This is a collective name for additives that counteract the degradation of polymers as a result of heat, sunlight, flexing, ozone, copper, etc.
Antidegradants can be roughly divided into two main groups:
Amine-based agents result in discoloration, but as a rule provide excellent protection against both thermo-oxidative aging and other degradation mechanisms, such as ozone and UV.
Phenol-based agents often provide good protection against oxidative degradation caused by heat aging and e.g. flex fatigue.
Some antidegradants also function as UV stabilizers. As a rule, phenol-based agents result in minimal discoloration, and some are listed by the FDA in §177.2600, Chapter XXI.
In addition to these two main groups, there are other types, which are derivatives of imidazoles, dithiocarbamates, or phosphites.