Antioxidant

Anti-oxidant: 

It helps to prevent oxidation. Its transfers electron or hydrogen from a substance to an oxidizing agent. 

For example:

Anti-oxidant (reducing agents):  Sodium bi sulphate / Butylated anisole / Thiourea 

Anti-oxidant (blocking agents):  Tocopherol / Ascorbic acid esters.

Synergist : Ascorbic acid (vitamin – C) / Phosphoric acid / Tartaric acid / Citric acid