Besides water-based infusions, alcohol-based digestion plays an important part of the Health Guardian’s medicine cabinet. Many herbs require an alcohol-based digestion because their bio-active chemicals aren’t soluble in water, it’s not because minors are looking for a party. Digestion is a form of maceration that involves application of a gentle heat to the substance being extracted. It's used in cases which a moderately elevated temperature will help increase the solvent powers on the menstruum. Digestion is alcohol based. When combining infusions, it's rarely necessary to combine water-based infusions with alcohol-based digestion processes, but it can and has been done.
A problem that faces all that faces all formulators of medicines is the possibility that incompatibilities will be encountered. These fall into three broad categories. A therapeutic incompatibility· is defined as an undesirable pharmacological interaction between two or more ingredients that may potentiate the therapeutic effects of the ingredients, reduce the effectiveness of one or more of the ingredients, or cause toxicity in the patient. Physical incompatibility refers to a physical or chemical interaction between two or more ingredients that leads to a visibly recognizable change. The latter may occur in the form of a precipitate, haze, or color change. Chemical incompatibility is classified as a reaction in which an undesirable change occurs, but is not visible. Since there is no visible evidence of deterioration, recognizing this type of incompatibility requires some skill.
Physical incompatibilities can often be altered or avoided. A common problem is the generation of insoluble precipitates. For example, alcohol extracts precipitate dissolved constituents when mixed with water. Such problems can often be avoided by manipulating the solvent or by adding a suspending or protective agent. The specific remedies for such problems will vary according to the substances involved.
Change the order of mixing. Combining resin-rich tinctures and water commonly causes the resin to precipitate. One possible solution is to add the tincture slowly to cold water when mixing. However, with very resin rich tinctures, such as tincture of myrrh, it is impossible to avoid some precipitation of resin out of solution.
Change the total volume of the mixture. By simply adding more solvent, whether water or ethanol, the increased volume will provide more bulk for material to start in solution, in effect diluting the problematic constituent. The percentage of water or ethanol may be crucial, but the final outcome depends on the chemistry of the constituents in the extract.
Alter the solvents or add protective agents. Water dissolves gums, mucilage, and starch, but these are not miscible in alcohol. Alcohol dissolves most constituents. Often, the presence of alkaloids, glycosides, volatile oils, resins, or balsams in an herb necessitates the use of a higher percentage of alcohol in the extract to ensure that the constituents are extracted and will not precipitate when water is added. Glycerin can be added to replace part of the water component to decrease the chance of precipitation.
Make an emulsification or suspension with gums or syrup. For example, with acacia, do not add strong alcohol directly or the solution will "congeal." Instead, make a dilute mucilage and add alcohol slowly. This method may be used for resinous tinctures. With tragacanth, add tincture or liquid extract directly to powdered gum. Shake to mix. Water should be added in a proportion of 1 part of gum to 20 parts of water.
Chemical incompatibilities are more difficult to overcome, but rarely are an issue in phototherapy. Chemical interactions can produce precipitation of insoluble compounds. Alkaloids form salts with metallic ions, and thus, in theory, many potential incompatibilities are possible. However, all of these can be overcome by using a solution made up of 15% to 30% alcohol.