Abstract:

Objective: To explore the effect of color change during maturation on the contents of total phenolic acids,
flavonoids, procyanidines and anthocyanins in Zhanhua winter jujube peel (Ziziphus jujube Mill. cv. Dongzao var. zhanhua)
and to evaluate the DPPH radical scavenging activity of methanol extracts of jujube peel at different stages of maturation.
Methods: The degree of maturity of winter jujubes was evaluated according to their color. The color parameters L*, a* and
b* and the contents of total phenolic acids, flavonoids and procyanidineins in winter jujube peel were measured, and the
DPPH radical scavenging activity of methanol extracts of jujube peel was investigated. Results: Winter jujube fruits were
divided into four stages of maturation according their color (dark green, DG; light yellow, LY; green-red, GR; dark red,
DR). The content of total phenolic acids varied from 7.528 to 19.312 mg/g, calculated on a dry basis, (DG ＞ GR ＞ LY ＞＞
DR). The content of total flavonoids was in the range of 0.025 to 2.466 mg/g (LY ＞ DG ＞ GR ＞ DR), and the content of
procyanidines was in the range of 4.297 to 30.186 mg/g (GR ＞ LY ＞ DG ＞＞ DR). The DPPH radical scavenging activity
of methanol extracts of winter jujube peel could be divided into two procedures: LY ＞ GR ＞ DG ＞＞ DR (0–15 min) and
LY ≈ GR ≈ DG ＞＞ DR (16－30 min). DR exhibited much lower DPPH radical scavenging activity than the other three
stages of maturation, presumably as a result of the lowest total phenolic acids, flavonoids and procyanidineins.

Key words: jujube peel, phenolic acids, flavonoids, procyanidins, anthocyanins, DPPH radical, antioxidant activity