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.)
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!
This post is part of a series on chlorophyll! Check out our previous post about how to easily extract chlorophyll from spinach and use it as a paint. Using a black light, you can also observe the beautiful red/pink fluorescence of chlorophyll, too! This post is how to further purify chlorophyll through a technique called liquid-liquid extraction or solvent extraction. Don’t be intimidated by the name! You are totally capable. This can be done with common, inexpensive things from your kitchen and it’s a great way to learn about solubility, polarity, and the way chemists approach problems. Younger kids will not grasp the concepts of polarity and solubility, but they can track the location of chlorophyll throughout the experiment (through color) to begin to learn about these concepts.
This tutorial is written for the parent or educator. There is a section called “A quick science lesson” to help give you a background to present this to a class or your kids. You can go as little or as much into the details as you want, so this project can be done with a large age range of kids.
This post is part of a series on chlorophyll, a molecule both plants and humans owe their lives to! This specific activity is a fun, easy, and art-inspired introduction to chlorophyll for children 2 years old and up where we will make paint from the chlorophyll in spinach leaves, then observe the fluorescence of the chlorophyll artwork with a black light! If you can paint, and not eat the paint, this activity is for you!