"I've mentioned before that the cyanide constituent in kernels of
almonds, peaches, apples, cherries, and apricots is not free
hydrogen-cyanide, which is a gas; rather, the compound is amygdalin. It
is cyanide bound safely to benzaldehyde and glued shut with a couple of
sugars. (For a picture, look in the Merck Index, or visit a "
https://web.archive.org/web/20151211034946/http://www.gov.sg/moh/mohiss/poison/pgamygdl.html">
http://www.gov.sg/moh/mohiss/poison/pgamygdl.html.)
As long as the molecule remains intact, it is harmless. Strong acid
should decompose the compound to release free HCN, but I was wondering
whether stomach acid is strong enough. Turns out, it isn't. The neat
thing about these plant seeds is that the compound is packaged within
them separately from three enzymes that rapidly decompose amygdalin. So
when the seed is thoroughly crushed under moist conditions, that is when
HCN is released an effective defense against insect predators. A
biologist is studying how the enzymes are manufactured separately from
amygdalin and compartmentalized into different tissues within black
cherries
Humans have bacteria in our gut that manufacture beta-glucosidase, and
to a degree this enzyme can act to release HCN as well, but there are
other enzymes and processes that can act to transform HCN to the
harmless thiocyanate nearly as fast.
Amygdalin was given as a quack, heavily-promoted cancer treatment in
the seventies. It was variously known as Laetrile, and even passed off
as Vitamin B17, which ostensibly was a nutrient that would prevent one
from getting cancer. Now, this was purified amygdalin, without the
enzymes that would cause it to spontaneously break down, so people could
ingest gram amounts daily without tremendous side-effects. (The theory
was that cancer cells would possess more b-glucosidase than normal
cells, so cyanide would selectively kill them over normal cells; but
these ideas about the disparity or even presence of these enzymes was
shown to be simply not true. And there were rigorous, double-blind
studies that demonstrated no benefit to laetrile in the treatment of
cancer.)
Lethal or near-lethal cyanide poisoning using laetrile would usually
involve ingestion of gram amounts of the purified 'drug' along with a
source of the hydrolyzing enzymes. In one case, a man ate a lot of
bitter almonds one day. In another, a woman ate freshly crushed apricot
pits with her laetrile pills.
Most of the poisonings (except in children) were nonlethal, and
side-effects were severe and damage occasionally permament. Laetrile is
still available in Mexico, and in fact I found a place on the web where
one could apparently order some, but they have a screening process of
sorts and depending on your location may not be able to deliver.
anonymous wrote:
but then if what you say is true, if we crush the see
and eat them, the enzymes within the seeds themselves
should activate to release the cyanic acid group.
Yep. In fact, if you eat the seeds, you will be releasing some HCN. I
like eating apple seeds because the benzaldehyde that is released along
with the HCN has a pleasing almondy taste. ([name omitted] suggested it
is rather like Dr. Pepper, and I think that's so.)
Anyway, you'd want the seeds to be thoroughly crushed and moist, and would want to ingest them immediately. (Alternatively, you could find some way to harvest the gas.)
The issue here is quantity. How much would you have to cram into
your stomach to get several grams of amygdalin? And it's possible, too,
that the enzymes won't work as well once they're in the mildly acidic
environment of the stomach. About that I'm not sure. But if it simply
slowed=down hydrolysis, the poisoning would be time-released:
excruciating, prolonged, and not necessarily effective.
So yes, certainly a possible method. But it would not be my choice, though; I wouldn't even consider it."
