Hairy Roots of Scutellaria spp. (Lamiaceae) as Promising Producers of Antiviral Flavones

Abstract

We measured and studied the growth parameters and the qualitative and quantitative composition of the flavones of hairy roots of the Scutellaria genus: S. lateriflora, S. przewalskii and S. pycnoclada. Hairy roots were obtained using wild-type Agrobacterium rhizogenes A4 by co-cultivation of explants (cotyledons) in a suspension of Agrobacterium. The presence of the rol-genes was confirmed by PCR analysis. The hairy roots of the most studied plant from the Scutellaria genus, S. baicalensis, were obtained earlier and used as a reference sample. HPLC-MS showed the predominance of four main flavones (baicalin, baicalein, wogonin and wogonoside) in the methanol extracts of the studied hairy roots. In addition to the four main flavones, the other substances which are typical to the aerial part of plants were found in all the extracts: apigenin, apigetrin, scutellarin and chrysin-7-O-β-d-glucuronide. According to the total content of flavones, the hairy roots of the studied skullcaps form the following series: S. przewalskii (33 mg/g dry weight) > S. baicalensis (17.04 mg/g dry weight) > S. pycnoclada (12.9 mg/g dry weight) > S. lateriflora (4.57 mg/g dry weight). Therefore, the most promising producer of anti-coronavirus flavones is S. przewalskii.

Keywords: HPLC-MS/MS; S. baicalensis; S. lateriflora; S. przewalskii; S. pycnoclada; baicalein; baicalin; hairy roots; wogonin; wogonoside.

Figure 1

Scheme for obtaining the hairy roots of plants of the genus Scutellaria by transformation with Agrobacterium rhizogenes. 1—seeds, 2—seed sterilization, 3, 4—seed germination on a solid nutrient medium, 5—damaging explants with an insulin syringe, 6—preparation of a daily culture of A. rhizogenes, 7—joint incubation of explants (cotyledons) with A. rhizogenes for 12 h, 8—transfer of explants on a solid medium with cefotaxime, 9—formation of hairy roots, 10—growth of hairy roots in a liquid nutrient medium.

Figure 2

Growth of the hairy roots in a liquid medium.

Figure 3

The pathways for synthesis of root-specific flavones (flavones-synthase II (SbFNSII-2) [8], flavones-6-hydroxylase (SbF6H) [39], flavones-8-hydroxylase (SbF8H) [39], 8-O-methyltransferase (8OMT) [40], baicalein 7-O-glucuronosyltransferase (UBGAT) [41], sGUS—baicalinase, β-glucuronidase [42]).

Figure 4

Comparison of the flavones in hairy roots of species of the genus Scutellaria (LM—in liquid medium, SM—on a solid medium). Values are presented as the means ± SD. Different letters indicate a significant difference between the means (one-way ANOVA, p < 0.05).

Figure 5

Comparison of the flavones content in the hairy roots of species of the genus Scutellaria, (a) in liquid medium, (b) on solid medium. Values are presented as the means ± SD. Different letters indicate a significant difference between the means (one-way ANOVA, p < 0.05).