Antiviral Research 64 (2004) 69–76 Antiviral activity of diterpenes isolated from the Brazilian marine alga Dictyota menstrualis against human immunodeficiency virus type 1 (HIV-1) H.S. Pereira a,∗ , L.R. Le˜ ao-Ferreira a , N. Moussatch´ e c , V.L. Teixeira b , D.N.Cavalcanti b , L.J. Costa d , R. Diaz d , I.C.P.P. Frugulhetti a a Departamento de Biologia Celular e Molecular/Programa de Neuroimunologia, Instituto de Biologia, Universidade Federal Fluminense, Niter´ oi, RJ, Brazil b Departamento de Biologia Marinha, Instituto de Biologia, Universidade Federal Fluminense, Niter´ oi, RJ, Brazil c Instituto de Biof´ ısica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil d UNIFESP-EPM, Universidade Federal de S˜ ao Paulo, S˜ ao Paulo, SP, Brazil Received 15 October 2003; accepted 9 June 2004 Abstract The antiviral effect of the CH 2 Cl 2 /MeOH-soluble fraction from the alga Dictyota menstrualis on HIV-1 replication was evaluated in vitro. The antiretroviral activity was attributed to two diterpenes: (6R)-6-hydroxydichotoma-3,14-diene-1,17-dial, named Da-1, and (6R)-6-acetoxi- dichotoma-3,14-diene-1,17-dial, named AcDa-1. Da-1 or AcDa-1 were added to the culture medium of HIV-1-infected PM-1 cells at different times post-infection or during virus adsorption/penetration. The results indicated that the compounds affected an early step of the virus replicative cycle. Virus binding and entry into the host cells were evaluated in the presence of each diterpene, but no inhibitory effect was observed. To evaluate provirus DNA synthesis/integration into the host genome, the viral protease coding sequence was amplified from total cellular DNA. Proviral DNA was not detected in infected cells incubated with the diterpenes. To investigate the effect of the diterpenes on the reverse transcription of the viral genomic RNA, the recombinant HIV-1 reverse transcriptase (RT) was assayed in vitro in the presence of each diterpene. Da-1 and AcDa-1 inhibited the RNA-dependent DNA-polymerase activity of HIV-1 RT in a dose-dependent manner. Taken together, our results demonstrate that both diterpenes inhibit HIV-1 RT and consequently virus replication. © 2004 Elsevier B.V. All rights reserved. Keywords: Dictyota menstrualis; HIV-1; Diterpenes; Antivirals; HIV-1 reverse transcriptase; HIV-1 RT 1. Introduction The acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV), has become a serious threat to global public health in the last decades. The first generation drugs, such as AZT, ddC, ddI and D4T (Huang et al., 1992; Sergheraert et al., 1993) have been extensively used in the clinic, but the rapid development ∗ Corresponding author. Current address: Instituto de Biologia–Bloco A- 2 andar-sala 121, Lab. de Virologia Molecular, Universidade Federal do Rio de Janeiro, Cidade Universit´ aria, RJ, 21941-570, Brasil. Tel.: +55-21-2629-2268; fax: +55-21-2629-2268. E-mail address: helena@biologia.ufrj.br (H.S. Pereira). of virus resistance to these nucleoside analogs represents a significant obstacle to anti-HIV therapy (Biesert et al., 1991; St. Clair et al., 1991; Najera et al., 1994; Menendez-Arias, 2002). Furthermore, these drugs have limited or transient ben- efits due to their adverse side effects (Tozser, 2001). In the light of these considerations, new classes of drugs that can supplement, or partially replace, existing drugs are definitely needed for a suitable long-term use. The discovery and characterization of new anti-HIV agents with novel structures or mechanism(s) of action and low toxicity to the host remain priority (Barreca et al., 2003). Specific inhibitors of several steps of the viral replicative cycle, including viral attachment and entry, reverse tran- scription, provirus DNA integration and RNA packaging, 0166-3542/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.antiviral.2004.06.006