Suppression of camptothecin biosynthetic genes results in metabolic modification of secondary products in hairy roots of Ophiorrhiza pumila

► Hairy root of Ophiorrhiza pumila is a feasible system for camptothecin production. ► Camptothecin related alkaloids were reduced in the RNAi hairy root of O. pumila. ► Analysis of RNAi hairy roots is a potential method to identify intermediates.