Abstract:

The fruit of Citrus paradisi was separated into albedo layer, oil gland layer, seed, pomace and juice. Active
substances were extracted from albedo layer, oil gland layer, seed and pomace with 70% aqueous ethanol by hot re?uxing.
The contents of total ?avonoids and phenolic substances in the resulting extracts were evaluated. Antioxidant activity was
tested in four systems. The results showed that the content of total ?avonoids in different fruit extracts of C. paradisi was
in the following order: oil gland layer (3.78%) > albedo layer (2.38%) > seed (1.67%) > pomace (0.77%). Similarly, the
content of total phenols was the highest in oil gland layer (21.30%) and the lowest in pomace (1.73%). The ethanol extract
of oil gland layer showed the highest antioxidant activity to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide
anion and hydroxyl radicals with IC50 of 0.37, 0.24 and 1.31 mg/mL, respectively. The ethanol extract of albedo layer
showed the highest ABTS＋· scavenging activity with IC50 of 0.015 mg/mL. The contents of total flavonoids and total
phenols in the fresh juice were 0.021% and 0.19%, respectively. The IC50 values for DPPH free radical, ABTS＋·, O2
－·, ·OH were 8.55, 18.97, 35.17 and 23.30 mg/mL, respectively. These results showed that oil gland layer and albedo layer had quite
good antioxidant activities, which were positively correlated with the contents of total ?avonoids and phenols. The pericarp
consisting of the two layers made up about one third of the total fruit weight, and was rich in potent antioxidant compounds.
To conclude, further study and development of C. paradisi fruit will have great practical signi?cance.

Key words: Citrus paradisi, different parts of whole fruit, alcohol extract, fresh juice, effective constituent; , antioxidant activity