Thesis (M.Sc.)--York University, 2006. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 118-125). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19667

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Diss. (sammanfattning) Göteborg : Univ., 2007. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 57-62).

Thesis (M. Med. Sc.)--University of Hong Kong, 2006.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Picornavirus proteins VP1 to VP3 are exposed on the surface of the virus particle whereas VP4 is internal and modified at its amino terminus by the addition of myristic acid (Chow et al., 1987; Paul et al., 1987). Myristic acid occupies a position in the core of mature poliovirus particles; it has been suggested that it may be important for particle integrity or in the localization of the capsid protein precursor on the hydrophobic membranes during virion assembly (Chow et al., 1987). To determine the function of the amino-terminal myristylation of VP4 in picornaviruses, and to establish whether competition for the acylation site is a possible approach to antiviral chemotherapy, the effect of fatty acids on virus replication has been examined. Some fatty acids are able to enter picornavirus-infected cells and compete for the myristylation site on VP4. Unexpectedly, it was found that short chain fatty acids also inhibit an early event in the replication of bovine enterovirus (BEV) at concentrations which have no detectable effect on cellular macromolecular synthesis and cloning. These findings indicate that fatty acids inhibit cell-mediated uncoating. Short chain fatty acids inhibit the replication of bovine enterovirus but are almost ineffective against poliovirus type 1, coxsackievirus B5, encephalomyocarditis virus and human rhinovirus lB. Lauric acid binds to bovine enterovirus, thereby stabilizing the virus particle to heat degradation. Fatty acid-bound virions attach to susceptible cells but fail to undergo cell-mediated uncoating. The inhibitory effect is reversible with chloroform and may result from a hydrophobic interaction between the fatty acid and a specific site on the virus particie.

Background: The emergence of viral diseases has been the major threat to public health and social stability. A hundred years ago, 1918 Spanish flu (H1N1) pandemic spread worldwide, and about 3% ~ 5% of the world's population died from the flu-related illnesses. It is known as the deadliest catastrophic pandemics in human history. There have been five Public Health Emergency of International Concern (PHEIC) declarations over the past decade, including the 2014 Ebola outbreak in west Africa, the 2016 Zika outbreak and the ongoing COVID-19 pandemic. There is always a new strain of virus emerging on the horizon. We have urgent need to develop more broad-spectrum antivirals, which work effective against multiple viruses, for thwarting outbreaks in the future. Objective: Based on our previous experience in search of anti-HIV compounds from topical plants, we aimed to discover novel antiviral lead compounds from Justicia plants collected in Hong Kong. Further, structure modification of the natural compounds can lead to optimization of their drug properties for further development as drug candidates. To determine the antiviral targets of the lead compounds will further provide insights to elucidate the mechanism of actions. The present studies are to discover the antiviral lead compounds from Justicia plants, to analyze the structure-activity relationship of the modified structures, to identify the molecular targets of the lead compounds as antiviral agents against the multiple viruses. Methodology: Four common Justicia plants were collected in Hong Kong. The plant extracts and compounds isolated from the plants were explored for their antiviral activities via our established "One-Stone-Two-Birds" antiviral assay. Time-of-addition experiments were performed to determine the target stages of the antiviral compounds on the viral replication. Computational techniques (3D-QSAR and in silico pharmacokinetics evaluation) were employed to elucidate the structure-activity relationship of the compounds and thereby optimize their structures to enhance the antiviral activity. Comprehensive activity-based protein profiling (ABPP) of biotin-linked compounds using SWATH-MS technique was performed to identify the protein target(s) of the lead compounds in an unbiased manner. The role of the molecular target in viral replication was further verified by mRNA knockdown using siRNA. Result: The extracts of Justicia procumbens and Justicia championii showed potent antiviral effects with low cytotoxicity among the collected Justicia plants. By correlating the antiviral activity with their HPLC-UV profiles, arylnaphthalene lignans (ANLs) were determined as the principle active components. Among the isolated compounds from J. procumbens, diphyllin exhibited strong antiviral activities against VSV/HIV, H5N1/HIV and EBOV/HIV pseudoviruses with EC50 values ranging from 30-100nM. In time-of-addition experiments, diphyllin mainly acts on the entry stage of the viral infection. Considering the broad-spectrum antiviral properties and antiviral mechanism together, diphyllin is probably a host-targeting antiviral agent. In a subsequent lead optimization, a reliable and predictive 3D-QSAR was established from 25 synthesized ANLs. Compound 31 was found as the most potent antiviral agent based on the 3D-QSAR model. It showed 70 times more potent antiviral activity than the parent diphyllin, with retained broad-spectrum antiviral properties and improved predicted ADMET properties. In addition, comprehensive ABPP analysis of the biotin-linked diphyllin was employed for the target identification of the ANL compounds. Total 2343 proteins were captured by the ABPP probes. By quantitative analysis, the protein TFAM showed significant affinity to the diphyllin-based ABPP probes. The viral susceptibility of TFAM-deficient cells was shown to be reduced in the subsequent validation. We thus determined TFAM as the potential antiviral drug target of the ANL compounds against a broad spectrum of viruses.

