Yellow indicator in tomatoes?

[Repeating Rifle]

This morning, I spent a fair amount of time clearing out excess growth of tomatoes in my little greenhouse. When I washed my hands, they turned very yellow. That had happened before but I did not know what the cause was. I thought that I had contacted nitrates from my nutrient solution and that it had somehow caused the yellow color the same way that exposure to nitrate does. I presumed that the alkaline soap was the proximate cause for turning a leuco compound yellow.

This time, after washing away the color, I went back out and handled the tomato plants some more. Hand washing brought out the yellow color again.

Is this typical of tomatoes? What is the substance involved?

Bill

[Uncle Al]

Sounds like lycopene from the tomatoes or another carotenoid from the foliage. Mild oxidation will then remove the color (benzoyl peroxide acne cream; Oxy-Clean, dilute bleach), as will electrophiles (skunk juice). Why don't you wear gloves?

[Repeating Rifle]

It could come from the foliage. That was all I handled for my second test.

It is not a skin problem yet. It washes off easily. Nevertheless, considering that only a small amount could have been carried on my hands, it has all the earmarks of a strongly absorbing indicator dye.

I was just curious as to what might be happening. It might be the basis for a good kitchen science experiment in these days of limited access to equipment and chemicals.

Bill

[Martin Brown]

Not necessary unless you are sensitised. The neutral/acid form is colourless and the alkaline soap form is very water soluble and an interesting shade of yellow not dissimilar to fluorosene in colour but without the obvious UV glow. Vegetable acid/base indicator dye.

The smell is also distinctive and I suspect it is a quite bit more toxic than the fruit - solanaceae are not to be messed with. You can eat tomatoes and potatoes but the rest of the plant is a really bad idea. And related species include some extremely toxic plants.

Regards, Martin Brown

[Repeating Rifle]

I have some more experimental data.

Certainly, my hands do have that tomato plant like smell after handling.

This last time, I did more foliage removal and staking. I washed my hands and got the same yellow color from using soap. I again got a sink full of yellow water. This time, I took a flake of potassium hydroxide and added to the sink. The color of the sink water became much deeper. So, does that describe solanin well enough to make solanin the likely candidate?

Bill

[guest]

Don't know what it is, but this always happens from handling tomato foliage. It's not just you, or your soap.

[Maryc]

The tomato plants are trying to protect themselves by the smell and th color on your hands. You will have the yellow substance every time yo handle the plants because it does come from the stems and leaves. I you are sensitive you can feel the stuff getting on you

-- Maryc

[MMu]

"Repeating Rifle" schrieb im Newsbeitrag news:BF0FB770.16A6% [e-mail]...

I'll bet on lycopene as well.

[muha]

And will I bet on picric acid if you grew them in abadoned ammunition dump.

[John Savage]

Nature frequently provides its own "antidote". Squash a rotten (i.e., waste overripe) tomato and lather your hands thoroughly with the mess. The yellow stain comes off your hands then without the need for much soap when you rinse.

I seem to recall nature providing an antidote for mulberry stain, and for stinging nettles, too. I think you squash some of the red fruit (i.e., the unripe ones) to remove from your hands the stain that the black mulberries cause.

[Repeating Rifle]

How can picric acid be acid when you add alkali to it? :=)

Bill

[<HLS]

I lived in Scotland for a period of time, and the locals quickly advised me about stinging nettles...Crushed dock takes the pain away quickly, and it seems that dock is almost found in the vicinity of nettles. Intelligent design? If it works, use it.

Never got around to eating any steamed nettles, but heard they are quite okay.

[~patches~]

Nettle tea is supposed to be a good pesticide in the garden. I haven't tried it myself so can't attest to its efficacy.

[Martin Brown]

No. Both plants happen to like heavy nitrogen rich soils.

Cornish Yarg cheese is wrapped in nettle leaves. Very good it is too!

Martin Brown

[Repeating Rifle]

For those of us not raised in the UK, please tell us a bit more about dock. I have had the opportunity to meet what I think is stinging nettle. Are Us nettles pretty much like European ones?

Speaking of intelligent design, I have been in places with soft pine needles or the like where you lie down to recover if hit with a rock that was nearby.

Bill