According to King's American Dispensatory (1898), 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.
Glycerites may consist of either vegetable source glycerin, animal source glycerin or a combination of the two. In the case of liquid herbal products (a segment of the dietary supplements industry), the general rule is to utilize vegetable glycerin only, while nutraceuticals (another segment of the dietary supplements industry) might use a combination of both vegetable and animal source derived glycerin.
A modern glycerite recently developed by a European research facility associated with aquaculture and fish bait preparations now includes botanical, fish and animal components (valued for its medicinal or therapeutic properties, flavor, and/or scent.) Such glycerites have a low glycemic load and are reputed to have antifreeze properties to -46.5 (°C) with an estimated shelf-life in excess of 20 years.
Some modern liquid botanical manufacturing endeavors utilize so called 'dynamic", truly alcohol-free (e.g. no alcohol (i.e. ethanol) ever used) glycerite manufacturing technologies resulting in high extractive potential. Such glycerites are a distinct and differentiated category of products, possessing unique properties and qualities.
It is now a well established fact that 'finished' glycerites that contain an adequate concentration of glycerin, approaching 70%, do not allow for microbial growth, and in fact are excellent microbial suppressants, even after opening. These are considered "self-preserving" formulations. This has been verified by a FDA Registered, cGMP compliant, Kosher certified commercial endeavor that produces glycerites listing a 4 year expiration date on product labels for their product - with no refrigeration required after opening (they have 'original' samples now over 30 years old, opened every 5 years for analysis, with preservability, stability, purity and intrinsic quality factors still intact).
Glycerol, when utilized in a 'passive' non-critical fashion, such as with tincturing, is generally considered a weaker solvent than either water or ethanol. It is nearly as polar as water, and a larger molecule than either water or ethanol. The same intermolecular forces that cause glycerol to be relatively thick, viscous, and dense at low temperatures, decrease its overall ability to passively extract and dissolve molecules from medicinal raw materials. When utilized in a traditional passive tincture method glycerites tend to result in much weaker than simple ethanol extracts. In addition, glycerol extracts specific kinds and amounts of chemical compounds. This behavior in a non-critical/non-dynamic state is primarily determined by glycerol's polarity, hydrogen bonding characteristics, and intermolecular forces, all of which determine its rate of mass transfer.
As detailed From "Herbal Preparations and Natural Therapies" by Debra St. Claire:
- glycerin will extract the following - sugars, enzymes (dilute), glucosides, bitter compounds, saponins (dilute), and tannins
- absolute alcohol will extract the following - alkaloids (some), glycosides, volatile oils, waxes, resins, fats, some tannins, balsam, sugars, and vitamins.
Unlike alcohol, with its di-atomic state, that has quick access to the liver, glycerine is approximately 30% slower absorbed by the digestive tract and is utilized through a secondary pathway in the liver (known as the 'gluconeogenic' pathway) resulting in a lower glycemic load on the body than happens with alcohol. Fluid extract manufacturers often extract herbs in alcohol and then remove the alcohol (called 'alcohol-removed') or hot water before adding glycerin to make glycerites to increase extraction potential.  However, there are those who consider it counter-productive to extract with alcohol, then remove alcohol, then add glycerin to 'increase extraction potential,' as the intrinsic denaturing and inert rendering effects of alcohol on the alcohol extracted mixture cannot be reversed, leaving post-alcohol glycerin extracts to extract already alcohol denatured and inert rendered components. From a clinical as well as nutritional perspective, an extracts components containing denatured and inert rendered compounds is not desired.
However, when glycerin is utilized in a dynamic contemporary non-tincturing based innovative processing methodology it has been shown to not only extract a wide range of compounds, it is widely accepted, both in literature and innovative applications, to extract many constituents and compounds previously thought not able to do and to extract those constituents and compounds at high concentrations and potency. This includes most alkaloids, glycosides, volatile oils, waxes, resins, gums, balsam, sugars (especially as non-denatured linked and cross-linked polysaccharides), vitamins, and minerals, all with none of the denaturing and inert rendering effects alcohol possesses.
From Glycerin versus Alcohol, Concerning Herbal Liquid Extracts, a White Paper by L. Carl Robinson, a Clinical & Formulary Herbalist:
- Another perquisite for the [xyz] process is that it must contain a high glycerin to water ratio (which varies from herb to herb) that is intended to be an intrinsic part of the proprietary [xyz] processing technology itself, as well as impart a distinctive stabilizing and ‘absolute’ preserving quality...
To preserve the biological viability and synergy of a botanical's extracted constituents glycerin is preferred for extraction of all aromatic-based compounds and polysaccharides, as it does not denature or render inert these highly complex molecule structures, which though these compounds may retain their aroma/taste quality, any denaturing (as alcohol intrinsically does) will substantially reduce or nullify the therapeutic quality of aromatic-based compounds. The biological viability preserving and synergy sparing effects of glycerin also apply to proteins, certain vitamins, enzymes and other 'co-factor' constituents that are glycerin extracted from botanicals.
