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    Small molecules blocking the entry of severe acute respiratory syndrome coronavirus into host cells. Yi Ling,Li Zhengquan,Yuan Kehu,Qu Xiuxia,Chen Jian,Wang Guangwen,Zhang Hong,Luo Hongpeng,Zhu Lili,Jiang Pengfei,Chen Lirong,Shen Yan,Luo Min,Zuo Guoying,Hu Jianhe,Duan Deliang,Nie Yuchun,Shi Xuanling,Wang Wei,Han Yang,Li Taisheng,Liu Yuqing,Ding Mingxiao,Deng Hongkui,Xu Xiaojie Journal of virology Severe acute respiratory syndrome coronavirus (SARS-CoV) is the pathogen of SARS, which caused a global panic in 2003. We describe here the screening of Chinese herbal medicine-based, novel small molecules that bind avidly with the surface spike protein of SARS-CoV and thus can interfere with the entry of the virus to its host cells. We achieved this by using a two-step screening method consisting of frontal affinity chromatography-mass spectrometry coupled with a viral infection assay based on a human immunodeficiency virus (HIV)-luc/SARS pseudotyped virus. Two small molecules, tetra-O-galloyl-beta-D-glucose (TGG) and luteolin, were identified, whose anti-SARS-CoV activities were confirmed by using a wild-type SARS-CoV infection system. TGG exhibits prominent anti-SARS-CoV activity with a 50% effective concentration of 4.5 microM and a selective index of 240.0. The two-step screening method described here yielded several small molecules that can be used for developing new classes of anti-SARS-CoV drugs and is potentially useful for the high-throughput screening of drugs inhibiting the entry of HIV, hepatitis C virus, and other insidious viruses into their host cells. 10.1128/JVI.78.20.11334-11339.2004
    Kaempferol derivatives as antiviral drugs against the 3a channel protein of coronavirus. Schwarz Silvia,Sauter Daniel,Wang Kai,Zhang Ronghua,Sun Bing,Karioti Anastasia,Bilia Anna Rita,Efferth Thomas,Schwarz Wolfgang Planta medica The protein coded by the open-reading-frame 3a of SARS coronavirus has been demonstrated to form a cation-selective channel that may become expressed in the infected cell. The activity of the channel is involved in the mechanism of virus release. Drugs that inhibit the ion channel can, therefore, inhibit virus release, and they could be a source for development of novel therapeutic antiviral agents. Various drugs found in Chinese herbs that are well known as anticancer agents also have an antiviral potency. Here we tested the flavonols kaempferol, kaempferol glycosides, and acylated kaempferol glucoside derivatives with respect to their potency to block the 3a channel. We used the Xenopus oocyte with a heterologously expressed 3a protein as a model system to test the efficacy of the flavonols. Some of these drugs turned out to be potent inhibitors of the 3a channel. The most effective one was the glycoside juglanin (carrying an arabinose residue) with an IC50 value of 2.3 µM for inhibition of the 3a-mediated current. Kaempferol derivatives with rhamnose residue also seem to be quite effective. We suggest that viral ion channels, in general, may be a good target for the development of antiviral agents, and that, in particular, kaempferol glycosides are good candidates for 3a channel proteins of coronaviruses. 10.1055/s-0033-1360277
    Toona sinensis Roem tender leaf extract inhibits SARS coronavirus replication. Chen Chung-Jen,Michaelis Martin,Hsu Hseng-Kuang,Tsai Chin-Chuan,Yang Kunder D,Wu Yang-Chang,Cinatl Jindrich,Doerr Hans Wilhelm Journal of ethnopharmacology AIM OF THE STUDY:Severe acute respiratory syndrome (SARS) is a life-threatening disease caused by the SARS coronavirus (SARS-CoV). The development of new antiviral agents for SARS-CoV is an important issue. We tried to find potential resource from Traditional Chinese medicine (TCM) for development of new drugs against SARS-CoV. MATERIALS AND METHODS:Our team recruited the potential TCM formulae (also known as Kampo) from two TCM