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. 2014 Feb 27;152(1):183-9.
doi: 10.1016/j.jep.2013.12.056. Epub 2014 Jan 8.

Simulated gastrointestinal tract metabolism and pharmacological activities of water extract of Scutellaria baicalensis roots

Shihua Xing  1 , Mengyue Wang  1 , Ying Peng  1 , Daofeng Chen  2 , Xiaobo Li  3
Affiliations

Simulated gastrointestinal tract metabolism and pharmacological activities of water extract of Scutellaria baicalensis roots

Shihua Xing et al. J Ethnopharmacol. .

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE SCUTELLARIA BAICALENSIS: Georgi (Labiatae) is a well-known traditional Chinese medicine to treat inflammation, cardiovascular diseases, respiratory and gastrointestinal infections, etc. The present study was to understand the metabolism of the root of Scutellaria baicalensis (a.k.a. Huangqin in Chinese) in the gastrointestinal tract and the correlation between the metabolites and their respective pharmacological activities.

Materials and methods: The water extract of the root of Scutellaria baicalensis (WESB) was incubated with simulated gastric and intestinal juices, and human fecal microflora for 24h at 37 °C. The HPLC-DAD analysis was used to monitor the in vitro metabolic process and identify its metabolites by comparing their absorption spectrum and retention time with those of chemical references. The in vitro anticomplementary and antimicrobial activity was evaluated with hemolysis assay, agar disc-diffusion method and MIC value, respectively.

Results: Main constituents of WESB remain unchanged during the incubation with simulated gastric juice (pH = 1.5) and intestinal juice (pH = 6.8), whereas four flavones, baicalin, wogonoside, oroxyloside and norwogonoside were metabolized into their respective aglycons by human intestinal bacteria. All four metabolites were demonstrated to have higher anticomplementary and antimicrobial activity than those of WESB. The anticomplementary active metabolites were identified to be baicalein, oroxylin A and norwogonin, among them, norwogonin is the most active compound.

Conclusion: The presence of intestinal bacteria is demonstrated to play an important role in the gastrointestinal metabolism of WESB, and the pharmacological effects of Scutellaria baicalensis may be dependent on the intestinal bacteria metabolism.

Keywords: Antibacterial; Anticomplementary; Baicalein (PubChem CID: 5281605); Baicalin (PubChem CID: 64982); Gastrointestinal tract; Metabolism; Norwogonin (PubChem CID: 5281674); Norwogonoside (PubChem CID: 44258552); Oroxylin A (PubChem CID: 5320315); Oroxyloside (PubChem CID: 38348319); Scutellaria baicalensis; Wogonin (PubChem CID: 5281703); Wogonoside (PubChem CID: 29927693).

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Figures

None
Graphical abstract
Fig. 1
Fig. 1
Chemical structures of eight flavonoids.
Fig. 2
Fig. 2
HPLC chromatograms of WESB. (1) baicalin; (2) norwogonoside; (3) oroxyloside; (4) wogonoside; (5) norwogonin; (6) baicalein; (7) wogonin; (8) oroxylin A.
Fig. 3
Fig. 3
The content changes of the main constituents in WESB when incubated in human intestinal bacteria. Data are presented as mean±SD, n=3. ⁎⁎p<0.01 as compared with the initial content of the compound.
Fig. 4
Fig. 4
Anticomplementary activity of WESB, metabolic samples at 24 h and the blank of intestinal bacterial liquid. (A) The classical pathway; (B) the alternative pathway. Data are presented as mean±SD, n=3.
Fig. 5
Fig. 5
Antimicrobial activity of WESB, metabolic samples at 24 h and the blank of intestinal bacterial liquid. Data are presented as mean±SD, n=3. ⁎p<0.05, ⁎⁎p<0.01, metabolic samples compared with the blank of intestinal bacterial liquid.
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