Photosensitivity from chlorophyll-derived pigments

The photosensitisation of young albino rats fed diets containing specially prepared lucerne leaf protein concentrates (LPC) or purified pigments has been investigated. Signs of intense photosensitivity including death occurred after a few hours of illumination in animals fed a diet containing 20% LPC prepared by holding lucerne juice at 70 °C for 55 min. However a sample prepared by briefly heating juice to 90 °C was not active. Mixed chlorophyllides and purified pheophorbide a were strongly photosensitising whereas pheophorbide b was much less active and pheophytin a was inactive. Where strong photosensitisation occurred pigments derived from chlorophyll could be extracted from blood plasma and livers. Examination of stomach and intestine contents showed that dietary chlorophyllides and chlorophylls were converted to pheophorbides and pheophytins in the gut. The photosensitising potential of a diet can be related principally to the combined content of pheophorbide a and chlorophyllide a.