a substance that retards or stops an activity

an enzyme in the body that is a powerful scavenger of free radicals

a toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite)

any of a class of highly unsaturated yellow to red pigments occurring in plants and animals

antioxidant that inhibits the formation of rust

an isomer of naphthol used in rubber as an antioxidant