Naphthoquinone glucosides of Drosera gigantea from in vitro cultures.

From the shoots of Drosera gigantea propagated under in vitro culture, the rare naphthoquinone glucosides droserone (3,5-dihydroxy-2-methyl-1,4-naphthoquinone) and hydroxydroserone (3,5,8-trihydroxy-2-methyl-1,4-napthoquinone) 5-O-beta-glucosides, together with the free naphthoquinones droserone, hydroxydroserone and plumbagin were isolated. The structures of the glucosides and hydroxydroserone were studied by 2D NMR techniques. The glucosides appear to be responsible for the brown-red (maroon) colour of this plant. Of the other naphthoquinones typical for the family Droseraceae only hydroplumbagin glucoside could be detected, whereas the presence of 7-methyljuglone and rossoliside (= 7-methylhydrojuglone glucoside) was excluded.