Quercetin

History   Quercetin   Spirulina   Baicalein   Quercetin and Vitamin C   CK-II Inhibitors   CK-II Abstracts   Winning Game   Dosage Strategies

The following article is the first article on quercetin that I published on my Yahoo site Nat_anti_hiv.

Quercetin appears to inhibit all of the following viral enzymes!
Integrase
Protease
Reverse Transciptase
Vpr

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Articles

Casein kinase II (CK-II)-mediated stimulation of HIV-1 reverse transcriptase activity and characterization of selective inhibitors in vitro.

The physiological significance of the casein kinase II (CK-II)-mediated phosphorylation of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) on its three enzymatic activities [RNA-dependent DNA polymerase (RDDP), DNA-dependent DNA polymerase (DDDP) and ribonuclease H (RNase H)] was investigated in vitro. It was found that (i) the purified recombinant RT (rRT) functioned as an effective phosphate acceptor for CK-II; (ii) the RDDP, DDDP and RNase H activity of rRT was stimulated about 2.8-, 4.1- and 3.9-fold, respectively, after full phosphorylation by CK-II; and (iii) this stimulation was selectively inhibited by potent CK-II inhibitors, such as neocarzinostatin-chromophore (NCS-chrom) and three polyphenol-containing anti-oxidant compounds [quercetin, epigallocatechin gallate (EGCG) and 8-chloro-3',4',5,7-tetrahydroxyisoflavone (8C-3',4',5,7-THI)]. These results suggest that (i) CK-II may be responsible for activation of RT in HIV-1-infected cells; and (ii) the selective inhibition of CK-II-mediated activation of HIV-1 RT by potent CK-II inhibitors may
be involved in the mechanism of their anti-HIV-1 effects at the cellular level.

Inhibition of Vpr-induced cell cycle abnormality by quercetin: a novel strategy for searching
compounds targeting Vpr.
Shimura M, Zhou Y, Asada Y, Yoshikawa T, Hatake K, Takaku F, Ishizaka Y
Department of Intractable Diseases, International Medical Center of Japan, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655, Japan.
Vpr, an accessory gene product of HIV-1 which induces cell cycle abnormality leading to the increased HIV replication, is supposed to be a possible target for anti-AIDS drugs. We recently established a cell line (MIT-23) in which Vpr-induced cell cycle perturbation could be manipulated by a tetracycline promoter.
Here, we screened anti-Vpr activity in 27 kinds of herb drugs using MIT-23 cells. One of the extracts prepared from Houttuyniae herba showed an inhibitory activity. Quercetin (QCT), a compound of this crude drug, efficiently inhibited Vpr function without affecting its expression. Furthermore, data suggested that Vpr-induced transcription from HIV-LTR was considerably abrogated by QCT. These data indicate that QCT, a flavonoid previously reported to inhibit HIV replication, also targets Vpr, implicating that MIT-23 cell provides a novel strategy for screening compounds possessing anti-Vpr activity which would be in turn
utilized for clarifying the mechanism of Vpr function.

Biol Pharm Bull 1998 Dec;21(12):1282-5
Biochemical characterization of recombinant HIV-1 reverse transcriptase (rRT) as a
glycyrrhizin-binding protein and the CK-II-mediated stimulation of rRT activity potently
inhibited by glycyrrhetinic acid derivative.
Harada S, Maekawa T, Haneda E, Morikawa Y, Nagata N, Ohtsuki K
Laboratory of Genetical Biochemistry, Kitasato University School of Allied Health Sciences, Sagamihara, Japan.
By means of successive Mono Q and glycyrrhizin (GL)-affinity column chromatography (HPLC), recombinant HIV-1 RT (rRT) was purified to apparent homogeneity from the Superdex 200 pg fraction of the crude protein extract of E. coli BL21 transfected with pET 21a(+)/HIV-1 PR-RT. It was found that (i) rRT functioned as an effective phosphate acceptor for recombinant human casein kinase II (rhCK-II) in vitro; (ii) this phosphorylation was inhibited by anti-HIV-1 substances [a glycyrrhetinic acid derivative (oGA) and quercetin] and a high dose (100 microM) of GL; (iii) RNA-dependent DNA polymerase (RDDP) activity was stimulated about 2.5-fold after full phosphorylation of rRT by rhCK-II; and (iv) oGA as well as NCS-chromophore effectively prevented the CK-II-mediated stimulation of RDDP activity. These results suggest that the anti-HIV-1 effect of oGA may be involved in the selective inhibition of the CK-II-mediated stimulation of HIV-1 RT at the cellular level.

