There are 5 types of solvents that are used traditionally in herbal medicine: water, vinegar, ethyl alcohol, wine, oil. Water is remarkable solvency extract for diverse substances. Vinegar is generally classed among the derivatives of alcohol because it is produced by the oxidation of alcoholic liquids. Wine could be a good solvent for the herbs. In ayurvedic medicine, the use of wine is a part of the pharmacopeia. Ayurveda calls Draksha the medicated wine used for a variety of remedies. Ethyl alcohol is a good solvent for extracting resins, essential oils, glycosides, chlorophyll, alkaloids, and bitter constituents. Oil is a good solvent too. Ayurvedic medicine use ghee that is clarified butter. Ghee is a very good substance to improve the absorption of medicinal properties of herbs particularly those who heal the nervous system.

Water 

Called the universal solvent, water is the most abundant solvent available on this planet. The cold water is a good solvent for plant constituents (proteins, coloring matter, tannins, mucilaginous substances), but hot water implicated that the plant swells and bursts the cells. It is important to know the medicinal properties of a plant to choose good water extraction. Heating a water menstruum encountered disadvantages like the separation out from the solution.

Vinegar

The use of apple cider vinegar is requested but we also use the rice vinegar, plum vinegar or balsamic vinegar. The vinegar is a sour liquid on account of acetic acid. It has valuable properties as a solvent. The role is to fix and extract certain alkaloids and can be substituted for alcohol. Vinegar’s action is excellent for the preservative of herbal properties. Pure vinegar preparations are said to be more liable to change than tinctures. Vinegar is commonly added as 5 percent to 10 percent of an alcohol-based for adjusting the pH.

Wine

The maceration of the herbs in wine is highly recommended. Wine has a low alcoholic content. White wine is preferred as menstrua for making medicinal wines because of their small proportion of tannins. With 16% of herbs, we use 24% alcohol.

Ethyl alcohol

Alcohol does not abstract mucilaginous, gums, starch, albuminous materials. Alcohol paralyzes enzymes and prevents the growth of yeast, fungi, and most bacteria.  It has the advantage to eliminate microbial activity, inactivate the enzymatic action which most of the time destroys the alkaloids and glycosides. Alcohol can be mix with water in all proportions for many active plant substances.

Oil

Fixed oil is obtained from both vegetable and the animal kingdom. There are insoluble in water but are capable of being mixed with water with the assistance of mucilage. The oils are decomposed in the intestine by the digestive juices into fatty acids.

Infusion: Methods of preparation

An infusion is a liquid preparation made by treating fresh or dehydrated vegetable substances. The nutritional and medicinal principles are extracted with cold or hot water. The infusions can be made in three ways which are maceration, digestion, and percolation. Maceration consists of soaking the chopped herb in a menstruum until complete dissolution. Digestion is a maceration subjected to moderate continual heat below boiling temperature. The herbs contain a valuable volatile constituent, the use of cold water is a better choice (chamomile, peppermint). We use the cold water when the herb contains a constituent that is not desired and not readily dissolved by cold water (Safran). Some principles could be deteriorated by the hot water like Wild Cherry bark.

The infusions made with boiling water extracted starch. The cold water extracted albumin (plant protein), but the gum, sugar, and other extractive are dissolved by both.

The most suitable vessels for infusions are made of glazed earthenware, porcelain or glass. When the plant contained an astringent constituent, the iron, aluminum, and other metallic vessels are unsuited.

Hot infusion is made by pouring boiling water upon the herb. We can let it stand for 20 minutes in a warm place. For some herbs, it is important to strain and press out the marc (pulp) for bulky herbs and flowers. This method retains a considerable proportion of the extract.

Cold infusions are made by putting the herb into the water overnight at room temperature. It is recommended to suspend the herb in a small cotton pouch and to squeeze out when the infusion process is completed.

Cold infusion: burdock root, chamomile, cleavers, comfrey root, crampbark, marshmallow root, mugwort, nettle, peppermint, uva ursi, slippery elm.

Reference : James Green: The Herbal Medicine-Maker’s Handbook: A Home Manual