Aspects of positron emission tomography radiochemistry as relevant for food chemistry

Positron emission tomography (PET) is a medical imaging technique using compounds labelled with short-lived positron emitting radioisotopes to obtain functional information of physiological, biochemical and pharmacological processes in vivo. The need to understand the potential link between the ingestion of individual dietary agents and the effect of health promotion or health risk requires the exact metabolic characterization of food ingredients in vivo. This exciting but rather new research field of PET would provide new insights and perspectives on food chemistry by assessing quantitative information on pharmocokinetics and pharmacodynamics of food ingredients and dietary agents. To fully exploit PET technology in food chemistry appropriately radiolabelled compounds as relevant for food sciences are needed. The most widely used short-lived positron emitters are C-11 (t(1/2) = 20.4 min) and F-18 (t(1/2) = 109.8 min). Longer-lived radioisotopes are available by using Br-76 (t(1/2) = 16.2 h) and I-121 (t(1/2) = 4.12 d). The present review article tries to discuss some aspects for the radiolabelling of food ingredients and dietary agents either by means of isotopic labelling with C-11 or via prosthetic group labelling approaches using the positron emitting halogens F-18, Br-76 and I-124.