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Fagopyrin is a naturally occurring substance in the buckwheat plant.
Its chemical structure contains a naphthodianthrone skeleton similar that of to hypericin.
References
Brockmann, Hans; Weber, Erhard; Sander, Elsbeth (1950). "Fagopyrin, ein photodynamischer Farbstoff aus Buchweizen (Fagopyrum esculentum)". Die Naturwissenschaften. 37 (2): 43. doi:10.1007/BF00645366.