Celery seed extract contains an important compound known as 3-n-butylphthalide, or 3nB for short, that is also responsible for the characteristic flavor and odor of celery. 3nB was discovered as the active component of celery in response to investigations by researchers seeking to explain some of the medicinal effects of celery, including the lowering of blood pressure and the relief of arthritis.

3nB first drew significant scientific attention when researchers at the University of Chicago Medical Center identified it as the factor in celery responsible for the blood pressure lowering effect of celery. The research was prompted by one of the researcher's father, who after eating a quarter-pound of celery every day for one week observed his blood pressure dropped from 158 over 96 to a normal reading of 118 over 82. Subsequent animal studies found that a very small amount of 3nB lowered blood pressure by 12 to 14 percent and also lowered cholesterol by about 7 percent.