Abstract:

The antioxidant activities of 15 major phenolic compounds in citrus were evaluated by 1,1-diphenyl-
2-picrylhydrazyl (DPPH), 2,2’-azino-bis (3-ethylbenzthiozoline-6)-sulphonic acid (ABTS) radical scavenging capacity and
ferric reducing/antioxidant power (FRAP) assays alone and in combination with high performance liquid chromatography-
DPPH/ABTS (HPLC-DPPH/ABTS) post-column reaction system. The results showed that the antioxidant potency
composite (APC) index was a valid comprehensive index for evaluating antioxidant activities of phenolic compounds, and
an obvious difference in antioxidant activities of these major phenolic compounds was observed. Four phenolic acids had
the highest antioxidant activities in the declining order of gallic acid (92.32%) > caffeic acid (85.29%) > chlorogenic acid
(69.75%) > ferulic acid (50.97%), eriodictyol (39.38%), eriocitrin (39.36%) and rutin (27.42%) were in the middle, and the
antioxidant activities of hesperitin, naringenin, diosmin, hesperidin, nobiletin, sinensetin, naringin and tangeretin (< 5%)
were very low. The antioxidant activities of these phenolic compounds were reduced by glycosylation or methoxylation, but
increased with increasing number of phenolic hydroxyl groups.

Key words: phenolic acid, flavanone, antioxidant activity, DPPH method, ABTS method, FRAP method;