Compared with CTS, ICTS exhibited a stronger inhibitory effect on STAT3 phosphorylation and on A549 cytotoxicity. ICTS induced autophagy as evidenced by the accumulation of autophagic vacuoles and the increased expression of LC3 protein and autophagosomes. ICTS-induced cell death was partially reversed by the autophagy inhibitor chloroquine. The docking assay predicted that both ICTS and CTS bind the SH2 domain of STAT3. ICTS formed hydrogen bonds and pi–pi interaction with the nearby amino acid residues of Lys591, Arg609, and Ser636. These findings suggested that ICTS, a natural compound, is a potent STAT3 inhibitor. ICTS induced apoptosis and pro-death autophagy in A549 cells.

Ameliorative effects of baicalein in MPTP-induced mouse model of Parkinson's disease: A microarray study

Baicalein, a flavonoid from Scutellaria baicalensis Georgi, has been shown to possess neuroprotective properties. The purpose of this study was to explore the effects of baicalein on motor behavioral deficits and gene expression in N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice model of Parkinsons disease (PD). The behavioral results showed that baicalein significantly improves the abnormal behaviors in MPTP-induced mice model of PD, as manifested by shortening the total time for climbing down the pole, prolonging the latent periods of rotarod, and increasing the vertical movements. Using cDNA microarray and subsequent bioinformatic analyses, it was found that baicalein significantly promotes the biological processes including neurogenesis, neuroblast proliferation, neurotrophin signaling pathway, walking and locomotor behaviors, and inhibits dopamine metabolic process through regulation of gene expressions. Based on analysis of gene co-expression networks, the results indicated that the regulation of genes such as LIMK1, SNCA and GLRA1 by baicalein might play central roles in the network. Our results provide experimental evidence for the potential use of baicalein in the treatment of PD, and revealed gene expression profiles, biological processes and pathways influenced by baicalein in MPTP-treated mice.