Several commercial fruits and vegetables contain small amounts of natural toxins. These natural toxins help protect the plants and create resistance to diseases and certain types of insects. See Secondary Metabolites in Leaves and Stems
The kernels within the pits of some stone fruits contain a natural toxin cyanogenic glycoside. These fruits include apricots, cherries, peaches, pears, plums and prunes. The flesh of the fruits itself is not toxic. Normally, the presence of cyanogenic glycoside alone is not dangerous. When kernels are chewed cyanogenic glycoside can transform into hydrogen cyanide, poisonous to humans. The lethal dose of cyanide ranges from 0.5 to 3.0 mg per kilogram of body weight. It is not recommended to eat the kernels inside the pits of stone fruits.
Ackee, akee or achee - Blinghia sapida - is a food staple in many Western Africa, Jamaican and Carribean diets. There are two main varieties, hard and soft ackees, that are available for consumption. Both canned and fresh forms of this fruit are consumed. However, unripe fruit contains natural toxins called hypoglycin that can cause serious health effects. The only part of this fruit that is edible, is the properly harvested and prepared ripe golden flesh around the shiny black seeds. The fruit is poisonous unless ripe and after being opened naturally on the tree.