A review of in vivo studies of porphyrins and unexpected fluorescences. An interpretation of the results.

Clinical applications of porphyrins lead research biologists to characterize these compounds according to their fluorescence. These measurements revealed unexpected fluorescence spectra in addition to those of the injected porphyrins. The general characteristics of the spectra of porphyrins are reviewed. The technique permitting studies on animals in a waking state and the advantages of this method are shown. The studies in this field are reviewed and spectra reproduced. Among the observed fluorescences, those which cannot be attributed to injected porphyrins are divided into two groups. The first group, above 580 nm, seems to result from molecular associations (polymers or micelles of injected porphyrins). The second group, from 560-575 nm, seems to belong to a natural compound. Some spectroscopic observations and some medical reports lead us to identify it as an unusual natural porphyrin and perhaps as metalloporphyrin. Some authors have mentioned a Zn porphyrin. Finally, the importance of continuing the study of this natural porphyrin is discussed.