Abstract

Baicalein (a), baicalin (b), daidzein (c), myricetin (d), oroxylin A (e), quercetin (f), quercetin pentaacetate (g), quercitrin (h), and wogonin (i) were isolated from regular anti-inflammatory Chinese herbs which contain many flavonoids compounds, also the radical-scavenging and liver mitochondrial lipid peroxidation (LPO) inhibitory capabilities were elucidated. The 50% inhibitory concentrations (IC₅₀) for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capability of (a), (b), (d), (f), and (g) were 3.61, 3.28, 2.41, 2.16, and 3.74 μg/ml, and for LPO inhibition were 9.32, 9.52, 19.63, 16.15, and 20.22 μg/ml, respectively. The antioxidant capacities of (d), (f), (g), (h), (b), and (a) were 20.46, 16.42, 14.46, 13.98, 12.74, and 8.13 μMTrolox equivalents, respectively. To compare with the structure-activity relationships of the flavonoids, two flavones of baicalein and baicalin which have 5,6-hydroxy group which contain ortho-hydroxyl group characteristic reveal better LPO inhibitory activity, and two flavonols of myricetin, quercetin which have 5,7-trihydroxy group have more DPPH activity and ferrous chelating ability. The hydroxyl groups might play a role in increasing the activity of the flavonoids and exhibit potent antioxidant activities. In view of these results, five of the nine natural flavonoids (baicalein, baicalin, myricetin, quercetin and quercetin pentaacetate) can be lead compounds for preventing liver damage and related iron-overload disease.

Key words: Anti-inflammatory Chinese herbs, ferrous ion, flavonoids, lipid peroxidation.