DISTRIBUTION OF TOTAL POLYPHENOLICS AND ANTIOXIDANT POTENTIALS IN DIFFERENT TISSUES OF CITRUS PARADISI, CITRUS GRANDIS AND CITRUS SINENSIS

摘要

Flavonoid glycosides in citrus fruits are known for their antioxidant qualities. Despite the availability of data on flavonoid glycoside levels in citrus fruits and juices, little is known on how various flavonoid glycosides are distributed in citrusplants and how that distribution relates to the tissue's antioxidant potential. The objective of the current study was to test the correlation between the levels of phenolic compounds including flavonoid glycosides in a tissue and the tissue's antioxidant potential in three citrus species. Fruit outer peel, juice vesicles, juice vesicle membranes, flavedo, albedo, young leaves and mature leaves of grapefruit, sweet orange and pummelo tissues were quantitatively extracted using a solvent mixture. The extracts were evaluated for their antioxidant potential and total phenolics. Analysis of the phenolics in pummelo leaf tissue suggested that most UV-positive compounds in the tissue extracts were flavonoid glycosides. Antioxidant potential (AOP), as measured by a ferric reducing/ antioxidant power (FRAP) assay, was correlated to the levels of total phenolics in leaf extracts. The significance of species-specific and tissue-specific differences in their antioxidant potentials is discussed.