High-Yield Biocatalysis of Baicalein 7-O-β-d-Glucuronide to Baicalein Using Soluble Helix pomatia-Derived β-Glucuronidase in a Chemically Defined Acidic Medium

Biologically active compounds in Scutellaria baicalensis L. callus extract: Phytochemical analysis and isolation

Plant cells and tissue cultures are sources of secondary plant metabolites. Substances produced by callus cultures can expand the raw material base in pharmacy and food production. However, isolating biologically active substances from medicinal plants is a labor- and time-consuming process. As a result, new and efficient technological processes adapted for extraction from callus cultures are in high demand, and new algorithms of isolation and purification of biologically active substances remain a relevant task. This research featured callus cultures of Scutellaria baicalensis. The procedures for phytochemical analysis and isolation of biologically active substances involved such physicochemical research methods as high-performance chromatography (HPLC), thin-layer chromatography (TLC), UV spectrometry, and IR spectrometry. The high performance liquid chromatography confirmed the presence of flavonoids represented by baicalein (5,6,7-trioxyflavone), baicalin (baicalein 7-O-glucuronide), scutellarein (5,6,7,4-tetraoxyflavone), scutellarin (7-O-glucuronide scutellarein), vagonin, and oroxylin. The spectral analyses also detected skutebaicalin. The highest total content of diterpene belonged to the samples extracted with 70% ethanol at 70°C. The content of diterpene was 0.09 mg/cm3 in terms of betulin. The biologically active substances were isolated from the callus extracts of S. baicalensis with a recovery rate of ≥ 80%. The purification scheme made it possible to obtain highly-pure individual biologically active compounds: trans-cinnamic acid, baicalin, and oroxylin A had a purity of ≥ 95%; baicalein had a purity of ≥ 97%; scutellarin and luteolin reached ≥ 96%. The new technological extraction method made it possible to obtain extracts from S. baicalensis callus cultures, which were tested for the component composition. The developed isolation algorithm and purification scheme yielded biologically active substances with a purification degree of ≥ 95%.

Enhancement of the flavone contents of Scutellaria baicalensis hairy roots via metabolic engineering using maize Lc and Arabidopsis PAP1 transcription factors

Baicalin, baicalein, and wogonin are valuable natural flavonoid compounds produced by Scutellaria baicalensis. In this study, we showed that the maize transcription factor Lc can enhance the production of these three flavonoids in hairy root cultures of S. baicalensis by comprehensively upregulating flavonoid biosynthesis pathway genes (SbPAL1, SbC4H, and Sb4CL) and baicalein 7-O-glucuronosyltransferase (UBGAT), ultimately yielding total flavonoid contents of up to 80.5 ± 6.15 mg g^-1 dry weight, which was 322% greater than the average value of total flavonoid contents produced by three GUS-overexpressing lines. Similarly, the Arabidopsis transcription factor PAP1 was found to enhance flavonoid accumulation by upregulating SbPAL1, SbPAL2, SbPAL3, SbC4H, Sb4CL, SbCHI, and UBGAT, ultimately yielding total flavonoid contents of up to 133 ± 7.66 mg g^-1 dry weight, which was 532% greater than the average value of total flavonoid contents produced by three GUS-overexpressing lines. These findings indicate that metabolic engineering in S. baicalensis can be achieved using Agrobacterium rhizogenes-mediated transformation and that the production of baicalin, baicalein, and wogonin can be enhanced via the overexpression of ZmLc and AtPAP1 in hairy root cultures. These results also indicate that ZmLc and AtPAP1 can be used as positive regulators of the flavonoid biosynthetic pathway of S. baicalensis hairy root cultures.