title: Different extraction pretreatments significantly change the flavonoid contents of Scutellaria baicalensis.
abstract: BACKGROUND
  Scutellaria baicalensis Georgi (Labiatae) is one of the most commonly used medicinal herbs, especially in traditional Chinese medicine. However, compared to many pharmacological studies of this botanical, much less attention has been paid to the quality control of the herb's pretreatment prior to extract preparation, an issue that may affect therapeutic outcomes.
  
  
  OBJECTIVE
  The current study was designed to evaluate whether different pretreatment conditions change the contents of the four major flavonoids in the herb, i.e., two glycosides (baicalin and wogonoside) and two aglycones (baicalein and wogonin).
  
  
  METHODS
  A high-performance liquid chromatography assay was used to quantify the contents of these four flavonoids. The composition changes of four flavonoids by different pretreatment conditions, including solvent, treatment time, temperature, pH value and herb/solvent ratio were evaluated.
  
  
  RESULTS
  After selection of the first order time-curve kinetics, our data showed that at 50 °C, 1:5 herb/water (in w/v) ratio and pH 6.67 yielded an optimal conversion rate from flavonoid glycosides to their aglycones. In this optimized condition, the contents of baicalin and wogonoside were decreased to 1/70 and 1/13, while baicalein and wogonin were increased 3.5- and 3.1-fold, respectively, compared to untreated herb.
  
  
  CONCLUSIONS
  The markedly variable conversion rates by different pretreatment conditions complicated the quality control of this herb, mainly due to the high amount of endogenous enzymes of S. baicalensis. Optimal pretreatment conditions observed in this study could be used obtain the highest level of desired constituents to achieve better pharmacological effects.
authors.affiliation: School of Life Science and Chemical Engineering, Huaiyin Institute of Technology, Jiangsu, China.
authors.forename: Chunhao
authors.initials: C
authors.lastname: Yu
authors.forename: Fengyun
authors.initials: F
authors.lastname: Qu
authors.forename: Yanyong
authors.initials: Y
authors.lastname: Mao
authors.forename: Dong
authors.initials: D
authors.lastname: Li
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhen
authors.forename: Rachael
authors.initials: R
authors.lastname: Nass
authors.forename: Tyler
authors.initials: T
authors.lastname: Calway
authors.forename: Yunwei
authors.initials: Y
authors.lastname: Wang
authors.forename: Chun-Su
authors.initials: CS
authors.lastname: Yuan
authors.forename: Chong-Zhi
authors.initials: CZ
authors.lastname: Wang
mesh_terms: D005591:Chemical Fractionation / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D044950:Flavanones / Q000032:analysis; D005419:Flavonoids / Q000032:analysis* / Q000592:standards; D005960:Glucosides / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008517:Phytotherapy; D010936:Plant Extracts / Q000032:analysis* / Q000592:standards; D010946:Plants, Medicinal; D011786:Quality Control; D031364:Scutellaria baicalensis / Q000737:chemistry* / Q000201:enzymology; D012997:Solvents / Q000737:chemistry; D013696:Temperature
chemical_list: D044950:Flavanones; D005419:Flavonoids; D005960:Glucosides; D010936:Plant Extracts; D012997:Solvents; C038044:baicalin; C006680:baicalein; C473995:wogonoside; C085514:wogonin