Feasible production of camptothecin by hairy root culture of Ophiorrhiza pumila

Camptothecin derivatives are used clinically as anti-tumor alkaloids. Camptothecin and its related compounds are at present obtained by extraction from intact plants, but transformed plant cell cultures may be an alternative source of production. We have established a hairy root culture of Ophiorriza pumila (Rubiaceae) transformed by Agrobacterium rhizogenes strain 15834. This hairy root culture grew well, increasing by 16-fold during 5 weeks in liquid culture, and it produced camptothecin as a main alkaloid up to 0.1% per dry weight of the cells. Interestingly, not only the hairy root cells contained camptothecin, but the culture medium also accumulated substantial amounts. Camptothecin content in the medium was increased by the presence of a polystyrene resin (Diaion HP-20) that absorbed camptothecin. Camptothecin was easily recovered from the resin. Our method is the most feasible and commercially applicable way to produce camptothecin by in vitro cell culture.