Background: Natural products have been a rich source for the discovery of lead compounds in modern drug discovery. 6,7'-Cyclolignans are a class of secondary metabolites which are widely distributed in more than 20 families. This important class of lignans continue to attract the interest of the pharmaceutical industry owing to their remarkable biological benefits, particularly for their anti-tumor and antiviral properties. Arylnaphthalene lignans (ANLs) belong to 6,7'-cyclolignans which contain a 2,3-dimethyl-1-phenyl-naphthalene core structure. ANLs are widely distributed in plants. Justicia cf. patentiflora was identified as an anti-HIV (human immunodeficiency virus) plant lead through the screening of more than 3,500 plant extracts. Bioassay-directed fractionation of the methanol extract of the stems and barks of this plant has led to the isolation of three ANL glycoside compounds, which displayed potent inhibitory activity against broad HIV clinical strains with EC50 values in the range of 14-37 nM [Zidovudine (AZT): 77-95 nM]. They also showed significant inhibitory effects against drug-resistance HIV strains. Thus, the ANL glycosides have high potential as lead molecules for the development of new therapeutic drugs for HIV/AIDS. Objectives: 1) To establish an efficient route for the total synthesis of ANL compounds and to synthesize a library of ANL compounds through the established total synthetic approach; 2) To evaluate the cytotoxicities and anti-HIV activities of the synthesized ANLs; 3) To elucidate the structure activity relationship (SAR) of ANLs as a basis for the optimization of drug efficacy, improvement of pharmacokinetic properties as well as minimization of the toxicity of ANLs; 4) To synthesize potent anti-HIV ANL molecules with high selectivity. Methods: To achieve these objectives, a synthetic route for ANL was designed and a broad series of ANL derivatives were synthesized via modifications of rings A and B, as well as the functionalities at C-7. The synthesized compounds had been evaluated for their toxicity and antiviral activities. Cytotoxicity was determined using the SRB (Sulforhodamine B) assay, while anti-HIV activity was evaluated by utilizing the "One-Stone-Two-Birds" protocol. Results: We have accomplished the total synthesis of the key intermediate diphyllin with more than 20 g. Our modification of ANL derivatives focused on substitutions, additions and different configurations of the C-7 position, ring A and ring B. Specifically, the different structural components of the ANLs were systematically modified, resulting in the formation of six groups of compounds. A total of 72 ANL compounds with various functional groups were synthesized. Their structures have been confirmed by the MS and NMR spectral data. All the synthesized ANL compounds were purified to have purity ≥ 95%. The SAR of ANL compounds was revealed based on the analysis of the antiviral and cytotoxicity data of these synthetic analogues. After structural modification, all the modified derivatives based on rings A and B (groups 1 and 2) showed activity reduction in terms of both cytotoxic and anti-HIV activities. However, the modification of C-7 yielded divergent results, which included the groups of 3-6. Most compounds in groups 3-5 displayed comparable inhibitory effect with diphyllin (5). Group 6 represents the largest number of analogues among the six groups. In this group, the stereochemical properties and functionalization of the hydroxy groups on the sugar units are essential for their activities. Among these series of derivatives, compound 17b showed significant high potency of anti-HIV activity with an EC50 value of 2.6 nM and SI of 815. Conclusion: Using the synthesized diphyllin as the key intermediate, a compound library of 72 ANL derivatives was obtained. These compounds have been evaluated for their cytotoxicity and anti-HIV activity. Our bioactivity data revealed that the functionalization of the C-7 hydroxy group could significantly reduce the cytotoxicity and increase anti-HIV activity, while the modification on rings A and B would rather result in the reduction of both cytotoxicity and anti-HIV activity. Subsequently, novel diphyllin glycosides containing various sugar moieties were further synthesized. Several of these ANL analogues showed high anti-HIV activity with EC50 values in the nM range and low cytotoxicity (selective indices > 500). Future Perspective: This study clearly suggests ANLs as anti-HIV lead compounds and they have high potential to be developed as therapeutic drugs for the treatment of HIV. To further confirm the antiviral potential of ANLs, live HIV strains including some drug resistant strains should be further investigated. Although our data have shown that the ANL compounds are targeting the viral post-entry stages, their antiviral molecular targets are still unknown. However, since our SAR information has clearly revealed that the substitution of rings A and B are not involve in the antiviral activity for enhancing ANL compounds, the carbon positions in these rings may be explored to link a biotin unit, which can be used as a viable approach to pull down the antiviral target proteins of ANLs. Once the target proteins are identified, molecular docking is then made possible for a rational synthetic design to fine tune the chemical structures of ANLs in order to improve their antiviral properties such as high antiviral activity, low toxicity and enhanced water solubility. A further step to advance ANLs as anti-HIV drugs is the investigation of their drug properties in in vivo studies including the assessment of their anti-HIV efficacy in the rhesus model as well as obtaining their pharmacokinetic and safety parameters. These studies will help to provide more evidence about the anti-viral properties of ANLs

