By the late 1940s, Combs and Norris using chick growth as their bioassay procedure were fairly close to the isolation of vitamin B12.
In 1926, Vitamin B12 was discovered by two physician George Richard Minot and William Perry Murphy became inspired by George Whipple’s studies that showed daily beef liver a pound could indeed control the deadly anemia.
Minot and Murphy of Harvard showed that feeding the large amounts of raw liver, that is a quarter to half a pound per day, restored the normal level of red blood cells in cases of pernicious anemia.
Following this discovery and for the next twenty years, liver was the main source of this unknown curing factor, which has prepared, as time passed, in more and more concentrated form.
In 1929, William B. Castle of Harvard hypothesized that the liver was the organ of the body contained a factor essential for the cure of pernicious anemia.
Its chemical structure as elucidated in 1955, through the collaboration of chemists from the University of Cambridge, led by Alexander Todd, with X-ray crystallographers from the University of Oxford, led by Dorothy Hodgkin and a team from Glaxo led by Lester Smith.
However, Vitamin B12 only finally synthesize by Robert Burns Woodward in 1971.
Discovery of Vitamin B12