Production of verbascoside and its analogues in in vitro cultures of Verbascum thapsus L

In this work an effective method to start axenic cultures of Verbascum thapsus L. was developed. This allowed to obtain a high percentage of callus generation from leaf explants (around 70%) and to start the cultivation of suspension cultured cells rapidly growing in liquid culture medium. Moreover, the production in these materials of the phenylethanoid glycoside compound verbascoside was verified and quantified ascertaining that both calli and cultured cells maintain the ability to accumulate it at levels similar or superior to those found in plant leaves. Moreover, since HPLC–UV chromatograms of extracts of both calli and suspension cultured cells revealed the presence of other relevant peaks close to the verbascoside one, an HPLC–DAD–MS analysis was carried out leading to identify and quantify three further phenylethanoid glycosides i.e. iso-verbascoside, leucosceptoside A and eucosceptoside B, compounds which had been previously detected and identified also in extracts from leaves. On the whole, the above summarized findings confirm and reinforce the attractiveness and reliability of using in vitro cultures as a convenient source of this class of natural plant products, particularly taking into account that a number of biotechnological approaches allowing to increase the yield of the synthesized phytochemicals are currently available and can be applied in plant tissue culture.