Alcohol as a solvent
When considering alcohol, or more precisely ethyl alcohol or ethanol, most people recognize its place in society as a common recreational drug. Few any longer associate its use with medicine, but the development of higher quality and concentrated alcohol has paralleled advances in pharmacy through the ages. It is second only to water in importance as a solvent in medicine and is used particularly to extract active constituents from inert parts of crude drugs. This concentrates the medicinally active compounds and makes the remedy easier to dispense and consume while also improving its absorption. The compounds that normally dissolve in alcohol include alkaloids, glycosides, resins, and volatile oils but not polysaccharides, gums, sugars, or proteins. Combined with water to make a hydroalcoholic solvent, it acts as a preservative by preventing hydrolysis and inhibiting fermentation that would occur if water was used alone.
Early discoveries and uses
Probably all early civilizations produced fermented beverages from local produce. In the areas of China, Mesopotamia, and Egypt it is known that these beverages were sometimes used to administer herbal medicines. In Greece the practice of mixing herbs in wine began before the time of Hippocrates who was born in 460 B.C.. This practice spread throughout Europe and continued through the Middle Ages. The process of distillation was probably discovered about 900 B.C. in China, but alchemists at Islamic universities are credited with its application to medicine over 1500 years later. In the Middle East the Persians Geber (8th cent.) and Rhazes (10th cent.) developed the art of distillation and used it to concentrate alcohol which was then taken as an anaesthetic. In the late 10th century in Spain the Arab surgeon Abulcasis described using distilled alcohol as a solvent for drugs.
From the 12th to the 14th centuries alchemists in Europe began experimenting with the distillation of many items, but medicines were still mostly given as infusions or decoctions of single herbs. Arabic writings and universities in Spain began to influence Christian schools of medicine in Italy and France. Two contemporary 13th century Spanish alchemists, Arnold of Villanova and Raymond Lully, introduced wine spirits, which they called aqua vitae (water of life), as a solvent into European medicine. This later became known as brandy, shortened from the Dutch term for “burnt wine.” In the 14th century during the Black Death brandy began to be used as a medicine by itself. It was thought of as a polycrest, a remedy of many virtues. By the next century brandy had also become popular as a recreational beverage. Yet wines and vinegars were still preferred for the extraction of herbs. In Ireland, England, Scotland, and northern Europe alcohol was being distilled from fermented grain beverages. It was given the name whiskey, a shortened form of the Gaelic term for “water of life.” The pot stills used to distill wine and beer at that time could concentrate the alcohol to as much as 65-70%.
In the 16th century the Swiss physician Paracelsus popularized the use of distilled alcohol as a solvent to prepare tinctures from herbs and chemicals. The production of compound alcoholic extracts called elixirs then began to flourish in European monasteries. These elixirs contained from dozens to over 100 different herbs and were prepared in stages with secrete, complex procedures. At that time most were bitter and were usually taken before meals as digestive tonics. Some of these elixirs were also sweetened and are now sold as liqueurs such as Benedictine and Chartreuse.
Widespread production of brandy began in France in the 17th century as a means to utilize poor quality wines. Brandy became the preferred form of alcohol for medicine, but in northern areas whiskey was also used due to its local availability. By the end of the 18th century tinctures were an important class of medical preparations. In the early 19th century Aeneas Coffey discovered that by using a continuous column still most impurities could be removed and 94-96% pure ethanol could be produced. To eliminate the remaining impurities this distilled alcohol could be diluted, filtered through charcoal, and then rectified, or redistilled. This type of neutral spirit then became the standard solvent in the manufacture of most cordials, liqueurs, and tinctures. Liqueurs that contain one predominant herb were developed to be used after meals as digestive aids such as Anisette, Kummel, and Creme de Menthe.
Pharmacies were known for having large bottles, called carboys, sitting in their windows. These were used for making tinctures by soaking crude herb drugs or chemical substances in alcohol, a procedure known as maceration. In the early 19th century the process of percolation was developed to help concentrate the extracts. They could then also be standardized in content to produce fluid extracts of plants. Percolation was further refined through the invention of the Lloyd extractor, or cold still, by the American John Uri Lloyd. He contributed to the standardization of cordial elixirs and developed his specific medicines as the epitome of quality in herbal medicine in the late 19th century.
After that time the popularity of alcoholic extracts of herbal medicine began to steadily decline as the production of purified active constituents and synthetic drugs took precedence. A few tinctures, fluid extracts, and elixirs are currently officially recognized, but many are only used as flavors. On the other hand public interest in herbs and their use has increased over the last several decades and continues to grow.
Differences in alcohol
Brandy and whiskey were listed as official drugs in the U. S. Pharmacopeia until the 1940’s and ethanol was listed until 1975. Though brandy, whiskey, and neutral spirits can all be used as solvents, there is usually no designation on herbal extracts as to what type of alcohol is actually employed. Yet significant differences exist between them. The different congeners in each produce different flavors, aromas and effects of the distillate. These compounds vary depending upon what plant source was fermented. The main congeners are higher alcohols that make up what is called the fusel oil. These are more potent depressants and more toxic than an equal amount of ethanol. Alcohol distilled from potatoes has the highest amount of fusel oil which is almost pure amyl alcohol. Grain alcohol has more fusel oil than the alcohol distilled from grapes. The fusel oil from grains consists mostly of amyl alcohol while that from grapes has more butyl alcohol in addition to many volatile fatty acid congeners. In the production of neutral spirits potato or grain alcohol is preferred over grape alcohol because of the lower cost of production. Highly purified neutral spirits with the fusel oil and impurities removed can still be identified according to the original source of the alcohol. Whether it is from grapes, corn, rye, wheat, potatoes, sugar cane, or is produced synthetically, the concentration of isotopes of carbon, hydrogen, and oxygen gives the purified alcohol distilled from each source a unique “fingerprint.”
Because the source of the alcohol used as a solvent is so seldom considered by those who take herbal extracts, the issue of individual sensitivity to these minor components is also ignored. This is a matter of concern when whiskey is used, since grains are among the foods most frequently associated with hypersensitivity reactions and intolerances. Though the protein antigens common to allergies are not present, it could be important to avoid exposure to other components of the fermented grain distillate. Neutral spirits are usually used to make tinctures, and most neutral spirits are derived from grain alcohol. Though the congeners have been removed, there still exists in the alcohol an energy pattern that is unique to the grain from which it was derived. In certain cases of hypersensitivity a sublingual challenge with such a highly dilute form of the sensitizing agent can still produce reactions. Using herbal extracts made with alcohol distilled from grapes may be the best way to assure that agents from grains are not an aggravating factor.
Dr. Francis Brinker practices in Tuscon, Arizona and can be reached at (520)747-1898