Grapefruit is a hybrid originating in Barbados as an accidental cross between two introduced species, sweet orange (C. sinensis) and pomelo or shaddock (C. maxima)
Grapefruit comes in many varieties. One way to differentiate between varieties is by the flesh colour of fruit they produce. The most popular varieties currently cultivated are red, white, and pink hues, referring to the internal pulp colour of the fruit. Grapefruit mercaptan, a sulphur-containing terpene, is one of the substances which has a strong influence on the taste and odour of grapefruit, compared with other citrus fruits.
Grapefruit has many carotenoids, especially in pink/red grapefruit and grapefruit juices, but the most concentrated are beta-carotene, lycopene, lutein, and zeaxanthin.
Pink/red grapefruit and 100% pink/red grapefruit juice have lycopene, the same carotenoid that makes tomatoes red. Test tube studies show lycopene has one of the highest antioxidant activities of the carotenoids.