Flavonoids in Grapefruit and Commercial Grapefruit Juices: Concentration, Distribution, and Potential Health Benefi ts

Florida is the main producer of grapefruit (Citrus paradisi Macf.) in the world. Grapefruit provide not only the traditional nutrients (carbohydrates, proteins, vitamins, minerals), but also phytochemicals such as fl avonoids, which are not essential for life, but may provide many health benefi ts. Flavanones are the dominant fl avonoids, and account for about 98% of the total fl avonoids in grapefruit. Major fl avanones in grapefruit are present as glycosides. In grapefruit, identifi ed fl avanone glycosides include didymin, dihydrokaempferol glucoside, eriocitrin, naringin, poncirin, hesperidin, neohesperidin, neoeriocitrin, narirutin, narirutin-4’-glucoside, naringin-6’’-malonate (open form), and naringin-6’’-malonate (closed form). Flavones or fl avonols found in grapefruit include apigenin 6,8-di-C-glucoside, apigenin 7-(malonylapiosy)-glucoside, kaempferol glycoside, luteolin, myricetin, neodiosimin, quercetin, rutin, and rhoifolin. Reported polymethoxylated fl avones in grapefruit include heptamethoxyfl avone, nobiletin, and tangeretin. The presence of naringenin (an aglycone form of naringin and narirutin) in grapefruit remains controversial. Naringin is present at the highest concentration followed by narirutin, hesperidin, poncirin, neohesperidin, didymin, and quercetin. The presence and their concentrations of individual fl avonoids vary with grapefruit variety, fruit tissue, juice extraction method, and geographic location. Flavonoids have been linked to many health benefi ts including antioxidant, anti-infl ammatory, and anti-tumor activity. Grapefruit and grapefruit juice are a rich source of fl avonoids, especially naringin. By consuming grapefruit and grapefruit juice, individuals not only will obtain essential nutrients but also will get health-benefi cial fl avonoids.