Siddiqui was born in Subeha near Lucknow,India on 19 October 1897. He received his early education from Lucknow,India. He graduated in Philosophy and Persian language, from M.A.O College in 1919. He received Doctor of Philosophy under the supervision of Prof Julius Von Bram in 1927.
In 1924, he married his German classmate, Ethel Wilhelmina Schneeman. He named the newly discovered chemical compound as Ajmaline, after his mentor Hakim Ajmal Khan who was one of the illustrious practitioners of Unani system of medicine in South Asia.
Siddiqui was the first scientist to bring the anthelmintic, antifungal, antibacterial, and antiviral constituents of the Neem tree to the attention of natural products chemists.
He had more than 50 chemical compounds patented in his name in addition to those discovered as a result of his joint research with other colleagues and students.
In addition to his scientific talents, Siddiqui was also an avid painter, a poet, and a great connoisseur of music. His paintings were exhibited in Germany, India, and Pakistan. Siddiqui migrated to Pakistan in 1951, four years after the emergence of Pakistan in 1947.
He was appointed as Director of the Pakistan Department of Research that was reformulated in 1953 as Pakistan Council of Scientific and Industrial Research (PCSIR).
Also in 1958, the Government of Pakistan awarded him with Tamgha-e- Pakistan.In 1960, he became the President of Pak-Indian Ocean Science Association.
In 1962, he was awarded the Sitara-e-Imtiaz for distinguished merit in the fields of science and medicine. In that year, the President of Pakistan awarded him the Pride of Performance Medal for the respectable completion of his service.
His tireless efforts for the promotion of science and technology earned him Hilal-e-Imtiaz by the Government of Pakistan in 1980.In 1983, he played a major role in the establishment of the Third World Academy of Sciences and became its Founding Fellow.
Siddiqui died on April 14,1994 due to cardiac arrest after a brief illness in Karachi. He was buried in the Karachi University Graveyard.
He was a leading Pakistani scientist in Natural products Chemistry.
He is credited for pioneering the isolation of unique chemical compounds
from the Neem ,Rauwolfia and various other floras.