Methanolic extracts from in vitro grown Scutellaria lateriflora shoots cultured on five Murashige and Skoog (MS) medium variants supplemented with different combinations of 6-benzylaminopurine (BAP) and α-naphthaleneacetic acid (NAA) under different light conditions (monochromatic light, white light and no light) were analysed by HPLC for three groups of metabolites: flavonoids (26 compounds), phenolic acids and their precursors (19+2) and phenylethanoid glycosides (2). The analyses revealed the presence of baicalein, baicalin, wogonin, wogonoside, 3,4-dihydroxyphenylacetic acid and verbascoside. There was clear evidence of the influence of plant growth regulators and light conditions on the accumulation of the analysed groups of secondary metabolites. The amounts of the compounds changed within a wide range-for the total flavonoid content, 30.2-fold (max. 1204.3 mg·100 g-1 dry weight (DW)); for 3,4-dihydroxyphenylacetic acid, 5.5-fold (max. 33.56 mg·100 g-1 DW); and for verbascoside, 1.5-fold (169.15 max. mg·100 g-1 DW). The best medium for the production of most of the compounds was the Murashige and Skoog variant with 1 mg l-1 BAP and 1 mg l-1 NAA. For verbascoside, the best 'productive' medium was the MS variant supplemented with 0.5 mg l-1 BAP and 2 mg l-1 NAA. The accumulation of the metabolites was stimulated to the greatest extent by blue light, under which the extracts were found to contain the highest total amount of flavonoids and the highest amounts of flavonoid glucuronides, baicalin and wogonoside, as well as of verbascoside. Their amounts were, respectively, 1.54-, 1.49-, 2.05- and 1.86-fold higher than under the control white light.
Keywords: American skullcap; Baicalin; Darkness; Flavonoids; Monochromatic light; Plant growth regulators; Secondary metabolites; Verbascoside.