The HIV-1 reverse transcriptase (RT) is an asymmetric heterodimer enzyme that, during the viral replication, carries out RNA- and DNA-dependent DNA polymerization, strand displacement synthesis, strand transfer, and that degrades the RNA strand in RNA:DNA hybrids. The latter activity is termed Ribonuclease H (RNase H) [1]. The two catalytic sites are inter-dependent and, in fact, mutations in the polymerase domain affect the RNase H activity, and vice versa. Both RT activities are essential for viral replication, and therefore are considered excellent targets for drug development. While all RT inhibitors approved for therapy target the DNA polymerase activity, there is the pressing need of new RT inhibitors possibly targeting the RNase H function and also active on RTs resistant to the known non-nucleoside inhibitors (NNRTI). Within a project to find new natural agents inhibiting the replication of HIV-1 virus from Sardinian plants [2], the dried aerial parts of Hypericum hircinum L. (Clusiaceae) was soxhlet extracted to obtain three extracts (acetone, acetone:ethanol and ethanol). All three extracts have been assayed on the two enzymatic associated activities, the RNA-dependent DNA polymerase (RDDP) and the RNase H activities and they were shown inhibit both functions at a low micromolar range. Subsequently, the acetone:ethanol extract was fractionated and a high, medium and low polarity fractions were obtained which were active in inhibiting both RT wt activities. When tested on the K103N and Y181C RTs, the acetone:ethanol extract and all fractions, inhibited both RDDP and RNase H functions. These fractions will be further fractionated to isolate the active principles. The analysis of NMR profile of all active fractions, indicates that, together with known hypericin and hyperforin, other aromatoid and unsaturated compounds are present, that are possibly responsible of the biological activity. We are now determining the structures of these unknown compounds. References [1] E. Tramontano Mini-Rev. Med. Chem. 2006, 6, 727; [2] C. Bicchi, P. Rubiolo, M. Ballero, C. Sanna, M. Matteodo, F. Esposito, L. Zinzula, E.Tramontano, Planta Medica, 2009, 75, 1331-1335.
Hypericum hircinum L. come nuovo duplice inibitore delle funzioni di DNA polimerasi e di ribonucleasi H associate alla trascrittasi inversa (RT) di HIV-1 efficace anche su mutanti resistenti ad analoghi non-nucleosidici della RT
BALLERO, MAURO;
2010-01-01
Abstract
The HIV-1 reverse transcriptase (RT) is an asymmetric heterodimer enzyme that, during the viral replication, carries out RNA- and DNA-dependent DNA polymerization, strand displacement synthesis, strand transfer, and that degrades the RNA strand in RNA:DNA hybrids. The latter activity is termed Ribonuclease H (RNase H) [1]. The two catalytic sites are inter-dependent and, in fact, mutations in the polymerase domain affect the RNase H activity, and vice versa. Both RT activities are essential for viral replication, and therefore are considered excellent targets for drug development. While all RT inhibitors approved for therapy target the DNA polymerase activity, there is the pressing need of new RT inhibitors possibly targeting the RNase H function and also active on RTs resistant to the known non-nucleoside inhibitors (NNRTI). Within a project to find new natural agents inhibiting the replication of HIV-1 virus from Sardinian plants [2], the dried aerial parts of Hypericum hircinum L. (Clusiaceae) was soxhlet extracted to obtain three extracts (acetone, acetone:ethanol and ethanol). All three extracts have been assayed on the two enzymatic associated activities, the RNA-dependent DNA polymerase (RDDP) and the RNase H activities and they were shown inhibit both functions at a low micromolar range. Subsequently, the acetone:ethanol extract was fractionated and a high, medium and low polarity fractions were obtained which were active in inhibiting both RT wt activities. When tested on the K103N and Y181C RTs, the acetone:ethanol extract and all fractions, inhibited both RDDP and RNase H functions. These fractions will be further fractionated to isolate the active principles. The analysis of NMR profile of all active fractions, indicates that, together with known hypericin and hyperforin, other aromatoid and unsaturated compounds are present, that are possibly responsible of the biological activity. We are now determining the structures of these unknown compounds. References [1] E. Tramontano Mini-Rev. Med. Chem. 2006, 6, 727; [2] C. Bicchi, P. Rubiolo, M. Ballero, C. Sanna, M. Matteodo, F. Esposito, L. Zinzula, E.Tramontano, Planta Medica, 2009, 75, 1331-1335.
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