The seeds, like those of other Annona species, are crushed and used as insecticide. Paul Allen, in his Poisonous and Injurious Plants of Panama, (see Bibliography), implies personal knowledge of a case of blindness resulting from "the juice of the crushed seeds coming in contact with the eyes. " The seeds contain several alkaloids: caffeine, ( + )-reticuline, (-)-anonaine, liriodenine, and lanuginosine.
Human ingestion of 0.15 g of the dark-yellow resin isolated from the seeds produces dilated pupils, intense photophobia, vomiting, nausea, dryness of the mouth, burning in the throat, flatulence, and other symptoms resembling the effects of atropine. A dose of 0.5 g, injected into a medium-sized dog, caused profuse vomiting.
Wilson Popenoe wrote that hogs feed on the fallen fruits in southern Ecuador where there are many cherimoya trees and few people. One wonders whether the hogs swallow the hard seeds whole and avoid injury.
The cherimoya fruit skin and its crushed seeds are toxic; ingestion of either is discouraged except by those well familiar with their medicinal qualities. The seeds have been used for insecticides while a dilution of the skin can induce paralysis.
The dried flowers are used as flavoring in snuff in Jamaica while rural Mexicans sometimes use a dilution of the seeds to induce vomiting or defecation (Morton). The pulverized seeds are also used to kill lice and treat parasitic skin problems. The skin can also be brewed into a tea for treatment of pneumonia.
One of the common internet myths that I wanted to take an opportunity to dispel was the idea that a Cherimoya can kill you if you eat the skin and seeds. According to Mr. Ruskey, the skin is tannic but not poisonous. The seeds of the Cherimoya do contain alkaloids, similar to a number of other plant seeds, and while you could do a fair amount of processing to collect the alkaloids, accidentally swallowing one seed won't harm you. Lucky for my readers, I recently swallowed a Cherimoya seed and I am still here typing this post (or am I....?) so rest assured that Mr. Ruskey is indeed correct in his analysis.
Dear Laurie ♥
many seeds are toxic to humans if they are chewed up, if however they are just swallowed down with the fruit then they will tend to pass undigested through the body and just pass out ready to be fertilized!
I would not think there would be any problem, many seeds are designed to 'slip down' with the fruit and hence be distributed and fertilized.
The toxins may be there to discourage the seed being chewed and destroyed.