Salicylic acid and aspirin

The chemical name of salicylic acid is o-hydroxybenzoic acid, the molecular formula is C7H6O3, and the relative molecular weight is about 138. it is a colorless needle-like crystal, easy to sublimate and can be volatilized with water vapor. It has the chemical properties of phenol and carboxylic acid, reacts with ferric trichloride in purple, and its acidity is stronger than benzoic acid due to the influence of phenolic hydroxyl group.

Salicylic acid, originally used in dermatology, was first extracted from poplar and willow. It has a history of nearly a hundred years. Clinically, various concentrations of salicylic acid are widely and safely used, even known as a sharp weapon of dermatology.

Salicylic acid can promote cutin metabolism, continuously and gently release dark withered cells on the surface of the skin, have the best effect on cleaning the cortex, make the process of skin metabolism normal, help cells regenerate and activate, and accelerate the renewal of skin cells.

In addition, salicylic acid itself has bactericidal ability, and its sodium salt can be used as a preservative for food. Salicylic acid is also a raw material for the preparation of drugs. For example, salicylic acid reacts with acetic anhydride to obtain acetylsalicylic acid, commonly known as "aspirin". It is a commonly used analgesic and antipyretic drug.

Aspirin (acetylsalicylic acid) can treat colds, relieve pain and fever, and play a good role in preventing thrombosis. The active pharmacological ingredient of aspirin is acetylsalicylic acid, whose molecular formula is C9H8O4.

When aspirin and poly (methacrylic acid) are grafted with diol, there is the following relationship between their properties and molecular structure: at this time, the hydrolysis property of the whole graft (that is, the ability of hydrolysis to release effective acetylsalicylic acid) is related to the m in the O (CH2) mO of the graft, and the hydrolysis property of the graft increases sharply when it is increased from mCl2 to mCl7, that is, the speed of releasing acetylsalicylic acid is accelerated. If the m value can be controlled, the release rate of acetylsalicylic acid will be controlled. As for the treatment of disease, it is always hoped that this drug will become a long-acting drug, that is, it can release acetylsalicylic acid continuously and slowly, so that acetylsalicylic acid can exist in the human body for a long time, which can be used in antithrombotic therapy. This is the origin of taking medicine once for many days.

From the grafting of aspirin to turning it into a long-acting drug, one cannot help admiring the ingenuity of chemists. (author: Chen Gang)