Figure 17.
Pyrrolizidine alkaloids found in Borago officinalis (borage): (A) Flower of B. officinalis. Young flowers show a bright blue color while older flowers exhibit, because of a lower pH, a slightly reddish coloration. (B) Leaves of B. officinalis contain the supinidine-type PAs amabiline and supinine and the retronecine-type lycopsamine and intermedine as well as their 7-acetylated derivatives. Seeds contain mainly the (-)-isoretronecanol-type PA thesinine and its glucoside thesinine-4′-O-β-d-glucoside.