pheophytin
noun
pheo·phy·tin
variants:
or British phaeophytin \ ˌfē-ə-ˈfīt-ᵊn 
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Medical Definition of pheophytin
: a bluish black waxy pigment that can be formed from chlorophyll by replacement of the magnesium with two hydrogen atoms by treatment with a weak acid (as oxalic acid)