A therapeutic phenolic extract derived from plant biomass, and more specifically the indigenous Jamaican plant guaiacum officinale L. (Zygophyllaceae), for use in regressing or controlling HIV-1 replication in infected patients, and to help prevent sexual transmission of HIV-1, as well as the method for inhibiting HIV-1 by administering a pharmaceutically-acceptable amount of the crude extract to prevent HIV-viral replication without causing excessive damage to normal cells.