The blood–brain barrier permeability of ginkgolide B was examined using positron emission tomography (PET) probes of a 18F-incorporated ginkgolide B ([18F]-2) and a 11C-incorporated methylbenzyl-substituted ginkgolide B ([11C]-3). PET studies in monkeys showed low uptake of [18F]-2 into the brain, but small amounts of [11C]-3 were accumulated in the parenchyma. Furthermore, when cyclosporine A was preadministered to rats, the accumulation of [18F]-2 in the rat brain did not significantly change, however, the accumulation of [11C]-3 was five times higher than that in the control rat. These results provide effective approaches for investigating the drug potential of ginkgolides.

The synthesis and in vivo evaluation of 11C -labeled uric acid ([11C]1), a potential imaging agent for the diagnosis of urate-related life-style diseases, was performed using positron emission tomography (PET) image analysis. First, the synthesis of [11C]1 was achieved by reacting 5,6-diaminouracil (2) with 11C-labeled phosgene ([11C]COCl2). The radiochemical yield of [11C]1 was 37 ± 7% (decay-corrected based on [11C]COCl2) with specific radioactivities of 96–152 GBq/μmol at the end of synthesis (n = 6). The average time of radiosynthesis from the end of bombardment, including formulation, was about 30 min with >98% radiochemical purity. Second, the synthetic approach to [11C]1 was optimized using 5,6-diaminouracil sulfate (3) with [11C]COCl2 in the presence of 1,8-bis(dimethylamino)naphthalene. [11C]1 was synthesized in 36 ± 6% radiochemical yield, 89–142 GBq/μmol of specific radioactivities, and 98% radiochemical purity by this method (n = 5). This allowed the synthesis of [11C]1 to be carried out repeatedly and the radiochemical yield, specific radioactivities, average time of synthesis, and radiochemical purity of [11C]1 were similar to those obtained using 2. PET studies in rats showed large differences in the accumulation of radioligand in the limbs under normal and hyperuricemic conditions. Thus, an efficient and convenient automated synthesis of [11C]1 has been developed, and preliminary PET evaluation of [11C]1 confirmed the increased accumulation of radioactivity in the limbs of a rat model of hyperuricemia.