Noun
ionone (plural ionones)
(chemistry) Any of a series of closely related aromatic chemical substances that are part of a group of compounds known as rose ketones, including damascones and damascenones, found in a variety of essential oils.
Animal species differ greatly in their ability to convert retinyl (beta- ionone ) containing carotenoids to retinals. Source: Internet
The carotenoid beta- cryptoxanthin possesses an ionone group and has vitamin activity in humans. Source: Internet