Detection of furocoumarins in plants and plant products with an ultrasensitive biological photoassay employing a DNA-repair-deficient bacterium.

The application of an ultrasensitive photobiological assay which detects photosensitizing furocoumarins with sensitivities as high as 1 × 10(-11) g is discussed in relation to these molecules as phytoalexins. Examples of the utilization of this technique, verified by both HPLC and TLC, are the analyses of healthy and diseased celery and carrots, dry seeds, plant extracts and oils, and whole plants and leaves. The usefulness of this method in following the metabolic detoxification of furocoumarins is also illustrated. The extreme sensitivity of the test has permitted the detection, for the first time, of both 5-methoxypsoralen and 8-methoxypsoralen in fresh carrot roots.