Effects of Scutellariae Radix Extract and its Components (Baicalein, Baicalin, and Wogonin) on the Experimental Elevation of Aqueous Flare in Pigmented Rabbits

Abstract

Purpose: To evaluate the possible inhibitory effects of hot water extract of Scutellariae radix and its major components (baicalein, baicalin, and wogonin) on experimental elevation of aqueous flare in pigmented rabbits. Methods: To produce aqueous flare elevation in rabbits, prostaglandin E 2 (PGE 2), 25 μg/mL, was applied to the cornea with the use of a glass cylinder, or lipopolysaccharides (LPS), 0.5 μg/kg, were injected into an ear vein. Animals were pretreated by the oral administration of 150 g/day of food containing 0.02%, 0.07%, or 0.2% (w/w) extract of Scutellariae radix for 5 days, or by intravenous injection of baicalein, baicalin, or wogonin, 60 μg/kg or 600 μg/kg, 30 minutes before experimental uveitis was induced. Aqueous flare was measured with a laser flare-cell meter. Aqueous flare intensity was expressed as the area under the curve (AUC) in arbitrary units. Results: The AUC of PGE 2- and LPS-induced aqueous flare elevation was 1,343 and 5,066 arbitrary units, respectively. Pretreatment by oral administration of 0.07% or 0.2% extract of Scutellariae radix did not inhibit PGE 2-induced aqueous flare elevation (AUC: 1,252 and 1,210, respectively), but it did inhibit LPS-induced aqueous flare elevation (AUC: 2,248 and 1,973, respectively). Pretreatment by intravenous injection of 600 μg/kg of baicalein, baicalin, or wogonin inhibited LPS-induced aqueous flare elevation (AUC: 2,289, 2,163, and 1,509, respectively). Pretreatment with 60 μg/kg of wogonin also inhibited LPS-induced aqueous flare elevation (AUC: 1,980). Conclusion: Hot water extract of Scutellariae radix may have an inhibitory effect on experimental anterior uveitis induced by LPS in pigmented rabbits.