Rutin (C27H30O163H2O) is a glucoside derived from flavonol. It was first isolated from tobacco at the Eastern Regional Research Laboratory, United States Department of Agriculture.9 It was found to be present, however, in a number of other plants and to be especially plentiful in buckwheat, as first discovered by E. Schmuck.10 Previously, Szent-Györgi and his co-workers11 had extracted from lemon a substance belonging to the flavonol group for which they gave the formula C28 H36-38O17. They demonstrated that the administration of this substance would decrease the permeability of the capillaries for proteins
as well as for water. It also prevented hemorrhages in certain cases of purpura. They called it citrin, or vitamin P (P stands for permeability). Because of the close chemical relationship of the two substances, citrin and rutin, the latter was tested