Stories: The Forbidden Grape

Long long time ago, Adam and Eve were banished to Earth after they ate the Forbidden Fruit. I honestly envy Adam and Eve because they met a talking snake, what luck is that! But here's a fruit that's absolutely forbidden. Adam and Eve would be better off fallen naked onto Earth, than eating this fruit, or all of fruits you see featured in my blog. Today, I'll tell you my story of how I uncovered the toxin of the forbidden grape. 

Cayratia mollissima (Vitaceae). The forbidden grape, or so I call it.

Behold Cayratia mollissima (Vitaceae), a species of climbing plant that's native to Malaysia. Unfortunately this plant doesn't have a common name, and so I'm calling it the forbidden grape for reasons that will become apparent. If you think Cayratia mollissima looks like a grape, you're absolutely spot-on because it belongs to the same family as grapes. I've found mine growing wild at forest fringes, so I took it home.

Specimen growing in my Poison Garden.

Despite their cute and tasty appearance, I've never thought of eating them, nor could I find any scientific literature regarding Cayratia's toxicity. But Nature gave me a clue, no animals in the vicinity, may it be birds, monkeys or squirrels eat this fruit. They simple drop to the ground and rot. That's a powerful warning sign for you, one that is called common sense! But then I came across an interesting lead from Facebook, a comment from a fellow acquaintance who told me that his friends ingested the berries of this plant, and that their lips went numb with burning sensations in the throat. He also noted that his friends only took a small bite, and they were sickened for at least two days. In short, this pinkish little grape is forbidden to humans and animals alike. Even today, I'm not sure why Cayratia's fruits appear so palatable, while nothing eats them. Perhaps it relies on specific species of birds to spread its seeds, and that animals only consume them when they age and have lower concentration of toxin? What toxin is that?

The forbidden grape juice. Anyone?

Inspired, I prepared a fruit juice out of the grapes and took them into my lab for analysis. For one, it's not terribly sour with a pH of 5, and it does not contain the usual plant toxins that are my area of expertise. My panel of tests for alkaloids, cardiac glycosides and isoflavone (rotenone type) all turned out negative. It was not until I put the fruit juice under a microscope that the toxin was revealed. And here you see them in their full glamour. Bear in the mind that the gross fruit juice looked perfectly fine and smooth to the naked eye, but under 400X – 1000X magnification, you see the 'evil' within. Those needle like substances are indeed microscopic needles, crystals of a chemical compound called calcium oxalate. Precisely, we call them raphide. If you ingest raphides, they will poke your body's cells to death. That is why raphide has such a powerful irritant (burning) effect on the mouth and the throat. While not usually fatal, many instances of injuries caused by raphides (plant oxalate crystals) are known, mostly involving ingestion or eye contact. I've dealt with this subject matter in my post on Araceae plants. What's most scary with Cayratia mollissima is that there's a lot of raphides in these berries, and if you ingest a whole bunch, your airway may swells up, you might not be able to breath and that can be fatal real quick! This is the deadly secret of the forbidden grape, which I can confirm now. 

Crystals of raphides in the fruits of Cayratia mollissima. You're looking at less than one drop of sample.

In conclusion, the lesson of my story is that you don't simply eat random berries however nice they appeal!  Some of them can indeed be your last. As I always say, it's what you don't know that will get you. So next time, you'll hear my story about what I didn't know that almost ended my life.