The (5Z)-5-Pentacosenoic and 5-Pentacosynoic Acids Inhibit the HIV-1 Reverse Transcriptase.

The natural fatty acids (5Z)-5-pentacosenoic and (9Z)-9-pentacosenoic acids were synthesized for the first time in eight steps starting from either 4-bromo-1-butanol or 8-bromo-1-butanol and in 20-58% overall yields, while the novel fatty acids 5-pentacosynoic and 9-pentacosynoic acids were also synthesized in six steps and in 34-43% overall yields. The ∆(5) acids displayed the best IC50's (24-38 µM) against the HIV-1 reverse transcriptase (RT) enzyme, comparable to nervonic acid (IC50 = 12 µM). The ∆(9) acids were not as effective towards HIV-RT with the (9Z)-9-pentacosenoic acid displaying an IC50 = 54 µM and the 9-pentacosynoic acid not inhibiting the enzyme at all. Fatty acid chain length and position of the unsaturation was important for the observed inhibition. None of the synthesized fatty acids were toxic (IC50 > 500 µM) towards peripheral blood mononuclear cells. Molecular modeling studies indicated the structural determinants underlying the biological activity of the most potent compounds. These results provide new insights into the structural requirements that must be present in fatty acids so as to enhance their inhibitory potential towards HIV-RT.