ortho-Thioquinones and Mediterranean Diet: The Sulfur Connection

The antioxidant activity of several hydroxy-4-thiaflavanes was determined either by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) bleaching method or by measuring their ability to inhibit the autooxidation of styrene or cumene. Based on this, the role played by the number and position of hydroxy groups and by the oxidation state of sulfur was rationalized and quantified, providing good indications for optimizing the structural features required to make these "double-faced" antioxidants perform at their best. The ability of selected 4-thiaflavanes to protect DNA by oxidative damage in vitro is also discussed.