HIV- 1 Reverse Transcriptase Inhibitors fromThai Medicinal Plants and Elephantopus scaber Linn.C. Wiwat* and S. Kwantrairat
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Twenty- two selected Thai medicinal plants were extracted with water and 80% ethanol method and tested for their inhibitory effects on the HIV-1 RT by in vitro radiometric method. The results showed that eleven water extracts and seven ethanol extracts exhibited the anti-HIV-1 RT activities. Potent HIV-1 RT inhibitory actions were obtained from the water extract of Jatropha curcas L. stem barks, water extract of Elephantopus scaber L. leaves and root, and ethanol extract of Securinega virosa Baill. branches and leaves. They exhibited the percentage of inhibition ratio (% IR) at 97.5, 96.9, and 88.2, respectively. Positive tannin reaction were found from the extracts of J. curcas and S. virosa, but not found from E. scaber extract. Therefore, the water extract of E. scaber was selected for further study. IC50 of leaves and root were 69.9 and 107.57 ?g/ml, respectively. The inhibitory mode of action of E. scaber was non-competitive with respect to the substrate. The water extract of E. scaber was fractionated with ammonium sulfate at 30%, 30-60%, and 60-80% saturation. The proteins were separated by sodium dodecyl sulfate acrylamide gel electrophoresis. The interesting protein band was cut-off, eluted, and assayed for the anti-HIV-1 RT activity. Its IC50 was approximately 4.29 ?g/ml. The molecular weight of the protein was calculated to be 34.5 kDa. Its isoelectric point (pI) was 4.65 and the amino acid sequence of the N-terminus was analyzed to be Alanine-Alanine-Alanine-Glutamine-Proline-Phenylalanine-Glycine-Asparagine.
Keyword:
Elephantopus scaber, Compositae, Anti-HIV-1 reverse transcriptase.
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