A reductone is a special class of organic compounds.
They are enediols with a carbonyl group adjacent to the enediol group, i.e. RC(OH)=C(OH)-C(O)R. The enediol structure is stabilized by the resonance resulting from the tautomerism with the adjacent carbonyl.
[1] Reductones are reducing agents, thus efficacious antioxidants.
Some are fairly strong acids.
[2] Examples of reductones are tartronaldehyde, reductic acid and ascorbic acid.