Hemiketals

Nystatin, sold under the brand name Mycostatin among others, is an antifungal medication. It is used to treat Candida infections of the skin including diaper rash, thrush, esophageal candidiasis, and vaginal yeast infections. It may also be used to prevent candidiasis in those who are at high risk. Nystatin may be used by mouth, in the vagina, or applied to the skin.

Nigericin is an antibiotic derived from Streptomyces hygroscopicus. Its isolation from soil from Nigeria was described in the 1950s, by R.L Harned (et. al), and in 1968 the structure could be elucidated by X-ray crystallography. The structure and properties of nigericin are similar to the antibiotic monensin. Commercially it is obtained as a byproduct, or contaminant, at the fermentation of geldanamycin. It is also called polyetherin A, azalomycin M, helixin C, antibiotic K178, and antibiotic X-464.