Necatorin is a highly mutagenic chemical compound with the molecular formula C15H8N2O3.

It is found in some mushrooms including Lactarius necator (ugly milk-cap), from which it was first isolated and characterized.

[3] Crude extracts of L. necator are also highly mutagenic in a bacterial test system, and this effect it attributed to necatorin.

[4] Necatorin is present in L. necator at concentrations of 3 to 20 mg/kg, and blanching the mushroom can reduce it to about 25% of its original amount.

[5] In boiling water, the chemical compound is stable except under acidic conditions (pH = 5).