Pyrithione
Pyrithione zinc, or zinc pyrithione or zinc pyridinethione, is a coordination complex consisted of pyrithione ligands chelated to zinc (2+) ions via oxygen and sulfur centers. In the crystalline state, it exists as a centrosymmetric dimer. Due to its dynamic fungistatic and bacteriostatic properties, pyrithione zinc is used to treat dandruff and seborrheic dermatitis. Dandruff is a common scalp disease affecting >40% of the world's adult population, and may be caused by fungi such as Malassezia globosa and M. restricta.  Pyrithione zinc is commonly found as an active ingredient in OTC antidandruff topical treatments such as shampoos. It mediates its action by increasing the cellular levels of copper, and damaging iron-sulfur clusters of proteins essential for fungal metabolism and growth. Due to low solubility, pyrithione zinc released from the topical formulations is deposited and retained relatively well onto the target skin surfaces. Other uses of pyrithione zinc include additive in antifouling outdoor paints and algaecide. While its use has been approved in the early 1960's by the FDA, safety and effectiveness of pyrithione zinc has been reported for decades. It is not shown to have any significant estrogenic activity according to the in vivo and in vitro assays.