Originally reported to inhibit PKC isoforms, with selectivity for PKCδ (Ki values are 30, 42, 40, 3-6, 100, and 100 μM for α, β, γ, δ, ε, λ respectively). Also reported to inhibit CAM kinase III. However, recently shown to inhibit a wide range of protein kinases, and most potently to inhibit PRAK and MAPKAP-K2 (IC50 values are 1.9 and 5 μM respectively). Also shown to act as a direct mitochondrial uncoupler.