The ionones are a series of closely related chemical substances that are part of a group of compounds known as rose ketones, which also includes damascones and damascenones. Ionones are aroma compounds found in a variety of essential oils, including rose oil. Я-Ionone is a significant contributor to the aroma of roses, despite its relatively low concentration, and is an important fragrance chemical used in perfumery.[1] The ionones are derived from the degradation of carotenoids.

The combination of α-ionone and Я-ionone is characteristic of the scent of violets and used with other components in perfumery and flavouring to recreate their scent.[2][3]

The carotenes α-carotene, Я-carotene, γ-carotene, and the xanthophyll, and Я-cryptoxanthin, can all be metabolized to Я-ionone, and thus have vitamin A activity because they can be converted by plant-eating animals to retinol and retinal. Carotenoids that do not contain the Я-ionone moiety cannot be converted to retinol, and thus have no vitamin A activity.