Salicylic acid and its derivatives in plants: medicines, metabolites and messenger molecules

This chapter discusses salicylic acid and its derivatives in plants. The medicinal uses of concoctions of the bark of willow, spiraea, and related plants, were the cause of salicylates receiving early attention from both chemists and pharmacologists. The medicinal uses of these barks seems to have been appreciated by “pre-industrial” cultures as far apart as South Africa and North America and were known in a more systematic way to the medical philosophers of classical Greece and Rome. Salicylates, especially aspirin, but also salicylic acid itself, its sodium salt, its methyl ester and its amide are important medicinally because of their analgesic, anti-inflammatory, and anti-pyretic properties. They are comparatively safe, non-sedative, non-narcotic, nonaddictive, and cheap. More recently aspirin has been used to decrease the likely occurrence of secondary thromboses in people with appropriate cardiovascular diseases and its use as a prophylactic against the occurrence of cardiovascular and cerebrovascular thrombotic events has been the source of much study and comment. Because of their widespread use, often in massive doses, the toxicity of salicylates has also received much attention. Therapeutic doses of aspirin can induce gastric bleeding in sensitive patients. This had led to changes of tablet formulation, including more rapidly disintegrating, more readily soluble and buffered, effervescent preparations. Other acute symptoms of salicylate toxicity, occurring in long-term medication with very high doses, include deafness, tinnitus and extreme nausea, and vomiting. Chronic, event fatal, salicylate poisoning, either accidental or deliberate, has been comparatively common.