Exploring the influence of organ differentiation on biosynthesis and accumulation of camptothecin in Ophiorrhiza rugosa var. decumbens

Genus Ophiorrhiza has recently emerged as one of the promising sources of Camptothecin (CPT), an antitumour monoterpene indole alkaloid. It possesses CPT in its every part and has a relatively short life span. To determine whether differentiation plays any role in the synthesis and/or accumulation of CPT, the concentration of CPT was analyzed across various tissues of Ophiorrhiza rugosa var. decumbens obtained through both direct as well as indirect modes of regeneration. The results revealed that the plants obtained from both types of regeneration showed similar levels of CPT. It was also observed that with differentiation, the accumulation of CPT increases, as the callus, being an undifferentiated mass of cells, had only traces of CPT. In contrast, the completely differentiated in-vitro plant obtained from it showed a significantly higher percentage of CPT in shoots (0.22% dry weight) and roots (0.247% dw). The CPT when analyzed after hardening, varied among different organs of the plant. It was also observed that the inflorescence accumulated the highest concentration of CPT (0.348% dw) once the flowering began, accompanied by a decrease in remaining organs. This decrease may result from CPT being mobilized to the inflorescence as a chemical defense mechanism. These findings allowed us to determine the ideal plant harvesting age for CPT extraction. The findings could be used to decide the right stage of plant harvest, which is just before the onset of blooming.