Snippets of Science: Glowing Pumpkin Seeds (pepitas) and Protochlorophyllide

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Pepitas, the inside of pumpkin seeds, fluoresce under UV light! It is a stunning coral orange color. This photo doesn’t quite do it justice. The compound causing the fluorescence is protochlorophillide, a precursor to chlorophyll. (Chlorophyll is also fluorescent under UV light, but it glows a deep red.)

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Chlorophyll biosynthesis

The seeds themselves have a slight glow if you shine a black light on them but in my picture at the top, they are crushed with isopropanol (rubbing alcohol), which solubilizes the pigment.  We found this fluorescence by mistake actually. Several things in your pantry fluoresce under UV light (like honey, canola oil, tonic water, and peanut butter) and my daughter and I were scanning our shelves for other surprises. Sure enough we saw a faint glow on some of the hulled pumpkin seeds. I did a little research online and found out about protochlorophyllide. We also saw a similar glow from brown rice that was slightly green on the edge and I wonder if it’s the same molecule!

Sources:

Chlorophyll biosynthesis: spotlight on protochlorophyllide reduction

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