Highly substituted terphenyls as inhibitors of parasite cGMP-dependent protein kinase activity.

Parasite cGMP-dependent protein kinase (PKG) is one of the validated biochemical targets for the treatment of coccidiosis. We screened our library of natural product extracts for inhibitors of parasite PKG for the discovery of anticoccidial leads. Terferol (1) and three new terphenyls (2, 3, and 4) were isolated using bioassay-guided fractionation of the microbial extract of a Phoma sp. by a high-throughput two-step isolation method employing LH-20 and reversed-phase HPLC. These compounds inhibited parasite PKG with IC(50) values in the range 0.9-5.8 microM.