books, Shang-Han Lun (Discussion of Cold-Induced Disorders) and Wen-Bing Tiau-Bein (Differential Management of Febrile Diseases). Several herbs, which were believed to be beneficial for SARS by experienced TCM doctors were also recruited. In addition, a vegetable polular in Taiwan, China and Malaysia, the tender leaf of Toona sinensis Roem (also known as Cedrela sinensis, belongs to the family Meliacceae) was also recruited under the suggestion of botanic experts. These TCM products and plant extrats were then tested for the effectiveness against SARS-CoV in vitro. RESULTS:Only TSL-1, the extract from tender leaf of Toona sinensis Roem was found to have an evident effect against SARS-CoV with selectivity index 12 approximately 17. CONCLUSION:This paper reports for the first time that extract from a vegetable, the tender leaf of Toona sinensis Roem, can inhibit SARS-CoV in vitro. Thererfore, the tender leaf of Toona sinensis Roem may be an important resource agninst SARS-CoV. 10.1016/j.jep.2008.07.048
    Flavonoid-mediated inhibition of SARS coronavirus 3C-like protease expressed in Pichia pastoris. Nguyen Thi Thanh Hanh,Woo Hye-Jin,Kang Hee-Kyoung,Nguyen Van Dao,Kim Young-Min,Kim Do-Won,Ahn Sul-Ah,Xia Yongmei,Kim Doman Biotechnology letters The 3C-like protease (3CL(pro)) of severe acute respiratory syndrome associated coronavirus (SARS-CoV) is vital for SARS-CoV replication and is a promising drug target. Recombinant 3CL(pro) was expressed in Pichia pastoris GS115 as a 42 kDa protein that displayed a K ( m ) of 15 ± 2 μM with Dabcyl-KTSAVLQSGFRKME-Edans as substrate. Purified 3CL(pro) was used for inhibition and kinetic assays with seven flavonoid compounds. The IC(50) of six flavonoid compounds were 47-381 μM. Quercetin, epigallocatechin gallate and gallocatechin gallate (GCG) displayed good inhibition toward 3CL(pro) with IC(50) values of 73, 73 and 47 μM, respectively. GCG showed a competitive inhibition pattern with K ( i ) value of 25 ± 1.7 μM. In molecular docking experiments, GCG displayed a binding energy of -14 kcal mol(-1) to the active site of 3CL(pro) and the galloyl moiety at 3-OH position was required for 3CL(pro) inhibition activity. 10.1007/s10529-011-0845-8
    Tetrandrine inhibits differentiation of proinflammatory subsets of T helper cells but spares de novo differentiation of iTreg cells. Zou Huimin,He Tianzhen,Chen Xin International immunopharmacology Tetrandrine (TET) is an anti-inflammatory compound isolated from Chinese herb Stephania tetrandra S. Moore. It was reported recently that the differentiation of Th17 cells was inhibited, while the generation of induced Treg cells (iTregs) was promoted, by TET treatment. We therefore carefully examined the effect of TET on the differentiation of four major subsets of T helper cells. The results showed that in vitro treatment with TET potently inhibited the differentiation of Th1, Th2 and Th17 cells. Administration of LPS resulted in a mixed Th1, Th2 and Th17 responses in normal mice, and such effect of LPS was inhibited by in vivo TET treatment as well. In contrast, TET did not promote or inhibit the in vitro generation of iTregs from naïve CD4CD25Foxp3/gfp T cells. Furthermore, spontaneous and rapamycin-induced conversion of naïve CD4CD25Foxp3/gfp T cells into Foxp3-expressing iTregs in congenic mice was not affected by TET treatment. Thus, TET had the capacity to inhibit the differentiation of proinflammatory Th1, Th2 and Th17 cells, while sparing the generation of Tregs. As a Treg-friendly and broad spectrum anti-inflammatory agent, the molecular mechanism and the therapeutic potential of TET in various human inflammatory diseases should be further studied. 10.1016/j.intimp.2019.01.040