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J Med Chem 1998 Oct 8;41(21):3948-60
Geometrically and conformationally restrained cinnamoyl compounds as inhibitors of HIV-1
integrase: synthesis, biological evaluation, and molecular modeling.
Artico M, Di Santo R, Costi R, Novellino E, Greco G, Massa S, Tramontano E, Marongiu ME, De Montis A, La Colla P
Istituto Pasteur - Fondazione Cenci Bolognetti, Dipartimento di Studi Farmaceutici, Universita di Roma "La Sapienza", Piazzale A. Moro 5, I-00185 Roma, Italy.
Various cinnammoyl-based structures were synthesized and tested in enzyme assays as inhibitors of the HIV-1 integrase (IN). The majority of compounds were designed as geometrically or conformationally constrained analogues of caffeic acid phenethyl ester (CAPE) and were characterized by a syn disposition of the carbonyl group with respect to the vinylic double bond. Since the cinnamoyl moiety present in flavones such as quercetin (inactive on HIV-1-infected cells) is frozen in an anti arrangement, it was hoped that fixing our compounds in a syn disposition could favor anti-HIV-1 activity in cell-based assays. Geometrical and conformational properties of the designed compounds were taken into account through analysis of X-ray structures available from the Cambridge Structural Database. The polyhydroxylated analogues were prepared by reacting 3,4-bis(tetrahydropyran-2-yloxy)benzaldehyde with various compounds having active methylene groups such as 2-propanone, cyclopentanone, cyclohexanone, 1,3-diacetylbenzene, 2, 4-dihydroxyacetophenone, 2,3-dihydro-1-indanone,
2,3-dihydro-1, 3-indandione, and others. While active against both 3'-processing and strand-transfer reactions, the new compounds, curcumin included, failed to inhibit the HIV-1 multiplication in acutely infected MT-4 cells. Nevertheless, they specifically inhibited the enzymatic reactions associated with IN, being totally inactive against other viral (HIV-1 reverse transcriptase) and cellular (RNA polymerase II) nucleic acid-processing enzymes. On the other hand, title compounds were endowed with remarkable antiproliferative activity, whose potency correlated neither with the presence of catechols (possible source of reactive quinones) nor with inhibition of topoisomerases. The SARs developed for our compounds led to novel findings concerning the molecular determinants of IN inhibitory activity within the class of cinnamoyl-based structures. We hypothesize that these compounds bind to IN featuring the cinnamoyl residue C=C-C=O in a syn disposition, differently from flavone derivatives characterized by an anti arrangement about the same fragment. Certain inhibitors, lacking one of the two
pharmacophoric catechol hydroxyls, retain moderate potency thanks to nonpharmacophoric fragments (i.e., a m-methoxy group in curcumin) which favorably interact with an "accessory" region of IN. This region is supposed to be located adjacent to the binding site accommodating the pharmacophoric dihydroxycinnamoyl moiety. Disruption of coplanarity in the inhibitor structure abolishes activity owing to poor shape complementarity with the target or an exceedingly high strain energy of the coplanar conformation.

Biochemical characterization of HIV-1 Rev as a potent activator of casein kinase II in vitro.
Ohtsuki K, Maekawa T, Harada S, Karino A, Morikawa Y, Ito M
Laboratory of Genetical Biochemistry, Kitasato University School of Allied Health Sciences, Sagamihara, Japan. [email protected]
The stimulatory effects of several DNA-binding basic proteins (histone and protamine) and HIV-1 Rev with arginine (Arg)-rich clusters on the activity of casein kinase II (CK-II) were investigated in vitro. It was found that recombinant Rev (rRev) and the synthetic oligo-fragments corresponding to the amino acid sequences of its Arg-rich cluster stimulate CK-II activity in a dose-dependent manner. The activated CK-II phosphorylates several cellular and viral proteins in HIV-1 infected human MOLT-4 cells, and also phosphorylates HIV-1 structural proteins, including recombinant reverse transcriptase (rRT). These phosphorylations are selectively inhibited by CK-II inhibitors, such as quercetin, oGA (a glycyrrhetinic acid derivative) and NCS-chrom (an enediyne containing antibiotic). The data presented here suggest that HIV-1 Rev acts as an effective potent activator of CK-II, which may be a cellular mediator promoting HIV-1 replication in virus-infected cells.

