Naringin, the bitter principle of grapefruit, is found in the juice, flower, and rind of the fruit and constitutes up to 10% of the dry weight.
The flavonoid naringin occurs naturally in citrus fruits, especially in grapefruit. Naringin and its aglycone naringenin belong to this series of flavonoids and were found to possess strong antioxidant and anti-inflammatory activities both in vitro and in vivo. Several lines of investigation suggest that naringin supplementation is beneficial for the treatment of obesity, diabetes, hypertension, and metabolic syndrome.
Naringin (with the molecular formula C27H32O14 and a molecular weight of 580.4 g/mol) is a flavanone glycoside found in grapes and citrus fruits. It possesses the distinct bitter taste of grapefruit juice. Two rhamnose units are attached to its aglycon portion, naringenin, at the 7-carbon position.
Naringin has been shown to inhibit cell proliferation and to promote cell apoptosis in tumour cells, including triple-negative breast cancer (TNBC) cells, human cervical cancer (SiHa) cells and bladder cancer cells. In TNBC cells, the pro-apoptotic activity of naringin results from G1-phase cell cycle arrest. Suppression of the growth of breast cancer cells by naringin is mediated by inhibition of the β-catenin pathway, leading to a significantly increased p21 level and decreased cell survival.
It has antioxidant potential and plays an important role in the development of leaves, flowers, buds and fruits of plants. It has further induced bitterness to the fruits as in grape fruit. However, the bitterness can be reduced upon reduction by the enzyme naringinase.
Both naringin and naringenin are strong antioxidants; however, naringin is less potent compared with naringenin because the sugar moiety in the former causes steric hindrance of the scavenging group. Naringin is moderately soluble in water. The gut microflora breaks down naringin to its aglycon naringenin in the intestine; it is then absorbed from the gut.
The skin of pummelo contained a higher amount of naringin (3910 μg/g fresh weight) than the juice (220·0 μg/g fresh weight) whereas the amounts of naringin obtained from the skin, juice and seed of rough lime were 517·2 μg/g, 98·4 μg/g and 29·2 μg/g fresh weight, respectively.
Three steps are needed to isolate naringin from fruits: extraction, separation and purification. The naringin content in fruit depends on a number of factors the time of fruit collection, the part of the fruit used and if the peel is the source of naringin, the drying time.
Naringin: Flavonoid of citrus fruit