    Characteristics of flavonoids as potent MERS-CoV 3C-like protease inhibitors. Jo Seri,Kim Hyojin,Kim Suwon,Shin Dong Hae,Kim Mi-Sun Chemical biology & drug design Middle East respiratory syndrome-coronavirus (MERS-CoV) is a zoonotic virus transmitted between animals and human beings. It causes MERS with high mortality rate. However, no vaccine or specific treatment is currently available. Since antiviral activity of some flavonoids is known, we applied a flavonoid library to probe inhibitory compounds against MERS-CoV 3C-like protease (3CLpro). Herbacetin, isobavachalcone, quercetin 3-β-d-glucoside and helichrysetin were found to block the enzymatic activity of MERS-CoV 3CLpro. The binding of the four flavonoids was also confirmed independently using a tryptophan-based fluorescence method. The systematic comparison of the binding affinity of flavonoids made it possible to infer their scaffolds and functional groups required to bind with MERS-CoV 3CLpro. An induced-fit docking analysis revealed that S1 and S2 sites play a role in interaction with flavonoids. The experimental and computational study showed that flavonol and chalcone are favourite scaffolds to bind with the catalytic site of MERS-CoV 3CLpro. It was also deduced that some flavonoid derivatives with hydrophobic or carbohydrate attached to their core structures have a good inhibitory effect. Therefore, we suggest that flavonoids with these characteristics can be used as templates to develop potent MERS-CoV 3CLpro inhibitors. 10.1111/cbdd.13604
    Antiviral effects of saikosaponins on human coronavirus 229E in vitro. Cheng Pei-Win,Ng Lean-Teik,Chiang Lien-Chai,Lin Chun-Ching Clinical and experimental pharmacology & physiology 1. Saikosaponins represent a group of oleanane derivatives, usually as glucosides, that are found in a number of plant families. Saikosaponins isolated from medicinal plants such as Bupleurum spp., Heteromorpha spp. and Scrophularia scorodonia have been reported to possess various biological activities, specifically antihepatitis, antinephritis, antihepatoma, anti-inflammation, immunomodulation and antibacterial effects. 2. The aim of the present study was to examine the anticoronaviral activity of saikosaponins (A, B2, C and D) and their mode of action. Using the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-5-[(phenylamino) carbonyl-2H-tetrazolium hydroxide] (XTT) assay, results showed that all saikosaponins tested demonstrated antiviral activity at concentrations of 0.25-25 micromol/L, with the strongest activity being noted for saikosaponin B2 (IC50 = 1.7 +/- 0.1 micromol/L). Interestingly, both saikosaponins A (50% cellular cytotoxicity (CC50) concentration = 228.1 +/- 3.8 micromol/L; selectivity index (SI) = 26.6) and B2 (CC50 = 383.3 +/- 0.2 micromol/L; SI = 221.9) exhibited no cytotoxic effects on target cells at concentrations that achieved antiviral activity. In the time-of-addition studies, saikosaponin B2, at 6 micromol/L, significantly inhibited human coronavirus 229E infection following its addition at various time pre-infection (-4 to -1 h), coinfection (0 h) and post-infection (1-4 h). Furthermore, saikosaponin B2 also showed an inhibitory effect on viral attachment and penetration. 3. The present results indicate that saikosaponin B2 has potent anticoronaviral activity and that its mode of action possibly involves interference in the early stage of viral replication, such as absorption and penetration of the virus. 10.1111/j.1440-1681.2006.04415.x
    Identification of myricetin and scutellarein as novel chemical inhibitors of the SARS coronavirus helicase, nsP13. Yu Mi-Sun,Lee June,Lee Jin Moo,Kim Younggyu,Chin Young-Won,Jee Jun-Goo,Keum Young-Sam,Jeong Yong-Joo Bioorganic & medicinal chemistry letters Severe acute respiratory syndrome (SARS) is an infectious disease with a strong potential for transmission upon close personal contact and is caused by the SARS-coronavirus (CoV). However, there are no natural or synthetic compounds currently available that can inhibit SARS-CoV. We examined the inhibitory effects of 64 purified natural compounds against the activity of SARS helicase, nsP13, and