In vitro HIV type 1 reverse transcriptase inhibitory activities of Thai medicinal plants and Canna indica L. rhizomes

Water and 80% ethanol extracts of 20 Thai medicinal plants used to treat AIDS were tested for their HIV type 1 reverse transcriptase inhibitory activity. The water extracts of Ipomoea carnea subsp. fistulosa (aerial parts), Vitex glabrata (branch), Vitex trifolia (aerial part), Vitex negundo (aerial part), Canna indica (rhizome), and Justicia gendarussa (aerial part) showed HIV-1 RT inhibition ratio (% IR) higher than 90% at a 200 μg/ml concentration. The water extract of Canna indica rhizomes (IC50 22.56 μg/ml) was selected for further study, i.e. for its HIV-1 RT inhibition activity and the purification and characterization of the active proteins. Proteins in water extract were fractionated by ammonium sulfate precipitation and separated by sodium dodecyl sulfate acrylamide gel electrophoresis (SDS-PAGE), yielding two proteins, Cip31 (31 kDa) and Cip14 (14 kDa) with IC50 of 17.41 and 19.25 μg/ml and isoelectric point (pI) of 3.5 and 6.35, respectively. Both proteins showed significant HIV-1 RT inhibition.