Antiretroviral activity of two polyisoprenylated acylphloroglucinols, 7-epi-nemorosone and plukenetione A, isolated from Caribbean propolis.
Int J Clin Pharmacol Ther. 2010 Oct ;48(10):670-7. PMID: 20875373
Institute for Molecular Oncology and Experimental Therapeutics, Marienhospital Herne, Ruhr University of Bochum, Herne, Germany. firstname.lastname@example.org
OBJECTIVES: Polyisoprenylated acylphloroglucinols have recently emerged as antitumoral agents. This study aims at elucidating the antiretroviral activity of two such compounds which were isolated from Caribbean propolis: 7-epi-nemorosone and plukenetione A, the structure of which is based on an adamantane moiety. Plukenetione A is for the first time shown to have antiretroviral activity.
MATERIAL AND METHODS: The isolation of both small molecules was carried out using RP-HPLC. Their antiretroviral activity was studied based on lentiviral particles produced in HEK293T cells from the SIV-based vector VLDBH; their cytotoxicity was monitored by MTT proliferation assay. The antiviral activity of 7-epi-nemorosone was studied in CEMx174-SEAP infected with the HIV-1-strain pNL4.3wt. Reverse transcriptase inhibition was determined by a standard two-step RT-PCR using MMLV RT.
RESULTS: 7-epi-nemorosone and plukenetione A were found to be potent antilentiviral agents in the employed system, inhibiting viral infection at concentrations below 1µM/2 µM, respectively. Whereas 7-epi-nemorosone was not able to inhibit the reverse transcriptase in vitro (IC50>25µM), plukenetione A effectively inhibited its enzymatic activity at an IC50 of 1.75 µM.
CONCLUSIONS: Despite 7-epi-nemorosone and plukenetione A sharing some structural core elements, the mechanism of action involved in their antiretroviral activity seems to be different. We propose that 7-epi-nemorosone inhibits the viral replication by interrupting the Akt/PKB signaling cascade, as was demonstrated previously in various cell lines. Since plukenetione A effectively inhibits the enzymatic activity of MMLV reverse transcriptase at concentrations that show antilentiviral activity, we suggest that this small molecule acts by interfering with the enzyme's catalytic site.