Two prenylated benzophenones, guttiferones O (1) and P (2), were isolated from the stem bark of the Papua New Guinean plant Garcina solomonensis. The structures of these compounds and their relative configurations were determined by spectroscopic methods. Both compounds inhibited the phosphorylation of the synthetic biotinylated peptide substrate KKLNRTLSVA by the serine/threonine protein kinase MAPKAPK-2 with IC(50) values of 22.0 microM.