Salicylic acid in the context of "Salix"

Medicinal plants, also called medicinal herbs, have been discovered and used in traditional medicine practices since prehistoric times. Plants synthesize hundreds of chemical compounds for various functions, including defense and protection against insects, fungi, diseases, against parasites and herbivorous mammals.

The earliest historical records of herbs are found from the Sumerian civilization, where hundreds of medicinal plants including opium are listed on clay tablets, c. 3000 BC. The Ebers Papyrus from ancient Egypt, c. 1550 BC, describes over 850 plant medicines. The Greek physician Dioscorides, who worked in the Roman army, documented over 1000 recipes for medicines using over 600 medicinal plants in De materia medica, c. 60 AD; this formed the basis of pharmacopoeias for some 1500 years. Drug research sometimes makes use of ethnobotany to search for pharmacologically active substances, and this approach has yielded hundreds of useful compounds. These include the common drugs aspirin, digoxin, quinine, and opium. The compounds found in plants are diverse, with most in four biochemical classes: alkaloids, glycosides, polyphenols, and terpenes. Few of these are scientifically confirmed as medicines or used in conventional medicine.

In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (−O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, C
₆H
₅OH. Phenolic compounds are classified as simple phenols or polyphenols based on the number of phenol units in the molecule.

Phenols are both synthesized industrially and produced by plants and microorganisms.

Systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals, and although there are many shared aspects between the two systems, it is thought to be a result of convergent evolution. The systemic acquired resistance response is dependent on the plant hormone, salicylic acid.

In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research. Some phenols are germicidal and are used in formulating disinfectants.

Methyl salicylate (oil of wintergreen or wintergreen oil) is an organic compound with the formula C₈H₈O₃. It is the methyl ester of salicylic acid. It is a colorless, viscous liquid with a sweet, fruity odor reminiscent of root beer (in which it is used as a flavoring), but often associatively called "minty", as it is an ingredient in mint candies. It is produced by many species of plants, particularly wintergreens. It is also produced synthetically, used as a fragrance and as a flavoring agent.

A tincture is typically an extract of plant or animal material dissolved in ethanol (ethyl alcohol). Solvent concentrations of 25–60% are common, but may run as high as 90%. In chemistry, a tincture is a solution that has ethanol as its solvent. In herbal medicine, alcoholic tinctures are made with various ethanol concentrations, which should be at least 20% alcohol for preservation purposes.

Other solvents for producing tinctures include vinegar, glycerol (also called glycerine), diethyl ether and propylene glycol, not all of which can be used for internal consumption. Ethanol has the advantage of being an excellent solvent for both acidic and basic (alkaline) constituents. A tincture using glycerine is called a glycerite. Glycerine is generally a poorer solvent than ethanol. Vinegar, being acidic, is a better solvent for obtaining alkaloids but a poorer solvent for acidic components. For individuals who choose not to ingest alcohol, non-alcoholic extracts offer an alternative for preparations meant to be taken internally.