Study Of Bioassay-guided Isolation Of Antitumor Compounds From Scutellaria Barbata & Its Pharmacokinetics

Scutellaria barbata D. Don (S. barbata), a perennial herb, is natively distributed throughout southern China. It has been widely used in traditional Chinese medicine for treating hepatoma, lung cancer, digestive system cancers, and so on. The chemical composition and pharmacologies of S. barbata have recently reported, but no systematic study concerning the phytochemistry and antitumor activity has been reported.In this thesis, bioassay-guided isolation of flavonoids with antitumor activities from S. barbata was investigated. Cytotoxicity assay demonstrated that methylene chloride and ethyl acetate fractions from 5. barbata were potential and high efficient antitumor fractions with IC₅₀ 16.43-42.76 μg/ml and 52.29-104.98 μg/ml against the four tumor cell lines, respectively. Through bioassay-guided fractionation and isolation procedures 12 compounds, apigenin ( â…  ), luteolin ( â…¡ ), stigmasterol (â…¢), isoscutellarein (â…£), 4'-hydroxywogonin (â…¤), isoscutellarein-8-O- β-D-glucuronide (â…¥), scutellarin (â…¦), hispedulin-7-O-β-D-glucuronide (â…§), rutin (â…¨), hexacosanol (â…©), octacosanol (â…ª) and kaempferol (â…«) were isolated and their structures were elucidated by spectral techniques. Apigenin (IC₅₀ 3.25-11.54 μg/ml), luteolin (IC₅₀ 9.45^>25 μg/ml) and kaempferol (IC₅₀ 6.78-22.07 μg/ml) were found to possess potent antitumor activity against a broad spectrum of human tumor. Scutellarin (IC₅₀ 20.90 μg/ml) and 4'-hydroxywogonin (IC₅₀ 20.33 μg/ml) were sensitive to HL-60 cells. The flavonoids, therefore, are the major antitumor constituents of S. barbata.An RP-HPLC method was developed to study the pharmacokinetics of scutellarin (SCU), isoscutellarein-8-O-glucuronide (ISO) and luteolin (LUT) in SD rats. The peak-area ratio (Y) of analytes to internal standard versus drug concentration (C) was found to be linear over the range of 0.044-2.20 μg/mL for SCU, 0.042-2.08 μg/mL for ISO, 0.056-2.80 μg/mL for LUT, respectively. The accuracy of assay was between 88.4-103%. The inter-day and intra-day precisions (RSD) were less than 14.7%. The total flavonoids of S. barbata were orally administrated, and the blood was collectedat the concerned time. The SCU, ISO and LUT in the plasma were determined by HPLC method. The pharmacokinetic parameters were calculated with the software 3P97. The concentration-time profiles of SCU and ISO showed double peaks. The concentration-time profile of SCU was found to fit non-compartment model, Cmax 0.73 ±0.19 Hg/mL, T^ 5.3 ± 0.5 h, AUCo^, 3.29 ± 0.41 μg?h/mL. The concentration-time profile of LUT was found to fit three-compartment model, Cmax 0.20 ± 0.04 Hg/mL, Tmax 0.75 ± 0.16 h, AUC 0.43 ± 0.20 Hg-h/mL. SCU and ISO were absorbed slowly and eliminated quickly, and LUT was absorbed quickly.