Anti-HIV-1 protease- and HIV-1 integrase activities of Thai medicinal plants known as Hua-Khao-Yen

Ethanolic- and water extracts from five species of Thai medicinal plants known as Hua-Khao-Yen were tested for their inhibitory effects against HIV-1 protease (HIV-PR) and HIV-1 integrase (HIV-1 IN). The result revealed that the ethanolic (EtOH) extract of Smilax corbularia exhibited anti-HIV-1 IN activity with an IC50 value of 1.9 μg/ml, followed by the water extract of Dioscorea birmanica (IC50 = 4.5 μg/ml), the EtOH extract of Dioscorea birmanica (IC50 = 4.7 μg/ml), the water extract of Smilax corbularia (IC50 = 5.4 μg/ml), the EtOH extract of Smilax glabra (IC50 = 6.7 μg/ml) and the water extract of Smilax glabra (IC50 = 8.5 μg/ml). The extracts of Pygmaeopremna herbacea and Dioscorea membranacea were apparently inactive (IC50 > 100 μg/ml). Interestingly, only the EtOH extract of Dioscorea membranacea showed appreciable activity (IC50 = 48 μg/ml) against HIV-1 PR, while the other extracts possessed mild activity. This result strongly supported the basis for the use of Smilax corbularia and Dioscorea membranacea for AIDS treatment by Thai traditional doctors.