Original Article

Structure-activity relationship of natural flavonoids in hydroxyl radical-scavenging effects.

Authors: Ji-Wu CHEN, Zhen-Qin ZHU, Tian-Xi HU, Da-Yuan ZHU


AIM: To study the relationship between the structure and hydroxyl radical
(*OH)-scavenging activity of twelve natural flavonoids.
METHODS: The hydroxyl radical-generating chemiluminescence system with
ascorbate-CuSO4-yeast-H2O2 was used to determine the hydroxyl radical-scavenging
activity of twelve natural flavonoids.
RESULTS: Guercetin, heliosin, hyperoside, kaempferol, baicalin, corylifolin,
lysionotin, matteucinol, corylifolinin, and genistein could effectively scavenge.
OH and inhibit the chemiluminescence of the system. The IC50 values (95 %
confidence limits) of the flavonoids were 12.1 (9.9-14.5) g/L, 15.8(14.0-19.2)
g/L, 19.5 (16.8-27.4) g/L, 20.1 (13.6-29.0) g/L, 34.6 (28.4-43.4) g/L, 66.8
(63.2-74.4) g/L, 187 (147-235) g/L, 211 (165-284) g/L, 262 (190-346) g/L, and 708
(498-994) g/L, respectively; whereas nobilelin and corylifolin-Ac could not
scavenge *OH.
CONCLUSION: (1) Phenolic hydroxyls in flavonoids were the main active groups
capable of scavenging *OH; (2) Hydroxyl groups in ring B and A were important
*OH-scavenging active groups; (3) The ortho-dihydroxyl groups in ring A and/or B
could greatly enhance the *OH-scavenging activity of the rings; (4) Comparing the
IC50 values of guercetin, heliosin, hyperoside, baicalin, lysionotin, and
matteucinol, it was suggested that the hydroxyl groups on 3',4' position of ring
B possessed high *OH-scavenging activity and the scavenging activity of hydroxyl
groups in ring B was higher than that of hydroxyl groups in ring A. The hydroxyl
group or glucoside on 3 position of ring C of the above mentioned 6 flavonoids
was also related to the. OH-scavenging ability. (5) The structural types of
flavonoids themselves could influence their *OH-scavenging activity.

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