A glycerite is a fluid extract of an herb or other medicinal substance made with glycerin.
According to King's American Dispensatory (1898)a glycerite is:
Glycerita.—Glycerites. By this class of preparations is generally understood solutions of medicinal substances in glycerin, although in certain instances the various Pharmacopoeias deviate to an extent. The term Glycerita as here applied to fluid glycerines, or solutions of agents in glycerin, is preferable to the ordinary names, "glyceroles," "glycerates," or "glycemates," etc., and includes all fluid preparations of the kind referred to, whether for internal administration or local application. Many solutions of glycerin or glycerin and water, are apt upon standing to develop microscopic cryptogams, unless a certain proportion of alcohol is added to the solutions. On this account, it is better to prepare many members of this class of solutions in small quantity at a time, and only as they are wanted .
Glycerites are frequently used as a substitute for alcohol in tinctures, as a solvent that will create a therapeutic herbal extraction. Glycerine is less extractive and is approximately 30% less able to be absorbed by the body due to processing in the liver. Fluid extract manufacturers often extract herbs in hot water before adding glycerin to make glycerites to increase extraction.
Glycerin will not extract the same constituents from plants that alcohol will. From "Herbal Preparations and Natural Therapies" by Debra St. Claire:
glycerin will extract the following - sugars, enzymes (dilute), glucosides, bitter compounds, saponins (dilute), and tanninsabsolute alcohol will extract the following - alkaloids (some), glycosides, volatile oils, waxes, resins, fats, some tannins, balsam, sugars, and vitamins.