Star Fruit, Caramboxin, and Neurotoxins

Sliced star fruit and the chemical structure of caramboxin.

I’ll preface this with “I still ate it,” but star fruit contains a deadly neurotoxin called caramboxin. 😱*clutches pearls*

Luckily, if you have normally functioning kidneys, caramboxin gets flushed out of your system and does absolutely no harm. In fact, my friend from Taiwan says they eat star fruit daily, and they’re all doing fine so, again, totally fine for most people to eat. However, if you have kidney disease, the toxin does not get removed and it can go on to interfere with your neurons.

Neurons pass messages around your body. Molecules called neurotransmitters are released from one neuron and passed to another in order to relay that message. The neurotransmitters fit snuggly into proteins called receptors on the next nerve. This is kind of like a lock and key. Once the receptor is “unlocked” by the neurotransmitter “key,” the nerve passes the message to another nerve, and so on. Caramboxin can “unlock” and stimulate some of these nerves by snuggling up to the receptor. Normally, turning on neurons is a very controlled process, so when caramboxin gets in there, it messes things up. Symptoms include mental confusion, vomiting, and seizures, and in some cases, coma and death.

Interestingly, an early symptom of caramboxin poisoning is intractable hiccups, so if that happens to you after eating star fruit, call the doctor and ask about some kidney labs!

This was my first star fruit ever! I don’t think I let it ripen enough, but it tasted like a wet tart apple. Should I wait longer next time based on that green color? No hiccups yet!😉

Source: Garcia-Cairasco et al 2013

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


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.)

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!


Chlorophyll biosynthesis: spotlight on protochlorophyllide reduction

Snippet of Science: Newly Discovered Elements and Uncle Goose Periodic Table Blocks


Who else has these adorable periodic table blocks from Uncle Goose? We’ve been given two sets, one for each kid, and today we discovered something was different between the first set from 4 years ago (bottom) and the new set (top). Four new elements had been named! I had no clue! (And bravo to Uncle Goose for updating them!)

The “U” words on the bottom row were official placeholders for these yet-to-named elements. They are Latin for the individual numbers in the atomic number (118 is ununoctium for 1-1-8). The atomic number is the number of protons in the nucleus. If the number of protons is changed, you have a different element; whereas, if the number of neutrons is changed (the other subatomic particle in the nucleus), you have a different isotope.

Fun thing about all these super heavy elements is that the scientists who got to name them MADE them. We knew their existence was possible, but you just don’t find these on Earth. The nucleus is so heavy and unstable that they decay to another element almost immediately. Elements after atomic number 104 decay within minutes or less, and elements after Uranium (92) are generally not found on Earth (with a few exceptions).

Why do scientist make these huge elements if they don’t last long enough to do anything with them? Elements on the periodic table are arranged in a certain way because electrons arrange themselves into predictable groups/patterns called orbitals. Arrangement of electrons in orbitals dictates an element’s properties. Elements in the same vertical period on the table have similar reactivities. Through some (I imagine) pretty complicated math, one can calculate the orbital filling order and energies and begin to predict characteristics of these elements that haven’t been made yet. Being able to make these short-lived elements is the first step to exploring their chemistry. And supposedly, things get pretty freaky around 164.

Get your set here (affiliate link will take you to Amazon). We’ve used our blocks quite a bit. We haven’t done any science-y things with them, just building and working on sounding out letters, but they are a cute novelty to have around!

Morss, L., et al. (2006) Dordrecht: Springer ISBN 978-4020-3555-5

Karol, et al. Pure Appl. Chem. 88 (2016) 139.

Karol, et al. Pure Appl. Chem. 155 (2016)

Snippets of Science: Radioactive Fiestaware

Snippets of Science are short tales of fascinating science for a quick read.

Would you like some uranium with your tea?

From 1936-1972, the makers of Fiestaware (and also many other ceramics from that time) used uranium oxide in the glaze, making the dining sets radioactive.
They initially used natural uranium which contains a mix of uranium-238 and uranium-235, but during World War II, the US government seized uranium supplies around the country to collect the fissile U-235 for use in atomic weapons. After the war, the ceramics were glazed with depleted uranium oxide, which has a smaller percentage of U-235. Other uses of depleted uranium are armor piercing bullets and golf clubs because it is so dense, hard, and cheap. (Don’t let the “depleted” term fool you, they are still radioactive. It just refers to the amount of U-235). You probably won’t get sick using this dinnerware, but there’s also lead in it that could leach out (along with the uranium) so I’m not gonna be using our set.

“But if I buy some at a thrift shop, will they still be radioactive all these year later?!” you also ask?! Fear not, the half life of uranium-238 is 4.5 billion years, so they are essentially just as radioactive as the day they were forged.

If you’ve been dreaming of teaching your kids about radioactivity, check out Nuclear Physics for Babies for their first taste of this wild subject. 😉


Oak Ridge:


Landa, E. and Councell, T. Leaching of Uranium from Glass and Ceramic Foodware and Decorative Items. Health Physics 63 (3): 343-348; 1992.

Piesch, E, Burgkhardt, B, and Acton, R. Dose Rate Measurements in the Beta-Photon Radiation Field from UO2 Pellets and Glazed Ceramics Containing Uranium. Radiation Protection Dosimetry 14 (2): 109-112; 1986.