Uptake of baicalein into mouse tissues after administration of Scutellaria baicalensis extract

The root of Scutellaria baicalensis ( SB; Chinese Skullcap or Huang Qin) has a history of traditional use as an anti‐inflammatory agent, suggesting inhibition of arachidonic acid metabolism, which could also reduce carcinogenesis. The uptake of the aglycone baicalein, the major bioactive ingredient, into target tissues has been little studied. A 75% ethanol extract of SB (Botanica Biosciences, Ojai, CA) containing 224 mg baicalin (the glycoside) and 10.3 mg baicalein/g SB was used. C57BL/6 mice (n=5‐12) were given a single oral dose (0.87 mg SB/g BW) of SB extract. Plasma, prostate, pancreas, colon, and liver were collected at 0, 0.5, 1, 2, 3, 4, 5, 6, 8, 10 and 15 h post‐gavage. Tissue extracts treated with β‐glucouronidase/sulfatase were assayed by HPLC‐ECD for levels of total baicalein (free + conjugated). Plasma levels of baicalein increased within 0.5 h of gavage, peaked at 3 h to 0.38±0.06 μM, and returned to baseline by 10 h. Levels in colon and liver followed a similar time course, with concentrations peaking at 3 h to 1.3±0.4 μg/g colon and 1.15±0.2 μg/g liver. Concentrations in prostate (0.18±0.04 μg/g) and pancreas (0.16±0.06 μg/g) were lower and peaked at 4–5 h, however levels in the prostate remained elevated at least 10 h. These results indicate that the appearance of baicalein in plasma is rapid, but the compound is taken up by a number of tissues at various levels. The pharmacokinetic profile of baicalein in blood and target tissues is an important factor to be investigated in understanding the mechanism of action of SB extracts on carcinogenesis. Supported by NIH AT1535, CA42710.