A new flavonol glycoside gallate ester from Acer okamotoanum and its inhibitory activity
against human immunodeficiency virus-1 (HIV-1) integrase.
Kim HJ, Woo ER, Shin CG, Park H
Division of Applied Science, Korea Institute of Science & Technology, Seoul, Korea.
Bioassay-directed chromatographic fractionation of an ethyl acetate extract of the leaves of Acer okamotoanum using HIV-1 integrase afforded a new acylated flavonol glycoside, quercetin 3-O-(2",6"-O-digalloyl)-beta-D-galactopyranoside (1), together with six known flavonol glycosides and three known phenolic compounds. The structure of the new compound was determined by spectroscopic methods. The most active compounds were quercetin 3-O-(2"-galloyl)-alpha-L-arabinopyranoside (6) and 1, which exhibited IC50 values of 18.1 +/- 1.3 and 24.2 +/- 6.6 micrograms/mL, respectively, against HIV-1 integrase.

Biochem Biophys Res Commun 1996 Dec 4;229(1):73-9
The anti-HIV activity and mechanisms of action of pure compounds isolated from Rosa damascena.
Mahmood N, Piacente S, Pizza C, Burke A, Khan AI, Hay AJ
MRC Collaborative Centre, London, United Kingdom.
Water and methanol extracts of Rosa damascena exhibited moderate anti-HIV activity. The anti-viral activities of 9 compounds isolated from the methanol extract were compared. The tetrahydroxyflavanone (kaempferol, 1), was effective in reducing the maturation of infectious progeny virus apparently due to selective inhibition of the viral protease. On the other hand the pentahydroxyflavone (quercetin, 2) and two 3-substituted derivatives of kaempferol appeared to inhibit HIV-infection by preventing binding of gp120 to CD4. 2-Phenylethanol-O-(6-O-galloyl)-beta-D-glucopyranoside 8 interacted irreversibly with gp120 and neutralized virus infectivity. The differences in the modes of action of 1 and 8 can account for the apparent synergy of their anti-viral activities.

PMID: 8954085, UI: 97112405
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Proc Natl Acad Sci U S A 1993 Mar 15;90(6):2399-403
Inhibitors of human immunodeficiency virus integrase.    
Fesen MR, Kohn KW, Leteurtre F, Pommier Y

In an effort to further extend the number of targets for development of antiretroviral agents, we have used an in vitro integrase assay to investigate a variety of chemicals, including topoisomerase inhibitors, antimalarial agents, DNA binders, naphthoquinones, the flavone quercetin, and caffeic acid phenethyl ester as potential human immunodeficiency virus type 1 integrase inhibitors. Our results show that although several topoisomerase inhibitors--including doxorubicin, mitoxantrone, ellipticines, and quercetin--are potent integrase inhibitors, other topoisomerase inhibitors--such as amsacrine, etoposide, teniposide, and camptothecin--are inactive. Other intercalators, such as chloroquine and the bifunctional intercalator ditercalinium, are also active. However, DNA binding does not correlate closely with integrase inhibition. The intercalator 9-aminoacridine and the polyamine DNA minor-groove binders spermine, spermidine, and distamycin have no effect, whereas the non-DNA binders primaquine, 5,8-dihydroxy-1,4-naphthoquinone, and caffeic acid phenethyl ester inhibit the integrase.
Caffeic acid phenethyl ester was the only compound that inhibited the integration step to a substantially greater degree than the initial cleavage step of the enzyme. A model of 5,8-dihydroxy-1,4-naphthoquinone interaction with the zinc finger region of the retroviral integrase protein is proposed.

