DNA Polymerase β Specific Inhibitors, a Loliolide Derivative and Pubinernoid A, Isolated from the Brown Algae Laminaria sp.

Two mammalian DNA polymerase β (pol β) inhibitors have been isolated independently from the brown algae Laminaria sp. These molecules were determined by spectroscopic analyses to be a loliolide derivative, 2,3a-dihydroxy- 4,4,6,7a-tetramethyl-3-oxo-octahydro-1-benzofuran-6-yl acetate (compound 1), and pubinernoid A (compound 2). Compounds 1 and 2 selectively inhibited the activity of rat pol β, and 50% inhibition was observed at concentrations of 18.4 and 38.8 µ M, respectively. By contrast, these compounds did not influence the activity of 10 other mammalian pols [pols α, γ, δ, ε, η, ι, κ, λ, μ and terminal deoxynucleotidyl transferase (TdT)] tested, and showed no effect even on the activity of fish pol δ, plant pols α and λ, prokaryotic pols, or any other DNA or RNA metabolic enzymes tested. Inhibition of rat pol β activity by compounds 1 and 2 was competitive with both DNA template-primer and nucleotide substrate. The structure- activity relationship of these compounds is discussed.