Limettin and furocoumarins in beverages containing citrus juices or extracts

Phototoxic and photo-genotoxic furocoumarins occur, e.g., in citrus species, parsnip, parsley, celery, and figs. They exhibit phototoxic and photo-genotoxic properties in combination with UV radiation, while less is known about the phototoxicity of the coumarin derivative limettin mainly found in limes and lemons. Risk assessment of dietary furocoumarins is based on a threshold approach and on estimates of 1.2-1.45 mg for the average daily exposure for adults via the diet in several countries. In these estimates, the major contribution to overall daily exposure has been attributed to citrus-flavored non-alcoholic beverages, in spite of a lack of analytical data for those products. Therefore, we analyzed a number of furocoumarins in a variety of citrus-containing beverages and included limettin in the pattern of analyzed constituents. Our findings provide strong evidence that grapefruit juice and not citrus-flavored non-alcoholic beverages is the major source of furocoumarin exposure in a Western diet. Based on these findings it can be assumed that the average dietary exposure to furocoumarins is about 3-fold lower than previously estimated, i.e. in the range of 548 and 2237 microg/day for the average and high consumer, respectively. The coumarin derivative limettin was mainly found in lime products.