Natural product to modern discovery of their active ingredients and eventually to the development of new drugs. A large number of currently prescribed drugs have been either directly derived from or inspired by natural products. A few representative examples are listed below. Some of the oldest natural product based drugs are analgesics. The bark of the willow tree has been known from antiquity to have pain relieving properties. This is due to presence of the natural product salicin which in turn may be hydrolyzed into salicylic acid. A synthetic derivative acetylsalicylic acid better known as aspirin is a widely used pain reliever.
Etacrynic acid resolves after taking the drug for a few weeks. Ethacrynic acid can also cause low potassium levels, which may manifest as muscle cramps or weakness. It has also been known to cause reversible or permanent hearing loss (ototoxicity) and liver damage when administered in extremely high dosages. On oral administration, it produces diarrhea; intestinal bleeding may occur at higher doses. Ethacrynic acid acts by inhibiting NKCC2 in the thick ascending loop of Henle and the macula densa. Loss of potassium ions is less marked but chances of hypochloremic alkalosis are greater. The dose response curve of ethacrynic acid is steeper