the hepatitis C virus (HCV) helicase, NS3h, by conducting fluorescence resonance energy transfer (FRET)-based double-strand (ds) DNA unwinding assay or by using a colorimetry-based ATP hydrolysis assay. While none of the compounds, examined in our study inhibited the DNA unwinding activity or ATPase activity of human HCV helicase protein, we found that myricetin and scutellarein potently inhibit the SARS-CoV helicase protein in vitro by affecting the ATPase activity, but not the unwinding activity, nsP13. In addition, we observed that myricetin and scutellarein did not exhibit cytotoxicity against normal breast epithelial MCF10A cells. Our study demonstrates for the first time that selected naturally-occurring flavonoids, including myricetin and scultellarein might serve as SARS-CoV chemical inhibitors. 10.1016/j.bmcl.2012.04.081
    Immunomodulatory and anti-SARS activities of Houttuynia cordata. Lau Kit-Man,Lee Kin-Ming,Koon Chi-Man,Cheung Crystal Sao-Fong,Lau Ching-Po,Ho Hei-Ming,Lee Mavis Yuk-Ha,Au Shannon Wing-Ngor,Cheng Christopher Hon-Ki,Lau Clara Bik-San,Tsui Stephen Kwok-Wing,Wan David Chi-Cheong,Waye Mary Miu-Yee,Wong Kam-Bo,Wong Chun-Kwok,Lam Christopher Wai-Kei,Leung Ping-Chung,Fung Kwok-Pui Journal of ethnopharmacology BACKGROUND:Severe acute respiratory syndrome (SARS) is a life-threatening form of pneumonia caused by SARS coronavirus (SARS-CoV). From late 2002 to mid 2003, it infected more than 8000 people worldwide, of which a majority of cases were found in China. Owing to the absence of definitive therapeutic Western medicines, Houttuynia cordata Thunb. (Saururaceae)(HC) was shortlisted by Chinese scientists to tackle SARS problem as it is conventionally used to treat pneumonia. AIM OF THE STUDY:The present study aimed to explore the SARS-preventing mechanisms of HC in the immunological and anti-viral aspects. RESULTS:Results showed that HC water extract could stimulate the proliferation of mouse splenic lymphocytes significantly and dose-dependently. By flow cytometry, it was revealed that HC increased the proportion of CD4(+) and CD8(+) T cells. Moreover, it caused a significant increase in the secretion of IL-2 and IL-10 by mouse splenic lymphocytes. In the anti-viral aspect, HC exhibited significant inhibitory effects on SARS-CoV 3C-like protease (3CL(pro)) and RNA-dependent RNA polymerase (RdRp). On the other hand, oral acute toxicity test demonstrated that HC was non-toxic to laboratory animals following oral administration at 16 g/kg. CONCLUSION:The results of this study provided scientific data to support the efficient and safe use of HC to combat SARS. 10.1016/j.jep.2008.03.018
    Anti-SARS coronavirus 3C-like protease effects of Isatis indigotica root and plant-derived phenolic compounds. Lin Cheng-Wen,Tsai Fuu-Jen,Tsai Chang-Hai,Lai Chien-Chen,Wan Lei,Ho Tin-Yun,Hsieh Chang-Chi,Chao Pei-Dawn Lee Antiviral research The 3C-like protease (3CLpro) of SARS-coronavirus mediates the proteolytic processing of replicase polypeptides 1a and 1ab into functional proteins, becoming an important target for the drug development. In this study, Isatis indigotica root extract, five major compounds of I. indigotica root, and seven plant-derived phenolic compounds were tested for anti-SARS-CoV 3CLpro effects using cell-free and cell-based cleavage assays. Cleavage assays with the 3CLpro demonstrated that IC50 values were in micromolar ranges for I. indigotica root extract, indigo, sinigrin, aloe emodin and hesperetin. Sinigrin (IC50: 217 microM) was more efficient in blocking the cleavage processing of the 3CLpro than indigo (IC50: 752 microM) and beta-sitosterol (IC50: 1210 microM) in the cell-based assay. Only two phenolic compounds aloe emodin and hesperetin dose-dependently inhibited cleavage activity of the 3CLpro, in which the IC50 was 366 microM for aloe emodin and 8.3 microM for hesperetin in the cell-based assay. 10.1016/j.antiviral.2005.07.002