Epinephrine is a colorless crystalline compound which is optically active; that is it causes a plane of polarized light to rotate, indicating centres of asymmetry in the molecule. It is comparatively stable in acids solution, but in the presence of alkali, it combines readily with oxygen. The synthesis of epinephrine was first achieved by F. Stolz in 1904. Although norepinephrine was shown by U.S von Euler in 1946 to be secreted at the sympathetic nerve endings and to serve as sympathetic nerve transmitter it was not until1949 that S. Bergstrom isolated the hormone in the form of a crystalline base from the adrenals of cattle, where it occurs together with epinephrine in the approximate proportions of 1:4.

In humans the adrenal medulla 2.4-4 mg/g of both these hormones together; 10-30% of this amount is norepinephrine. In other species, for example cat, toad, and pigeon, the amounts of epinephrine and norepinephrine in the adrenal glands are nearly equal. Small may be found in nerve extracts, but there is no evidence that it is produced by the adrenergic or sympathetic nerve fibres