Abstract:

Two monomer compounds, namely A and B, respectively, were purified on Sephadex LH-20 column by gradient
elution with aqueous methanol at a flow rate of 0.8 mL/min from crude flavonoids extracted from apple and chromatographed
on a macroporous resin column. High performance liquid chromatograph (HPLC) was employed to identify the monomers
with a mobile phase consisting of methanol-water using diode array detector. The detection wavelengths were 280 and 358
nm. The results showed that compound A was chlorogenic acid and compound B was another flavonoid. The structure of
compound B was identified by color reaction and UV spectroscopy as a flavonol with 7-bit and 4’o-diphenol structure. Based
on peroxide value (POV), the antioxidant capacity of compound B, rutin and BHT were measured by oven-storage method.
The effects of these three substances on sesame oil auto-oxidation were not obvious. The oxidative rancidity of lard could
be prevented in the presence of either butylated hydroxy toluene or compound B. The decreasing order of the antioxidant
capacity of these three substances was BHT ＞ compound B ＞ rutin.

Key words: apple, flavonoids, isolation, purification, inhibition of lipid oxidation