Background: The emergence of viral diseases has been the major threat to public health and social stability. A hundred years ago, 1918 Spanish flu (H1N1) pandemic spread worldwide, and about 3% ~ 5% of the world's population died from the flu-related illnesses. It is known as the deadliest catastrophic pandemics in human history. There have been five Public Health Emergency of International Concern (PHEIC) declarations over the past decade, including the 2014 Ebola outbreak in west Africa, the 2016 Zika outbreak and the ongoing COVID-19 pandemic. There is always a new strain of virus emerging on the horizon. We have urgent need to develop more broad-spectrum antivirals, which work effective against multiple viruses, for thwarting outbreaks in the future. Objective: Based on our previous experience in search of anti-HIV compounds from topical plants, we aimed to discover novel antiviral lead compounds from Justicia plants collected in Hong Kong. Further, structure modification of the natural compounds can lead to optimization of their drug properties for further development as drug candidates. To determine the antiviral targets of the lead compounds will further provide insights to elucidate the mechanism of actions. The present studies are to discover the antiviral lead compounds from Justicia plants, to analyze the structure-activity relationship of the modified structures, to identify the molecular targets of the lead compounds as antiviral agents against the multiple viruses. Methodology: Four common Justicia plants were collected in Hong Kong. The plant extracts and compounds isolated from the plants were explored for their antiviral activities via our established "One-Stone-Two-Birds" antiviral assay. Time-of-addition experiments were performed to determine the target stages of the antiviral compounds on the viral replication. Computational techniques (3D-QSAR and in silico pharmacokinetics evaluation) were employed to elucidate the structure-activity relationship of the compounds and thereby optimize their structures to enhance the antiviral activity. Comprehensive activity-based protein profiling (ABPP) of biotin-linked compounds using SWATH-MS technique was performed to identify the protein target(s) of the lead compounds in an unbiased manner. The role of the molecular target in viral replication was further verified by mRNA knockdown using siRNA. Result: The extracts of Justicia procumbens and Justicia championii showed potent antiviral effects with low cytotoxicity among the collected Justicia plants. By correlating the antiviral activity with their HPLC-UV profiles, arylnaphthalene lignans (ANLs) were determined as the principle active components. Among the isolated compounds from J. procumbens, diphyllin exhibited strong antiviral activities against VSV/HIV, H5N1/HIV and EBOV/HIV pseudoviruses with EC50 values ranging from 30-100nM. In time-of-addition experiments, diphyllin mainly acts on the entry stage of the viral infection. Considering the broad-spectrum antiviral properties and antiviral mechanism together, diphyllin is probably a host-targeting antiviral agent. In a subsequent lead optimization, a reliable and predictive 3D-QSAR was established from 25 synthesized ANLs. Compound 31 was found as the most potent antiviral agent based on the 3D-QSAR model. It showed 70 times more potent antiviral activity than the parent diphyllin, with retained broad-spectrum antiviral properties and improved predicted ADMET properties. In addition, comprehensive ABPP analysis of the biotin-linked diphyllin was employed for the target identification of the ANL compounds. Total 2343 proteins were captured by the ABPP probes. By quantitative analysis, the protein TFAM showed significant affinity to the diphyllin-based ABPP probes. The viral susceptibility of TFAM-deficient cells was shown to be reduced in the subsequent validation. We thus determined TFAM as the potential antiviral drug target of the ANL compounds against a broad spectrum of viruses.