Inhibitory effect of Tibetan medicinal plants on viral polymerases

For the purpose of developrhent of novel anti－virus agents from ethnical drugs, we examined 76 traditional Tibetan medicines for inhibitory effect on two viral enzymes, reverse transcriptase （RTase） of HIV and RNA dependent RNA polymerase （RdRp） of HCV. Although 28 methanol extracts inhibited RTase more than 70 90 at a concentration of 100 μg/ml, only 3 samples, T42（藏青果, Terminatia chebula RETZ. ）, T46（檳椰, Areca catechu L. ）and T61（紅檳榔）, were found still inhibitory after eliminating the effect of tannins by addition of BSA in the enzyme reaction mixture. ln the case of the RdRp, 7 extracts with IC50 values of less than 10 μg/ml contained less than 20 ％ tannins. The extract of Rhodiola sacra, whose IC50 for RTase was 25. 9 μg/ml, was subject to phytochemical investigation. Out of 8 compounds isolated from the extract, daucosterol was found effective for RTase.