Beta-carotene is a cyclic carotene obtained by dimerisation of all-trans-retinol. A strongly-coloured red-orange pigment abundant in plants and fruit and the most active and important provitamin A carotenoid. It has a role as a ferroptosis inhibitor, an antioxidant, a cofactor, a biological pigment, a provitamin A, a mouse metabolite, a plant metabolite and a human metabolite. It is a carotenoid beta-end derivative and a cyclic carotene.

7-ketocholesterol is a cholestanoid that consists of cholesterol bearing an oxo substituent at position 7. It has a role as a neuroprotective agent. It is a 3beta-hydroxy-Delta(5)-steroid, a 3beta-sterol, a 7-oxo steroid and a cholestanoid. It is functionally related to a cholesterol.