Julian was a pioneer in the industrial large-scale chemical synthesis of the human hormones progesterone and testosterone from plant sterols such as stigmasterol and sitosterol. His work laid the foundation for the steroid drug industry's production of cortisone, other corticosteroids, and birth control pills.
Julian later started his own company to synthesize steroid intermediates from the wild Mexican yam. His work helped greatly reduce the cost of steroid intermediates to large multinational pharmaceutical companies, helping to significantly expand the use of several important drugs.
Julian was one of the first African Americans to receive a doctorate in chemistry. He was the first African-American chemist inducted into the National Academy of Sciences.