Whereas alcohol is intrinsically a denaturing and inert rendering agent to many of a botanical's extracted constituent and compounds, glycerin possesses no such denaturing and inert rendering effects on a botanical's extracted constituents and compounds. From both clinical and manufacturing perspectives, this is possibly the most important defining differentiator between alcohol-based made tinctures versus 'true' alcohol-free glycerin-based made Glycerites, that includes: 'actual' levels or degrees of efficacy relative to actual concentrations (i.e. percentages) of constituents and/or constituent group(s) present in a finished tincture and/or Glycerite, now given what has previously been unaddressed concerning the denaturing/inert-rendering weighted factor for alcohol-based tinctures (a Clinical consideration); and the QA/QC related physical properties inherent in and chemically intrinsic to a finished tincture and/or Glycerite as regards inverting, REDOX, precipitation, scaling, novel constituent complexing, etc. (a Manufacturing consideration).
In the herbal products industry, 'Glycerite' is often implied to be Alcohol-Free. This is not always the case. For clarification and 'truth in labeling' within the botanical products industry and to quell rising consumer confusion, an emerging standard has been proposed that defines that:
Only If alcohol is never used at any time in the making of a liquid botanical preparation, or added thereafter, and glycerin is used as the primary extractive solvent, then it is deemed an 'Alcohol-Free' product (glycerite), whereas, if alcohol is used in making a liquid botanical preparation (whether with other solvents, such as glycerin, honey, etc.). at any time, and then the alcohol removed (i.e. post-process), then it is actually not 'Alcohol-Free' per se,' but should instead be designated as 'Alcohol-Removed.'
More ethically inclined liquid botanical products manufacturers who utilize alcohol in making their products are making this distinction in their literature and on product labels (some even not using the term 'Alcohol-Free' anywhere on their product labels to allay confusion) to better conform with this standard. (Consumers are encouraged to determine whether a product is 'true' alcohol-free or merely alcohol-removed before purchasing products that are listed as 'alcohol-free.')
Alcohol-Free (as opposed to alcohol-removed) glycerite products, in which alcohol is never used or added at any time, are highly sought for by those desiring and requiring that no alcohol be used in making products or added thereafter. Muslims (practicers of Islam) throughout the world represent the largest population requiring an 'Alcohol-Free' standard. Halal (def: 'Lawful' or 'Legal'), the Islamic Dietary Law, lists alcohol as one of the 'explicitly forbidden substances' (called Haram) in which anything made with and/or at any time containing alcohol is forbidden. USP Grade vegetable glycerin is acceptable for Halal certifying and in some instances a Halal standard may (but not always) accept Kosher certified USP Grade vegetable glycerin as meeting Halal standards (i.e. to be Halal 'compliant'). Where the issue of Halal Alcohol-Free versus Haram Alcohol-Removed glycerites is concerned, the Islamic community has taken the stance that products listed as alcohol-free does not always mean "Alcohol-Free" since many products listed as alcohol-free may in fact have been made using alcohol as an ingredient after which the alcohol is removed, which would still make any such products Haram by Islamic Dietary Law. The Islamic community is therefore encouraged to ascertain whether a botanical glycerite is actually Halal 'Alcohol-Free' or is Haram 'Alcohol-Removed' (with glycerin thereafter added).
- http://www.henriettesherbal.com/eclectic/kings/glycerita.html Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.,King's American Dispensatory 1898.
- Textbook of Medical Physiology, 6th Edition, by Arthur C. Guyton, M.D. © 1982 by W. B. Saunders Company.
- Biochemistry, by Lubert Stryer © 1981 by W.H. Freeman & Company, San Francisco.
- Walter S. Long. The Composition of Commercial Fruit Extracts Transactions of the Kansas Academy of Science (1903-), Vol. 28, Jan. 14, 1916 - Jan. 13, 1917 (Jan. 14, 1916 - Jan. 13, 1917), pp. 157-161 doi:10.2307/3624347
- David Winston www.herbaltherapeutics.com
- Does Alcohol Belong In Herbal Tinctures?
- Glycerin and the Glycols – Production, Properties and Analysis, by J. W. Lawrie, Ph.D., © 1928 American Chemical Society
- Glycerin – Its Industrial and Commercial Applications, by Leffingwell, Ph.D. & Lesser, B.S., © 1945 Chemical Publishing Co., Inc.
- The Manufacture of Glycerin, 2nd Edition, by G. Martin, D.Sc., Ph.D. & H.J. Strausz, M.A., © 1956 The Technical Press Ltd.
- LoR. Caarl (L. Carl) Robinson - Glycerin vs Alcohol, White Paper, http://www.cedarbear.com/CBNTechSpeakLinks/Glycerin_versus_Alcohol.pdf
- Gattefosse’s Aromatherapy, by Rene’-Maurice Gattefosse’ © 1993 (English Translation) by The C.W. Daniel Company, Ltd.