J Biochem (Tokyo) 1990 Oct;108(4):609-13
Mechanisms of inhibition of various cellular DNA and RNA polymerases by several flavonoids.
Ono K, Nakane H
Laboratory of Viral Oncology, Aichi Cancer Center Research Institute.
Four flavonoids (i.e., baicalein, quercetin, quercetagetin, and myricetin), known to be inhibitors of HIV-reverse transcriptase, have been shown to be more or less inhibitory to the activities of various cellular DNA and RNA polymerases. The degree of the inhibition varied depending on the combination of the flavonoid and the enzyme species: baicalein was moderately inhibitory to DNA polymerase gamma and E. coli DNA polymerase I; quercetin was strongly inhibitory to DNA polymerase beta and E. coli RNA polymerase and moderately inhibitory to DNA polymerase I; quercetagetin was a potent inhibitor for all of DNA polymerases alpha, beta, gamma, and I and RNA polymerase; myricetin was a strong inhibitor of DNA polymerases alpha and I and RNA polymerase. However, terminal deoxynucleotidyltransferase was virtually insensitive to inhibition by these flavonoids. The inhibition by the flavonoids was due to competition with the template.primer in the case of the DNA polymerases, whereas the inhibition was due to competition with the triphosphate substrate (GTP) in the case of RNA polymerase. The Ki values of these flavonoid inhibitors for DNA and RNA polymerases was determined.

Eur J Biochem 1990 Jul 5;190(3):469-76
Differential inhibitory effects of various flavonoids on the activities of reverse transcriptase and cellular DNA and RNA polymerases.
Ono K, Nakane H, Fukushima M, Chermann JC, Barre-Sinoussi F
Laboratory of Viral Oncology, Aichi Cancer Center Research Institute, Nagoya, Japan.
Four flavonoids, 5,6,7-trihydroxyflavone (baicalein), 3,3',4',5,7-pentahydroxyflavone (quercetin), 3,3',4',5,6,7-hexahydroxyflavone (quercetagetin) and 3,3',4',5,5',7-hexahydroxyflavone (myricetin), were found to be potent inhibitors of reverse transcriptases from Rauscher murine leukemia virus (RLV) and human immunodeficiency virus (HIV). Under the reaction conditions employed, any one of these flavonoids almost completely inhibited the activity of RLV reverse transcriptase at a concentration of 1 microgram/ml. HIV reverse transcriptase was inhibited by 100%, 100%, 90% and 70% in the presence of 2 micrograms/ml quercetin, myricetin, quercetagetin and baicalein, respectively. The mode of inhibition of these flavonoids was competitive (RLV reverse transcriptase) or partially competitive (HIV reverse transcriptase) with respect to the template.primer complex, (rA)n.(dT), and noncompetitive with respect to the triphosphate substrate, dTTP. The Ki values for RLV reverse transcriptase were found to be 0.37 microM and 0.08 microM for baicalein and quercetin, respectively and those for HIV reverse transcriptase were 2.52 microM, 0.52 microM, 0.46 microM and 0.08 microM for baicalein, quercetin, quercetagetin and myricetin, respectively.
Comparative studies with other flavonoids (hydroxyflavones, dihydroxyflavones and polyhydroxyflavones and flavanones) carried out to clarify the structure/activity relationships, revealed that the presence of both the unsaturated double bond between positions 2 and 3 of the flavonoid pyrone ring, and the three hydroxyl groups introduced on positions 5, 6 and 7, (i.e. baicalein) were a prerequisite for the inhibition of reverse transcriptase activity. Removal of the 6-hydroxyl group of baicalein required the introduction of three additional hydroxyl groups at positions 3, 3' and 4' (quercetin), to afford a compound still capable of inhibiting the reverse transcriptase activity. Quercetagetin which contains the structures of both baicalein and quercetin, and myricetin which has the structure of quercetin with an additional hydroxyl group on the 5' position also proved strong inhibitors of reverse transcriptase activity. The inhibition by baicalein of reverse transcriptase is highly specific, whereas quercetin and quercetagetin were also strong inhibitors of DNA polymerase beta and DNA polymerase I, respectively.
Myricetin was also a potent inhibitor of both DNA polymerase alpha and DNA polymerase I.